Aim: The aim of this study is to determine the outcomes following referral for glaucoma from routine optometric practice and the positive predictive value (PPV).
Methods: A prospective study of 441 referrals for glaucoma in the Portsmouth area was performed over 6 months. A positive outcome was defined when the patient had the diagnosis of glaucoma made or if there was a high index of suspicion of glaucoma requiring follow-up. The PPV was determined from positive outcome number/referral number.
Results: The overall PPV was 0.37 (95% confidence interval 0.33-0.42). Open-angle glaucoma (OAG) was confirmed in 33 (7%) patients. A diagnosis of ocular hypertension was made in 49 (11%) patients and glaucoma suspect in 92 (21%) referrals. Two-thirds of optometrists recorded all 3 assessments: fields, intraocular pressure (IOP) and disc appearance, a figure representing 293 referrals (PPV 0.37). However the greatest referral accuracy was seen when only discs and IOPs were recorded (PPV 0.47). When all three tests were given as reasons for suspicion for glaucoma, the PPV was 0.71. The number of patients diagnosed with OAG from Portsea Island during the study period was 7, whereas the expected number of diagnosed patients was 29.
Conclusion: Wider use of perimetry by optometrists and increased reporting of all three tests has not led to an increase in PPV. There remain a considerable number of undiagnosed patients with glaucoma in the population.