Radial peripapillary capillaries of the retina. I. Anatomy: human and comparative.

Abstract

DESCRIBED herein is a superficial layer of capillaries which occupies the peripapillary region of the retina in man and some animals.These vessels have received but scant attention in the past (Michaelson, 1954; Toussaint, Kuwabara, and Cogan, 1961; Franqois and Neetens, 1962), and then only in man.They may play an important role in some ocular disorders, and since their distribution and arrangement differ from that of the other capillaries of the retina they deserve a particular connotation.The most apt term for them would appear to be "radial peripapillary capillaries of the retina" (RPC) (Michaelson, 1954).This paper describes the RPC layer in man, rhesus monkey, cat, and pig.Material and Method Whole Indian ink-injected retinae of man (3 retinae: two from normal adults, one from a patient with hypertension), rhesus monkey (2 retinae), cat (20 retinae), and pig (4 retinae) were mounted on slides either in water or in glycerin jelly, and examined with the dissecting and light microscope.Descriptions of the inking and mounting procedures can be found in previous publications (Ashton, 1950;Henkind, 1966). ObservationsAll the specimens examined had a fairly well defined lamina of radial peripapillary capillaries, but there were species differences in the distribution and configuration of the vessels. ManExamination of flat, ink-injected human retinae with the low power (x 6) of the dissecting microscope revealed a particularly dense aggregation of small calibre vessels surrounding the optic nerve-head (Fig. 1, overleaf).These were most prominent immediately around the disc and in the infero-and supero-temporal segments adjoining the nerve-head (Fig. 2a, b, overleaf) where the configuration resembled a double Bjerrum arc (pointed out by Toussaint and others, 1961); to a lesser extent they could be seen infero-and supero-nasally (Fig. 2c), and they were not seen in the fovea or perifoveal region of the macula (Fig. 2d).Fig. 3 (overleaf) illustrates the distribution of these vessels in human eyes.