RISK FACTORS FOR UNDIAGNOSED GLAUCOMA

 

Undiagnosed glaucoma is a hidden, significant public health problem. Surveys have shown that almost 50%-90% of glaucoma cases are undiagnosed in a population.

Some risk factors associated with undiagnosed glaucomas include:

• Lower education levels
• Not consulting an ophthalmologist in the year prior to the diagnosis
• Being seen by an optometrist rather than an ophthalmologist

Features associated with undiagnosed glaucoma are:

• A smaller vertical cup-to-disc ratio (CDR)
• Negative family history of glaucoma
• Lower mean baseline intraocular pressure (IOP)
• Baseline hyperopia

In a study by Wong, the odds of having visual field defects among those with diagnosed glaucoma were lower than those with undiagnosed glaucoma (odds ratio [OR], 0.06; 95% confidence interval [95% CI], 0.01–0.69; P=0.02). In addition, the odds of undiagnosed glaucoma were 14 times higher (OR, 14.10; 95% CI, 2.83–7.08; P<0.0001) in participants with visual field defects compared with those without glaucoma. [1]

A study was performed by Chan et al, to examine the associations with previously undiagnosed primary open-angle glaucoma (POAG) in the European Prospective Investigation of Cancer (EPIC)-Norfolk Eye Study. [2]

30445 men and women aged 40–79 years were recruited in the baseline survey from the databases of 35 general practices. The predominant ethnicity of the cohort was white. Among the 314 POAG subjects, 160 of them had HTG and 154 had NTG; 207 (65.9%) were known cases, diagnosed before the start of the study and 107 (34.1%) were previously undiagnosed.

The study reported two factors associated with undiagnosed POAG:

• Lower IOP levels (OR 0.71/mm Hg, 95%CI 0.63 to 0.80, p<0.0001)
• Participants not reporting vision problems (OR 0.03, 95%CI 0.01 to 0.69, p<0.0001)

The first points to an over-reliance on the IOP level to exclude glaucoma in the community, leading to patients with lower IOP being missed.

This study demonstrates that it is easy for eye care providers to be reassured by an IOP level <24mmHg while other features of glaucoma are missed. 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.

In this study, other features of the severity of glaucoma such as vertical CDR and visual field mean deviation were not associated with missed OAG cases. It could be because CDR does not adequately capture features of a glaucomatous disc, and visual fields may not be done routinely at the optician. Even with advanced field defects, many patients with glaucoma are asymptomatic, so field defects will not necessarily provide a reason to visit the optician.

In conclusion, the most important healthcare implication from this analysis is to avoid being falsely reassured by a lower level of IOP in glaucoma case finding.

REFERENCES:

Wong EY, Keeffe JE, Rait JL, Vu HT, Le A, McCarty PhD C, Taylor HR. Detection of undiagnosed glaucoma by eye health professionals. Ophthalmology. 2004 Aug;111(8):1508-14. doi: 10.1016/j.ophtha.2004.01.029. PMID: 15288980.

Chan MPY, Khawaja AP, Broadway DC, Yip J, Luben R, Hayat S, Peto T, Khaw KT, Foster PJ. Risk factors for previously undiagnosed primary open-angle glaucoma: the EPIC-Norfolk Eye Study. Br J Ophthalmol. 2022 Dec;106(12):1684-1688. doi: 10.1136/bjophthalmol-2020-317718. Epub 2021 Jun 25. PMID: 34172506; PMCID: PMC9685696.