Automatic determination of vertical cup-to-disc ratio in retinal fundus images for glaucoma screening

Abstract

Glaucoma is a chronic progressive optic neuropathy that causes visual impairment or blindness, if left untreated. It is crucial to diagnose it at an early stage in order to enable treatment. Fundus photography is a viable option for population-based screening. A fundus photograph enables the observation of the excavation of the optic disc - the hallmark of glaucoma. The excavation is quantified as vertical cup-todisc ratio (VCDR). The manual assessment of retinal fundus images is, however, time-consuming and costly. Thus, an automated system is necessary to assist human observers. We propose a computer aided diagnosis system, which consists of localization of the optic disc, determination of the height of the optic disc and the cup, and computation of the VCDR. We evaluated the performance of our approach on eight publicly available data sets, which have in total 1712 retinal fundus images.We compared the obtained VCDR values with those provided by an experienced ophthalmologist and achieved a weighted VCDR mean difference of 0:11. The system provides a reliable estimation of the height of the optic disc and the cup in terms of the Relative Height Error (RHE = 0:08 and 0:09, respectively). Bland-Altman analysis showed that the system achieves a good agreement with the manual annotations especially for large VCDRs, which indicate pathology