Aim: To determine the inter-observer agreement in assessing vertical cup: disc ratio (VCDR) by using 78D lens with slit-lamp eyepiece measuring graticule (SLMP) and direct ophthalmoscope with standard photo (DOSP).
Methods: Four hundred and seventy-seven eyes of 257 subjects form one random selected community districts were examined. Two observers performed clinical estimations of VCDR. The cup to disc ratio (CDR) was assessed by slit-lamp biomicroscopy using a 78D lens and measuring eyepiece graticule (SLMP) and also by direct ophthalmoscope with standard photo (DOSP).
Results: The 95% limits of agreement on VCDR between observers was -2.2 to approximately +2.8 for SLMG, and -3.3 to approximately +3.8 for DOSP. DOSP method consistently overestimates the VCDR compared with the SLMG. The inter-observer agreements on disc and cup diameter estimation using SLMP were -4.3 to approximately +4.5, -7.2 to approximately +6.2 units respectively. The bias was not proportional to VCDR level.
Conclusion: 78D lens with slit-lamp eyepiece measuring graticule has a smaller inter-observer variability compared with direct ophthalmoscope with standard photo. This method is a more repeatable and cost-effective method of optic disc estimation in clinical and screening assessment.