Optical Coherence Tomography Measurements of the Retinal Nerve Fiber Layer Profile in Normal Eyes

Abstract

Abstract: : Purpose: To establish a normal optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness profile and to compare this findings with data provided by a previous human histological study Methods: Twenty eyes from 20 normal volunteers were studied. A circular scan was adjusted to the size of the optic disc and three images were captured at this radius (disc margin) and every 200 microns after it, around the optic disc until 1400 (a total of eight circles). The total of the scan length display is 500 units, and four different points were chosen to represent each section to be studied. Measurements were performed at points 63, 188, 313 and 438 of the scan length display in each of the three measurements, and the mean number was used for the statistical analysis Results: The RNFL thickness decreases with increasing distance from the disc margin for all four sections studied, but the slope of decrease is different among the sections (P < 0.001). At the optic disc margin, the RNFL was thicker at nasal sections comparing to the temporal sections (P < 0.02). After 600 µm, the RNFL was significantly thinner at the inferonasal section (P < 0.02). When comparing the mean values of the radial sections the inferonasal section was the thinnest (P < 0.017). There was no correlation between the disc diameter and RNFL thickness at 0, 600 and 1200 µm from the disc margin. When comparing the data from this study to the histological study, the RNFL thickness was significantly thicker at the disc margin, 200, 400 and 600 µm distance in the histological study, but after 600 µm there was no difference. Conclusions: A normal OCT RNFL profile was determined at four different radial sections, what may potentially help the OCT evaluation of glaucoma suspects. No relationship between the optic disc size and RNFL thickness at 0, 600 and 1200 µm distance from the disc margin was observed at this study. In comparison to the histological study, measurements were thinner with OCT from the disc margin up to 600 µm and comparable after that.

Keywords: nerve fiber layer • clinical (human) or epidemiologic studies: systems/equipment/techniques • anatomy