Longitudinal CD Ratio Unreliable for Monitoring Glaucoma Progression

Despite the measurement being routinely documented in EHRs, researchers found that longitudinal changes in cup-to-disc ratio were poor at differentiating glaucomatous progression on structural and functional testing. Therefore, they suggested, the requirement to report CDR annually may have limited clinical value. Photo: Andrew Rixon, OD. Click image to enlarge. The progressive nature of glaucoma warrants continual monitoring, requiring both functional assessments—typically through standard automated perimetry—and structural evaluations via OCT. While eyecare physicians are required to report cup-to-disc ratio (CDR) in glaucoma patients’ electronic health records, the clinical utility of this metric remains ambiguous. In a new study, published in American Journal of Ophthalmology, researchers aimed to assess whether longitudinal change in CDR can effectively predict disease progression. Its findings revealed that most eyes with significant changes in CDR were not classified as progressors according to OCT and SAP data.The retrospective cohort analysis used the Bascom Palmer Glaucoma Repository, which encompasses over 70,000 subjects evaluated for glaucoma. The research included adult subjects (≥18 years) diagnosed with primary open-angle glaucoma or normal-tension glaucoma, as well as glaucoma suspects. The demographics of the analyzed eyes revealed a mean age of 67.1 years, with 16.4% identifying as Black and 27.3% as Hispanic.Researchers analyzed 19,034 OCT tests from 3,313 eyes of 2,017 subjects and 13,237 visual fields from 2,174 eyes of 1,399 subjects over a mean follow-up period of approximately 5.5 years. The change in CDR was calculated as the difference between final and baseline CDR, sourced from EHRs.The results showed that only 7.1% of eyes classified as OCT progressors and 4.8% of non-progressors demonstrated a change in CDR ≥0.20. The change explained only 2% of the variation in OCT retinal nerve fiber layer slopes, leading to an area under the curve of 0.55—an indication of poor predictive ability.The perimetry results echoed this trend, showing that 7.7% of progressors had change in CDR ≥0.20. This was not statistically significant, with such change accounting for a mere 1% of the variability. With a specificity of 90%, the CDR change demonstrated a sensitivity of 16% for identifying visual field progressors.“Longitudinal CDR data performs similar to random selection in identifying glaucoma progression on both structural and functional testing,” the researchers noted in their paper. Given this weak association, they urge optometrists to rely on a comprehensive assessment that integrates both optic nerve head examination and ancillary testing to determine glaucomatous progression.“We would encourage national leadership to review the evidence supporting CDR reporting and consider alternative metrics with greater clinical relevance as part of Merit-based Incentive Payment System (MIPS) quality measures,” the study authors concluded.Click here for the journal source. Kamdar A, Medeiros FA, Swaminathan SS. Inefficacy of longitudinal cup-to-disc ratio measurements in identifying glaucoma progression. Am J Ophthalmol. July 11, 2025. [Epub ahead of print].