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Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image (focus) on an object as its distance changes. Accommodation acts like a reflex, but can also be consciously controlled. Mammals, birds and reptiles vary the optical power by changing the form of the elastic lens using the ciliary body (in humans up to 15 diopters). Fish and amphibians vary the power by changing the distance between a rigid lens and the retina with muscles. The young human eye can change focus from distance to 7 cm from the eye in 350 milliseconds. This dramatic change in focal power of the eye of approximately 12 diopters (a diopter is 1 divided by the focal length in meters) occurs as a consequence of a reduction in zonular tension induced by ciliary muscle contraction. The amplitude of accommodation declines with age. By the fifth decade of life the accommodative amplitude has declined so the near point of the eye is more remote than the reading distance. When this occurs the patient is presbyopic. Once presbyopia occurs, those who are emmetropic (do not require optical correction for distance vision) will need an optical aid for near vision; those who are myopic (nearsighted and require an optical correction for distance vision), will find that they see better at near without their distance correction; and those who are hyperopic (farsighted) will find that they may need a correction for both distance and near vision. The age-related decline in accommodation occurs almost universally, and by 60 years of age, most of the population will have noticed a decrease in their ability to focus on close objects. It is normally accompanied by a convergence of the eyes to keep them directed at the same point, sometimes termed accommodation convergence reflex. From Wikipedia under the
GNU Free Documentation License what happens to the accommodation of the human eye when exposed to red light? Q. -explain how the eye responds whether it relaxes or gets stimulated to red light ,if true ,how? -pls explin only with respect to human eye -and to add on can u correlate this concept to duochrometest? Asked by maharocky - Wed Jul 5 01:16:58 2006 - - 6 Answers - 0 Comments A. The duochrome test uses red and green light. The green light focuses slightly in front of the retina and the red light focuses slightly behind the retina. Therefore if a person was too nearsighted, the red side of the chart would appear clearer than the green side. The red light should not affect accommodation much since it is focused behind the retina, accommadating would not help bring it into focus on the retina. Green, however, could be focused on the retina with accommodation being used to move the image back to the retina. The goal of the duochrome test is to have the patient report both sides of the chart equally clear or distinct. This means the red and green are straddling the retina equally on each side and the patient is… [cont.] Answered by eyegirl - Mon Jul 10 18:50:54 2006 Accommodation Convergence Paralysis? Q. I've been diagnosed by my neurologist to have Accommodation Convergence Paralysis, which causes me to see everything in double vision up to a metre away. It's not a problem with the eyes, so any eye exercises won't help - he has explained that it's a small part of the brain that can't send signals to the eyes to converge, like it should normally. The neurologist telling me that it's extremely uncommon doesn't really help me, and I think I was better off not knowing why I've always seen in double vision, because I've tried looking it up on Google and there doesn't seem to be anything that deals with this problem in particular. I'm wondering if there's anyone here that has been diagnosed with the same problem, and if so, how they cope with… [cont.] Asked by Aurin - Fri Feb 5 08:34:27 2010 - - 2 Answers - 0 Comments A. Hi Aurin, I think what your neurologist trying to said is you are having convergence insufficiency.If that is the case you can see your optometrist or an orthoptic,they will be able to fix your double vision by adding prism base in on the spectacles lens. You can also look up on convergence insufficiency exercise on the internet. Wish you luck.It should work. Optometrist Answered by sim e - Fri Feb 5 09:40:48 2010 Biology help please on eyes?
Q. 1) which part of the eye contains cells which are sensitive to light. 2) your brain can build up a very clear image when light is focused onto the fovea. explain why it can do this. 3) what is the choroid, and what is its function. 4) list, in order the parts of the eye through which light passes to reach the retina 5) name 2 parts of the eye which refract light rays 6) what is meant by accommodation 7a) what do ciliary muscle do when you are focusing on a nearby object 7b) what affect does this on i) the suspensory ligaments ii) lens 8) many older people use two pairs of glasses or wear bifocal spectacle. explain this Asked by Al C - Thu May 21 16:13:44 2009 - - 1 Answers - 0 Comments A. 1 retina 2 more cones, more pixels, more accuity 8 older people have presbiopia. They lose the ability to change the focus of the lens in their eye. Since they cannot focus using their eye muscles, the different lens in their glasses focus for them. Part of the lens is for very near vision and part is for far away vision. Answered by jim z - Thu May 21 16:19:31 2009 From Yahoo Answer Search: "Accommodation (eye)"  ameinfo.com Thu, 08 Jul 2010 07:03:35 GMT+00:00 AME Info A unique accommodation package will offer a room on single or double occupancy together with a lavish Suhour buffet. In addition, everyone will be eligible ...  guardian.co.uk Thu, 24 Jun 2010 10:09:26 GMT+00:00 The Guardian He waved to the onlookers, catching the eye of a delighted mother and daughter. He was apparently animated by the human contact, especially the children ...  scoregolf.com Mon, 05 Jul 2010 17:29:07 GMT+00:00 SCOREGolf (blog) Merit Golf Vacations has donated a grand prize for participants consisting of roundtrip airfare for two on Westjet and three-nights accommodation at the ... From Google News Search: "Accommodation (eye)"  studios-london.com 400px x 600px | 199.80kB [source page] Studios london com London Eye From Yahoo Image Search: "Accommodation (eye)"  easyonlinejobsreview.com valeri hu, 20 May 2010 02:30:59 GM Reasons are several from plethora of . eye. -catching attractions, astonishing historic monuments to beautiful churches. However, one factor which has contributed significantly in the ever growing popularity of Prague is holiday ...  danceproof.com Arsene Hodali Mon, 22 Feb 2010 05:01:06 GM A one-eyed person lacks convergence and retinal disparity, and . accommodation. helps us judge only short distances. That basically means a person with only one . eye. will have limited depth perception (sucks to be you). ...  villadeayora.com adminjose Fri, 28 May 2010 15:36:43 GM Another interesting activity is to visit the Charles Darwin Station, there are seen with the naked . eye. the beautiful Galapagos tortoises, among other things, seeking to achieve fully operational show an island that is emerging as a living ... visitors should expect fewer hotels in Santa Cruz Island, although this time change will have the chance to walk the sandy streets Isabela and still find the hotel or . accommodation. that fits the bill, from cabins to a first-class. ... From Google Blog Search: "Accommodation (eye)" |
