Information

Do Colorblind People Have Stronger Sensitivity in Their Other Remaining Cones?

Do Colorblind People Have Stronger Sensitivity in Their Other Remaining Cones?


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

I came across this paper Color defect and color theory. The paper explained about how unilateral color blind (people who color blind only in 1 eye) actually see less bright in their color-blind eye (in graph : filled bullet) compared to the normal eye (in graph : white bullet). Especially to the scene that corresponds to the missing cone (in this paper, Deuteranopes. Missing cones = green)

I have 2 questions regarding this brightness loss in color blind people.

  1. Green cones response are near the red cones response, and they are overlapping. How is it possible that Deuteranopes loss brightness in Green and Blue (which will make more sense if they also loss brightness in Red, thus loss brightness in the whole spectrum) but instead, still achieve the same amount of brightness in Red ? Despite Red and Green color-blind have the same color combination possibility (gamut mapping) that they can perceive ?

  2. Could it be that color-blind people have stronger sensitivity in other cones (for example : stronger in red) and then this red opsin actually replace / fill the missing cones stimuli in retina, so their retina still able to perceive the same amount of brightness on that excessive cones ?


Kudos for Delta-S in Reddit for enlighten me. Original post is here.

The answer is no, color blind people don't have stronger sensitivity in their other remaining cones. This goes back to the Photopic Sensitivity Graph below.

As you can see, human vision are most sensitive to green. All responses of green cone are within the photopic sensitivity as well as most response of the red cones. And despite few responses of red cones are outside the Photopic sensitivity, the peak sensitivity of red cones is very close to the peak of Photopic sensitivity (560nm and 555nm).

  • Peak Photopic Sensitivity: 555nm
  • S cones peak : 420nm
  • M cones peak : 530nm
  • L cones peak : 560nm

So, in case of Deuteranopic, depending on which wavelength is loss (defected) from their eye, if it closer to the red response then they will likely to experience luminance loss as well. However, if the green cone that is defected is far from the red response, the red cones still have possibility to maintain the luminance they can achieve.

Unfortunately in the paper, it's not mentioned which sensitivity wavelength was defected from the unilateral participant. It is only mentioned "result indicate that she was deuteranopic".


Debunked the effectiveness of glasses for color blind people

IMAGE: The UGR researchers posing with the EnChroma® glasses for colorblind people studied in this research. From left to right: Luis Gómez, Eva Valero, Javier Hernández, Miguel Ángel Martínez and Rafael. view more

Credit: University of Granada

The EnChroma® glasses, commercialized by a North American company, do not improve color vision for color blind people or correct their color blindness, and their effect is similar to that of other glasses such as the ones used for hunting

48 color blind people participated in this research, carried out at the UGR Department of Optics, after a public call to which more than 200 volunteers responded

One of the authors of this research is also color blind, and he carries out his research in the field of color vision

The recent commercialization of theEnChroma®glasses has generated great expectations among the color blind thanks to a strong campaign in social networks and media. They hoped to see new colors or even correct their color blindness by using said glasses.

The North American company manufacturing them advertises an improvement in color vision for certain types of color blindness, protan and deutan, by extending the range of colors perceived by the subject without affecting the colors that are already distinguished without glasses. In fact, on their website,EnChroma®states that their glasses "alleviate red?green color blindness, enhancing colors without the compromise of color accuracy" but claiming that their glasses "may not work" for severe red?green deficiency.

One claim on the company's website (at least until October 2017) was that their glasses "are designed to improve the everyday experience of color vision". However, that claim has been recently substituted by a more subtle sentence: "the glasses are an optical assistive device for enhancement of color discrimination in persons with color blindness they are not a cure for color blindness", pointing out that "results vary depending on the type and extent of color vision deficiency per individual."

In an article published in Optics Express, one of the most relevant journals with a great impact in the field of optics, researchers from the University of Granada (UGR) have debunked the effectiveness of these glasses for color vision deficiency (CVD), proving that theEnChroma®glasses don't make color blind people's vision comparable to that of people without color blindness.

A study with 48 color blind volunteers

This UGR research has counted with the participation of 48 people with color blindness, after a public call to which more than 200 volunteers responded. The researchers have used, for the first time, two complementary strategies in order to evaluate the effectiveness of the glasses. The first strategy consisted in evaluating the color vision of the participants with and without glasses using different types of tests: the Ishihara test (recognition) and the Fansworth?Munsell test (arrangement). Besides, they have added a test based on the X?Rite Color Chart, which evaluates subjective color naming.

The second approach for evaluating the effectiveness of these glasses consisted in using the spectral transmittance of their lenses to simulate different observers, which allowed to evaluate the changes in color appearance.

According to Luis Gómez Robledo, professor from the UGR Department of Optics and one of the authors of this paper, "normal human color vision is trichromatic thanks to a cluster of three types of photoreceptors known as cones, which are present in the retina. These cones are sensitive to short wavelengths (S), medium wavelengths (M) and long wavelengths (L). However in Europe, about 8% of men and 0.5% of women in the Caucasian population suffer from some type of congenital anomaly in the performance of some of the cones, which causes color vision deficiencies. This anomaly is a sex?linked recessive trait, with the red?green color vision deficiency being the most frequent in humans." Said red?green CVD is in turn classified into two types:protan and deutan, depending on the affected cones. Moreover, there is another classification based on the severity of the deficiency: protanomalous or deuteranomalous, and protanopic or deuteranopic.

Glasses similar to those used for hunting

This study carried out by the UGR shows that a color blind person using theEnChroma®glasses will not perceive new colors, but rather the will see the same colors in a different way.

"This makes possible for some individuals using these glasses to distinguish some colors, but to the detriment of others which will be now confused. Even though a color filter as that used by theEnChroma®glasses may change the appearance of colors, it will never make color vision more similar to a normal observer's vision," the authors state.

The effect of using theEnChroma®glasses is similar to that achieved with glasses designed for specific activities (shooting, hunting, low eyesight etc.), where the use of colored glasses helps to better perceive certain stimuli thanks to an increased contrast with the surroundings.

Besides, during the research, the observers were asked to look at their surroundings with the glasses and to subjectively assess the possible improvement. None of the participants noticed any improvement to the colors of their surroundings when looking through the glasses, except for just one female participant with very mild deuteranomaly.

The results show that the glasses specifically used in this study have not revealed any improvement in the two types of color blindness tests: recognition and arrangement.Therefore, the glasses cannot help in cheating in professional screening tests, in agreement to what the company claims on its website.

The group of researchers, all of them belonging to the Department of Optics at the Faculty of Science of the University of Granada, is integrated by doctors Luis Gómez Robledo, Eva Valero Benito, Rafael Huertas Roa, Miguel Angel Martínez DomingoandJavier Hernández Andrés. It is worth mentioning that one of them, Luis Gómez Robledo, is also color blind, and he carries out his research in the field of color vision.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.


