Effect of cataract and pupil size on image quality with confocal scanning laser ophthalmoscopy.

OBJECTIVE: To determine the effect of pupil size and cataract on the reproducibility and image quality obtained with confocal scanning laser ophthalmoscopy. METHODS: Three image series were obtained with a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, Heidelberg, Germany) before and after pupillary dilation in each of 39 subjects (8 normal subjects, 5 glaucoma suspects, and 26 patients with glaucoma). The cataract density was measured with both a lens opacity meter and the Lens Opacities Classification System III system. The image quality of each image series was subjectively scored on a scale of 0 (poor) to 9 (high) by 2 independent observers who were unaware of the cataract density and pupil size during image acquisition. The image quality and reproducibility were objectively evaluated using the SD of the mean topography image of each subject. RESULTS: The mean pupil diameter in all subjects before and after dilation was 2.5 +/- 0.8 mm and 5.8 +/- 1.4 mm, respectively. After pupillary dilation, both the mean image quality score and mean SD of the mean topography image improved (from 4.5 +/- 3.5 to 7.4 +/- 2.3 and from 48.6 +/- 18.8 microns to 35.6 +/- 15.5 microns, respectively). The quality score of the images that were obtained before pupillary dilation was associated with the pupil size and density of nuclear and posterior subcapsular cataracts. The SD of the mean topography images that were obtained before pupillary dilation increased with a decreasing pupil size (P = .003) and an increasing density of the nuclear (P < .03), cortical (P = .02), and posterior subcapsular (P = .002) opacity. CONCLUSIONS: Although pupillary dilation improved the image quality in most subjects, the improvement was sometimes small. Those subjects with small undilated pupils and/or cataracts may benefit most from pupillary dilation.

Asymmetries in the normal short-wavelength visual field: implications for short-wavelength automated perimetry.

PURPOSE: To quantify short-wavelength sensitivity in normal eyes by hemifield location, eccentricity, and age. METHODS: We measured achromatic and short-wavelength thresholds across visual fields covering a radius of 21 degrees of visual angle in 115 normal eyes in subjects aged 17 to 77 years and out to 30 degrees of eccentricity in an additional 57 eyes in subjects aged 22 to 80 years. RESULTS: Results indicated significantly greater sensitivity for the inferior visual field compared with the superior field (P = .001). The amount of asymmetry increased with eccentricity (P = .001) but not with age (P = .357). A temporonasal field asymmetry was noted at the most eccentric points of the 30-degree field (P = .001) but not at 21 degrees (P = .821). CONCLUSIONS: In addition to increasing our understanding of normal retinal function, these results have implications for basic research in comparison with results of studies using different retinal locations to assess short-wavelength sensitivity and for clinical practice, where short-wavelength sensitivity is used to diagnose and manage a number of diseases, including glaucoma, diabetic retinopathy, and acquired immunodeficiency syndrome (AIDS)-related vision loss.

Change in optic disk topography after trabeculectomy.

PURPOSE: To investigate the relationship between optic disk topography and intraocular pressure before and after trabeculectomy with confocal scanning laser ophthalmoscopy. METHODS: The eyes of 49 consecutive patients undergoing trabeculectomy at a university-based glaucoma practice underwent preoperative and postoperative imaging using a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Three images of one eye of each patient were obtained with a 15-degree field of view. Preoperative images were obtained approximately 2 months before surgery (mean +/- SD, 2.4 +/- 1.6 months). Postoperative images were obtained at least 3 months after surgery (mean, 4.5 +/- 2.6 months). RESULTS: Mean preoperative intraocular pressure, postoperative intraocular pressure, and percent change in intraocular pressure respectively were 23.1 +/- 6.8 mm Hg, 12.7 +/- 7.1 mm Hg, and 43.8% +/- 29.9%. A significant association (P < .01) was found between percent decrease in intraocular pressure and decreases in cup area, cup volume, and cup/disk area ratio as well as between percent decrease in intraocular pressure and increases in rim area, rim volume, mean height contour, retinal cross-section area, and height in contour. Between 11.7% and 31.2% of the variability (R2) in these parameters was explained by the percent change in intraocular pressure. Topography changes were more strongly associated with percent change than with mean change in intraocular pressure. We found no association between percent decrease in intraocular pressure and reference plane height or maximum cup depth. CONCLUSIONS: Changes in optic nerve topography were associated with reduction in intraocular pressure after trabeculectomy.

Ethnic differences in optic nerve head topography.

PURPOSE: To investigate ethnic differences in optic nerve head topography. METHODS: This is a cross-sectional university-based comparative study of 180 normal subjects (43 African-American, 45 Asian, 48 Hispanic, and 44 white subjects) ages 19-40 years. Optic nerve head parameters including optic disc size, cup-disc ratio, rim area, rim volume, cup volume, and maximal cup depth were measured using a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Differences among groups were evaluated using analysis of variance. RESULTS: Disc area, cup volume, maximal cup depth, and vertical cup-disc ratio were largest in African-Americans, intermediate in Asians and Hispanics, and smallest in whites; for these parameters the differences between African-Americans and whites were statistically significant. Significant differences were also found between African-Americans and Hispanics for cup volume, and between African-Americans and Asians for vertical cup-disc ratio and maximal cup depth. Rim volume and rim area were not significantly different among the four ethnic groups. CONCLUSIONS: Ethnic differences in the normal optic nerve are present and should be taken into a ccount when evaluating the optic disc for glaucoma and other optic neuropathies.