. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. whereof respectively the points v v and h tiare the most external. After the refrac-tion both approach the visual axis (whichperpendicular to the plane of the drawingpasses through a), v v does so, however,more rapidly than h Ji. Before union they therefore lie, in the. FOCAL INTERVAL OF STURM. 453 ellipse A, as in Pig. 151, and where v v meet in one point B,h ti have not yet come to a focus. Thereupon we now find in fti Fig. 151. A B C D E F v f v V V V/ K-^ti V A ©A V 1%; V h --
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. whereof respectively the points v v and h tiare the most external. After the refrac-tion both approach the visual axis (whichperpendicular to the plane of the drawingpasses through a), v v does so, however,more rapidly than h Ji. Before union they therefore lie, in the. FOCAL INTERVAL OF STURM. 453 ellipse A, as in Pig. 151, and where v v meet in one point B,h ti have not yet come to a focus. Thereupon we now find in fti Fig. 151. A B C D E F v f v V V V/ K-^ti V A ©A V 1%; V h 7 V r; HA y succession v v already intersected, h ti approached to one another,C, D, and E; further, h ti united in one point, and v v after inter-section more widely separated, E; finally, both intersected, G. Thefocus of v v therefore lies most anteriorly, that of h ti most posteriorly,in the axis. The space between these two points, where rays of differentmeridians intersect, may be called focal interval {intervalle focal, orBrennstrecke of Sturm). From the above figures it is now evident, what successive formsthe section of the cone of light will exhibit. In the middle ofthe focal interval, D, it will be nearly round, and anteriorly throughoblate ellipses, C, with increasing eccentricity, it will pass into a hori-zontal line, B ; posteriorly through prolate ellipses
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Keywords: ., bookcentury1800, bookdecade1860, bookidonanomalieso, bookyear1864