Why do people mock? [Not color blind] but i noticed it.

Hi, im not color blind but i wanted to ask a question if that's okay? I noticed on youtube or even in my real life with my grandfather whos color blind people will always make jokes i find as mocking about him not being able see the color so he can't pick it. Or how someone whos color blind in a video may go oh i like this! And the other person tell them it doesn't match and they can't or shouldn't. Its always upset me because isn't that wrong? Does it matter why wont people let you have opinions to. Just because you see it differently shouldn't be the reason to why you can't or shouldn't be looked down on as stupid or silly. Idk it bothered me but im not colored blind maybe people are ok with it and i shouldn't be upset. But i wanted to see what you yourselves would say.

As far as "disabilities" go, it's not really the biggest of deals. To me, it's like making fun of someone for burning instead of tanning in the sun. It's so silly that it's hard to believe anyone is doing it maliciously rather than in a joking manner.

Agreed, if someone I barely knew did this, it would be rude, but my friends do it in the same way I "make fun" of them for liking a video game. But I can't image someone doing that if I didn't know them or barely know them. Color deficiency is life altering. But it's not a huge deal at all usually.

I agree. My brothers and I joke about my colourblindness all the time XD

It all really depends on context. As the other two posters have said, it's not really a huge deal, I mostly brush it off.

But there are times it can be. If it's something I'm frustrated with, like being unable to do something because of my colorblindness and then someone chimes in with a sort of condescending joke, then the joke doesn't hit as much as the mocking.

Or if I've worked hard on something, especially something creative like a painting or whatever, and people mock it, it especially feels like shit.

If it's just your friends making banter because you wore a yellow shirt on St. Patrick's day instead of green, then well, it's not such a big deal.

I'm a hobby painter (oil), and going by Art: If you paint WITH the aspect of being a Dichromat, and chose colours maybe also randomly (not looking on the tubes'/colours' name), you might as well make this your very own Dichromacy painting style.

It will look "strange" to Trichromats, but look in Art history, there are many "strange" painting styles.

I've heard of a Tetrachromat who's painting like she perceives the world, and it might be her exact selling point. So you, as a Dichromat, could do that as well, and call it "Dichromacy Art" or similar.

So if e.g. your grass would be Red and your flowers would be green, so what?
If that's what you see as a shade corresponding to a colour, then so be it.
This is how YOU see the world!

I personally would find such an approach very exciting, as it's different, and Art and its beauty is in the individual person's eye.

Making such Art may make people more aware of it, and maybe also have creators of all disciplines (e.g. game designers) try to account for it and create maybe more often CVD modes.

See my own comment in this post: Being a Dichromat can also have its benefits.

Imo nearly all disabilities or human divergences do have their strengths.


PSY 232 Chapter 6

b.
​can be described as the movement of tiny indivisible particles called photons.

c.
​is made up of tiny particles called electromagnetons.

a.
​passes through any medium.

b.
​is absorbed by the ozone layer of the atmosphere.

c.
​does not travel in straight lines.

a.
​it passes through objects rather than reflecting from them.

b.
​it is too abundant at the surface of the earth.

c.
​most ultraviolet light is blocked by the earth's atmosphere.

a.
​most longer wavelengths are blocked by the earth's atmosphere.

b.
​they travel at too slow a speed.

c.
​they are too abundant at the earth's surface to be useful in vision.

a.
​reflect short wavelengths while absorbing longer wavelengths.

b.
​reflect long wavelengths while absorbing shorter wavelengths.

c.
​refract short wavelengths while absorbing longer wavelengths.

a.
​primarily a prey species.

b.
​primarily a predator species.

c.
​both a prey and a predator species.

c.
​the placement of the eyes toward the front

a.
​blinks happen too quickly to be perceived by the cerebral cortex.

b.
​during a blink, the visual cortex is deactivated.

c.
​we learn to ignore these interruptions in visual input.

a.
​contain more protein than

b.
​contain more glucose than

c.
​contain less water than

a.
​they consist of special proteins found only in the eye.

b.
​we habituate to the sight of their blood vessels.

c.
​neither has a blood supply.

a.
​she would no longer be able to see from that eye.

b.
​she would need painkillers, as the cornea has a high density of pain receptors.

c.
​she wouldn't need any pain medication, because the cornea lacks pain reception.

a.
​vitreous humor, which circulates around the cornea and lens.

b.
​aqueous humor, which circulates around the cornea and lens.

c.
​vitreous humor, located in the main chamber of the eyeball.

b.
​adjusts to the temperature of the external environment.

c.
​responds only to the amount of light present in the environment.

c.
​the refraction of light by the anterior chamber.

a.
​Anthony's aqueous humor has a different composition than Samantha's.

b.
​Anthony's irises contain a denser blood supply than Samantha's.

c.
​Samantha's irises contain more melanin than Anthony's.

a.
​the pigmented tissue at the back of the eye that supports the photoreceptors.

b.
​a blockage of the tear ducts at the outer upper corner of the eye.

c.
​the fluid located in the main interior chamber of the eyeball.

a.
​aqueous humor is replenished and the vitreous humor is not.

b.
​vitreous humor is replenished and the aqueous humor is not.

c.
​aqueous humor nourishes the cornea, whereas the vitreous humor nourishes the lens.

a.
​identical in its spatial orientation.

c.
​right side up and reversed.

c.
​vitreous humor and several layers of neurons.

a.
​the visual system does not respond much to stimuli that never change.

b.
​these structures are made of special proteins whose fibers make them transparent.

c.
​they are blocked by the vitreous humor.

a.
​distortion of the eye's color by the aqueous and vitreous humors.

b.
​scattering of light from the iris of the eye.

c.
​reflection from the red epithelium behind the retina.

a.
​He will be totally blind.

b.
​He will be able to see only what is exactly in front of him.

c.
​He will be able to see only what is in his peripheral visual area.

a.
​highly sensitive to light and color.

b.
​less sensitive to light and color.

c.
​highly sensitive to light but not detail.

a.
​rods and cones are evenly distributed.

b.
​the concentration of rods decreases and the concentration of cones increases.

c.
​the concentration of cones decreases and the concentration of rods increases.

a.
​colorful objects in bright light.

b.
​black and white objects in bright light.

c.
​objects in fine detail in dim light.

a.
​continues to look straight ahead at the door, focusing light on his foveas.

b.
​continues to look straight ahead at the door to use his scotopic vision.

c.
​focuses on a point to the left or right of the door in order to use his scotopic vision.

a.
​saw the sweater earlier under brighter light, because she would be unable to see its color in the dark.

b.
​might not like the color of the sweater as well when she sees it under brighter light, because color vision in the dark is more reddish.

c.
​can see the color of the sweater perfectly well, as color vision is excellent even in starlight conditions.


When to get your child tested

It can be tricky to diagnose color blindness in children. Kids who are color blind might try to hide it. But being color blind can make it harder to read off a chalkboard or do other activities, so it’s important to get your child tested if you’re concerned.

