if a person uses glasses and another person does not?
how are their eyes different? i mean, inside the eyes.
2006-11-14 07:11:34 · 7 answers · asked by Ha!! 2 in Science & Mathematics ➔ Biology
The person who does not use glasses has an eye that is curved to focus light almost exactly on the retina. The person who does use glasses has eyes that focus light either in front of or behind the retina, and the glasses change the focus of the system to coincide with the retina as in a person who does not require vision correction.
2006-11-14 07:15:16 · answer #1 · answered by DavidK93 7 · 0⤊ 0⤋
It's all about the shape of the eyeball.
When the the lens at the front of the eyeball focuses exactly on the retina at the back, eyesight is very clear, and no glasses are needed.
If the shape of the eyeball causes the lens to focus either in front of, or behind the retina, eyesight will be blurred. Glasses can be custom made to adjust the focus point so that it is correctly on the retina, and the person can see clearly. This is the prescription for the glasses.
Some people also have a slight warp in their lenses that can also be corrected by glasses.
Hope this helps!
2006-11-14 15:27:09 · answer #2 · answered by fredshelp 5 · 0⤊ 0⤋
It depends on what exactly is wrong with their eyes. If you're farsighted, your eyes are a little too short and light from the lens focuses behind the back surface of your eye. If you're nearsighted, your eye is too long and the light is focused in front of the surface. Astigmatism is more complex and is caused by the lens not being quite round. Presbyopia, the farsightedness caused by old age, happens because the lens can no longer stretch enough to focus (they're still not sure if it gets less elastic, or if the muscles controlling it get weaker).
2006-11-14 15:19:27 · answer #3 · answered by Amy F 5 · 0⤊ 0⤋
The difference is the shape of the lens, which light passes through on its way to the retina. Some people need additional lenses (contacts, glasses) to get the image to focus in the right place.
2006-11-14 15:39:01 · answer #4 · answered by ally4 2 · 0⤊ 0⤋
It depends on the shape of the eye and curvature of the cornea or lens. Different visual defects have different causes.
2006-11-14 16:07:09 · answer #5 · answered by Anonymous · 0⤊ 0⤋
The one requiring corrective lens' generally has weakened mucles controlling the iris. It could also be a problem with the lens.
2006-11-14 15:14:47 · answer #6 · answered by Doc 7 · 0⤊ 0⤋
I think it has something to do with the curve or angle of your retina.
Not sure though.
2006-11-14 15:13:14 · answer #7 · answered by Anonymous · 0⤊ 0⤋