Eyesight in schools : a paper read before the Association of Medical Officers of Schools, on April 15th, 1885 / by R. Brudenell Carter.

Carter, Robert Brudenell, 1828-1918.

Date:: 1885

Credit: Eyesight in schools : a paper read before the Association of Medical Officers of Schools, on April 15th, 1885 / by R. Brudenell Carter. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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$eyes, in order to see under a larger visual angle, and thus to obtain larger retinal images, which, to some extent, compensate them for want of perfect defini- tion. The accommodation eflFort which attends this approximation of the object becomes established, and then a simulated myopia is produced. A young gentle- man was sent to me from Harrow, a few years ago, who was said to be short-sighted, and who suffered great distress from his eyes. He brought his books very close to them, and used for distance concave glasses which had been prescribed for him. The use of atropia for three or four days revealed a total hypermetropia of nearly seven dioptres. In myopia, as in hypermetropia, we often see the apparent degree of the defect increased by accommo- dation. The myopic subject has perhaps been accus- tomed to read in a bad light, and, in order to compen- sate for this, approximates the page even more than he is compelled to do. At any rate, it is quite common to find that, after an efficient application of atropia, the degree of short-sight, whether measured by lenses or by the ophthalmoscope, is materially less than it seemed to be before the application was made. It will be manifest, from the foregoing considerations, that no rough and ready method of testing refraction can be regarded as trustworthy. The method first employed by Cohn, for example, when examined by the light of more recent experience, is seen to be essentially defective. There can be no doubt that this method led him to regard very many hypermetropic persons as emmetropic, and probably to include others among his cases of myopia. The general terms, myopia and hypermetropia, are frequently used to include also the cases of astigmatism, which present themselves under five varieties : the simple and compound myopic, the simple and com- pound hypermetropic, and the mixed. Astigmatism denotes the existence of a difference in the refraction of the eye in different meridians ; the meridians of maximum and of minimum refraction being generally approximately vertical and horizontal, and always at right angles to each other. As a rule, to which there are exceptions, the maximum refraction is that of the vertical meridian, so that its focus is anterior to that of the horizontal. If the focus of one$