Optic Disc and EarIy Glaucomatous Visual Field Loss

ABSTRACT

In the early stages of glaucoma the disc changes prior to the visual field loss, so assessment of the optic disc is very important for the evalutation of the glaucoma patient. The most senstitive techniques for detecting changes of the optic disc require highly sophisticated instruments, such as computerized image analyzer, which are expensive and not generally available in clinical practice. Less expensive, but reliable, is color stereoscopic photography. The aim of this topic is to assess glaucomatous discs and look for the features of the optic disc that are commonly associated with early visual field defect. Forty-three eyes of 28 patients were included in this investigation. The criteria for inclusion were a cup/disc(C/D) ratio more than 0.4 by direct ophthalmoscopy, no visual field defect with Goldmann perimetry, and open anterior chamber angle. Each optic disc was photographed with a Canon fundus camera with Polaroid 600 Plus. Each photographic set was then examined stereoscopically for morphologic parameters: 1) comparison of vertical versus horizontal C/D ratio; 2) presence of nasal cupping; 3) presence of overpassing vessels; 4) presence of baring of circumlinear vessles; 5) presence of peripapillary atrophy; 6) ratio of the thinnest neuroretinal rim(NRR) width in the vertical sectors to the NRR width of the temporal sector. All subjects were examined for central visual field with the automated static perimeter, Humphrey program C 30-2 with STATPAC. The C/D ratio estimated by direct ophthalmoscopy consistently showed smaller C/D ratio than that by the stereophotographic method. Parameter with highest probability value to differentiate between the optic disc of early visual filed loss and the optic disc of normal subjects was "Ratio of the thinnest NRR width in the vertical sectors to the NRR width of the temporal sector