In this study the authors aimed to assess the variability of the well documented risk model from the Ocular Hypertension Treatment Study (OHTS) that identified higher intraocular pressure (IOP), older age, lower central corneal thickness (CCT), greater vertical cup-to-disc ratio (VCDR), and worse pattern standard deviation (PSD) on visual field analysis as independent risk factors for the onset of primary open-angle glaucoma (POAG). They attempted to assess the variability of the OHTS glaucoma risk prediction model in OHT subjects by applying updated risk factor information obtained during follow-up and measuring the variability in the calculated risk over time not just at baseline. This was a prospective longitudinal study over 60 months of 27 patients (54 eyes). Their results showed that seven individuals converted to POAG during the follow-up. At baseline the mean risk of conversion was 14.0 (12%); over the course of follow-up in this study the mean calculated risk was 13.4 (10.7%). The authors showed that there were substantial fluctuations from visit to visit and that reliance on baseline characteristics assumes that risk of progression is linear. Further work is needed to define the frequency with which updated risk factors should be incorporated into prediction models.