Get your child tested if they have a family history of color blindness or if they seem to be having trouble learning colors.

Ask your child’s eye doctor to test them. You also may be able to get your child tested at school.


Scientists debunk the effectiveness of EnChroma glasses for colorblind people

Credit: CC0 Public Domain

The recent commercialization of the EnChroma glasses has generated great expectations among the color blind thanks to a strong campaign on social networks and the media. Users of the glasses hoped to see new colors or even correct their color blindness.

The North American manufacturer advertises an improvement in color vision for certain types of color blindness, protan and deutan, by extending the range of colors users perceive without affecting the colors that are already distinguished without glasses. In fact, on its website, EnChroma states that their glasses "alleviate red-green color blindness, enhancing colors without the compromise of color accuracy," but say that their glasses "may not work" for severe red-green deficiency.

One claim on the company's website (at least until October 2017) was that their glasses "are designed to improve the everyday experience of color vision." However, that claim was recently changed to a more subtle statement: "The glasses are an optical assistive device for enhancement of color discrimination in persons with color blindness they are not a cure for color blindness," it says, pointing out that "results vary depending on the type and extent of color vision deficiency per individual."

In an article published in Optics Express, researchers from the University of Granada (UGR) have debunked the effectiveness of these glasses for color vision deficiency (CVD), proving that the EnChroma glasses don't make color blind people's vision comparable to that of people without color blindness.

This UGR research involved 48 people with color blindness, after a public call to which more than 200 volunteers responded. The researchers used two complementary strategies to evaluate the effectiveness of the glasses. The first strategy consisted of evaluating the color vision of the participants with and without glasses using different types of tests: the Ishihara test (recognition) and the Fansworth-Munsell test (arrangement). Additionally, they used a test based on the X-Rite Color Chart, which evaluates subjective color naming.

The second approach for evaluating the effectiveness of the glasses consisted of using the spectral transmittance of the lenses to simulate different observers, which allowed the researchers to evaluate the changes in color appearance.

Luis Gómez Robledo, professor from the UGR Department of Optics and one of the authors of this paper, says, "Normal human color vision is trichromatic thanks to a cluster of three types of photoreceptors known as cones, which are present in the retina. These cones are sensitive to short wavelengths (S), medium wavelengths (M) and long wavelengths (L). However in Europe, about 8 percent of men and 0.5 percent of women in the Caucasian population suffer from some type of congenital anomaly in the performance of some of the cones, which causes color vision deficiencies. This anomaly is a sex-linked recessive trait, with the red-green color vision deficiency being the most frequent in humans."

Red-green CVD is classified into two types: protan and deutan, depending on the affected cones. Moreover, there is another classification based on the severity of the deficiency: protanomalous or deuteranomalous, and protanopic or deuteranopic.

Glasses similar to those used for hunting

This study carried out by the UGR shows that a color-blind person using the EnChroma glasses will not perceive new colors, but rather sees the same colors in a different way.

"This makes it possible for some individuals using these glasses to distinguish some colors, but to the detriment of others, which will be now confused. Even though a color filter such as that used by the EnChroma glasses may change the appearance of colors, it will never make color vision more similar to a normal observer's vision," the authors state.

The effect of using the EnChroma glasses is similar to that achieved with glasses designed for specific activities (shooting, hunting, low eyesight etc.), where the use of colored glasses helps to better perceive certain stimuli thanks to an increased contrast with the surroundings.

Additionally, during the research, the observers were asked to look at their surroundings with the glasses and to subjectively assess the possible improvement. None of the participants noticed any improvement to the colors of their surroundings when looking through the glasses, except for one female participant with very mild deuteranomaly.

The results show that the glasses specifically used in this study don not confer any improvement in the recognition or arrangement color blindness tests. Therefore, the glasses cannot improve scores in professional screening tests, contrary to what the company claims on its website.


Glossary of Eye Conditions

Rare, inherited vision disorder in which a person has little or no ability to see color. People with achromatopsia also commonly experience some vision loss, especially in bright light, to which they are extremely sensitive. The severity of achromatopsia varies. Although there is no cure or treatment for this disorder, people with achromatopsia can manage its symptoms. For example, they can wear sunglasses or tinted contact lenses to cope with bright light. They can use magnifiers and other devices for low vision to help them read, and telescopes to help them see distant objects.

Acute Zonal Occult Outer Retinopathy (AZOOR)

Acute zonal occult outer retinopathy (AZOOR) is a retinal disease characterized by sudden onset of flashing lights and visual field changes in an individual with a normal retinal exam. It affects women 3 times more frequently than men most people affected are Caucasian, middle-aged, and myopic. A viral illness has preceded many of the reported cases. Initially only one eye is involved but the other eye may be affected months to years later.

Age-related macular degeneration (ARMD)

A hereditary condition characterized by a variable lack of pigment in the eyes, skin, or hair. People with albinism may have pale pink skin and blond to white hair, but there are different types of albinism, and the amount of pigment varies. The irises of their eyes may be white or pinkish. They are sensitive to bright light and glare and commonly have other vision problems. While some people with albinism can see well enough to drive, many have impaired vision or may even be legally blind. Albinism is often accompanied by nystagmus or strabismus. People with albinism are sensitive to bright light and glare and may wear tinted eyeglasses. Bifocals, magnifiers, and other optical devices can help people with albinism.

A condition in which a person's vision does not develop properly in early childhood because the eye and the brain are not working together correctly. Amblyopia, which usually affects only one eye, is also known as "lazy eye." A person with amblyopia experiences blurred vision in the affected eye. However, children often do not complain of blurred vision in the amblyopic eye because this seems normal to them. Early treatment is advisable, because if left untreated, this condition may lead to permanent vision problems. Treatment options include vision therapy exercises or prescription eyeglasses. People with amblyopia may need to wear an eye patch over their stronger eye in order to force the affected eye to function as it should.

Partial or complete absence of the iris of the eye. This rare condition, usually present at birth, results in impaired vision and sensitivity to light. People with aniridia are also at high risk for certain other eye conditions, such as glaucoma, nystagmus, and cataracts. People with aniridia may benefit from wearing tinted contact lenses or sunglasses, using magnifiers, and avoiding intense or glaring light.

Anophthalmia

Rare condition in which one or both eyes do not form during pregnancy. When both eyes are affected, blindness results. There is no cure for anophthalmia. Prosthetic eyes can promote proper growth of the eye sockets and development of facial bones and also serve cosmetic purposes.

Absence of the lens of the eye. Aphakia is usually associated with the surgical removal of a cataract but may also result from a wound or other cause. Without the lens, the eye cannot adjust its focus for seeing at different distances. Contact lenses or eyeglasses are used to correct the vision of someone with aphakia. In cataract surgery, an artificial lens is inserted to replace the lens removed. A person with aphakia will benefit from good, but not excessive, lighting and high-contrast reading materials.

