Retinal Sensitivity and Retinal Nerve Fiber Layer Thickness Measured by Optical Coherence Tomography in Glaucoma

Abstract

To define the relationship between retinal light sensitivity and peripapillary retinal nerve fiber layer (RNFL) thickness as measured using the Stratus optical coherence tomograph (OCT). Prospective study. Institutional. A total of 126 healthy subjects, 42 patients with ocular hypertension (OHT) and 64 patients with primary open-angle glaucoma (POAG) were examined by the 24/II program of the Humphrey Field Analyzer (Carl Zeiss Meditec, Inc, Dublin, California, USA), and the Fast RNFL Thickness examination of the OCT. Individual visual field (VF) test scores and peripapillary RNFL thickness measurements were grouped into six topographically corresponding sectors whose mean values were then calculated. One eye per patient was randomly chosen. The correlations between mean retinal sensitivity (expressed both in decibel and unlogged scales) and RNFL thickness were described with linear and logarithmic regression analyses. With reference to all 232 individuals, the equation that best explained the model was logarithmic when using the decibel scale, and either linear or logarithmic when using the unlogged scale. A statistically significant, age-adjusted correlation between function and structure was found in most sectors both using the decibel (logarithmic regression analysis r(2) 0.24 to 0.61, P < .001), and the unlogged scale (r(2) 0.37 to 0.53, P < .001 in both linear and logarithmic regression analyses). When using the decibel scale, the logarithmic equation may better explain the function/structure relationship between retinal sensitivity and OCT-measured RNFL thickness along a wide spectrum of glaucoma continuum. These results support the need to combine functional and structural tests in the detection of early glaucoma.