. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. assume that in the focalinterval a series of foci should lie on the obtains only for the beginning and endof this interval. The fasciculus is, as Sturmtaught, contained in a skew surface, and henceit is to be deduced that all the rays refracted inthe different meridians cut one another in thetwo intersecting lines, bounding the beginningand end of the focal interval, and that the above-described transition-forms of the sections of thebundle of light are found in the foca
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. assume that in the focalinterval a series of foci should lie on the obtains only for the beginning and endof this interval. The fasciculus is, as Sturmtaught, contained in a skew surface, and henceit is to be deduced that all the rays refracted inthe different meridians cut one another in thetwo intersecting lines, bounding the beginningand end of the focal interval, and that the above-described transition-forms of the sections of thebundle of light are found in the focal interval. In a recently published essay, Dr. J. H. Knapp(Archiv f. Ophthalmologic, B. viii. Abth. 2,p. 108), led by a remark of Professor Kirchhoff,that by simple analytical geometry of space wecan prove, that a bundle of rays refracted by asym-metrically curved surfaces, must pass throughtwo right lines, has mathematically determinedthe form of the whole refracted bundle ofrays. The form of the cornea leads us to expect, thatit in itself must produce an astigmatism, completely agreeing with that here V V V. 460 ASTIGMATISM. described. This I have, on investigation, found confirmed. For this purposeI have chosen cases in which, in congenital cataract, the lens had beenabsorbed after numerous punctures (so that the question of an alteration ofform of the cornea in consequence of operation could not be entertained), andwhere the pupil had remained quite round. Without exception, the limits of thefocal interval were by these eyes quite accurately defined as fine lines, andthe changes of form of the diffusion-images were also given, agreeably tothe theory. From the direction of the lines bounding the focal interval, themaximum and minimum of curvature of the cornea were immediately dedu-cible. Fig. 155 indicates the direction found in cases of aphakia in youngsubjects ; D represents a right, S a left eye ; h li is the diffusion-image atthe anterior, v v at the posterior boundary
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