The configuration of peripapillary tissue in unilateral glaucoma

We compared the peripapillary scleral and choroidal halos and crescents in the two eyes of 42 patients with unilateral glaucoma. In most cases, the edge of the three tissue layers (the retinal pigment epithelium [RPE], the choroid, and the sclera) that encircle the optic nerve head of the glaucomatous eye superimposed exactly on the mirror images of the edges in the fellow nonglaucomatous eye. Although the size of the peripapillary crescent or halo was the same in both eyes, it and the scleral rim were often more conspicuous in the eye with glaucomatous damage because the tissue edges were seen more easily through the reduced thickness of nerve fiber layer tissue. There were nine exceptions. In five cases, the peripapillary choroidal crescent (the area of choroid not covered by RPE) was larger in the glaucomatous eye. In four eyes, however, the crescent was larger in the nonglaucomatous eye, although the magnitude of the asymmetry was less in these four cases. Thus, in late stages of optic nerve damage, there was some RPE atrophy, but in most cases of glaucoma, the area of bared choroid was the inherent anatomic configuration of the optic nerve exit canal.