central optic zone

optic zone, central 

Central region of a contact lens that has a prescribed optical effect where there is a peripheral optic zone or zones (British Standard). See total diameter.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
The IOL has an overall diameter of 13mm with a central optic zone of 1.5mm.

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