Doctors can be pretty confident that patients with high IOP have either ocular hypertension or glaucoma worthy of intervention, but the reverse isn’t always true. New research suggests eye care providers shouldn’t rule out a POAG diagnosis in patients with low IOP.

This cross-sectional research paper was part of the European Prospective Investigation of Cancer-Norfolk Eye Study, a large cohort study in the UK that included 314 participants with POAG in either eye. Of these, 217 individuals had previously diagnosed POAG and 107 participants were newly diagnosed. Researchers also considered sociodemographic, ocular, physical and economic factors as barriers to eye care access.

After adjusting for covariables, the authors found that the factors significantly associated with previously undiagnosed POAG were a lower pretreatment IOP and if patients reported no problems with their eyesight.           

“This study demonstrates that it is easy for eye care providers to be reassured by an IOP level less than 24mm Hg while other features of glaucoma are missed,” the researchers wrote in their paper. “It must be stressed therefore that, among patients with non-elevated IOP, care should be taken to examine the optic disc carefully and with supportive disc imaging and visual field testing to improve the chances of identifying suspicious disc features.”

Additionally, the researchers found the type of glaucoma was strongly associated with pretreatment IOP, with IOP being significantly lower among normal tension glaucoma than high tension glaucoma patients.

Other indicators of glaucoma severity, such as vertical cup/disc ration and visual field mean deviation, were not associated with missed OAG cases.

The authors also suggest that raising public awareness of glaucoma and encouraging regular eye tests can help reduce undiagnosed glaucoma.

Chan MPY, Khawaja AP, Broadway DC, et al. Risk factors for previously undiagnosed primary open-angle glaucoma: the EPIC-Norfolk Eye Study. Br J Ophthalmol. June 25, 2021. [Epub ahead of print].