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appear aqueous humour asthenopia astigmatism becomes blind brain bring cataract cause centre child colour-blind colours concave glasses consequence constant convergence and accommodation convex glass convex lens cornea course cure curvature danger defective vision denser medium disease arises distant objects divergent rays double vision easily emmetropic eye eye-balls eye-diseases eye-lids eyelid eyesight focus focussed formed green habit human eye humour Hypermetropia inches indistinct infant inflammation injury interior Iris lamps large number lenses lids look medium less merely metropia muscles myope natural lens Night-blindness notice oculist ophthalmic optician ophthalmic surgeon ophthalmologist ophthalmoscope optic nerve overstrained owing pain pair of spectacles panthoscopic spectacles parallel rays patient patient's eye perpendicular person Presbyopia pupil Railway rays of light refraction remedy require seen shade short distance short-sighted soon squint Strabismus strain suffering from myopia suit suitable spectacles surface transparent turn visual axes vitreous humour weak sight yellow spot
Page 38 - This,jn its turn, produced giddiness; and the giddiness produced headache and sickness by disturbing the circulation. The strained muscles which had once given way became prompt to give way again when they were unduly called upon ; and the grave view which was taken of the symptoms by medical men...
Page 78 - By taking two of the old-fashioned highlycurved watch glasses, and fixing them in a ring with their concavities outwards, we enclose a portion of air of the shape of a double concave lens. Immersed in water, this air lens will refract the rays of light from objects reaching it through the water, convergently. It will resemble in its optical properties a double convex glass lens in air, as I have explained above (§ 20).
Page 37 - ... most complete possible rest to his brain, he was advised to make a voyage to Australia and back. He did so, and returned in the same condition. He was then considered to be incurable ; was told that he must abandon a career which had been open to him, and a matrimonial engagement which had been formed.