The refraction of the eye : a manual for students / by Gustavus Hartridge.

  • Gustavus Hartridge
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: The refraction of the eye : a manual for students / by Gustavus Hartridge. Source: Wellcome Collection.

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    say, his distant vision is normal; wo may, therefore, assume the absence of myopia or astigmatism; but he may have hypermetropia, and only be able to read ^ by using his accommodation; this we decide by holding a weak convex glass (+ 5 D.) in front of the eye, when, if he still be able to read the same line f, he has hypermetropia, and the strongest convex glass with which |^ can be read is the measure of the manifest hypermetropia; supposing + 1 D. the strong- est glass with which f can be read, then we record it thus : R. V. I Hm. 1 D. = f. I say manifest hypermetropia, because in all cases occurring in young people this is not the total hyper- metropia j for in these a great part is latent, which can only be discovered by using atropine, or by esti- mating the refraction by the direct ophthalmoscopic method. Many cases will come before us having two or three dioptres of hypermetropia, who com- plain that the weakest convex glass impairs distant vision; in these cases the hypermetropia is wholly latent. We may say, therefore, that a patient who is able to read |- with one eye, must be— Emmetropic or Hypermetropic, in that eye. If hypermetropic, a pai't of it is usually manifest, as found out by the strongest convex glass which does not impair distant vision; or it may be wholly latent, when it is necessary to atropise the patient before we can demonstrate it.