Validating and updating the OHTS-EGPS model predicting 5-year glaucoma risk among patients with ocular hypertension using electronic medical records: a cohort study.

Background: Ocular hypertension, that is intraocular pressure > 21 mmHg, is a risk factor for glaucoma. A glaucoma risk predictor, the Ocular Hypertension Study-European Glaucoma Prevention Study model, is available. Objectives: (1) To validate and update the Ocular Hypertension Study-European Glaucoma Prevention Study risk prediction model in a United Kingdom population; (2) to assess the relative efficiency of alternative monitoring pathways according to glaucoma risk; (3) to determine the clinical and cost-effectiveness of treating people with ocular hypertension with intraocular pressure of 22 or 23 mmHg and (4) to elicit patient preferences for monitoring. Design: (1) Retrospective data analysis of electronic medical records of ocular hypertension patients attending hospital eye services. The influence of the Ocular Hypertension Study-European Glaucoma Prevention Study predictors and additional ocular and systematic factors was explored. Validation: the Ocular Hypertension Study-European Glaucoma Prevention Study prediction model was applied. Update: the model was refitted by re-estimating baseline hazard and regression coefficients. (2, 3) Predictor versus standard care, with deterministic and probabilistic sensitivity analyses. Subgroup analysis for people with 22-23 mmHg intraocular pressure. (4) Discrete choice experiment. Setting and participants: People with intraocular pressure 22-32 mmHg in either eye, at least four visual field tests, 5 years of follow-up, no significant ocular comorbidities. Data sourced from secondary clinical settings. Main outcome measures: Discriminative ability (c-index) and calibration (calibration slope) to predict conversion to glaucoma in 5 years. Quality-adjusted life-years, incremental cost-effectiveness ratio, preferences. Data sources: Electronic medical records of 10 hospitals in England. Results: (1) Of 9030 patients with ocular hypertension who fitted the inclusion criteria 1530 (16.9%) converted to glaucoma. The Ocular Hypertension Study-European Glaucoma Prevention Study model provided a pooled c-index of 0.61 (95% confidence interval: 0.60 to 0.63). The updated model had a pooled c-index of 0.67 (0.51 to 0.84). (2) In the economic model almost all (99%) patients were treated in the risk predictor strategy, and less than half (47%) in the standard care strategy. The risk predictor strategy produced higher costs, but also higher quality-adjusted life-years and is likely to be cost-effective compared with standard care. (3) Patients with ocular hypertension and intraocular pressure 22-23 mmHg had similar risk of conversion to the rest of the cohort. A treat-all strategy may not be cost-effective. (4) Three hundred and sixty patients were recruited from four NHS hospitals. Almost all respondents (92%) had experienced face-to-face monitoring at a hospital; fewer respondents had experienced virtual clinics (47%) or community optometrist monitoring (43%). Most patients preferred hospital-based monitoring services by health professionals rather than community-based by optometrists but patients with prior experience of community optometrist monitoring preferred it. Patients preferred options associated with lower risk of conversion and lower costs. Limitations: Insufficient data to evaluate influence of ethnicity or ocular factors such as optic disc and retinal anatomy. Conclusions: We validated the Ocular Hypertension Study-European Glaucoma Prevention Study predictor model in a large population with ocular hypertension achieving modest improvements. The use of a risk prediction tool is likely to be cost-effective. Reducing the risk of conversion was the most important preference for patients with ocular hypertension. Future work: Future work should address the influence of genetic or other ocular factors in disease progression, evaluation of effectiveness and cost-effectiveness of different models of eye care, and on how to avoid late glaucoma presentation. Funding: This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number NIHR131808.