Quantitative assessment of optic disc photographs in normal and open-angle glaucoma patients

Abstract

Background: The purpose of the study was to quantitively assess the optic nerve head (ONH) parameters from fundus photographs in normal and open-angle glaucoma patients and to compare them with those provided by spectral-domain optical coherence tomography (SD-OCT). Material and methods: This study compares 30 glaucomatous eyes to 30 healthy control eyes. One eye from each subject was randomly enrolled. From color photographs, different parameters were measured using image processing software (Adobe Photoshop CS6) after delimiting the boundaries of the optic disc and the excavation. The correlation between these measurements and those obtained by SD-OCT was evaluated. Results: Glaucomatous and normal patients groups were comparable in terms of age (p = 0.94), sex (p = 0.57), presence of diabetes (p = 0.52), hypertension (p = 0.40), and smoking (p = 0.67). The areas of the optic disc and the cup were significantly larger in glaucomatous patients (p = 0.004 and p < 0.001, respectively). The area of the neuroretinal rim was smaller in glaucomatous patients (p < 0.001). The vertical and horizontal cup-to-disc ratios were larger in glaucomatous patients (p < 0.001). The thicknesses of the rim in the four meridians were significantly reduced in the glaucoma group. The “ISNT” rule was fully respected in 87% of normal eyes and in only 2 cases (7%) of the glaucoma group (p < 0.001). There was an excellent correlation between different measurements obtained on photography and those provided by the SD-OCT. Pearson’s correlation coefficient was R = 0.95 (p <0.0001) for the optic disc area, R = 0.94 (p < 0.0001) for the rim area, and R = 0.98 (p < 0.0001) for the vertical cup-to-disc ratio. Conclusion: Color photography is very useful in the diagnosis and monitoring of glaucoma. The determination of normative values can further corroborate its interest in this indication. Despite the relatively high interobserver variability, ONH parameters obtained on photography showed excellent correlation with those measured by OCT