An Increasing Global Concern
Glaucoma is a major global health problem, and all types of the disease combined are the second leading cause of blindness worldwide, with approximately 6.7 million people being blinded as a result of the disease.1 With the predicted increase in life expectancy, the anticipated number of people becoming blind from the disease will rise substantially in the near future. Despite increasing public health awareness and the availability of advanced-technology diagnostic tests in developed countries, a high proportion of glaucoma cases remain undiagnosed in the community. Improved strategies for achieving earlier and more accurate diagnosis of glaucoma will facilitate the prompt implementation of effective treatment options, and subsequently will minimise the anticipated rising burden of the disease in the near future.
The Problem of Early Detection of Glaucoma
Various population-based epidemiological studies have reported that more than 50% of glaucoma cases remain undiagnosed, even in developed countries.2–5 High prevalence estimates of undiagnosed glaucoma are consistent with the lack of cost-effective screening methods for glaucoma. Despite being a major risk factor for glaucoma, elevated intraocular pressure (IOP) lacks sensitivity and specificity in glaucoma diagnosis since it is not present in a high proportion of affected patients at the time of diagnosis, while many people without glaucoma present with elevated IOP. Also, possible reasons for thehigh prevalence of undiagnosed glaucoma include the fact that glaucoma is a silent, asymptomatic disease.
Visual function may not deteriorate significantly until advanced stages of the disease. However, even in the advanced stages of the disease glaucoma can remain undiagnosed due to lack of regular visits to an ophthalmologist or lack of thoroughness at the eye examination. In a recent population-based study of the major eye diseases in Greece – the Thessaloniki Eye Study – a high prevalence of undiagnosed glaucoma (approximately 50%) was reported. The majority of cases were not at early glaucoma stage: mean cup-to-disc (c/d) ratio of undiagnosed glaucoma cases was 0.7, and mean visual field Advanced Glaucoma Intervention Study (AGIS) score was 6.4.
A subsequent analysis of factors associated with non-diagnosis showed that glaucoma patients who had not seen an eye doctor during the previous year had six-fold increased odds of being undiagnosed compared with patients who had visited an eye doctor during the last year.6 Also, primary open-angle glaucoma (POAG) patients had a four-fold increased risk of being undiagnosed compared with pseudoexfoliative glaucoma patients, indicating that the thoroughness at the eye examination and the performance of the eye doctors in diagnosing glaucoma may increase when pseudoexfoliative material is present. Furthermore, the Visual Impairment Project (VIP), a population-based study in Australia, reported that an increased passage of time since the last visit to an eye-care provider was associated with an elevated risk of undiagnosed glaucoma.7 Additionally, the type of eye professional seen within the previous 12 months was statistically significantly different between the diagnosed and undiagnosed glaucoma groups, with the undiagnosed group being more likely to be examined by an optometrist.8
Increased patient motivation for regular visits to the eye care professionals, improved training of the latter and standardisation of examination protocols could facilitate better detection rates with conventional clinical examination diagnostic tools.