Agreement in Assessing Cup–To–Disc Ratio Measurement Between Stereoscopic Optic Nerve Head Photographs, Heidelberg Retinal Tomography, and Optical Coherence Tomography

Abstract

Abstract: : Purpose: To compare the level of agreement between subjective and new version of objective methods in estimating horizontal and vertical cup–to–disc ratio (HCDR and VCDR respectively) among healthy controls and patients with glaucoma. Methods: Fifty–one glaucoma patients and 49 controls underwent full ophthalmic examination, stereoscopic optic nerve head photographs, confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomography II (HRT II)) and optical coherence tomography (OCT 3). The HCDR and VCDR were evaluated subjectively using optic nerve head stereophotos (ONHP) by three masked observers and objectively with HRT II and OCT 3. Results were compared using intraclass correlation coefficient (ICC) for the agreement among methods. ANOVA was used to compare the HCDR and the VCDR mean estimates between techniques. Results:The ICC among the three clinicians were 0.72 and 0.69 for the HCDR of the OD and OS respectively, and 0.71 for the VCDR of either eye. Among the three methods the ICC were 0.68 and 0.65 for the HCDR and 0.77 and 0.67 for the VCDR (OD and OS respectively). The mean CDR estimates among the three methods were similar for either the OD or OS. For the HRT II, OCT 3, and ONHP respectively the mean HCDR was 0.53±0.19, 0.59±0.18, and 0.45±0.22, and the mean VCDR was 0.42±0.21, 0.51±0.17, and 0.47±0.23. All comparisons of mean VCDR and HCDR were significantly different at the p<0.0001 across the methods. Conclusions: Quantitative instruments may provide an equivalent and more reproducible estimation of CDR. The HRTII provides a lower VCDR than subjective assessment, while the OCT 3 estimates a larger VCDR than the other two techniques.

Keywords: clinical research methodology • optic disc