Vol. 60, 1909 - University of North Carolina at Chapel Hill

234 THP; CHARLOTTE MEDICAL JOORNAL
the presence of fusion faculty. The fusion tion causes an abnormal static convergence
faculty can seldom be awakened after the and squint is caused. !
sixth year. The recovery of the vision of The proper method of examination is,
j
the deviating eye is seldom accomplished First: Get the history of the case, whether -j
after the sixth year. A delay means a loss or not there are any other members of the j
of valuable time, most squint beginning by family, parents, brothers, or sisters, who '
or before the age of three. have squinting eyes; nature of the squint; |
There are three indications which require the state of central fixation; the movement j
attention. of each eye separately; visual acuity and ]
First; To prevent the vision of the de- the refraction of each eye. 5
viating eye from deteriorating. To determine the squint eye, place a card I
Second: To remove the cause by train- over one eye, having the patient look at a *
ing the defective fusion faculty, distant object. If there is no movement of •'
Third: Remove the disfigurement: the uncovered eye, it is the fixing eye
The means of correction are the removal Quickly move the card to the other eye, if
of the refractive error, the complete occlu- there is a movement, it will be the squintsion
of the fixing eye; training patient to ing eye. A more satisfactory test and the
use the deviatiag eye. This can be done one best applied with children, is with the
by using atropine in the fixing eye and light reflected upon the cornea. Place the
trainingthefusionfaculty by developing the child before you with the light at its back
brain centers; training the muscles of the and with the retinascope or opthalmoscope
eyes when defects exist, and operating when reflect the light upon one cornea. This atthe
above fails. tracts the child's attention. If the reflec-
*Two essential conditions are present in tion is in the center of the pupil, this is the
every case of concomitant squint. fixing eye. Shift the light to the other eye
First; Abnormal convergence of the vis- and if the reflex is not central, the eye is 1
ual axis. squinting, and by the position upon the ^
Second: Defective fusion faculty. Other cornea that you have the reflex, you can j
conditions may also be found. The vision determine the degree of deviation. ;
of the eye which is not being used for fixa- Reviewing the various theories, we must ^
tion is almost invariably suppressed. come to the conclusion that while, according i
Third: There is in rather rare instances, to Donders' theory, errors of refraction are |
more or less congenitial amblyopia. responsible for a certain per cent, of squint, |
Fourth: There is ver>' often acquired we can but accept Worth's theory, based j
amblyopia in the deviating eye as the result upon clinical experience, that the lack of j
of neglect or improper treatment. fusion power is the principal cause for ,
Fifth: There is usually a refractive error concomitant squint. While most divergent .
commonly hyperopia or hyperopic astigma- squints are myopic and convergent are ;
tism. hyperopic, and also where squint is perma-
In the normal eye with normal fusion nent, the squinting eye has a greater error '
faculty there is a desire for binocular vision, of refraction than the fixing eye; yet we find I
Binocular vision is formed by rays of light a certain degree of amblyopia in this eye •
falling upon corresponding sensual centers with an inability to fuse objects with the ;
of the retinue. Wlien the two eyes have fellow eye. ;
not the visual axis binocular vision is im- We can but give some credence to Don- •
possible and there is confusion of objects, ders' theory, as it is essential to correct all
with a tendency to diplopia. The most in" refractive errors, or we would not get re- I
distinct object is suppressed by the brain suits from our fusion training. To substan- i
centers and this produces an amblyopia tiate this theory, in most cases where stra- |
exanopsia. Where the hyperopia is greater bismus is present in eyes with a total loss
in one eye than the other, the retinal im- of sight or where corneal opacities exist,
pression is less distinct in the eye with a there is a tendency to divergent squint,
higher degree and there is required an extra This brings us to the line of treatment
tension in the effort to accommodate, which which should be followed up for correction,
increases the convergence with confusion of I. The correction of all refractive errors |
images. Tbe indistinct impression upon and in connection with this, the training of
the retina allows this abnormal dynamic of the fusion sense,
force to exert itself and renders the eye freer II. There are some cases in which we
to swing in, hence we have squint as a re- have binocular vision where eyes are brought
suit. Squint in these cases is at first occa- to the same focal axis and in these case
sional, but if the refraction is not corrected,
the excessive exercise of the dynamic functhe
correction of refractive error, allows the
muscles of co-ordination through relief from
extra stimulus of the accommodative ceu-
*Worth. ters, to keep the focal axis adjusted.
j