Report on ophthalmology and otology delivered before the Illinois State Medical Society at its thirty-second anniversary meeting, held at Quincy, May 1882 / by A. E. Prince.

Prince, A. E. (Arthur E.)

Date:: 1889

Credit: Report on ophthalmology and otology delivered before the Illinois State Medical Society at its thirty-second anniversary meeting, held at Quincy, May 1882 / by A. E. Prince. 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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$under an accommodation of one D. (Dioptric), the optical axes are converged by an associated action of the internal recti mus- cles by an equivalent force which is expressed in degrees, and for each D. and fraction of a D. of accommodation, there is an equivalent force expended in the convergence of the optica] axes, to produce bi-nocular vision for that point. This is what may be termed the law of reoto-Giliary relationship. When we place before the normal eye a convex glass of one we violate that law just three degrees, and it will re- quire a prism of 3°, with its base inwards, in connection with that glass of plus one D. to preserve that laM^ of recto- ciliary relationship. With such a glass as this, any normal eye will be able to see with absolute comfort, an object at the distance of a metre, with all the muscles of the eye at rest; at the distance-of half a metre, with fifty per cent, of rest; at one-third of a metre with thirty-three and one-third per cent, of rest, and so on. Now this is just what I recommend in all cases of atonic- asthenojpia, due to whatever cause; and having been myself re- lieved by such a combination, after having followed in vain the advice of some of our best oculists, and having the records of numerous similar cases, I take pleasure in recommending them to any of the profession who may see fit to give them a trial. The combination which I most frequently use is + 1.25 D. (= -f- -gL), combined with a prism of four de- grees with its base inwards, and this glass I have ground by A. S. Aloe, of St. Louis, who grinds a dozen pair at a time for a sum proportionately much less than a single pair would cost. In this way the expense is reduced to a minimum which is within the bounds of everyone. In the prescription of these glasses there is one difficulty, which unless borne in mind, will$