• In an effort to quantitate optic nerve head pallor, a method has been devised to measure pallor-disc ratio using optic nerve head photographs. After electronically scanning photographs through various Wratten filters, it was observed that a red filter produces good contrast between the disc and the retinal surface, while a green filter produces good contrast between the pale area of the disc and the remaining normal-appearing nerve head. A computer program fitted an elliptical form to both the disc region of red image and the pale area of green image. Pallordisc ratios were calculated on both area and radial bases. Reproducibility of 3.5% for the area ratios and 7% for the radial ratios were obtained.
Rosenthal AR, Falconer DG, Barrett P. Digital Measurement of Pallor-Disc Ratio. Arch Ophthalmol. 1980;98(11):2027-2031. doi:10.1001/archopht.1980.01020040879019