Comparing glaucomatous optic neuropathy in primary open angle and primary angle closure glaucoma eyes by scanning laser polarimetry-variable corneal compensation

Purpose: To study the retinal nerve fiber layer thickness difference between high-tension primary open angle glaucoma (HT-POAG) and primary angle closure glaucoma (PACG) eyes using scanning laser polarimetry-variable corneal compensation (GDx VCC) in Taiwan-Chinese population; to evaluate the usefulness of the GDx VCC for detecting POAG and PACG eyes in Taiwan-Chinese population. Patients and Methods: The study comprised 88 early to moderate glaucomatous eyes (one randomly selected eye from 47 HT-POAG patients and 41 PACG patients) and the control group consisted of 45 age-matched eyes from 45 normal individuals. Each subject underwent retinal nerve fiber layer thickness measurement by GDx VCC and Humphrey Field Analyzer Visual field testing. Measured GDx VCC parameters were compared among groups. We also calculated the area under the receive operator characteristic (AROC) curve, corresponding sensitivity/specificity and best cut off value for each parameter in differentiating normal from POAG and PACG eyes. Results: There was no significant difference between HT-POAG and PACG eyes in each parameter. The parameter with the best AROC curve for differentiating normal from POAG eye was nerve fiber indicator (AROC, 0.779; sensitivity = 57.4%, specificity = 100%; best cut off value > 27). The parameter with the best AROC curves for differentiating normal from PACG eyes was temporal-superior-nasal-inferior-temporal average (AROC, 0.829; sensitivity = 46.3%, specificity = 100%, best cut off value < 51.7). Conclusions: There was no significant difference between the HT-POAG and PACG eyes as far as the various parameters were concerned. GDx VCC shows fair discriminating ability in distinguishing normal from POAG and PACG eyes in Taiwan Chinese population.