Purpose: To assess whether the issuing of local guidelines for glaucoma detection including a protocol for the referral of suspects can improve the quality and accuracy of referrals from optometrists.
Methods: Universally agreed guidelines, which included a protocol for referring glaucoma suspects, were circulated to all optometrists in the catchment area of a major teaching hospital ophthalmic unit. Data on 207 new patients referred to one glaucoma clinic were collected from GOS18 forms and hospital records covering two 12 month periods spanning the guideline dissemination. Referral accuracy was calculated and the reasons for protocol violations and referral of normal individuals were determined. Where possible, data were compared with a similar study relating to referrals made to the same clinic in 1988 and 1993.
Results: The mean (SD) intraocular pressure (IOP) at which optometrists referred patients was 22.5 (6.6) in 1997 and 21.9 mmHg (6.6) in 1998/9, both significantly less than in 1988. A statistically significant upward trend with time was found in the number of patients referred with an assessment of cup/disc ratio and in those with details of a visual field assessment. The overall 'true positive diagnosis' was 40% (42/105) in 1997 and 32.3% (33/102) in 1998/9 after the guidelines (p = 0.32), both of which were significantly lower than the 1988 rate of 56% (34/75) (p = 0.03 and 0.003). Fifty per cent of false positive referrals in both 1997 and 1998/9 were associated with an assessment by the optometrist of the optic disc(s) that was at variance with the ophthalmologist's. False positive visual fields were associated with 22% and 35% of non-true positive referrals in 1997 and 1998/9. Protocol violations were observed in 48% of referrals after the guidelines had been disseminated. When the referral was both a false positive and the guideline protocol was not followed, 88% of violations were associated with IOP measurement in 1997 and 73% in 1998/9. The equivalent figures for visual field violations were 70% in 1997 and 76% in 1998/9. Normal individuals referred as suspects were significantly (p = 0.001) less likely to be referred on IOP grounds if their optometrist followed the referral protocol.
Conclusion: Local dissemination of glaucoma screening guidelines with a protocol for referral did not appear to improve the diagnostic accuracy of optometrists in our area. Optometrists who follow the guidelines refer fewer normal individuals on IOP grounds, but false positive visual fields and optic disc interpretation difficulties remain a factor in such referrals. Additional strategies will be necessary to improve the quality and accuracy of referrals for suspect glaucoma by optometrists.