Quantitative Effect Of Optic Zone Diameter Changes On Rigid Gas Permeable Lens Movement And Centration.

The effect of varying optic zone diameter on rigid contact lens positioning and visible post blink movement was determined on twenty patients using a 9.50 mm overall diameter lens with 7.40 mm, 7.90 mm and 8.40 mm optic zones. The smaller optic zone lens positioned more temporally and superiorly than the larger zone lenses. There was not a strong correlation between lens positioning and patient factors such as corneal shape, corneal apex position, lid position and corneal diameter. The strongest correlation was between lens position and the patient factors of actual corneal diameter and horizontal apex position. The smaller optic zone lens moved slightly less than the larger optic zone lenses.