Question: I just had an eye exam and I was noticing everything was the same as my old glasses except for the axis. What is the axis?
Answer:
In general, ophthalmic lenses are prescribed to correct the two main causes of light failing to strike the retina in good focus: sphere and cylinder. They do so by bending rays of light and only work properly when the rest of the eye (tear film, cornea, lens, vitreous, retina) are in good working order.
As you might suspect, spherical lenses bend light equally in all directions, while cylindrical ones are most effective in a single meridian and least effective 90 degrees away. Think of the difference in shape of a basketball and a football.
The axis of the cylinder is the path along which the cylinder is oriented, lining it up appropriately to coincide its maximum effect where it is most needed.
Answered by:
Richard G Shugarman, MD
Categories:
Eye Diseases
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