Photogrammetric analysis of volume asymmetry of the optic nerve head cup in normal, hypertensive, and glaucomatous eyes.

Recent studies of optic cup volume, depth, and orifice area demonstrated a large overlap of the range of these factors for normal and glaucomatous eyes, suggesting that it is usually not possible to distinguish abnormal disks on the basis of a particualr set of geometric quantifiers. Because of the knowledge that qualitative asymmetry of a person's optic cups may be a sign of glaucoma, calculation of the quantity of cup asymmetry using the aforementioned geometric parameters was undertaken in 90 patients. Results indicated that 90% of the bilaterally normal subjects who were studied and 80% of the ocular hypertensives had less than 0.20 mm3 cup volume asymmetry. In contrast, however, all of the unilateral glaucoma patients in this sample exceeded that value. It therefore appears that measurement of the amount of, volume asymmetry between a person's optic cups may be a useful tool in the diagnosis of glaucoma.