More than 5% of patients with ocular hypertension at baseline went on to develop POAG by six years in this Singapore-based study. Photo: Judy Hu, OD. Click images to enlarge.

The increasing incidence of glaucoma is a significant public health concern, given that the condition is the leading cause of irreversible blindness. In addition, the asymptomatic nature of glaucoma in its early stages contributes to the high percentage of cases that go undiagnosed. A population-based study in Singapore, known as The Singapore Epidemiology of Eye Diseases Study (SEED), reported that a whopping 72.1% of individuals with glaucoma were undiagnosed.

A team of researchers recently circled back to the SEED data to help identify risk factors for primary open angle glaucoma (POAG) and ocular hypertension (OHT) and reported their findings in Ophthalmology Glaucoma. The SEED study, which was conducted between 2004 and 2011, included individuals from three ethnic groups in Singapore between ages 40 and 80. Of these, 3,280 were Malay, 3,400 were Indian and 3,353 were Chinese.

The researchers of the present study reviewed the following data from SEED participants: slit-lamp biomicroscopy, intraocular pressure (IOP), pachymetry, gonioscopy, optic disc examination and perimetry. A diagnosis of POAG was given according to a combination of clinical evaluation, ocular imaging (fundus photo, visual field and OCT) and criteria from the International Society of Geographical and Epidemiological Ophthalmology. OHT was diagnosed in cases without glaucomatous optic disc change but where IOP was above the normal limits (20.4mm Hg, 21.5mm Hg and 22.6mm Hg for Chinese, Indian and Malay cohorts, respectively).

The overall, age-adjusted six-year incidence of POAG and OHT was 1.31% and 0.47%, respectively. Of patients who had OHT at baseline, 5.32% progressed to POAG by year six.

The Chinese and Indian cohorts had a similar POAG incidence (1.37%), though this was lower in the Malays (0.80%). On the other hand, OHT was more common in the Malay cohort, with an incidence of 0.79% compared with 0.38% for Indians and 0.37% for Chinese.

The data analysis revealed three prominent baseline parameters associated with a higher risk of POAG: older age (odds ratio [OR]: 1.90 per decade), higher baseline IOP (OR: 1.20 per mm Hg) and longer axial length (OR: 1.22 per mm). Additionally, patients who developed POAG during the six-year follow-up had lower socioeconomic status than those without POAG, on average.

While this study involved only Singapore residents, the POAG risk factors that were identified mirror those reported in many previous studies. However, this list is by no means exhaustive, which the researchers made sure to emphasize in their paper. For example, family history is a known risk factor for glaucoma but was excluded from this study, though the researchers note they’ve obtained that data for future analysis.

The study authors concluded, “These findings have potential to help clinicians in deciding frequency of monitoring, guide patient prognosis counselling and may affect public healthcare policies to optimize resource utilization across different ethnicities to help mitigate the burden of POAG.”