Structural evaluation of perimetrically normal and affected hemifields in open angle glaucoma

PURPOSE: To study macular ganglion cell layer-- inner plexiform layer complex (GCL + IPL) in relation to peripapillary retinal nerve fiber layer (RNFL) in glaucomatous eyes with superior or inferior hemifield defects (HD) and to study structural configuration in normal hemifield. METHODS: This was an observational cross-sectional study. Data from consecutive 45 superior HD (SHD) and 50 inferior HD (IHD) eyes were analyzed. Each patient underwent detailed ocular examination, standard automated perimetry, and spectral domain optical coherence tomography (SD-OCT). After adjusting for age, gender, and signal strength, area under receiver operating characteristic curve (AUC) was calculated to determine diagnostic ability of GCL + IPL and peripapillary RNFL. Apparently normal hemifield was compared with true normal hemifield. Data were analyzed with SPSS, analysis of variance, t-test, Chi-square test, and receiver operating curve. RESULTS: In the SHD glaucoma group, best parameters for discriminating normal eyes from glaucomatous eyes were inferotemporal GCL + IPL thickness (0.935) and inferior quadrant RNFL thickness (0.971). For IHD glaucoma, average GCL + IPL thickness (0.877) and average RNFL thickness (0.950) had best AUC values. When evaluating apparently normal hemifield in both groups, statistically significant difference was found in inferior GCL + IPL sector (0.865) and inferior quadrant RNFL (0.883) in IHD and superonasal GCL + IPL (0.725) and superior quadrant RNFL (0.842) in SHD groups. CONCLUSION: SD-OCT may be a useful ancillary diagnostic tool for evaluation of early macular and circumpapillary structural changes in glaucomatous eyes with localized visual field defects. Apparently normal hemifields show structural damage and should be considered in management of glaucoma.