Heidelberg Retinal Tomograph (HRT 2) parameters in primary open angle glaucoma and primary angle closure glaucoma: A comparative study in an Indian population

Aims: To compare the Heidelberg Retinal Tomograph (HRT 2) parameters in patients with primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) in an Indian population. Materials and Methods: Two groups of patients were recruited: group I comprised 78 eyes ( 78 patients) with POAG and group II 58 eyes ( 58 patients) with PACG. Based on visual field defects detected by automated perimetry, the groups were further classified into early, moderate, and severe glaucoma. All patients underwent a complete ophthalmic examination as well as an HRT 2 examination. The HRT parameters for the two groups were compared and the sensitivity and specificity of the parameters calculated. Results: All HRT parameters were similar in both groups: 85.9% (95% CI: 78.2, 93.6) of POAG and 81% ( 95% CI: 72.3, 89.3) of PACG had a positive F. S. Mikeleberg (FSM) discriminant function. Considering outside normal limits and borderline as abnormal, the Moorefield regression analysis had 83.3% ( 95% CI: 75, 91.6) sensitivity in POAG and 75.9% ( 95% CI: 64.9, 86.9) in PACG. In early POAG, the FSM discriminant function had a sensitivity of 74.3% ( 95% CI: 59.8, 88.8) compared to 58.3% ( 95% CI: 38.9, 77.7) for early PACG. The cup shape measure (p= 0.018) and the Moorfield regression analysis ( p = 0.011) had significantly higher sensitivity for early POAG than for early PACG: cup shape measure sensitivity 62.9% ( 95% CI 46.9, 78.9) for early POAG versus 33.3% ( 95% CI: 14.4, 52.2) for early PACG and Moorefield regression analysis 74.3% ( 95% CI: 59.8, 88.8) versus 45.8% ( 95% CI: 39.9, 65.7). Conclusions: HRT has moderate sensitivity in the detection of damage leading to glaucomatous field defects. The sensitivity of HRT for early PACG appears to be less than that for early POAG. This may indicate a difference in pathophysiology.