The student's guide to diseases of the eye . ary to disease of the optic nerve (optic neu-ritis, progressive atrophy, and glaucoma) only thelayers of nerve-fibres and ganglion-cells are atro-phied, the outer layers being found perfect, even aftermany years. A retina atrophied after retinitis oftendoes not regain perfect transparency, and if there havebeen choroiditis the retina remains especially hazyin the parts where this has been most severe. The disc in atrophy following retinitis or choroido-retinitis always passes into atrophy, often of peculiarappearance, being pale, hazy, homogeneous-l
The student's guide to diseases of the eye . ary to disease of the optic nerve (optic neu-ritis, progressive atrophy, and glaucoma) only thelayers of nerve-fibres and ganglion-cells are atro-phied, the outer layers being found perfect, even aftermany years. A retina atrophied after retinitis oftendoes not regain perfect transparency, and if there havebeen choroiditis the retina remains especially hazyin the parts where this has been most severe. The disc in atrophy following retinitis or choroido-retinitis always passes into atrophy, often of peculiarappearance, being pale, hazy, homogeneous-looking,and with a yellowish or brownish tint (p. 175). Detachment (separation) of the retina.*—As there isno continuity of structure between the choroid andretina, the two may be easily separated by effusion ofblood or serous fluid, the result either of injury ordisease, by morbid growths, and by the traction offibrous cords in the vitreous. Such fibrous bandsand strings develope in the vitreous in some cases of DISEASES OF THE RETINA 189. Fig. 76.—Section of eyewith partial detach-ment of retina. irido-cyclitis, and perhaps in myopic eyes withoutsigns of inflammation. Occasionally rents may beseen in the separated retina. It has been suggestedthat such rents occurring whilst the retina was stillin situ might initiate the detachment by allowing theintrusion of vitreous betweenthe retina and choroid; andthis explanation may possiblyhold good in very myopic retina is separated at theexpense of the vitreous (whichis proportionately absorbed),but always remains attachedat the disc and ora serrata,unless as the result of woundor great violence. The depth,area, and situation of the de-tachment are subject to much variety. Fig. 76 shows a diagrammatic section ofan eye in which the lower part of the retina is se-parated. The separated portion is usually far within thefocal length of the eye ; its erect image is, thereforevery easily visible by the direct method (p. 49, 1),
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Keywords: ., bookcentury1800, booksu, booksubjecteye, booksubjectophthalmology
