On the value of the prisoptometer in determining the degree of myopia / by H. Culbertson.

  • Culbertson, H. (Howard), 1828-1890.
Date:
[1884]
Catalogue details

Licence: Public Domain Mark

Credit: On the value of the prisoptometer in determining the degree of myopia / by H. Culbertson. 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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    21, 22 and 23, it being remembered that accommodation—cilta- sis—sometimes is, and again is not relaxed while being tested, and mydriatics not employed. The age-period, 21—25 years, reveals, through the instru- ment, 84.07per cent., and that of 26—30 years 80.40 per cent, of absolute myopia, after the use of mydriatics. As 100 per cent, is the apparent myopia, without the influence of these par- alyzing agents, the latter means develop at these age-periods respectively, 15.93 and 19.60 per cent, of this form of ametropia. During the age-period, 12—15 years, 96.53 per cent, of myopia is found, or 100—96.51 = 3.49 per cent, of ef- fect due to mydriatics. From 21—25 years the power of mydri- atics = 15.93 per cent., or 15.93—3.49 = 12.44 per cent. ; and from 26—30 years it = 19.60 per cent, or 19.60—3.49 = 16.11 percent, increased influence in these age-periods over the effed of such agents (mydriatics), found in those aged 12—15 years. To what is this effect due? Is it produced by the hyperopia present in these cases, shown when mydriatics have not been used \ To determine the cause of this, estimate the sum of diop- trics of hyperopia in the several cases up to 30 years, and deduct from the sum of dioptrics of myopia found up to that age in the column maximum myopia of the table, which will reduce the influence of age, as a factor, in causing the augmentation fa shown of the myopi^f from the use of mydriatics. This apparent hyperopia is evident in the following table: No. of cases. D H without mydriatics. 5 + D 1.50 8 + D 0.75 9 + D 0.75 17 + D 0.50 18 4- D 1.25 22 4- D 1.00 24 + D 0.50 25 + D 0.50 26 + D 0.50 31 4- D 1.75 32 + D 1.50 35 4- D 1.25 36 4- D 1.25 Total 13 4- D 13.00 Compare this with the following table: