How long is an eyeball?

For a roundish object, thinking about length doesn’t seem to make much sense. However, when we do cataract surgery, we have to think a lot about the distance between the front of the eye (the cornea) and the back of the eye (the retina). This is because, during cataract surgery, we place a lens implant in the eye that has to focus light onto the retina, so the power of the lens implant has to be correct in order to focus light exactly on the right point. A lot of eyes are between 22 and 25 millimeters, which is less than 1 inch. Eyes that are about an inch “long” (from front to back) are generally considered pretty long eyes.