Astigmatism

Common vision condition, usually present from birth, caused by an irregularly curved cornea or lens. People with astigmatism may experience blurred vision, eyestrain, or headaches. Two-thirds of Americans who have myopia also have astigmatism. Astigmatism can be corrected with eyeglasses or contact lenses. Corrective surgery is another option.

Rare, inherited condition that affects the macula, the area in the middle of the retina, and can cause blurred or distorted vision or a loss of central vision. Best's Disease, also known as Vitelliform Macular Dystrophy, may affect both eyes. The disease's effects on sight vary and may not become severe for many years, if ever. Most people are not significantly affected until after age 40. There is no treatment for Best's Disease, but a person whose vision is impaired by this disease may benefit from devices for low vision.

A condition in which the lens of the eye, which is normally clear, becomes cloudy or opaque. Cataracts generally form slowly and without pain. They can affect one or both eyes. Over time, a cataract may interfere with vision, causing images to appear blurred or fuzzy and colors to seem faded. Most cataracts are related to aging. In fact, cataracts affect more than 50 percent of all adults by age 80 and are the primary cause of vision loss in people 55 and older. People with early cataract may benefit from new eyeglasses, bright lighting, anti-glare sunglasses, or magnifying lenses. If, despite such devices, cataract interferes with daily activities, surgery is the only effective treatment. Cataract surgery, which is common, involves removal of the cloudy lens and replacement with an artificial lens.

Charles Bonnet syndrome

Visual disturbances usually occurring in people who have experienced visual impairment or sight loss later in life, as through macular degeneration. People with Charles Bonnet syndrome may see a wide range of images, from simple patterns to people, animals, and buildings. The visual disturbances associated with this syndrome are not signs of mental illness, and people realize that the images they are seeing are not real. There is no cure for Charles Bonnet syndrome. However, the symptoms often stop on their own. People who have Charles Bonnet syndrome should consult with an eye care specialist because treatment for vision disorders may help.

Chorioretinal Atrophy Chorioretinal atrophy is, as the name implies a degeneration, or atrophy of the retina. It affects males more than females. It is an autosomal dominant disorder caused by mutations in the CRB1 gene. Choroidal Neovascularization Choroidal neovascularization refers to new and abnormal blood vessels that grow, multiply, and develop into a cluster beneath the macula. The macula is the part of the retina that provides the clearest central vision. Choroideremia

Rare disorder that causes progressive loss of the choroid, an important layer under the retina that is responsible for some of its blood supply. Choroideremia is an inherited disorder that generally affects males only. It commonly begins as night blindness in childhood and gradually advances to increasing vision loss. Most people with this disorder are able to retain good vision until age 40 or 50. There is no treatment for choroideremia, but people who have the disorder may find it helpful to use optical, electronic, or computer-based devices for low vision.

A cleft or gap in some part of the eye, such as the iris, lens, or retina, that is caused by a defect in the development of the eyeball. How much coloboma affects a person's vision depends on the size and location of the cleft and on whether it occurs in one or both eyes. For example, someone with only a tiny defect in the iris may have normal vision. However, a person with large defects in the retina and optic nerve may have limited vision. Children whose vision is impaired by coloboma may benefit from using reading materials that have large black print and well-spaced letters and words. They may also find it helpful to read one line at a time with the aid of a cutout reading window.

Color blindness

A vision problem in which a person has difficulty distinguishing certain colors—most commonly red and green, but sometimes blue and green or blue and yellow. Color blindness is not really a form of blindness, but rather a deficiency in color perception. It usually affects both eyes and is much more common in males than in females. There is no treatment or cure for this problem, but a color-blind person can learn to adapt in various ways. For example, a color-blind driver can remember that the light positioned at the top of a traffic light is the red one. It is beneficial to diagnose color blindness in children at an early age so that steps can be taken to avoid learning problems related to color perception.

Cone-rod dystrophy

Inherited disease that, over time, causes deterioration of the specialized light-sensitive cells of the retina. People with cone-rod dystrophy typically experience decreased sharpness of vision followed by a loss of peripheral vision and color perception. The most common form of cone-rod dystrophy is retinitis pigmentosa. There is no treatment or cure for this disease, which is also referred to as cone-rod degeneration, progressive cone-rod dystrophy, and retinal cone dystrophy.

Congenital eye defects Any of various conditions present at birth that affect the eyes or vision. Some congenital eye conditions, such as retinitis pigmentosa, are passed on through genes. Others, such as vision loss due to German measles, result from a disease or deficiency during pregnancy. Sometimes, as in the case of coloboma, the cause of a congenital eye defect is not known. Congenital eye defects can impair vision or even cause blindness. Some conditions are immediately apparent in an infant, while others may not become known until later in life. Conjunctivitis

Conjunctivitis is inflammation of the conjunctiva, which is the thin translucent tissue that lines the inner surface of the eyelid and the outer surface of the sclera, which is the white part of the eye.

Conjunctivitis is usually associated with redness of the white part of the eyes, light sensitivity (photophobia), excessive tearing, ocular discomfort (gritty sensation, itching, burning), and/or discharge.

There are many different causes of conjunctivitis. Some types of conjunctivitis are infectious, while others are not. These can generally be differentiated from one another based on history and an examination by an eye doctor.

Corneal disease

Disease or disorder that affects the cornea, the clear, curved surface that covers the front of the eye. The effects of corneal disease vary. Some corneal conditions cause few, if any, vision problems. For example, infections of the cornea can often be treated with antibiotics. However, if the cornea becomes cloudy, light cannot penetrate the eye to reach the retina, and severe visual impairment, or even blindness, may result. Corneal dystrophies are usually inherited conditions in which one or more parts of the cornea lose their clarity due to a buildup of cloudy material. Keratoconus is the most common corneal dystrophy in the United States. When corneal disease causes the cornea to become permanently clouded or scarred, doctors may be able to restore vision with a corneal transplant—surgical replacement of the old cornea with a new one.

Cortical visual impairment

Visual impairment caused by damage to those parts of the brain related to vision. Although the eye is normal, the brain cannot properly process the information it receives. The degree of vision loss may be mild or severe and can vary greatly, even from day to day. Also known as cerebral visual impairment, cortical visual impairment (CVI) may be temporary or permanent. People with cortical visual impairment have difficulty using what their eye sees. For example, they may have trouble recognizing faces, interpreting drawings, perceiving depth, or distinguishing between background and foreground. Children with cortical visual impairment are often able to see better when told in advance what to look for. Cortical visual impairment is also known as neurological visual impairment (NVI).

Eye condition that results from the damaging effect of diabetes on the circulatory system of the retina. The longer someone has had diabetes, the greater the person's likelihood of developing diabetic retinopathy. Changes in the tiny blood vessels of the retina can lead to vision loss. People with diabetes should have routine eye examinations so that diabetes-related problems can be diagnosed and treated as soon as possible. Maintaining strict control of blood sugar levels helps to prevent diabetic retinopathy. Surgical and laser treatments can help many people affected with this condition.

