Sector-based analysis of optic nerve head shape parameters and visual field indices in healthy and glaucomatous eyes

Purpose: To evaluate the correlations between the sector optic nerve head parameters measured by Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany), version 1.11S, and the visual field. Methods: One eye was randomly chosen from 55 individuals with glaucoma and 50 healthy individuals. Each participant had at least one Humphrey visual field, program 30-2 (Humphrey Instruments, San Leandro, CA, U.S.A.), and three 10 degrees HRT pictures. From the mean of the three HRT pictures, global measurements, superior (45 degrees-135 degrees), nasal (135 degrees-225 degrees), inferior (225 degrees-315 degrees), and temporal (315 degrees-45 degrees) sector measurements were calculated for the following parameters: disc area, effective area, area below reference, mean height of contour, volume below surface, volume above surface, volume below reference, volume above reference, and third moment. From the visual field results, mean deviation (MD), superior MD, and inferior MD were calculated. For each HRT parameter we calculated the ''r'' Pearson correlation with the corresponding visual field measures. Results: Within the combined healthy and glaucomatous groups we found highly significant (p < 0.001) correlations between the following HRT parameters and the visual field MD: inferior and mean hight of contour (r = -0.53), inferior and third moment (r = -0.52), global and third moment (r = -0.49), inferior and volume above reference (r = 0.47), superior and third moment (r = -0.46), and superior and area below reference (r = -0.44). Correlations between global mean deviation and nasal or temporal sector parameters were generally smaller and less significant. Conclusions: inferior and superior HRT sector parameters were correlated with the respective visual field indices. In many cases these correlations were as strong or stronger than with the global equivalent shape measures.