A comparison of glaucoma patients identified through mass screening and in routine clinical practice.

PURPOSE: To study differences between glaucoma patients identified through a population screening and glaucoma patients diagnosed in routine clinical practice (self-selected patients).
METHODS: A total of 402 individuals with newly detected open-angle glaucoma were identified through a large population screening programme that ran from October 1992 to January 1997. The screening programme was attended by a total of 32918 citizens of Malmö, Sweden, aged between 57 and 79 years. Citizens who had visited the Eye Department of Malmö University Hospital in the year before the screening of their birth cohort were not invited to participate (n = 4117). Among the latter, we identified 354 patients with open-angle glaucoma through a retrospective examination of patient records.
RESULTS: At detection, 52.9% of the glaucoma patients identified through screening had normal tension glaucoma (NTG), defined as intraocular pressure (IOP) < 21 mmHg in both eyes, compared to 13.5% of the self-selected patients (p < 0.0001). Mean IOP at the time of diagnosis was 22.9 mmHg in the screened group and 32.5 mmHg in the self-selected group. Pseudoexfoliation was present in 16.4% of the screened group and 44.0% of the self-selected group (p < 0.01). Bilateral disease was present in 40.1% of the screened group and 34.6% of the self-selected group (p = 0.1160). Median MD (mean deviation from the age-corrected normal visual field) in the worse eye was -8.0 dB in the screened group and -16.2 dB in the self-selected group (p < 0.0001). Visual acuity was lower in the self-selected group, which was also on average slightly more myopic. Of the patients detected through screening, 62% had seen an ophthalmologist previously, 17% within the preceding 2-year period.
CONCLUSIONS: Normal tension glaucoma was four times as common in patients identified through population screening as in self-selected patients, suggesting that patients with NTG are easily overlooked in clinical practice. Even though the patients detected through population screening had lower mean IOP, lower prevalence of pseudoexfoliation, better visual fields and a lower incidence of bilateral disease than self-selected patients, many still had considerable damage. Special efforts, such as glaucoma screening, are needed if manifest glaucoma, and especially NTG, is to be detected at an earlier stage than it currently is.