Dry eye syndrome

Persistent dryness of the eyes resulting from too little production of tears or too rapid evaporation of tears. People with dry eye syndrome may experience such symptoms as itching, burning, or stinging eyes. Some people feel as though something is caught in their eye, causing an irritation. Dry eye syndrome has many causes. For example, it may be linked to wearing contact lenses for long periods of time or to living in a dry or dusty climate. It may be a side effect of medication or a symptom of certain diseases. An eye doctor may recommend the application of special eye drops—"artificial tears"—to moisten the eyes or the use of a humidifier to increase humidity in the air. Not rubbing the eyes and avoiding such irritants as tobacco smoke can also help persons with dry eye syndrome.

Specks or strands that seem to float across the field of vision. Floaters and spots are actually shadows on the retina cast by tiny bits of gel or cells inside the clear fluid that fills the eye. Floaters and spots usually are normal and harmless. However, in some cases they may warn of serious conditions such as retinal detachment, diabetic retinopathy, or infection. Someone who experiences a sudden decline in vision accompanied by flashes and floaters or a sudden increase in the number of floaters should consult an ophthalmologist urgently.

Disease in which the pressure of the fluid inside the eye is too high, resulting in a loss of peripheral vision. If the condition is not diagnosed and treated, the increased pressure can damage the optic nerve and eventually lead to blindness. Vision lost as a result of such damage cannot be restored. A person who has glaucoma may not realize it at first, because the disease often progresses with no symptoms or warning signs. Early detection through regular eye examination and prompt treatment is essential to prevent vision loss. Daily medication (usually eye drops), surgery, or a combination of both enables most people to control their intraocular pressure and retain their vision.

Blindness affecting half of the field of vision. Hemianopia, also known as hemianopsia, may be caused by various medical conditions, but usually results from a stroke or brain injury. It may affect either the right or left side of the visual field and is usually permanent. Hemianopia can produce various effects, from minor to severe. For example, a person may be able to see only to one side when looking ahead, or objects that the person sees may differ in clarity or brightness. Such visual impairment can make it difficult to perform daily tasks, from reading to crossing streets. There is no specific treatment for hemianopia, but low vision rehabilitation specialists can help people learn to make the most of the sight that they have. In addition, some people with hemianopia benefit from the use of magnifiers or special prism lenses.

This common vision problem, also known as farsightedness, occurs when light rays entering the eye focus behind the retina, not directly on it. People with hyperopia are usually able to see distant objects well, but close objects appear blurry. Hyperopia may cause eyestrain or headaches, especially with reading. Eyeglasses or contact lenses can correct hyperopia. For people who do not want to wear glasses or contact lenses, laser vision correction is sometimes possible.

Rare condition, often inherited, in which the cornea becomes progressively thinner and gradually bulges outward, causing blurred or distorted vision. Keratoconus usually affects both eyes. At first, people with this condition can correct their sight with eyeglasses. However, as symptoms worsen over time, specially designed contact lenses are needed to improve vision. Most people with keratoconus will not experience severe visual impairment. However, as many as one in five will eventually require a corneal transplant (surgical replacement of the old cornea with a new one).

Rare, inherited disorder affecting many parts of the body. People with this condition have retinitis pigmentosa accompanied by mental retardation, paralysis of the legs, and various other symptoms.

Leber's congenital amaurosis

Inherited condition, probably caused by degeneration of the retina, in which an infant is born blind or develops severe vision loss soon after birth. Children with Leber's congenital amaurosis typically also have nystagmus, and some also have mental retardation and hearing disorders. At present, there is no treatment for this condition.

Legal blindness A level of visual impairment that has been defined by law to determine eligibility for benefits. It refers to central visual acuity of 20/200 or less in the better eye with the best possible correction, or a visual field of 20 degrees or less. Low vision

Vision loss that may be severe enough to impede a person's ability to carry on everyday activities, but still allows some functionally useful sight. Low vision may be caused by macular degeneration, cataracts, glaucoma, or other eye conditions or diseases. Low vision may range from moderate impairment to near-total blindness. It cannot be fully corrected by eyeglasses, contact lenses, or surgery. However, a person with low vision may benefit from any of a variety of available optical devices, such as electronic magnifying glasses or eyeglass-mounted telescopes. In addition, special software developed for computer users with low vision can display type in large size or read text aloud.

Disease that causes dysfunction of the macula, the area in the middle of the retina that makes possible the sharp central vision needed for such everyday activities as reading, driving, and recognizing faces and colors. The condition is commonly known as age-related macular degeneration (AMD) and is the leading cause of visual impairment among older people. However, there are also other types of macular degeneration, such as Stargardt's Disease and Best's Disease. Macular degeneration causes blurred, distorted, or dim vision or a blind spot in the center of the visual field. Peripheral vision is generally not affected. This condition is painless and may progress so gradually that the affected person at first notices little change. There is no cure for macular degeneration, but drug therapy, laser surgery, or other medical treatment may in some cases be able to slow the disease's progression or prevent further vision loss. People with macular degeneration can also benefit from the use of various devices for low vision, such as magnifiers, high-intensity lamps, and pocket-sized telescopes.

Macular hole

A macular hole is a full thickness hole in the central part of the retina called the macula. It may be caused by injury or inflammatory swelling of the retina, but most commonly occurs as an age-related event without any predisposing conditions. Macular holes are thought to be caused by tractional forces associated with the vitreous gel separating from the retina in the macula and around the central macula called the fovea. Surgery is the treatment of choice for full-thickness macular holes.

Marfan Syndrome

Disorder of the connective tissue, affecting the heart and blood vessels, skeletal system, eyes, and other parts of the body. The condition is present at birth. Symptoms vary from person to person, ranging from mild to severe. People with Marfan syndrome are often nearsighted (see myopia), and about half have dislocation of one or both lenses of the eye. There is no cure for Marfan syndrome. Treatment depends on which body systems are affected. Early eye examinations can detect vision problems related to the disorder, which can usually be corrected with eyeglasses, contact lenses or eye surgery.

Microphthalmia

Rare disorder, usually inherited, in which one or both eyes are abnormally small. The degree of visual impairment varies, from reduced vision to blindness. Extreme microphthalmia resembles some forms of anophthalmia. There is no treatment or cure for microphthalmia. In certain cases, artificial eyes can be used to promote proper growth of the eye sockets and to help with cosmetic appearance.

This condition, commonly known as nearsightedness, occurs when light rays entering the eye focus in front of the retina, not directly on it. People with myopia are usually able to see close objects well, but objects in the distance—such as highway signs or writing on a chalkboard—appear blurred. People with this condition may squint to see distant objects and experience eyestrain or, sometimes, headaches. Eyeglasses or contact lenses can correct myopia. Surgery is another alternative.

