. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. Fiff. : = In the former case divergent (dotted in Fig. 52), in the latter con-vergent rays (dotted in Fig. 53) come to a foens on the retina. In thefirst case, therefore, in the condition of rest, ohjects are accuratelyseen which are situated at a definite finite distance (Fig. 52 i); inthe second they are at no distance accurately seen, for the rays infalling upon the cornea must, in order to unite in the retina, alreadyconverge towards a point situated behind the eye (Fig.
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. Fiff. : = In the former case divergent (dotted in Fig. 52), in the latter con-vergent rays (dotted in Fig. 53) come to a foens on the retina. In thefirst case, therefore, in the condition of rest, ohjects are accuratelyseen which are situated at a definite finite distance (Fig. 52 i); inthe second they are at no distance accurately seen, for the rays infalling upon the cornea must, in order to unite in the retina, alreadyconverge towards a point situated behind the eye (Fig. 53 i). In thefirst case the farthest limit lies within the normal measure : themeasure is too short, and the condition might, therefore, be calledbrachymetropia. In the second case, the boundary lies beyond themeasure, and I have, therefore, called this state hypermetropAa. Hence it is perfectly clear, that brachymetropia and hypermetropiaare two opposite conditions. The definitions are now extremely simple : the posterior principalfocus <p of the media of the eye at rest falls :— in emmetropia on the most external
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Keywords: ., bookcentury1800, bookdecade1860, bookidonanomalieso, bookyear1864
