The correlation of the physiological blind spot and the disc area

Abstract

Peripapillary crescents of choroidal atrophy occur commonly in patients with glaucoma [6], particularly in those with low tension glaucoma [4] and may indicate the part of the optic nervehead that seems to be susceptible to glaucomatous damage [1]. It has been suggested that the absence of a peripapillary choroidal atrophy may indicate a more resistant optic nervehead in which much higher levels of intraocular pressure elevation are required to produce damage. In such resistant discs it is thought that the damage may be manifested by a generalized enlargement of the cup with diminution of the neuroretinal rim indicating diffuse as opposed to localized damage of the nerve. It has not yet been worked out whether peripapillary atrophy occurs as an acquired change together with localized damage, or whether it constitutes a congenital misalignment which makes the tissue more susceptible to the subsequent effects of intraocular pressure. Peripapillary crescents were found to be more common in patients with glaucoma than in normal controls or ocular hypertensives [7]. Some degree of peripapillary chorioretinal atrophy was even reported to be present in all cases of glaucoma [3].

Peripapillary choroidal atrophy also occurs in myopia and is known to occur with age. It has not yet been shown whether the area of peripapillary choroidal atrophy changes with aging, but changes in the peripapillary choroidal crescents in glaucoma are known to occur.

Not all peripapillary crescents are alike as there are several tissue layers which can overlap in a variety of ways. The details of these Variations may be important as they may denote various factors that make optic nerveheads susceptible. Such dfferences have not yet been clearly analyzed.

It was the purpose of this paper to correlate the size of the optic nervehead with the size of the physiological blind spot and to see whether the relationship between them breaks down with age which might indicate a change of size of the peripapillary chorioretinal atrophy with aging.