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Editors Selection IGR 12-4
Glaucoma Screening and Detection: Late detection of Glaucoma
Comment by Paul Healey on:
54763 Why do people present late with advanced glaucoma? A qualitative interview study, Prior M; Francis JJ; Azuara-Blanco A et al., British Journal of Ophthalmology, 2013; 97: 1574-1578
A flaw in many studies sent for review is too small a sample size. How then might we be expected to learn anything from this qualitative study by Prior et al., which samples 11 patients with advanced glaucoma? The reason why small sample size is a problem is that it reduces statistical certainty when making quantitative estimates. A qualitative study does not aim to estimate a mean but rather describe themes and variations in personal accounts of participants. In effect it is a case series. Participants in this study were those with glaucomatous visual field loss of ≤ 20 dB in one eye or ≤ 12 dB in both eyes, attending glaucoma outpatient clinics at one of two hospitals in Scotland and England. Eleven (79%) of the 14 patients identified participated.
The stories of the participants give insight which reflects both well and poorly on the health system. On the positive side, most patients referred to ophthalmology services were seen quickly. This occurred when referral arose from both GPs and optometrists. A concerning theme was glaucoma being diagnosed on the first visit to a new optometrist, having been missed for many years by the patient's regular optometrist. While the authors state the study was not intended to be representative, its generalizability is critical for its utility as a tool to change practice. There would be little value in changing health interventions based on the testimonies of 11 people if they were the only people to have such an experience.
..progressive glaucomatous optic neuropathy not being detected despite regular eye checks (some for many decades) should send a warning signal to all eye care
The theme of missed diagnosis at a primary eye care level is supported by data from a very much larger study (the Melbourne Visual Impairment Project) which showed participants whose glaucoma was diagnosed by the study, had been seen previously by primary eye care providers1. This is an important issue to consider in the discussion of improving glaucoma screening. The theme of progressive glaucomatous optic neuropathy not being detected despite regular eye checks (some for many decades) should send a warning signal to all eye care providers. A patient who has been examined and classified as normal may yet develop asymptomatic disease. Comprehensive ophthalmic examination is always required for periodic visits. This study suggests that the insidious nature of glaucomatous damage applies to both sides of the slit lamp.
References
- Wong EY, Keeffe JE, Rait JL, Vu HT, Le A, McCarty PC, et al. Detection of undiagnosed glaucoma by eye health professionals. Ophthalmology 2004; 111(8): 1508-1514.
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