Besides this, however, in the relation between accommodation and
convergence of the visual axes there is a very essential cause which is
able to lessen the immediate effect of the operation. Persons who squint
inwards, even if emmetropic, have the habit of combining accommodation
for near objects with excessive convergence of the visual axes, thus
the immediate effect of the operation is diminished as soon as they
begin to use their eyes again. This happens, not by a lessening of the
effect of the tenotomy, which could, indeed, only be increased by
exertion of the internal recti, but in that sufficient time is not given
for the external rectus to regain its normal elastic tension. Nothing is
changed at first by the operation in the customary relation between
accommodation and innervation of the internal recti--it is a question,
then, of avoiding every exertion of the accommodation for some time, in
order that no inducement for strong convergence should be given. I am
accustomed, therefore, even in the case of emmetropes, to paralyse the
accommodation by means of atropine twenty-four hours after the
operation, and to remove the far-point by convex glasses to about 0·70
m.; the spectacles must, of course, be worn constantly, for only by that
means can we be sure that they are always used for near objects. After a
few weeks the spectacles are discontinued, first for distance, then for
near objects also. This after-treatment is not necessary under all
circumstances; but I have repeatedly assured myself that an originally
sufficient result which perceptibly diminished after a few days, could
by this means be restored and permanently maintained even in emmetropes.
In the case of hypermetropes, we more often meet with the same
experience; in permanent convergent squint it is by no means necessary
to neutralise the hypermetropia permanently after the operation, but it
happens here more often than in emmetropia, that a perfectly good
immediate effect is lost within the first week after the operation, and
can be restored again by permanently wearing the correcting convex
glasses. In such cases also, I am accustomed after a few months to
discontinue the spectacles for distance as an experiment, while they are
still used for working.
Simple tenotomy of both internal recti does not, as a rule, suffice for
deviations of more than 7 mm.; therefore, even if both eyes possess good
visual power, we must still decide on tenotomy of both internal recti
together with advancement of the external rectus of the squinting eye,
or anticipate repeated tenotomies of the internal recti, or seek to
obtain the greatest possible effect by means of slight modification of
the method of procedure.
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