The eye’s ability to refract or focus light sharply on the retina is primarily based on three eye anatomy features:

  • the overall length of the eye,
  • 2) the curvature of the cornea and
  • 3) the curvature of the lens inside the eye.

Eye length:

If the eye is too long, light is focused before it reaches the retina, causing nearsightedness. If the eye is too short, light is not focused by the time it reaches the retina. This causes farsightedness or hyperopia.

Curvature of the cornea:

If the cornea is not perfectly spherical, then the image is refracted or focused irregularly to create a condition called astigmatism. A person can be nearsighted or farsighted with or without astigmatism.

Curvature of the lens:

If the lens is too steeply curved in relation to the length of the eye and the curvature of the cornea, this causes nearsightedness. If the lens is too flat, the result is farsightedness.

More obscure vision errors are also related to flaws in the way light rays are refracted as they travel through the eye’s optical system.

More on the eye and ‘recfractive errors’ next week

Very important: Always make sure you discuss and make decisions about your eye care based upon a formal appointment with your optician or doctor.

For more information please call us or visit

KOBRIN & MARTIN OPTOMETRISTS, SANDTON

Tel: 011 884 8413  |  kobrinmartin@telkomsa.net