V 728
Contact Lenses with Aspherical and Asymmetric Surfaces (CLAAS), new ways of improving contrast sensitivity and visual selectivityJ. de Brabander, G. Marin, N. Chateau, P. Artal, P. H. van Goinga
Introduction: Practitioners are often faced with the clinical finding that despite good Snellen visual acuity, the patient reports visual discomfort. Usually in these cases Contrast Sensitivity (CS) and Visual Selectivity (VS) are compromised. Examples are patients with cataracts and contact lens wearers especially in the correction of high ametropia, and presbyopia. Since contact lenses can introduce significant amounts of optical aberration it is worthwhile to investigate higher visual functions with aberration-free and varifocal contact lenses.
Methods: CS with wearing normal spherical soft contact lenses and lenses corrected for in air spherical aberration was measured and compared. Visual function of various optical profiles in varifocal lenses was compared in far and near conditions and related to pupil size. The results of both studies were used to find explanations for the typical complains of visual discomfort despite good Snellen visual acuity.
Results: Testing contact lenses with and without correction of spherical aberration showed that systematic correction of the spherical aberration of contact lenses has no use clinically. However, in 30% of the cases CS with one of the contact lenses was significantly higher than without. In varifocal contact lenses the optical profile of the lens is a significant factor in far vision. In near vision the balance between the available power areas for near and far in combination with the pupil size plays a role in success.
Discussion: Higher visual functions as CS and VS are individually based and related to the eye/brain system. By manipulating the optical surfaces and power profiles of contact lenses it is in principle possible to positively influence higher visual functioning. However, one should find ways to incorporate measured data from the eye into the design of the contact lens and a sophisticated system to manufacturing the individually designed lens.
The EC subsidised CLAAS project investigates ways of designing and manufacturing contact lenses from topographic and optical aberration data.
Eye Research Institute Maastricht, AZM, University of Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands.