Eyesight in relation to compensation : being a paper read in the Section of Ophthalmology at the Annual Meeting of the British Medical Association, Toronto, August, 1906 / by Freeland Fergus.

  • Fergus, A. Freeland (Andrew Freeland), 1858-1932.
Date:
[1906?]
Catalogue details

Licence: In copyright

Credit: Eyesight in relation to compensation : being a paper read in the Section of Ophthalmology at the Annual Meeting of the British Medical Association, Toronto, August, 1906 / by Freeland Fergus. Source: Wellcome Collection.

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    and accordingly applied to a railway company, but was rejected on account of his sight. He came to the hospital, and then I found that he had a myopia of 10 D in one eye and of 15 D in the other. The acuteness of the better eye was only -^5 Snellen. Yet this lad had no idea that there was anything wrong with his eyes. Some of the facts connected with concomitant con¬ vergent squint may be adduced quite appropriately in this connexion. Take a person with this form of stra¬ bismus and a high degree of amblyopia in the squinting eye. If by accident the good one is lost, such a patient is nevertheless often able to do a great amount of work, and that even when the form sense of the squinting eye does not materially improve. In conclusion, I wish to mention an experiment which I have recently made. I placed a lad with excellent visual acuteness at 5 metres from the ordinary types invented by Snellen for the measurement of the form sense. One of his eyes was kept covered, and with the other he followed my finger as it moved along the wall on which the types were suspended at the level of the largest letter—that is, of the letter corresponding to of the usual scale. So soon as the finger was taken to a distance of 14 cm. from the types, he was quite unable to make out the form of that letter which should be seen by a healthy eye, such as his, at 60 metres on direct fixation. The retina at a small distance from the macular region, as is well known, has practically no form sense. In the case of this lad, the form of this comparatively large object was not recognized when the angle between the visual axis and the line joining the object with the eye was approximately one degree. The same lad was then stood before a table which was covered with white paper, and was given a small black mark as a fixation point. A sixpenny-piece was put on the table at such a distance outwards from the point of fixation that the angle between the visual axis and a line joining the coin with the eye was about 45°. It was then found that when he kept steadily looking at the black mark he was able to bring down his clenched fist without any hesitation or difficulty on the top of the coin. This he did again and again without once missing it. Before long I hope to make a series of experiments on the same subject with the view of determining limits; any one, however, can perform the experiment for him¬ self. It seems to go a long way to prove my original pro¬ position that for many kinds of work the form sense, commonly called the visual acuteness, does not appre¬ ciably come into play at all. In these cases it is a ques¬ tion of alignment, for which the ordinary light sense of the retina appears to be amply sufficient.