=Eye strain, weak sight or asthenopia= embraces the group of symptoms
dependent upon fatigue of the ciliary muscles or of the extraocular
muscles.
There are three varieties of asthenopia. (1) Retinal or nervous, (2)
muscular and (3) accommodative.
The symptoms are headache—frontal, fronto-temporal or fronto-occipital.
It may extend into the neck between the shoulders. Eye balls may be
tender, diplopia at times, may be photophobia, lachrymation, congestion
of the eye, itching and burning of the lids.
=Accommodative Asthenopia.=—In this form the ciliary muscle is
fatigued. The cause is usually overuse of the eye when hyperopia and
astigmatism exist; sometimes in myopia or presbyopia.
=Treatment.=—In this form the treatment is the proper fitting of
glasses and improvement of the general health.
=Muscular Asthenopia= is due to tiring of the extraocular muscles,
usually the internal rectus. This may result in a phoria or a
non-paralytic squint.
Ametropia may exist but asthenopia may come even in emmetropia due to
overuse of the eye.
=Treatment.=—Correct ametropia if present, with glasses. Exercise the
weakened muscle. Correct the nerve supply to the weak muscle. Treat
cervical and upper dorsal. Manipulate tissues of the orbit. Spring the
jaw. Correct any nose and throat pathology.
=Nervous, Neurasthenic or Reflex Asthenopia.=—The cause is supposed to
be some functional disorder, more often found in females. May be due to
too dim or too bright light, overuse of the eyes. Hysteria may follow
ametropia.
=Treatment.=—Often the treatment is troublesome and the case is very
obstinate according to old school methods. Rest, hygiene, general
health and habits are looked after. The cause must be found or the
treatment cannot be specific.
These are the different forms of eye strain as ordinarily classified.
Now as we study the reflex symptoms from these and attempt to trace
out the reflexes from an osteopathic point of view, we may find some
more definite causes of these conditions and consequently some methods
of treatment not found in standard text books might naturally suggest
themselves.
Reflex symptoms that have been traced to eye strain by ophthalmologists
are as follows:
Constipation, indigestion, heartburn, nausea, vomiting, nervous
attacks, fear of impending calamity, irritability, despondency,
insomnia, restless sleep, epilepsy, nervous twitchings and enuresis.
All these symptoms have been seen to disappear after eye strain was
corrected. There is no absolute way of proving that all these symptoms
have existed because of eye strain. The existence and disappearance
of some of them at the time of treatment for eye strain may be a
coincidence. It is evident that eye strain in varying degrees may
produce a train of symptoms similar to many above mentioned.
A patient, nervous, anxious, uneasy, and despondent, constipated,
and having some indigestion, showed on examination contractures and
tenderness at the third dorsal. It was found he was suffering from eye
strain from overuse of glasses that were too strong for him. The eyes
were refitted. He was wearing a
(R)+4.50 D. S. = +.50 cyl. Ax. 180.
(L)+4.50 D. S. = +.50 cyl. Ax. 90
for close work and a (R)+2.00 D. S. = +.50 cyl. Ax. 180
(L)+2.50 D. S. = +.25 cyl. Ax. 90
for distance. The new glasses were—Reading—
(R)+3.00 D. S. = +.25 cyl. Ax. 180
(L)+3.00 D. S. = +.25 cyl. Ax. 180
Distance:
(R) + 1.50 D. S. = +.25 cyl. Ax. 180
(L) + 1.50 D. S. = +.25 cyl. Ax. 180
He was fitted two years previously. At that time the stronger glasses
were correct. Eyes change more or less constantly, especially between
the ages thirty-five to fifty-five years. When glasses are fitted, a
weak ciliary muscle after a rest may become stronger and allow weaker
glasses to be worn.
If a young person is fitted for myopia, in a few years he may discard
his glasses as presbyopia develops. A person fitted correctly, who has
a strong ciliary muscle may not be able for awhile to see as well with
the glasses as without them. After they are worn awhile the ciliary
muscle will cease its efforts to accommodate so much and the glasses
give the desired effect. In some cases the doctor’s reputation to fit
glasses properly may suffer at the hands of such people who sometimes
refuse to take glasses, or after getting them refuse to wear them.
In the case of the man just mentioned a refitting quieted the nervous
symptoms—he became more cheerful and ceased to worry. Indigestion and
constipation improved. The soreness and contractures were overcome in a
few treatments.
Now let us ask the question, why is it that eye strain will cause
nausea and vomiting? Also why will indigestion affect the eyes by
causing “spools” in the vision?
A little osteopathic logic, based as it always is or should be, upon
anatomy and physiology, may throw some light on this subject. No doubt
every one of us has demonstrated many times clinically that indigestion
from overeating will cause soreness and contractures at the third and
fourth dorsal, the nerve center in the spine for the stomach.
The reflexes between the viscera and the eye are complex and difficult
to follow. In giving the probable course of the nerve reflexes from
the optic nerve to the third nerve Dr. Louisa Burns suggests the
following: “The nerve elements of the retina start the impulse; it
passes over that portion of the optic nerves which enter the anterior
quadrigeminates, the cells of the quadrigeminates where the impulses
are coordinated, then by axons of these cells to the lateral or
viscero-motor nucleus of the third nerve, thence to the cells of the
ciliary ganglion, and by the non-medulated (sympathetic) fibers of
these, the short ciliary nerves to the non-striated muscles concerned,
viz: the ciliary muscle, some fibers of the levator palpebral and the
sphincter of the iris.”
The third nerve arises in the floor of the aqueduct of Sylvius from
two nuclei; a lateral nucleus which is a viscero-motor group of nerve
cells, and a central nucleus or a somato-motor group of cells. The
somato-motor nucleus supplies all the extrinsic muscles of the eye
except the external rectus and superior oblique which are supplied by
the sixth and fourth respectively. The nasal branch of the ophthalmic
division of the 5th sends fibers to the ciliary muscle. Association
fibers connect the nuclei of the 3rd, 4th, 6th and 7th. The evidence is
in favor of the 10th or pneumogastric having such association fibers.
We noted four places in the brain to which the optic tracts go before
the radiations reached the center of sight in the occipital lobe. If
we cannot follow all the reflexes through the brain and cord at least
with the facts we have it is not difficult to imagine abnormal impulses
coming over the third nerve from a straining of the ciliary nucleus,
thence over viscero-motor fibers in the lateral horn of the cord, over
the white ramicommunicantes, through the sympathetic ganglia, over the
splanchnics to the stomach, producing abnormal peristalsis, nausea and
vomiting. In turn we would have the somato-motor nerves to the muscles
affected as before described, contraction and congestion of muscles of
the spine.
When we have patients consult us and describe a train of symptoms
like nausea, vomiting, nervousness, frontal and occipital headache,
we should have eye strain in mind and inquire for lachrymation,
photophobia, itching and burning lids and congestion of the eye. Any
of these things should make us think of testing for ametropia in its
various refractive errors, as well as a careful spinal and a nose and
throat examination. General physical and laboratory diagnosis should
not be neglected.