Ocular aberrations measured by the Fourier-based WaveScan and Zernike-based LADARWave Hartmann-Shack aberrometers.

PURPOSE: To evaluate agreements in lower and higher order aberration measurements by two Hartmann-Shack wavefront-sensing devices. METHODS: Using the VISX WaveScan and Alcon LADARWave aberrometers, ocular aberrations at a fixed optical zone of 6 mm were measured on 36 eyes of 18 patients. A tunable light intensity source was used to control pupil size, which was checked using infrared pupillometry. Repeatability of measurements was evaluated using the intra-class correlation coefficient with 3 consecutive measurements on each aberrometer. RESULTS: Mean absolute defocus for WaveScan and LADARWave was 2.82 +/- 2.69 and 2.93 +/- 3.24 root-mean-square (RMS) microm, whereas astigmatism was 0.81 +/- 0.49 and 0.87 +/- 0.57 microm, respectively. Pearson correlation coefficients between the two aberrometers were 0.908 and 0.870 for defocus and astigmatism, respectively, whereas higher order aberration correlation was less tight (Pearson correlation coefficient=0.596 for coma, 0.746 for trefoil, 0.836 for spherical aberration, 0.637 for secondary astigmatism, and 0.963 for quadra-foil [P<.001 for all]). The LADARWave had a tendency to display more spherical aberration than the WaveScan, especially at high aberration values, with mean absolute difference in measurement of 0.12 +/- 0.08 microm, and only 44% of eyes having less than +/-0.10 RMS microm of difference. The mean total higher order aberration absolute difference was 0.14 +/- 0.14 microm, with only 50% of eyes within +/-0.1 RMS of agreement. Vector analysis revealed appreciable discrepancies in third- and fourth-order directional Zemike components, while showing similar values for fifth-order components. Intra-class correlation coefficient values for both aberrometers over different aberration orders showed excellent repeatability. CONCLUSIONS: The WaveScan and LADARWave share similar lower order aberration measurements, but display significantly different higher order aberration values.

Comparative ocular anatomy of the western lowland gorilla.

OBJECTIVE: To examine the lowland gorilla (Gorilla gorilla gorilla) eye and determine similarities to and differences between the mountain gorilla (Gorilla gorilla beringei) and the human eye. In addition, we compare our findings of G. g. gorilla to previous reports on the eye of this subspecies. PROCEDURES: A 13-year-old deceased male lowland gorilla and a 34-year-old deceased female lowland gorilla were included in the study. Gross and microscopic examinations of the formalin-fixed right eyeball of each gorilla were carried out. RESULTS: Globe dimensions of G. g. gorilla were similar to G. g. beringei and to humans. The limbal conjunctival epithelium and the choroid were densely pigmented. However, the distribution of the conjunctival pigment ring was different to that of G. g. beringei and the melanocytes of the choroid were unusually round. There were deep crypts in the anterior border layer of the iris, and the epithelium of the pars plana was uniquely irregular. Vertical corneal diameter was observed to be equal or greater than horizontal diameter in G. g. gorilla, which is in contrast to humans and to previous findings for G. g. beringei. Corneal thickness was closer to that of humans than to G. g. beringei. Posterior lens capsule thickness was noticeably greater than that of humans. CONCLUSIONS: Although some variation between the ocular anatomy of G. g. gorilla and G. g. beringei does exist, the gross and microscopic findings closely resemble each other in these two subspecies. In addition, the eye of Gorilla appears remarkably similar to the human eye. However, comparison of measurements with those in humans is somewhat limited because formalin-fixation can introduce tissue shrinkage and artifact.