Optometry by the subjective method : a paper read at the meeting of the British Medical Association, London, July, 1895 / by George J. Bull.

  • Bull, George Joseph, 1848-
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Optometry by the subjective method : a paper read at the meeting of the British Medical Association, London, July, 1895 / by George J. Bull. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    5/12
    OPTOMET A Paper read at the Meeting of the British Medical Association, London, July, 1895. By Dk. GEORGE J. BULL (Paris). TN the present state of ophthalmological science it is obviously impossible to dispense with the subjective methods of optometry. Every experienced practitioner, however, will be aware that the exactitude of these methods is impaired by many serious sources of error. The object of the present paper is to direct attention to certain considerations by which some of the most important of these dangers may be largely eliminated. Subjective optometry is, by the nature of the case, to be divided in practice into the diagnosis of ametropia in general, and the specific diagnosis of astigmia. The considerations to which I would direct attention have relation to the relative priority of these parts of the examination. If the patient be first examined by general tests for the purpose of deter- mining the degree of myopia or hypermetropia, as the case may be, while the possible presence or degree of his astigmia is undetermined, the conclusions to be drawn from his answers will, according to my experience, be liable to very large elements of error. It is a commonplace of ophthalmological practice that it is much more difficult to determine correctly mixed or hyperopic astigmia than it is to determine the exact correction of myopic astigmia. This difficulty led me, for my own guidance, to state the problem presented in our practice in the following form : — The presence of astigmia manifestly affects the range of accom- modation towards the remote point and also towards the near point, but leaves it practically unaffected in the intervening space. Let us say, therefore, that the range in the case of the astigmic patient may be divided into three zones. Supposing, for the sake of clearness, that we assume a full range of 4D. of accommodation in an eye of which the horizontal meridian is emmetropic, while the vertical meridian has ID. of myopia. The result of this ID. of astigmia is to resolve the range into what I venture to call a remote zone of ID. in extent, within which the patient can accommodate for vertical lines,