Quality of Image of Grating Target Placed in Model Eye and Observed Through Toric Intraocular Lenses

Abstract

To evaluate the quality of an image ofa grating target placed in a model eye and viewed through implanted toric intraocular lenses (IOLs). Laboratory investigation. Toric IOLs, SN6AT5 with a cylinder power of 3.0 diopters (3.0 D, Alcon), ST6AT9 (6.0 D, Alcon), 311T5 (3.0 D, HOYA), or 311T9 (6.0 D, HOYA), were placed in a fluid-filled model eye. A United States Air Force test target was placed internally on the posterior surface of the model eye. A flat contact lens or a wide-angle contact lens was placed on the cornea. The contrast and length of the grating targets perpendicular (vertical) or parallel (horizontal) to the flat meridian of the toric IOL were compared with those obtained through aspheric IOLs. The contrast of the targets viewed through the flat contact lens and toric IOLs in the vertical direction was significantly lower than that viewed through the aspheric IOL at 16 cycle/mm (SN6AT9, P=.002; SN6AT5, P=.028; 311T9, P=.002; 311T5, P=.011) but not with the wide-angle viewing lens at 16, 32, and 64 cycle/mm. The vertical length of the target with a flat contact lens was longer and the horizontal length was shorter than that through the aspheric IOL by 1% to 3% with the SN6AT5 and 311T5 IOLs and by 3% to 5% with the SN6AT9 and 311T9 IOLs. However, the vertical and horizontal lengths were not significantly different through the wide-viewing lens. Toric IOLs affect the contrast ofa grating target viewed through a flat contact lens but not through a wide-angle viewing lens. The wide-angle viewingsystem is not influenced by cylindrical aberrations.