A Theoretical and Practical Treatise on AstigmatismJ.H. Chambers & Company, 1887 - 245 pages |
Contents
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Other editions - View all
Theoretical and Practical Treatise on Astigmatism (Classic Reprint) Swan M. Burnett No preview available - 2018 |
A Theoretical and Practical Treatise on Astigmatism Swan M 1847-1906 Burnett No preview available - 2016 |
Common terms and phrases
accommodation ametropia anomaly appear asthenopia astig astigmatic eye atropine auxiliary lens axes ciliary muscle circles concave concave lens condition conic convex convex lens cornea corneal astigmatism correcting glasses corresponding curved cylindrical lens degree of astigmatism diagnosis diameter difference diffusion dioptries direct method disk distinct Donders edge ellipse ellipsoid emmetropic faulty meridian focal distance focal interval focal line foci focus form of astigmatism fundus gives glasses and direction horizontal meridian hypermetropic inches incident ray indistinct inverted image irregular Javal keratoconus keratometer keratometry KERATOSCOPIC lenses light matism measurements meridian of greatest millimetres mirror movement mydriatic myopic nodal points normal object oblique observer Ophth ophthalmoscope parallel passing patient perpendicular placed plane position principal meridians pupil radius of curvature rays coming refracting power refracting surface regular astigmatism retina retinal image right angles rotated seen simple Snellen's fan spherical lens tion tism vertical meridian vessels vision visual axis
Popular passages
Page 117 - REFRACTION OF THE EYE: Its Diagnosis, and the Correction of its Errors, with Chapter on Keratoscopy.
Page 150 - MM in my left eye, was not circular, as it is in the eye which has no other defect than that of being near-sighted, but elliptical, the major axis making an angle of about 35° with the vertical, and its higher extremity being inclined to the right.
Page 185 - VIL fig. 1.) as a regular surface, resembling very much that of a hyperboloid ; for the only indistinctness occasioned by a cornea of this form, would arise from the concentration of the rays before they fell upon the retina. When I had the pleasure of examining the eye itself, the difficulty of explanation was in no respect diminished. In every aspect in which the cornea could be viewed, its section appeared to be a regular curve, increasing in curvature towards the vertex ; a form which could produce...
Page 109 - has been sometimes led to the discovery of tegular astigmatism of the cornea, and the direction of the chief meridians by using the mirror of the ophthalmoscope much in the same way as for slight degrees of conical cornea. The observation is more easy if the optic disc is in the line of sight and the pupil large. The mirror is to be held at...
Page 122 - Knowing now the size of the object, the size of the image and the distance...
Page 151 - All these circumstances indicated that the refraction of the eye was greater in its plane nearly vertical, than in that at right angles to it, and that, consequently, it would not be possible to see distinctly by the assistance of lenses with spherical surfaces.
Page 150 - I found also that if I drew upon paper two black lines crossing each other at right angles, and placed the paper in a proper position, and at a certain distance from the eye, one line was seen perfectly distinct, while the other was barely visible...
Page 9 - Fig. 86, and shall lie on the longest line that can be drawn in the ellipse which is called the major axis; the shortest line is called the minor axis; and is perpendicular to the major axis at its middle point...
Page 185 - When you first mentioned to me the case of Miss , I was much surprised at the number of images which she observed round luminous objects. As this multiplication of images could arise only from some irregularity in the cornea, or crystalline lens, which gave their surface the form of a polyhedron, it was completely inexplicable from the shape of the cornea itself, which your drawing represented (see Plate VIL fig.
Page 151 - To discover the necessary data, I made a very fine hole with the point of a needle in a blackened card, which I caused to slide on a graduated scale; then strongly illuminating a sheet of paper, and holding the card between it and the eye, I had a lucid point upon which I could make observations with great ease and exactness.