What are cylindrical eye powers, how is it different from normal eye power?

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What are cylindrical eye powers, how is it different from normal eye power?

In: Biology

The cylindrical power of the lens is the corrective element for the shape of your eye, it’s used to correct astigmatism.

a person with a cyl of 0 has an eye which is near enough perfectly round and ball like, the further away from 0 you get (+ or -, they are the same but the way they are written changes the spherical power) the more squished, or like a rugby/american football the patients eyeball is.

Now, the cyl has a second part to it, called the axis, this is measured between 1 and 180, and it’s the angle the eye is squished at (I can’t remember whether 90 is vert or horizontal, it’s been a decade since I sold glasses).

Cyl powers affect the spherical power by making it weaker on one axis, by the given value. so if you have a -1.00 spherical and -0.25 cyl at a right angle to the part of the lens that is -1.00 the lens would be different by 0.25 (+/-, again it’s been a decade, sorry)

If you want a fun experiment find someone you know who has cyl in their lens, and something square or rectangular. Hold the lens so you can see the square/rectangle thing through it and then rotate the lens. you should see that the square/rectangle changes shape as the lens rotates.