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Primary angle-closure glaucoma (PACG) is typically a high pressure disease and factors other than the intraocular pressure are considered to be less likely involved, at least during early stages of the disease. Therefore, structure-function relationships in PACG may be different from primary open angle glaucoma (POAG), which is considered to be a multifactorial disease.
Manassakorn and Aupapong (210) demonstrate that the patterns of retinal nerve fiber layer (RNFL) thickness loss in PACG, as measured by optical coherence tomography (OCT) ,is different from those of POAG in the early stage of disease. Specifically, they found focal RNFL defect in the inferior area in the mild POAG group, but not in the mild PACG group. In addition, the number of affected points in each sector in the mild subgroups was greater in the POAG group than in the PACG group. At the moderately advanced and advanced stages, both glaucoma types shared a similar pattern of diffuse RNFL loss. Different patterns of RNFL damage provide support that the mechanism of optic nerve damage may be different between PACG and POAG. However, as the authors stated, this study is limited in that it had a small sample size (43 patients with PACG and 60 patients with POAG). This led to inclusion of only 19 PACG eyes and 30 POAG eyes in the subgroup analysis for mild glaucoma eyes (MD < -8D), where the authors found difference between the two glaucoma types. A larger scale study is needed to confirm the finding observed in this study.