Page:Plates illustrating the natural and morbid changes of the human eye.djvu/24

18 be that atrophic changes of the optic nerve prevent the free return of blood from the retina, and give rise to the varicose condition of its veins.)

The retina is transparent. The brownish irregular-shaped defined patches are situated beneath the retina, and represent groups of stellate pigment cells of the choroid (their shape is not correctly represented). The blood in the choroid (the brilliant red colour in the figure) and in the retinal vessels has a peculiar cherry-red tint, which has repeatedly been observed with this state of the optic nerve.

This form of anæmia and atrophy of the optic disc occurs, as a rule, in both eyes, and is observed in amaurosis from cerebral causes, and especially in the form described as "Tobacco amaurosis."

Fig. 9

''Inflammation of the optic disc. The swollen optic disc. Neuritis optica.''

Bight eye. The optic disc and the tunics immediately adjoining it. The oval-shaped optic disc occupies the middle of the figure. Its centre appears white, the rest greyish-white, opaque, and unusually projecting (towards the vitreous chamber). The margin of the disc is slightly ill-defined; it shades off—and more so in some places than in others. This appearance of the optic disc is caused by swelling of its connective tissue.

Many of the retinal blood-vessels are lost sight of, others are less distinct where they pass from the optic disc upon the retina; some are unusually bulged forwards, like the surface of the disc. The arteries and veins appear numerous. Many of the latter are tortuous and much enlarged in the retina (probably through the return of blood from the retina into the optic disc being somewhat impeded by the swelling, &c., of the disc). The blood-vessels appear thin in the disc itself.

The retina and choroid round the optic disc appear healthy.

The stage of acute inflammation of the optic disc, as represented in Pig. 9, is preceded by hyperemia and followed by atrophy. In all cases, hitherto observed, the change of the optic disc appeared in both eyes, with grave cerebral disturbances (as a rule, with tumour at the surface of the cerebellum.)