Relationship between contrast sensitivity and spherical aberration: comparison of 7 contrast sensitivity tests with natural and artificial pupils in healthy eyes.

PURPOSE: To find a contrast sensitivity test that can be used clinically to evaluate interventions aimed at minimizing spherical aberration and determine the circumstances under which these tests should be performed. SETTING: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. METHODS: Contrast sensitivity tests were performed using 2 experimental designs. Design 1 was with a natural pupil under mesopic and photopic conditions. Design 2 was with a 5.0 mm artificial pupil after cycloplegia under photopic conditions only. Two computerized tests (vertical sine-modulated gratings [VSG] and Holladay circular sine-modulated patterns [HACSS]) and 5 chart tests (Pelli-Robson, acuity-measuring letter charts at low contrast [2.5% and 10%], VectorVision, and edge contrast sensitivity) were used. Spherical aberration was assessed with a Hartmann-Shack wavefront analyzer. RESULTS: Forty-nine healthy subjects aged 20 to 35 years (n = 24) and 55 to 70 years (n = 25) participated. Design 2 showed a significant relationship between contrast sensitivity and spherical aberration with the HACSS at 3 cycles per degree (cpd) (P = .03) and 6 cpd (P = .01) and with the VSG at 6 cpd (P = .01). Design 1 yielded no significant relationships. CONCLUSIONS: Using an artificial pupil, a relationship between contrast sensitivity and spherical aberration was established with the VSG and HACSS tests but not with the chart tests. No test showed a relationship using natural pupils under either lighting condition. Chart tests are unsuitable for uncovering contrast sensitivity differences related to differences in spherical aberration, as typically found in healthy phakic eyes.

Comparison of Optical Performance in Eyes Implanted with Aspheric Foldable, Spherical Foldable, and Rigid PMMA IOLs.

PURPOSE: To compare the optical performance of rigid spherical polymethylmethacrylate (PMMA), foldable spherical, and foldable aspheric intraocular lenses (IOLs). METHODS: Measurements were obtained monocularly from pseudophakic patients with a PMMA IOL (Ophtec PC265y or Rayner 105U), spherical AcrySof MA30 IOL (Alcon Laboratories Inc), or aspheric Tecnis ZA9003 IOL (Abbott Medical Optics). Contrast sensitivity was measured using the Holladay automated contrast sensitivity test with 5.0-mm artificial pupil at 3 and 6 cycles per degree at optimal focus and at several defocus levels. The myopic shift (shift of the optimal focus toward more myopic values at lower spatial frequencies) and depth of focus were determined. Wavefront aberrations were assessed with a Hartmann-Shack wavefront analyzer; straylight was measured using the C-Quant meter (Oculus Optikgeräte GmbH). RESULTS: Nine patients with a spherical rigid PMMA IOL, 19 patients with a spherical foldable IOL, and 24 patients with an aspheric foldable IOL met the inclusion criteria. Eyes with an aspheric IOL showed less spherical aberration than eyes with other IOLs; no differences were found in overall higher order aberrations. No differences in contrast sensitivity at optimal focus and in straylight were found among the IOLs. Eyes with a PMMA IOL showed a larger depth of focus compared to eyes with an aspheric IOL. Eyes with an aspheric IOL had a smaller myopic shift than eyes with other IOLs. CONCLUSIONS: Optical performance differences among the IOLs in this study are small, concurring with similar higher order aberrations found in the three groups. Reduction in myopic shift appears to be the most obvious effect of aspheric IOLs.

Straylight measurements in pseudophakic eyes with natural and dilated pupils: one-year follow-up.

PURPOSE: To compare the amount of straylight in natural pupils and dilated pupils in pseudophakic eyes 6 weeks and 1 year after cataract extraction. SETTING: Laboratory of Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. METHODS: This study evaluated patients with bilateral age-related cataract who had cataract surgery with implantation of an aspheric Tecnis ZA9003 or spherical Sensar AR40e intraocular lens (IOL). Straylight measurements were performed with a C-Quant straylight meter 6 weeks after surgery (with natural pupils) and 1 year after surgery (with natural and dilated pupils) in a randomly chosen eye. Retroillumination photographs of dilated pupils were taken to document posterior capsule opacification. The main outcome variable for straylight measurements was the logarithmic straylight parameter, log(s). RESULTS: Twenty-two patients were evaluated. There was a statistically significant decrease in straylight in a natural pupil between 6 weeks (mean 1.44 log[s]) and 1 year (mean 1.30 log[s]) postoperatively (P = .012). The straylight parameter was greater after dilation (mean 1.48 log[s]) than with a natural pupil (1.29 log[s]) at 1 year (P = .012). This difference was greater when more anterior capsule was visible in the pupillary area (P = .031). CONCLUSIONS: Straylight decreased significantly in the first year after cataract surgery. Furthermore, it increased with increasing pupil size, which was associated with a capsulorhexis smaller than the pupil. This indicates the capsulorhexis should be as large as possible to prevent straylight, especially under low-luminance conditions when the pupil is large.

Clinical comparison of the optical performance of aspheric and spherical intraocular lenses.

PURPOSE: To compare the optical performance of aspheric Tecnis ZA9003 and spherical Sensar AR40e intraocular lenses (IOLs). SETTING: Laboratory of Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. METHODS: An aspheric IOL was implanted in 1 eye and a spherical IOL in the other eye of patients with bilateral age-related cataract. Contrast sensitivity was measured using 2 computerized tests (vertical sine-modulated gratings and circular sine-modulated patterns) with cycloplegia and a 5.0 mm artificial pupil under photopic conditions at optimum refractive correction and at several defocus levels. The depth of focus and the myopic shift (shift of optimum focus toward more myopic values at lower spatial frequencies) were determined. Higher-order aberrations were assessed using a Hartmann-Shack wavefront analyzer; straylight was measured with a straylight meter. RESULTS: In the 60 eyes evaluated, there were no statistically significant differences in contrast sensitivity measured at optimum focus, depth of focus, or straylight between the 2 IOLs. The mean spherical aberration was significantly lower with the aspheric IOL (-0.036 microm) than with the spherical IOL (0.064 microm) (P<.001) and the mean myopic shift, statistically significantly smaller (0.05 diopter [D] and -0.47 D, respectively) (P<.001). CONCLUSIONS: Eyes with the aspheric IOL had lower spherical aberration than eyes with the spherical IOL and, related to that, a smaller myopic shift. No significant differences were found between the 2 IOLs in contrast sensitivity measured at optimum focus, depth of focus, or straylight. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.