Neuromyelitis optica (NMO) Neuromyelitis optica (NMO), also known as Devic's disease, is an autoimmune disorder in which immune system cells and antibodies mistakenly attack and destroy myelin cells in the optic nerves (neuritis) and the spinal cord (myelitis). NMO leads to loss of myelin, which is a fatty substance that surrounds nerve fibers and helps nerve signals move from cell to cell. The syndrome can cause blindness in one or both eyes and can be followed by varying degrees of paralysis in the arms and legs. Most individuals with the syndrome experience clusters of attacks months or years apart, followed by partial recovery during periods of remission. The onset of NMO varies from childhood to adulthood, with two peaks, one in childhood and the other in adults in their 40s. The syndrome is sometimes confused with multiple sclerosis (MS) because both can cause attacks of optic neuritis and myelitis. Non-24-Hour Sleep-Wake Disorder (Non-24)

Non-24-Hour Sleep-Wake Disorder (Non-24) is a serious, chronic, and rare circadian rhythm disorder that affects a majority of totally blind individuals who lack light perception and cannot reset their master body clocks to the 24-hour day. Non-24 is most commonly found in blind individuals who cannot perceive light, the primary environmental cue for synchronizing their circadian rhythm to the 24-hour day. In the United States, this disorder affects approximately 80,000 totally blind individuals who lack the light sensitivity necessary to reset their internal "body clocks." In general, individuals with Non-24 suffer from a variety of clinical symptoms as they cycle into and out of phase, resulting in disrupted nighttime sleep patterns and/or excessive daytime sleepiness.

Condition that involves involuntary, rapid, repetitive movements of one or both eyes from side to side, up and down, or in a circular motion. Nystagmus may be present at birth or, less commonly, may result from disease or injury. In some cases, the condition can reduce or interfere with vision. For example, children with nystagmus may frequently lose their place when reading. Placing a cutout reading window over words or using a card to "underline" text can be helpful.

Condition, present at birth, in which the optic nerve is underdeveloped, so that adequate visual information is not carried from the eye to the brain. The effects of optic nerve hypoplasia have a broad range, from little or no visual impairment to near-total blindness. The condition may affect one or both eyes. There is no treatment or cure for optic nerve hypoplasia. However, depending on the degree of visual impairment, a person with this condition may benefit from the use of devices for low vision.

The eye's gradually decreasing ability to focus on nearby objects. Presbyopia is a normal part of aging and affects virtually everyone, usually becoming noticeable after age 40. People with presbyopia typically hold reading materials at arm's length in order to bring the words into focus. They may experience headaches or eyestrain while reading, viewing a computer screen, or doing close work. Presbyopia can be corrected with reading glasses, bifocal or variable focus lenses, or contact lenses. Using bright, direct light when reading is also helpful.

Separation of the retina from the underlying supportive tissues. Retinal detachment may result from injury, disease, or other causes. A person with retinal detachment usually does not experience pain, but may see floaters (see floaters and spots) or bright flashes of light, may have blurred vision, or may see a shadow or curtain over part of the field of vision. Retinal detachment requires prompt medical attention to prevent permanent vision loss. There are several methods of treatment for retinal detachment, including laser surgery.

Retinitis pigmentosa

Degeneration of the retina, resulting in decreased night vision, a gradual loss of peripheral vision, and in some cases, loss of central vision. The degeneration progresses over time and can lead to blindness. Retinitis pigmentosa is a rare, inherited disease for which there is as yet no treatment or cure. Some ophthalmologists believe that treatment with high doses of Vitamin A can slow the progression of retinitis pigmentosa, and that taking Vitamin E makes it worse. Early diagnosis enables a person with the disease to plan and prepare for its progression. In addition, depending on the degree of vision loss, electronic magnifiers, night-vision scopes, and other such special devices for impaired vision can provide some benefit for people with the disease.

Retinoblastoma

Malignant tumor (cancer) of the retina, generally affecting children under the age of 6. Usually hereditary, retinoblastoma may affect one or both eyes. Retinoblastoma has a cure rate of over 90 percent if treated early. Without prompt treatment, the cancer can spread to the eye socket, the brain, and elsewhere, and can cause death. Depending on the size and location of the tumor, treatment options include laser surgery, cryotherapy (a freezing treatment), radiation, and chemotherapy. In some cases, the affected eye may need to be removed.

Retinopathy of prematurity (ROP)

Condition associated with premature birth, in which the growth of normal blood vessels in the retina stops, and abnormal blood vessels develop. As a result, the infant has an increased risk of detachment of the retina (see retinal detachment). Retinopathy of prematurity can lead to reduced vision or blindness. Laser therapy can help this condition if diagnosis and treatment occur early. Children who experience minor effects may benefit from the use of devices for low vision as they get older. Retinopathy of prematurity was formerly called retrolental fibroplasia.

Retrolental fibroplasia See retinopathy of prematurity. Rod-cone dystrophy

Gap or blind spot in the field of vision that may result from damage to the retina. How much a scotoma impairs sight depends mainly on whether it affects central or peripheral vision. Common causes of scotoma include macular degeneration, glaucoma, and inflammation of the optic nerve. People who experience significant vision loss because of scotomas may benefit from the use of magnifiers, bright lighting, and large-print reading materials.

Septo-Optic Dysplasia (SOD)

Stargardt's Disease

Inherited disease that causes gradual degeneration of the macula, the area in the middle of the retina that makes possible the central vision needed for reading, driving, recognizing colors, and other activities of daily life. Effects of Stargardt's Disease, which start at an early age, vary from minor to total loss of detail vision. Over a period of years, people with the disease typically lose sharpness of vision, experience decreased color vision, and may have blind spots. However, peripheral and night vision usually remain unaffected, and complete loss of sight is rare. There is no cure or treatment for Stargardt's Disease, but such devices as magnifying screens and binocular lenses can help people cope with vision limitations.

Condition in which the eyes are not both directed toward the same point simultaneously. Strabismus occurs when eye muscles are not working together properly. It is most commonly an inherited condition, but may also be caused by disease or injury. If diagnosed early, strabismus can usually be corrected. The condition may be treated with corrective eyeglasses, eye-muscle exercises, surgery, or a combination of these approaches. Young children with this condition may need to wear an eye patch over their stronger eye to force their weaker eye to function correctly. Children whose strabismus is not corrected may develop amblyopia.

Sturge-Weber Syndrome

Disorder, present at birth, characterized by a facial birthmark and any of various neurological, visual, and developmental symptoms. People with Sturge-Weber syndrome may, for example, experience seizures, glaucoma, partial paralysis, and learning disabilities. There is no cure for Sturge-Weber syndrome, but many of the symptoms can be treated. For instance, medications may be prescribed to control seizures, and surgery or eye drops may be used to treat glaucoma.

