The prescribing of spectacles / by Archibald Stanley Percival.

  • Percival, A. S. (Archibald Stanley), 1862-
Date:
1910
Catalogue details

Licence: In copyright

Credit: The prescribing of spectacles / by Archibald Stanley Percival. 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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    The test for concomitancy is made by turning the patient's head in different directions and noting, while he is still fixing the mirror, whether the position of the corneal image in the squinting eye is unchanged ; if there is an alteration in its position, the squint is nonconcomitant or paralytic. 3. Maddox Rod.—The mounted row of red glass rods and the tangent scales that were introduced by Dr. Maddox are too well known to need any detailed description. It is the simplest, most rapid, and most reliable of any subjective test for detecting any want of balance in the ocular muscles. It is assumed that the tangent scales are affixed to the wall at the end of the consulting-room in the form of a cross, one horizontal, and the other vertical, with a small light at the zero point of intersection of these scales. (a). Vertical.—The rods are placed vertically in the right cell of the trial frames, and a green glass is placed in the hinder cell on the left. The patient, armed with these trial frames at 6 metres' distance, is directed to look attentively at the light. His right eye will see a red horizontal line, while his left eye will see the light coloured green. The eyes, being thus dissociated, will take up a position of rest; and if the right eye has a tendency to deviate upwards, it will be revealed by the displacement downwards of the red line below the level of the light. The patient can at once say through which figure on the vertical scale the red line passes. This tells us at once the amount in degrees of deviation of the hyperphoria. If the red line passes exactly through the light, there is no hyperphoria. Should the patient have such deficient visual acuity that he cannot distinguish the figures on the scale, we place a 5° d. prism exactly horizontally in the anterior cell of the trial frames before the left eye. The patient will tell us that the red line occupies the same place, but on slowly rotating the prism edge downwards