Optical characteristics of oblique incident rays in pseudophakic eyes

To demonstrate visually the change in the optical path of oblique incident rays in pseudophakic eyes with intraocular lenses (IOLs) of different shapes using a 3-dimensional, computer-simulated model eye with an aspherical corneal surface.

Department of Ophthalmology, Hamamatsu Red Cross Hospital, Hamamatsu, Japan.

A Gullstrand schematic eye was created using an optical design program (Zemax), and the anterior and posterior surfaces of the cornea were replaced by rotationally symmetrical, aspherical surfaces expressed as polynomial equations based on the corneal topography (Orbscan II, Bausch & Lomb). The lens was replaced by an IOL (anterior convex or posterior convex). The model eye was displayed 3-dimensionally, and an incident ray 45 degrees from the visual axis was projected. The astigmatic difference was compared by visually confirming the convergence profile of tangential and sagittal rays. Coma aberration was also compared by the shape of the spot diagram.

The distance between the tangential and sagittal foci was larger with an anterior-convex IOL than with a posterior-convex IOL. Coma aberration markedly deformed the spot diagram at the retinal surface in the eye with an anterior-convex IOL.

The optical characteristics of the oblique incident rays in a pseudophakic eye were visually represented with sufficient clarity. Aberrations in the oblique incident rays were larger in the eye with an anterior-convex IOL than in the eye with a posterior-convex IOL, making examination and retinal photocoagulation of the peripheral fundus difficult.