Frequency of the vertical cup-to-disc ratio to normal optical disc size

Abstract

The relationship between the optic disc area and the vertical cup/disc ratio is presented by means of a graphic nomogram after studying a total of 365,356 normal optic nerves. For this purpose, the Laguna ONhE application was used, which analyses the distribution of hemoglobin based on the colorimetric analysis of fundus color images. The 1%, 5%, 50% and 95% percentiles are given for disc areas between 1 mm² and 4 mm². The highest cup-to-disc ratios (1%–5% percentiles) were close to 0.7 for large discs, while for more common sizes (1.9–2.0 mm²) they were close to 0.6 and for small ones to 0.5. Data allowed the Laguna ONhE Globin Discriminant Function (GDF) index to be corrected, in such a way that it could, then, be verified in 544 normal eyes that it was less dependent on the vertical cup/disc ratio, whereas in 436 confirmed and suspected glaucoma an intimate relationship was reported.