Optic disc topography in Malay patients with normal-tension glaucoma and primary open-angle glaucoma

Background: There are limited data concerning the optic disc topography in normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG) patients living in Southeast Asian countries. This study aims to compare optic disc parameters in patients with NTG and POAG in Malaysia and to discuss the results in comparison with studies of NTG and POAG in other Asian countries.

Methods: This prospective cross-sectional study was performed in two hospitals with glaucoma service in Malaysia from 2010 to 2012. Seventy-seven patients of Malay ethnicity were enrolled in this study, including 32 NTG patients and 45 POAG patients. Using the Heidelberg Retinal Tomograph III, we measured optic disc area, cup area, rim area, cup volume, rim volume, cup-to-disc area ratio, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness, and retinal nerve fiber layer cross-sectional area.

Results: The eyes for NTG patients had significantly larger optic disc areas (2.65 [standard deviation, 0.41] vs 2.40 [standard deviation, 0.36] mm(2), respectively; P=0.006) and cup areas (1.54 [standard deviation, 0.43] vs 1.32 [standard deviation, 0.40] mm(2), respectively; P=0.027) compared with the eyes of POAG patients. Comparison of the other parameters between the two groups revealed no significant difference (P>0.050). The moderate and severe NTG patients showed significantly deeper cups and larger disc and cup areas when compared with the moderate and severe POAG patients (P<0.050).

Conclusion: The NTG patients in this study have notably larger optic disc and cup areas than the POAG patients. Our observations are consistent with those reported in studies of NTG and POAG patients in Korea. The deeper cups and larger disc and cup areas may serve as indicators of severity when comparing NTG with POAG. However, these findings require verification with IOP and visual field results.