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Medical Forum / General / Vision / July 2006Albinism and reduction of high definition receptiors
Hi, I've been told that in the eye of a person with albinism, there are fewer rods to 'see' fine detail of an image. So even if all the other eye conditions were corrected, there would still be a problem seeing. Does anyone know what % the reduction of Rods is as compared to a normal eye ?  SignatureAdrian Parker > Hi, > [quoted text clipped - 7 lines] > -- > Adrian Parker I read that albinos have less rods/cones so they are often legally blind. I read the posts of one in another forum who sees 20/150 and he considers himself lucky because some see much worse. Another described her vision as pixalized with antialising as the best description she could give. A normal person could look at an "E" and see it perfectly sharp. She would also see it sharp but it may be too small. http://www.yorku.ca/eye/popepix.gif This is the best description I can find. Again, albinos would NOT see blurry, but more like pixelized but not this exaggerated, just lacking any fine details due to low density of rods/cones. | > Hi, | > [quoted text clipped - 20 lines] | blurry, but more like pixelized but not this exaggerated, just lacking | any fine details due to low density of rods/cones. Sorry, should have explained, I have albinism, so I know what the vision is like, I am trying to find out about the general reduction of fine detail receptor cells (rods) in the eye. I've been having neurofeedback to correct the nystagmus and it has helped for near sight, but not long distance, and I'm wondering if it is because of the fine receptors not being able to resolve down to a small enough resolution. My vision is betwen 6/24 and 6/36 (20/80 and 20/120) Ah I see. I will do more research on that. Do you see the world pixelized with anisometropia blurring? Can you describe what you see exactly? | Ah I see. I will do more research on that. Do you see the world | pixelized with anisometropia blurring? Can you describe what you see | exactly? With albinism, there are several other factors that affect vision:- Nystagmus, Astigmatism, Photophobia, Squint and Strabismus. I'm told that when I squint, it adversely affects the vision centres of the brain, so I've been working on reducing that. Nystagmus.. causes a problem because the brain has to snapshot images instead of getting constant updates, so for a moving target, I'd see less detail than a normal sighted person because of what is probably like a strobing effect, you see the movement, but your brain only gets images now and then and so has to fill in the gaps with a best guess. Astigmatism.. in my case, my last eye test gave me figures of Right Eye : Sph +7 Cyl -4 Axis 15 Left Eye : Sph +6 Cyl -2 Axis 175 So, as you can see, I need quite a high corrective lens, so my eyes are trying to compensate for the imprecise nature of the lenses. Photophobia.. this causes me to squint, so I have to ensure I wear a brimmed hat and dark glasses outside else I have to squint a lot. Strabismus.. With the treatment I've been having, this seems to have been reduced quite a bit, my eyes are far more convergent than they used to be, and my binocularity seems much improved. So, to describe what I see compared to a normal sighted person has to take into account several factors, including how tired my eyes are, or how stressed I am (stress affects nystagmus a lot). I do not see the world moving from side to side because of my congenital nystamus as my brain edits it out, nor do I see the world as a blur (like in your image), I see a clear picture, but like you, when you look at a very distant object, you can see it ok and it isn't blurred, you just can't make out fine detail. Adrian, Ace is just a kid who spends too much time on the computer. I'm sorry that he has hijacked the thread and no credible people have yet replied. I just wanted to warn you, and hopefully someone knowledgeable will give you a good response. > > Ah I see. I will do more research on that. Do you see the world > > pixelized with anisometropia blurring? Can you describe what you [quoted text clipped - 34 lines] > very distant object, you can see it ok and it isn't blurred, you just > can't make out fine detail. I did get the idea that he wasn't a professional when he asked about how I see, hence I gave an explanation of all that is occurring.. as I believe that the more people who understand the visual problems people have, the better :) Albinism in particular is a very misunderstood and often vilified condition (take the da vinci code file for example). | Adrian, | [quoted text clipped - 41 lines] | > very distant object, you can see it ok and it isn't blurred, you just | > can't make out fine detail. Until I saw your post (and followed up with some Googling) I didn't realize that albinism so frequently caused (or came along with) poor vision. One site I read pointed out how albino characters are almost exclusively villains... for what it's worth, when I was a kid I was addicted to a fantasy book series in which the hero/main character was albino. ;) Best of luck. > I did get the idea that he wasn't a professional when he asked about > how I see, hence I gave an explanation of all that is occurring.. as > I believe that the more people who understand the visual problems > people have, the better :) Albinism in particular is a very > misunderstood and often vilified condition (take the da vinci code > file for example). > exclusively villains... for what it's worth, when I was a kid I was > addicted to a fantasy book series in which the hero/main character was > albino. ;) Reminds me of a favorite Dean Koontz character, from Sieze The Night. - "'The night is a kingdom of predators, in which every hunter is also the hunted.' The night is also the favored realm of Christopher Snow, whose XP (xeroderma pigmentosum) renders him extremely vulnerable to all forms of light. When an old flame's son is abducted, Snow and his faithful dog Orson track them to Fort Wyvern, an abandoned military base--and the site of genetic research experiments gone awry. To recover the boy, Snow and his friends must unearth Wyvern's darkest secrets. .. Though long, Seize the Night will certainly hold your interest. (Running time: 12 hours, 10 cassettes)" -MT > I've been having neurofeedback to > correct the nystagmus and it has helped for near sight, but not long > distance, and I'm wondering if it is because of the fine receptors not > being able to resolve down to a small enough resolution. There are a variety of methods used to decrease the congenital nystagmus associated with albinism, and there success rates usually correlate to how well you could see if the nystagmus isn't there. An inexpensive approach that might work real well and doesn't require any training or repeated visits and such is simple base out prisms, with an extra -1 cut in to account for the increased accomodation at far. SignatureScott Reverse name to reply > Hi, > [quoted text clipped - 7 lines] > -- > Adrian Parker Don't know the percentage, don't know if has been calculated. In any case, it will vary from individual to individual depending upon the type and severity of the albinism. It isn't actually rods that are reduced and rods are not responsible for fine detail, cones are. In albinism, the retinal pigment epithelium (RPE) is very thin or missing, since it is a pigmented tissue and pigment is what people with albinism lack. The RPE supports the photoreceptors, both rods and cones, and when it is lacking then the photoreceptors either don't develop or develop poorly. Fine detail is lacking because the cones in the macula, the most detail senstive part of the retina, are lacking or defective. So yes, even if other conditions like strabismus or refractive error are corrected, the malfunctioning photo receptors means that acuity will be reduced. The lack of good quality central vision often causes nystagmus as the eye searches for the lacking crisp spot, provides less of a stimulus to fusion so strabismus is common with albinism and interferes with the emmetropization process so that high refractive error is common with albinism. For more info, see http://www.revoptom.com/handbook/SECT58a.HTM Dr Judy |
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