CASE 32.--In November, 1873, I operated on Fritz F-- for a slight
divergent squint of the left eye. Slight hypermetropia was present on
both sides, and nearly full visual acuteness. In October, 1880,
perfectly normal position of the eyes showed itself with the same visual
acuity and emmetropia in both eyes; at the same time, however, the boy
affirmed that when reading he could never see with his left eye but only
with the right; in reality only the right visual field was perceived in
the stereoscope.
The second reason brought forward is, that the variety of amblyopia from
non-use is quite a peculiar one; "it consists of a functional
disturbance of those parts of the retina whose images belong to the
common V. F., and are suppressed in squint in order to render vision
distinct--the macula and the temporal and only a part of the nasal
halves of the retina." Does this hold good for all cases of amblyopia in
squint, or do those cases only belong to amblyopia from non-use where
excentric fixation takes place with an inward deviating visual axis? It
would be difficult to draw the line. I have seen a case in which the
squinting eye possessed a visual acuteness of 5/36 together with
excentric fixation and nystagmus; however, I attach no value to isolated
cases. We frequently find excentric fixation with a visual acuteness of
1/12 to 1/36. Further, those cases cannot possibly be regarded as
results of squint, which possess unsteady oscillating fixation or
rapidly trembling nystagmus, which occurs as soon as the squinting eye
fixes. But this conclusion is false, even for the excentric fixation
with visual axis deviating inwards; if it were right the angle at which
the eye deviates inwards on fixation in convergent squint would always
be greater than the squint angle. Those cases are, of course, more
remarkable where this is not the case; however, on close investigation
those cases are more frequent where the angle of deviation is about the
same size or smaller than the squint angle, and is fixed with a part of
the retina which undoubtedly belongs to the common visual field.
On p. 91 I have described two cases of excentric fixation in children
who had never squinted, and it is only necessary to take a little
trouble to repeat the mirror test which I described, to be convinced
that squinting eyes have not lost the power "of using those parts of the
retina," even if they are amblyopic to an extreme degree; without the
slightest doubt the reflection is perceived as soon as it falls on the
retina.
Public-domain text, read in full here on John Shaqi.
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