Thyroid Eye Disease

Thyroid eye disease (TED) is an inflammatory condition closely associated with Graves' disease. In thyroid eye disease (also called Graves’ Orbitopathy, Graves’ Eye Disease, or Graves' ophthalmopathy), the immune system sets off an abnormal reaction to the muscles and fatty tissue around the eyes. The symptoms that occur in thyroid eye disease include bulging eyes, swollen eyes, redness, misaligned eyes, tenderness or eye pain, and problems with vision such as light sensitivity, blurriness, or double vision. Although many patients with thyroid eye disease will have abnormal blood tests for thyroid hormone levels, some people experience eye symptoms even though their hormone levels are normal.

Contagious eye infection, caused by bacteria, that affects the eyelid and cornea. Trachoma can lead to scarring and blindness if not treated. The infection is spread by contact with discharge from the eyes or nose of infected persons and also transmitted by certain flies. Trachoma is rare in the United States, but it affects millions of people around the world, many of them children. Antibiotics are generally an effective treatment for trachoma, especially if used early in the infection. In certain cases, eyelid surgery may be needed.

Inherited condition that causes partial or total hearing loss accompanied by gradual vision loss resulting from retinitis pigmentosa. Some people with Usher Syndrome also have problems with balance. There is no cure for the condition. However, early diagnosis makes it possible to help people with Usher Syndrome by providing hearing aids, training in sign language and lip reading, devices for impaired vision, and counseling for preparing for the future.

Inflammation inside the eye, affecting the structures that provide most of the blood supply to the retina. Uveitis may affect one or both eyes. The condition may be associated with an underlying disease or have other causes, but in many cases it affects people who are otherwise healthy. People with uveitis typically experience redness of the eye, blurred vision, and light sensitivity. They may also feel pain and see floaters (see floaters and spots). If not properly treated, uveitis can lead to scarring and vision loss. Treatment depends on which eye structures are affected and whether there is an underlying disease. Eye drops and other medications are commonly prescribed to reduce inflammation.


Causes & risk factors

Usually, color deficiency is an inherited condition caused by a common X-linked recessive gene, which is passed from a mother to her son. But disease or injury that damages the optic nerve or retina can also cause loss of color recognition. Some diseases that can cause color deficits are:

    . . .
  • Alzheimer's disease.
  • Parkinson's disease.
  • Multiple Sclerosis.
  • Chronic alcoholism.
  • Leukemia.
  • Sickle Cell Anemia.

Other causes for color vision deficiency include:

  • Medications. Drugs used to treat heart problems, high blood pressure, infections, nervous disorders and psychological problems can affect color vision.
  • Aging. The ability to see colors can gradually lessen with age.
  • Chemical exposure. Contact with certain chemicals&mdashsuch as fertilizers and styrene&mdashhave been known to cause loss of color vision.

In many cases, genetics cause color deficiency. About 8% of white males are born with some degree of color deficiency. Women are typically just carriers of the color-deficient gene, though approximately 0.5% of women have color vision deficiency. The severity of inherited color vision deficiency generally remains constant throughout life and does not lead to additional vision loss or blindness.


Contents

The retina of the human eye contains photoreceptive cells called cones that allow color vision. A normal trichromat individual possesses three different types of cones to distinguish different colors within the visible spectrum from 380 nm to 740 nm. [1] The three types of cones are designated L, M, and S cones, and each type is sensitive to a certain range of wavelength of light depending on what photopigment it contains. More specifically, the L cone absorbs around 560 nm, the M cone absorbs near 530 nm, and the S cone absorbs near 420 nm. [1] Contrary to popular belief, the peak absorption frequency for L, M, and S cones do not exactly correspond to red, green, and blue wavelength. Rather, the peak frequency for the L cone is orange, yellowish green in M cones, and blue-violet in S cones. These cones transduce the absorbed light into electrical information to be relayed to neurons in the retina such as retinal bipolar cells and retinal ganglion cells, before reaching the brain. [1]

The signals from different cones are added or subtracted from each other to process the color of incoming light. For instance, the color red stimulate L cones more than M cones, whereas the color green stimulates the L and M cones more than the S cones. [1] The colors are perceived in an opponent process, such that red and green are perceived in opposition, as are blue and yellow, black and white. [1]

The gene loci coding for the photopigments: M-opsin and L-opsin are located in close proximity within the X chromosome and are highly polymorphic. [1] Among the population, some have a deleted gene for the M photopigment in the X chromosome (such as in deuteranopia), whereas others have a mutated form of the gene (such as in deuteranomaly). Individuals who can express only two types of opsins in the cones are called dichromats. Because males have only one copy of the X chromosome, dichromatism is much more prevalent among men. [1] With only two types of cones, dichromats are less capable of distinguishing between two colors. In the most common form of color blindness, deuteranopes have difficulty discriminating between red and green color. [1] This is shown by their poor performance in Ishihara test. Although dichromatism poses little problem for daily life, dichromats may find some color-coded diagrams and maps difficult to read.

Less common forms of dichromacy include protoanopia (lack of L-cones), and tritanopia (lack of S-cones). If a person lacks two types of photopigments, they are considered monochromats. People lacking the three types of photopigments are said to have complete color blindness or achromatopsia. Color blindness can also result from damages to the visual cortex in the brain. [1]

Experiments using a variety of mammals (including primates) demonstrated that it is possible to confer color vision to animals by introducing an opsin gene that the animal previously lacked. Using a replication-defective recombinant adeno-associated virus (rAAV) as a vector, the cDNA of the opsin gene found in the L or M cones can be delivered to some fraction of the cones within the retina via subretinal injection. Upon gaining the gene, the cone begins to express the new photopigment. The effect of therapy lasts until the cones die or the inserted DNA is lost within the cones.

While gene therapy for humans has been ongoing with some success, a gene therapy for humans to gain color vision has not been attempted to date. However, demonstrations using several mammals (including primates such as a squirrel monkey) suggest that the therapy should be feasible for humans as well. It is also theoretically possible for trichromats to be "upgraded" to tetrachromats by introducing new opsin genes.

The goal of the gene therapy is to make some of the cones in the retina of a dichromat individual to express the missing photopigment. Although partial color blindness is considered to be a mild disability and even an advantage under certain circumstances (such as spotting camouflaged objects), it can pose challenges for many occupational fields such as law enforcement, aviation, railroad, and military service. [2] More generally, color codes in maps and figures may be difficult to read for individuals with color blindness.

Because only a single gene codes for a photopigment and the gene is only expressed in the retina, it is a relatively easy condition to treat using gene therapy compared to other genetic diseases. However, there remains the question of whether the therapy is worthwhile, for an individual to undergo an invasive subretinal injection to temporarily treat a condition that is more of an inconvenience than a disorder.

However, complete color blindness, or achromatopsia, is very rare but more severe. Indeed, achromats cannot see any color, have a strong photophobia (blindness in full sun), and a reduced visual acuity (generally 20/200 after correction).

