Optic disc topographic measurements after pupil dilation

Abstract

Purpose To determine the effect of pupil dilation on topographic optic disc parameters measured with confocal scanning laser ophthalmoscopy. Design Prospective, comparative, observational case series. Participants Thirty-eight subjects (25 glaucoma patients, 5 glaucoma suspects, and 8 normal subjects) representing a range of lens opacities participated in this study. Methods Topographic optic disc parameter measurements were obtained before and after pupil dilation with a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Cataract severity was measured with the LOCS III grading system. Image quality was assessed using the standard deviation of the mean topography image and an image quality score. Multiple regression techniques were used to evaluate the effect of image quality, cataract density, and pupil size on the change in topographic parameters after dilation. Main outcome measures Topographic optic disc parameter measurements. Results With dilation, mean change in most topographic optic disc parameters was not significantly different from zero. Changes in topographic optic nerve parameters tended to be relatively small when undilated images were of good quality and larger in images of relatively poor quality. The strongest predictor of the absolute value of change in topographic optic disc parameters was the standard deviation of the undilated mean topography image. Conclusions When confocal scanning laser ophthalmoscope images are of good quality, topographic optic disc parameter measurements obtained with a dilated pupil are similar to those obtained with an undilated pupil. However, caution should be exercised when interpreting information from poor quality confocal scanning laser ophthalmoscopic images.