On long, short, and weak sight

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J. & A. Churchill, 1873 - 254 pages
 

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Page 74 - Every progressive myopia is threatening with respect to the future. If it continues progressive, the eye will soon, with troublesome symptoms, become less available, and, not unfrequently, at the age of fifty or sixty, if not much earlier, the power of vision is irrevocably lost...
Page 25 - ... ie, adjusted for its far point — of bringing certain rays to a focus upon the retina without any active effort or participation of the muscular apparatus of accommodation. This power of refraction is due to the form of the eye and to its different refracting media.
Page 206 - has been sometimes led to the discovery of regular 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 27 - The refractive power of the eye is so low, or its optic axis so short, that when the eye is in a state of rest, parallel rays are not united upon the retina, but behind it, and only convergent rays are focussed upon the latter.
Page 229 - The action of the Calabar bean, and its peculiar effect upon the pupil, were fully investigated in 1862, by Dr. Fraser,* in his valuable graduation thesis for the University of Edinburgh, on the " Characters, Actions, and Therapeutic uses of the Ordeal Bean of Calabar.
Page 158 - IT has been already stated (p. 27) that by the term hypermetropia is meant that peculiar condition of the eye in which its refractive power is too low, or the optic axis too short, so that the focal point of the dioptric system lies behind the retina, and, when the eye is in a state of rest, even parallel rays are not brought to a focus upon the retina, but behind it, and only convergent rays are united upon the latter. The emmetropic eye unites parallel rays upon the retina without any effort of...
Page 39 - In the myopic eye, it will be remembered, the state of refraction is too great, or the optic axis too long, so that when the eye is in a state of rest, the focus of the dioptric system lies in front of the retina, and parallel rays (emanating from objects at an infinite distance) are brought to a focus before the retina, and only more or less divergent rays are united upon the latter. " Now, in hypermetropia we have just the reverse of this. The refractive power of the eye is so low, or its optic...
Page 143 - ... the tendon, and only a portion of the latter be caught up ; the direction of the point should, therefore, be rather upwards and inwards. When the tendon has been secured on the hook, the conjunctiva which covers its upper portion may be gently pushed off with the points of the scissors, so as to expose the tendon, which is then to be carefully snipped through with the scissors as closely as possible to its insertion. When it has been completely cut through, the conjunctiva is to be slightly elevated...
Page 60 - ... appear to find their explanation chiefly in the fact that the inner tunics of the eyeball become congested...
Page 37 - The circular fibres of the ciliary muscle exert a pressure upon the edge of the lens, by means of which the latter becomes thicker." 2. "The longitudinal fibres of the muscle cause an increase of tension in the vitreous humor, on account of which the posterior surface of the lens is prevented from shifting and the action of the peripheral pressure is chiefly confined to the anterior surface...

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