When a cataract extraction is performed, the cataract (cloudy natural lens) is replaced with a clear synthetic lens (intraocular lens or IOL).
Both eyes are measured before the surgery; the curvature of the cornea and length of the eye are then used to calculate the strength of lens required as well as to find out whether a premium toric IOL would be worthwhile.
These measurements are known as biometry or and A-scan and are made without any contact being made with the eye and are completely comfortable.
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