Abstract
Purpose: :
This study evaluates the structure–function relationship of retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT) to visual field (VF) sensitivity.
Methods: :
A retrospective cross–sectional study was conducted using 474 eyes (143 glaucoma, 194 glaucoma suspect and 137 normal) from 312 patients. Mean RNFL thickness was measured by OCT within three months of VF testing. The correlation of mean RNFL thickness to mean deviation (MD) of the visual field was calculated for each group of patients.
Results: :
Mean RNFL thickness of glaucoma patients was thinner, compared to glaucoma suspect and normal patients (64.9 ± 19.5 µm, 86.5 ± 16.5 µm and 96.1 ± 13.8 µm, respectively, P<0.0001). Glaucoma patients had reduced MD compared to glaucoma suspect and normal patients (–8.5 ± 6.9 dB, –2.9 ± 2.6 dB, and –1.4 ± 1.2 dB, respectively, P<0.0001). Mean RNFL thickness highly correlated to MD in glaucoma patients (r=0.70, P<0.0001) as opposed to glaucoma suspect (r=0.29, P<0.0001) and normal (r=0.07, P=0.43) patients.
Conclusions: :
Mean RNFL thickness was significantly thinner and MD was reduced in glaucoma patients compared to glaucoma suspect and normal patients. Mean RNFL thickness highly correlated with MD in glaucoma patients, but not in the glaucoma suspect and normal patients. Correlation of structure to function strengthens with disease progression. RNFL thinning precedes loss of vision measured by perimetry. OCT detects early RNFL loss in glaucoma suspects. Early detection of structural changes may aid in identifying glaucoma suspects in the absence of visual field deficits.
Keywords: imaging/image analysis: clinical • visual fields • nerve fiber layer