Differences by Quadrant of Retinal Nerve Fiber Layer Thickness in Healthy Eyes

PURPOSE: The purpose of this study was to determine the distribution of retinal nerve fiber layer thickness by quadrant in healthy eyes. PATIENTS AND METHODS: Forty subjects with healthy eyes were included in the study. A complete ophthalmic examination was performed, including determination of visual fields by automated perimetry. The subjects had no family history of retinal disease or glaucoma. Forty right eyes and 40 left eyes were measured. Retinal nerve fiber layer thickness was measured using simultaneous stereophotographs with stereophotogrammetry at the disc margin. For the total disc and four quadrants, absolute retinal nerve fiber layer thickness and optic disc area was determined using a magnification correction formula. RESULTS: Comparison of the quadrants showed that the retinal nerve fiber layer thicknesses of the superior, inferior, and nasal quadrants were significantly thicker than the temporal quadrant (P = 0.00006 for right and left eyes). No significant differences were observed between the superior, inferior, and nasal quadrants in the right eye. In the left eye, the superior retinal nerve fiber layer thickness was significantly greater than the inferior (P = 0.028) and nasal retinal nerve fiber layer thicknesses (P = 0.00006), while the inferior was not significantly different from the nasal. No significant difference in quadrant retinal nerve fiber layer thickness was noted between eyes. CONCLUSIONS: Measurements of retinal nerve fiber layer thickness in healthy eyes show the thinnest quadrant to be the temporal, with the other three quadrants having similar thicknesses. This pattern corresponds to the histologic measurements of retinal nerve fiber layer thickness.