Agreement in assessing glaucomatous discs in a clinical teaching setting with stereoscopic disc photographs, planimetry, and laser scanning tomography

Purpose: Agreement between three observers-two recently trained fellows and their supervisor-was measured using estimations of cup/disc ratio from ste reoscopic optic nerve head photographs and planimetric measurements of cup/ disc ratio. Agreement between the clinicians' planimetric measurements of c up/disc ratio and laser scanning tomographic measurements of cup/disc ratio also was assessed. Methods: From 16 stereoscopic optic nerve head photographs of 16 subjects, the three observers performed clinical estimations of horizontal and vertic al cup/disc ratios and planimetric measurements of cup/disc ratios. Interob server agreement was measured using intraclass correlation coefficients (IC Cs). Agreement between the planimetric cup/disc ratios and laser scanning t omographic cup/disc ratios obtained with the Heidelberg Retina Tomograph (H RT; Heidelberg Engineering, Heidelberg, Germany) also was measured using IC Cs. The difference between the planimetric and HRT cup/disc ratios was calc ulated. Results: The agreement between observers for clinical estimations from ster eoscopic optic nerve head photographs (ICC = 0.74 horizontally and 0.83 ver tically) was substantial. Agreement between the observers' planimetric meas urements of cup/disc ratio was substantial (ICC = 0.79). Agreement between HRT cup/disc ratio and each observer's planimetric cup/disc ratio was moder ate (ICC = 0.57-0.65), with large confidence intervals. The cup/disc ratio measured with HRT was an average of 0.07 to 0.11 larger than the planimetri c cup/disc ratio. Conclusion: Substantial agreement between observers can be achieved when es timating cup/disc ratios with stereoscopic optic nerve head photographs and with planimetric measurements of cup/disc ratios, provided there is a stan dard protocol and sufficient training period. Good agreement is critical in a teaching institution to ensure accurate follow-up care of patients with glaucoma, especially if patients are examined by different clinicians. Lase r scanning tomography is a more repeatable and objective method, which may provide further standardization of optic nerve head assessments. Future stu dies will determine the reference plane that optimizes agreement between th e HRT findings and each clinician's estimations.