In contrast to the common belief that IOP is elevated in primary angle-closure glaucoma (PACG), a study in Korea found that 60.6% of PACG eyes had normal intraocular pressure (IOP) at initial glaucoma diagnosis. Without gonioscopy clinicians may misdiagnose the patients with normal tension glaucoma.

Researchers compared the ocular biometric parameters between 160 PACG eyes with normal IOP and those with high IOP at their first visit in order to identify factors associated with normal IOP at the first visit. PACG eyes with normal IOP at their first visit had longer AL, deeper ACD, more hyperopic refractive errors, and flatter corneas than those with high IOP at their first visit.

The prevalence of disc hemorrhage was higher in PACG patients with initially normal IOP than in those with initially high IOP. Because of the higher prevalence of disc hemorrhage in normal tension glaucoma than PACG, clinicians may misdiagnose if they do not perform gonioscopy in cases with normal IOP at their first visit wherein disc hemorrhage is observed more frequently during follow-up.

The study concludes that anterior chamber depth measurement with recently developed optical biometry devices is useful in diagnosing PACG. Early recognition of angle closure in glaucoma patients can change the overall disease course and improve patient outcomes.