Anatomy of the Eye

Posted by CooperVision on Thursday, December 23, 2010

Did you know?  The human eye has the sharpest vision when light rays passing through the various structures of the eye meet at a sharp focal point on the foveal area of the retina.  Although the cornea and lens of the eye may be perfectly round, if light rays are focused before they reach the retina (a condition known as Myopia or Nearsightedness), distance vision will not be clear.   If light rays are focused behind the plane of the retina (a condition known as Hyperopia or Farsightedness) vision may or may not be clear depending on the amount of hyperopia and the amount of someone’s focusing ability.  Although a hyperopic person may see clearly both at distance and near, if too much focusing effort is needed, discomfort, headaches, etc. may occur.  If not enough focusing ability is available, vision will not be clear up close or at both up close and distance. 

Distortion of vision can also occur when the curvature of the cornea is football-shaped (a condition known as Astigmatism) rather than uniformly round as light rays will not be focused at a sharp focal point.

                                                

Comments

12/29/2010 1:45:22 PM #

this is totally wrong. The ye gives the best vision when the optics of the lens and cornea focus directly on the retina..In fact it would be even better if the cornea was corrected for abberations to produce a retinal image in focus in the peripheral retina

DR. Steve Silbreberg United States | Reply

12/29/2010 4:09:27 PM #

Thank you for providing your comments regarding the OnEye blog about the anatomy of the eye.  You are correct – the best vision is achieved when light rays passing through the various structures of the eye meet at a sharp focal point on the fovea.  An eye that is uniformly round does not necessarily provide that focal point.  We will issue a correction to that blog as well as make the necessary corrections to our website from which that information was taken.

Dr. Harvard Sylvan, O.D. United States | Reply

1/6/2011 9:16:51 AM #

Again WRONG: Most people with a round (spherical cornea) have aginst the rule astigmatism induced by the crytaline lens (Javal's rule look it up). It is in fact the non round corneas with a little with the rule astigmatism that show no overall astigmatism in their refraction.

Also only the central cornea is somewhat spherical. The cornea becomes flatter toward the periphery

Dr. Steve Silberberg

Dr. Steve Silberberg United States | Reply

1/12/2011 12:19:47 PM #

Dr. Silberberg,

These blogs are meant to be read by the public.  Unfortunately, it is unrealistic to provide a detailed explanation as these blogs are meant to be short, to the point and easily understandable.  The description given is meant to convey the message that regardless of the shape of the cornea and lens, if the resultant optics are spherical, that alone does not ensure clear, sharp vision.  Light rays must focus on the fovea for that to occur (assuming the cornea, lens and vitreous are clear and there are no underlying retinal problems).  A simple explanation of myopia and hyperopia follow.  We appreciate your taking the time to contact us with your astute observations, but please try to understand the rationale behind the descriptions.

Dr. Harvard Sylvan, O.D. United States | Reply

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