Page:Handbook of Ophthalmology (3rd edition).djvu/51

Rh equator and about the posterior pole. In the former position they appear oftenest in the under part of the choroid, in the form of round spots which sometimes, through loss of color and atrophy, are bright red or white, sometimes are noticeable from the dark coloring of the choroidal epithelium; both appearances may be combined, presenting bright spots with black edges. On account of their peripheral position they do not cause much disturbance of vision; they are, however, symptomatic of a predisposition to serious disease.

The changes about the posterior pole of the eye are more frequent. The originally crescentic or annular choroidal atrophy surrounding the disc loses its regular boundaries and spreads irregularly, mostly in the temporal direction.

Insular atrophied spots appear in the neighborhood, and finally coalesce with the principal one. Black, irregular spots, formed evidently of groups of changed choroidal epithelium, often appear upon the white background.

The increase in size of Mariotte's blind spot, under these circumstances, ought scarcely ever to cause disturbances of vision, since the inner layer of the retina remains intact, and therefore the conducting power of the nerves from the periphery is not diminished.

On the contrary, affections of the macula lutea, occurring simultaneously with the above-mentioned changes, or even independent of them, give rise to very serious disturbances of vision. At first, even in eyes whose vision has not yet suffered, there appear a number of irregular bright lines of perhaps the breadth of the principal retinal vessel, or somewhat broader, and of various lengths. These are, perhaps, consequences of the stretching which in places separates the pigment-cells one from another, or flattens, stretches, and depigments them. If central vision is already essentially affected, we generally find changes of an inflammatory nature in the macula lutea, irregularly diffused pigment changes, collections of black pigment interspersed with bright-red or white spots; or exactly in the centre of the macula lutea there may be a black spot, of about the size of the optic disc; or there may be a larger, bluish, elevated spot, perhaps surrounded by a black ring of pigment and often accompanied by hemorrhages in the neighboring retina.