Timothy R. Willis

Intraocular lens resolution in air and water

ABSTRACT The resolution of 96 polymethylmethacrylate intraocular lenses with convexo‐plano optics, ranging in power from 13 to 27 diopters, was measured in air and water. The resolution of each lens was expressed in linear units of resolving power, which is the maximum number of line‐pairs that can be resolved per millimeter, as described in the current ANSI Standard Z80.7‐1984. There was no clearly defined relationship between linear resolving power measured in air and that measured in water. Measurements on high power lenses (> 20 diopters) indicate that it is possible for an intraocular lens to meet the current 100 line‐pair per millimeter standard for resolution and still be a limiting factor in a patients best attainable visual acuity. An alternative method for evaluating lens resolution is to determine the resolution efficiency (the relative percentage performance of a lens compared to a diffraction‐limited lens of the same dioptric power). Using these units, a consistent and predictable relationship from air to water was demonstrated. Our findings confirm that if a minimum standard of 30% resolution efficiency in air is established, in contrast to linear resolving power, the lens will perform near its diffraction limit when implanted in the eye. For intraocular lenses of materials other than polymethymethacrylate, a minimum resolution efficiency in air other than 30% may be required.

Silicone intraocular lens resolution in air and in water

ABSTRACT The resolution efficiencies of 31 biconvex silicone intraocular lenses, ranging in power from 10.0 to 23.5 diopters, were tested in air and in water to see if a predictable relationship existed as previously reported with polymethylmethacrylate lenses. Resolution efficiency is defined as the percentage ratio of the actual resolving power of a lens to that of a perfect lens of the same focal length which is only limited in resolution by diffraction. The lenses ranged from 29% to 58% resolution efficiency in air. No lenses exhibiting multiple images were included. All 31 lenses achieved at least 73% resolution efficiency in water, and one lens achieved 82%. Based on these findings, a biconvex silicone lens that exceeds 30% resolution efficiency in air and does not produce multiple images can perform near its diffraction limit when implanted in the eye.

Preliminary Evaluation of the Koziol-Peyman Teledioptric System for Age-Related Macular Degeneration

Allergan Medical Optics has recently developed a bioptic optical implant with central minus and peripheral positive components (AMD-100B) that is used in conjunction with specially constructed bi-element spectacles to improve visual performance in patients with age-related macular degeneration. The Koziol-Peyman Teledioptric R system has been evaluated in both the laboratory and a limited clinical trial and found to be capable of producing a magnified image of high resolution, accompanied by enhanced visual perception in the absence of any apparent postoperative complications.

Intraocular lens performance in air, in water, and in situ : a computer study

ABSTRACT Computer analysis is used to predict performance of four intraocular lenses with assigned values of aberration. Cylinder error and asphericity error are used as examples of possible manufacturing errors. Three measures of performance are calculated: maximum optical path difference, root mean square optical path difference, and modulation transfer function. For evaluation in air these standard test conditions are assumed: collimated green light incident on the convex surface of a plano‐convex lens, with a 3 mm aperture. All four lenses show substantially improved performance in water compared to air, and a further improvement in the simulated eye (i.e., in situ). However, an aberrated 30 diopter (D) lens with performance in air comparable to an aberrated 20 D lens, performs worse in situ than does the 20 D lens. This suggests that a performance test in air that is suitable for a 20 D lens (e.g., 100 line pairs per millimeter resolution) may not be adequate for a 30 D lens. A test in air at 30% resolution efficiency may be more suitable.

Comparison of the keratometer and the lens bench in measuring intraocular lens power

ABSTRACT Intraocular lenses (IOLs) from six manufacturers were measured on a Terry keratometer and on a calibrated lens bench for lens power. Differences between the two methods appeared when the IOLs were (1) a different refractive index than polymethylmethac:rylate (PMMA) and (2) a shape other than planoconvex. These differences were consistent for ultraviolet absorbing PMMA and for meniscus lenses.