Validating and Updating the OHTS-EGPS Model Predicting 5-year Glaucoma Risk among Ocular Hypertension Patients Using...

Area of Science:

• Ophthalmology
• Public Health
• Biostatistics

Background:

• Ocular hypertension (OHT) is a precursor to glaucoma, a leading cause of irreversible blindness.
• Accurate risk prediction models are crucial for timely intervention and glaucoma prevention.
• The Ocular Hypertension Treatment Study-European Glaucoma Prevention Study (OHTS-EGPS) model is widely used but requires external validation.

Purpose of the Study:

• To externally validate and update the OHTS-EGPS risk prediction model for glaucoma conversion.
• To assess the model's performance in a large, contemporary English population using electronic medical records (EMR).
• To improve glaucoma risk prediction by refitting the OHTS model with local data.

Main Methods:

• Utilized EMR data from 9030 OHT patients across 10 English hospital glaucoma services.
• Included risk factors such as age, ethnicity, IOP, corneal thickness, and visual field parameters.
• Defined glaucoma conversion based on visual field tests and need for glaucoma surgery.
• Employed meta-analysis to pool discriminative ability (c-index) and calibration (calibration slope).

Main Results:

• The OHTS-EGPS model showed a pooled c-index of 0.61, indicating limited discriminative ability.
• The pooled calibration slope was 0.45, suggesting poor calibration.
• A refitted model demonstrated improved performance with a pooled c-index of 0.67.
• 16.9% of OHT patients converted to glaucoma during the follow-up period.

Conclusions:

• External validation revealed suboptimal performance of the OHTS-EGPS model in this English cohort.
• Refitting the model led to modest improvements in predicting glaucoma conversion.
• Caution is recommended when applying the OHTS-EGPS model to populations dissimilar to those in the original studies.