Moreover, the research may have strong implications toward genetic therapy of other cone diseases. Other cone diseases such as Leber's congenital amaurosis, cone-rod dystrophy, and certain types of maculopathies may be treatable using the same techniques as the gene therapy used for color blindness. [3] [4]

Experimental treatments for Leber's congenital amaurosis, a genetic disorder in photoreceptors that can lead to vision loss and blindness have been performed. These treatments use AAV vector and is delivered in much the same way as the gene therapy for color blindness. [5] [6]

Human L-cone photopigment have been introduced into mice. Since the mice possess only S cones and M cones, they are dichromats. [7] M-opsin was replaced with a cDNA of L-opsin in the X chromosome of some mice. By breeding these "knock-in" transgenic mice, they generated heterozygous females with both an M cone and an L cone. These mice had improved range of color vision and have gained trichromacy, as tested by electroretinogram and behavioral tests. However, this is more difficult to apply in the form of gene therapy.

Recombinant AAV vector was to introduce the green fluorescent protein (GFP) gene in the cones of gerbils. [8] The genetic insert was designed to only be expressed in S or M cones, and the expression of GFP in vivo was observed over time. Gene expression could stabilize if a sufficiently high dose of the viral vector is given.

Adult dichromat squirrel monkeys was converted into trichromats using gene therapy. [9] New world monkeys such as squirrel monkeys lack the L-opsin gene and are incapable of discriminating between certain shades of red and green. [9] Recombinant AAV vector was used to deliver a human L-opsin gene into the monkey’s retina. Cones that gained the missing genes began expressing the new photopigment. [9]

If the therapy worked — the monkeys would either remain dichromatic with greater sensitivity for longer wavelength of light, or they would become trichromats. [9] Electroretinogram recordings demonstrated that they are able to discriminate blue-green from red-violet, and have indeed gained trichromacy. [9] The treated monkeys were also more successful when their color vision was tested with a modified Ishihara test. [9]

Gene therapy was to restore some of the sight of mice with achromatopsia. The results were positive for 80% of the mice treated. [10]

Gene therapy for a form of achromatopsia was performed in dogs. Cone function and day vision have been restored for at least 33 months in two young dogs with achromatopsia. However, this therapy was less efficient for older dogs. [11]

According to research by David H. Hubel and Torsten Wiesel, suturing shut one eye of monkeys at an early age resulted in an irreversible loss of vision in that eye, even after the suture was removed. [1] [12] The study concluded that the neural circuitry for vision is wired during a "critical period" in childhood, after which the visual circuitry can no longer be rewired to process new sensory input. Contrary to this finding, Mancuso et al.’s success in conferring trichromacy to adult squirrel monkeys suggests that it is possible to adapt the preexisting circuit to allow greater acuity in color vision. The researchers concluded that integrating the stimulus from the new photopigment as an adult was not analogous to vision loss following visual deprivation. [9]

It is yet unknown how the animals that gain a new photopigment are perceiving the new color. While the article by Mancuso et al. states that the monkey has indeed gained trichromacy and gained the ability to discriminate between red and green, they claim no knowledge of how the animal internally perceives the sensation. [9]

While red/green color blindness among deuteranopes can be treated by introducing M-opsin genes, rarer forms of color blindness such as tritanopia can in principle be treated as well. For tritanopia, the S-opsin gene must be introduced instead of M-opsin gene.

Despite the success in animals, there still remain challenges to conducting gene therapy on humans for treating color blindness.

Safety Edit

How to deliver the viral vector into the retina is probably the main obstacle to making gene therapy a practical treatment for color blindness. Because the virus has to be injected directly by using a needle to penetrate the sclera of the eye, the treatment may be highly unpleasant and is a risk for eye infection. Without a way to deliver the virus noninvasively, the treatment is rather risky for the benefit gained.

It is not known yet how frequently the gene needs to be injected to maintain trichromacy among congenitally colorblind individuals. At the time of publication, Mancuso et al. reports that the treated squirrel monkeys have maintained 2 years of color vision after the treatment. [9] If repeat injections are needed, there is also the concern of the body developing an immune reaction to the virus. If a body develops sensitivity to the viral vector, the success of the therapy could be jeopardized and/or the body may respond unfavorably. An editorial by J. Bennett points to Mancuso et al.'s use of an "unspecified postinjection corticosteroid therapy". [4] Bennett suggests that the monkeys may have experienced inflammation due to the injection. [4] However, the AAV virus that is commonly used for this study is non-pathogenic, and the body is less likely to develop an immune reaction. [13] Needless to say, an extensive review of the safety of the treatment must precede any human trials.

The subject should first be evaluated to identify which photopigment they need to gain trichromacy. Also, while gene therapy may treat congenital color blindness (such as dichromacy), it is not intended to treat non-retinal forms of color blindness such as damage to the visual cortex of the brain.

Ethics Edit

As a way to introduce new genetic information to change a person’s phenotype, a gene therapy for color blindness is open to the same ethical questions and criticisms as gene therapy in general. These include issues around the governance of the therapy, whether treatment should be available only to those who can afford it, and whether the availability of treatment creates a stigma for those with color blindness. Given the large number of people with color blindness, there is also the question of whether color blindness is a disorder. [14] Furthermore, even if gene therapy succeeds in converting incomplete colorblind individuals to trichromats, the degree of satisfaction among the subjects is unknown. It is uncertain how the quality of life will improve (or worsen) after the therapy.


Is Red-Green Color Blindness Hereditary?

Red-green color blindness is the most common inherited form of color vision deficiency. It is caused by a fairly common X-linked recessive gene.

Mothers have an X-X pairing of chromosomes carrying genetic material, and fathers have an X-Y pairing of chromosomes. A mother and father each contribute chromosomes that determine the sex of their baby.

When an X chromosome from one parent pairs with an X chromosome from the other parent, the baby will be a girl. And when an X chromosome from the mother pairs with a Y chromosome from the father, the baby will be a boy.

If you have red-green color blindness caused by an X-linked recessive gene, your mother will be a carrier of the gene or be color deficient herself.

Fathers with this inherited form of red-green color blindness pass the X-linked gene to their daughters but not to their sons, because a son cannot receive X-linked genetic material from his father.

A daughter who inherits the color-deficient gene from her father will be a carrier of the gene but she will not be colorblind — unless her mother carries the gene, and she receives a paired color-deficient gene from her mother as well. If a daughter inherits the X-linked trait from both her father and her mother, then she will be color blind.

When a mother passes along this X-linked trait to her son, he will inherit the color vision deficiency and have trouble distinguishing reds and greens.

Again, a daughter can be a carrier but will have this form of color blindness herself only when both her father and mother pass along the X-linked gene. This is why more men than women are color blind.



Comments:

  1. Golden

    In this something is I think that it is the excellent idea.

  2. Minos

    I apologize, but it's not quite what I need.

  3. Efrain

    I'm sorry, but we can't do anything.

  4. Griswold

    A fun time

  5. Allen

    I suggest you visit the site where there are many articles on the topic that interests you.

  6. Anwell

    He is certainly not human



Write a message