The American encyclopedia and dictionary of ophthalmology Edited by Casey AWood, assisted by a large staff of collaborators . ds of white glass are exposed formany years to the suns rajs they assume a light purplish (ame-thyst) color, and are then useful in the manufacture of tintedlenses and other forms of eye proteetives. The amethyst color inthe glass (due to chemical changes in its constituents) is also pro-duced in a short time artificially, as it were, and is doubtless quiteas efficient for the purpose as the variety first described. 310 AMETHYSTVIOLETT Amethystviolett. (G.) Amethyst vio
The American encyclopedia and dictionary of ophthalmology Edited by Casey AWood, assisted by a large staff of collaborators . ds of white glass are exposed formany years to the suns rajs they assume a light purplish (ame-thyst) color, and are then useful in the manufacture of tintedlenses and other forms of eye proteetives. The amethyst color inthe glass (due to chemical changes in its constituents) is also pro-duced in a short time artificially, as it were, and is doubtless quiteas efficient for the purpose as the variety first described. 310 AMETHYSTVIOLETT Amethystviolett. (G.) Amethyst violet. Ametrometer. An instrument for measuring ametropia, or errors ofrefraction. Ametrometer, Thomsons. This instrument has two small gas-flamesabout five millimeters in diameter, one stationary and the othermovable on a metal arm, which can be changed or revolved to anymeridian. Each eye is tested separately at a distance of twentyfeet, preferably under a cycloplegic. The method of the test is tomove one flame along the metal arm until the two lights appear tofuse. The scale, as marked on the arm, gives the approximate. Thomsons Ametrometer. strength of lens necessary to correct the ametropia. By raising orlowering the arm any meridian may be tested. It is a most ingen-ious test, but not in common use. (Thorington.) Ametropia, Adjunct treatment of. See Adjunct treatment of ame-tropia. Ametropia, or abnormal refraction. When the eye is in a state ofrest, parallel rays of light come to a focus not on but at some pointbehind or in front of the retina and instead of presenting a clearimage of the object looked at, vision is blurred and indistinct andthe eye has to exert its accommodative power to see clearly, therebycausing fatigue and other symptoms of discomfort, setting up acondition known as asthenopia. Ametropia is divided into 1. Hypermetropia, 2. Myopia, 3. Astig- AMETROPIA, OR ABNORMAL REFRACTION 311 matism, Avhicli Edward Jackson prefers to call astigmia. In thefirst, whe
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectophthalmology, bookye
