Natural history of glaucoma suspects in a tertiary eye centre in Singapore

To evaluate the conversion rate of glaucoma suspects to glaucoma in a tertiary eye centre in Singapore over 5 years.

This is a retrospective cohort study of 101 glaucoma suspects followed up in a tertiary outpatient clinic at National University Hospital over 5 years from their first presentation. The cumulative incidence of conversion to glaucoma diagnosis and intervention was recorded. Risk factors for glaucoma conversion were calculated using Cox proportional hazard analysis, and cost analysis for glaucoma monitoring was performed.

The probabilities of glaucoma suspects developing a clinical diagnosis of glaucoma at 1-, 2-, 3-, 4- and 5-years were 17.8%, 22.3%, 23.0%, 25.6% and 25.6%, respectively. Significant risk factors for conversion include: (1) family history of glaucoma (hazard ratio [HR] = 6.46, 95% confidence interval [CI] 1.72-24.21; p = 0.006), (2) intraocular pressure [IOP] >21 mmHg (IOP 22-24 mmHg, HR = 8.60, 95% CI 1.64-45.01; IOP > 24 mmHg, HR = 22.36, 95% CI 4.94-101.25; p = 0.011 and p < 0.001 respectively) and (3) age >75 years (HR = 6.28, 95% CI 1.88-20.93; p = 0.003). The mean annual direct cost incurred by a glaucoma suspect through their follow-up period (up to 5 years) was USD 336.97 ± USD 157.37.

About 1 in 4 glaucoma suspects progressed to glaucoma over 5 years. Positive family history of glaucoma, IOP >21 mmHg and age >75 years were independent risk factors for conversion. Further guidelines to ensure more cost-effective healthcare resource allocation are advisable.