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Headaches
and other Ocular Conditions
Such
headaches may be considered under the following headings: (1) those
caused by organic disease of the eye or orbit; and (2) those associated
with "eyestrain."
Ocular
disease as a cause of eye and orbital pain have been discussed above. It
remains here only to reiterate that inflammatory disease of the eye and
orbit, acute angle closure glaucoma, and occasionally ocular and orbital
tumors may cause pain in the eye or in the region surrounding the eye.
Two excellent reviews of this subject have been written by Behrens
(1976, 1978). Pain on exposure to excessively bright light comprises
photophobia. Photophobia represents a referred type of pain through
close association of cephalic and sensory centers. Some individuals
complain of severe pain in the eyes and headache after exposure to
ordinary light. During examination, however, they easily tolerate even
the brightest of the lights used by the examiner. They have no
appreciable refractive error or muscle imbalance. Such persons are
described as suffering from retinal asthenopia. Unfortunately, this term
has little meaning with respect to any positive findings. We have
certainly not been impressed with any consistent, objective
abnormalities that have been identified in such patients. Thus, their
treatment is quite difficult. After a thorough search for ocular
disorders that might be responsible for the patient's discomfort (e.g.,
ocular inflammation, corneal dystrophy, retinal pigmentary disease), it
has been our personal practice to emphasize to the patient the normalcy
of his or her eyes. We have also found that wearing tinted or polarizing
lenses occasionally makes these individuals more comfortable.
Eyestrain
The
importance of refractive errors and muscle imbalance in producing ocular
discomfort and headaches has received disproportionate emphasis in
ophthalmologic quarters. For example, of 50 patients referred to Cameron
(1976) with headaches, only 5 patients had headaches that bore some
temporal relationship to using the eyes, and only 2 of these patients
had improvement when glasses were prescribed. We have used the
time-honored term ``eyestrain,'' introduced by S. Weir Mitchell (1876)
who attributed it to Tyrell of England, since it expresses clearly what
seems to be fundamental in the production of certain headaches. Mitchell
wrote:
(1)
What I desire, therefore, to make clear to the profession at large is
that there are many headaches which are due to the disorders of the
refractive or accommodative apparatus of the eyes; (2) that in those
instances the brain symptom is often a most prominent and sometimes the
sole prominent symptom of the eye troubles, so that while there may be
no pain or sense of fatigue in the eye, the strain with which it is used
may be interpreted solely by occipital and frontal headaches; (3) that
the long continuance of eye troubles may be the unsuspected source of
insomnia, vertigo, nausea, and general failure of health; (4) that in
many cases the eye trouble becomes suddenly mischievous owing to some
failure of the general health, or to the increased sensitiveness of the
brain from moral or mental cause.
Derby
(1930) in a valuable paper on the ocular neuroses, objected to the term
``eyestrain'' on the grounds that many patients became eye-conscious as
a result of its widespread use, but he failed to provide a substitute
term.
By the
use of spherical and cylindrical lenses, Eckardt et al. (1943)
artificially produced hyperopia, astigmatism, and myopia. They found
that the hyperopes and astigmatics developed eyestrain and headache,
whereas the myopes complained only of blurring. They reproduced
extraocular muscle imbalances with less consistent results. Maximal
convergence so produced caused a tense drawn feeling in the forehead
spreading to the temples but without radiation to the occiput. Vertical
prisms within the limits of fusion failed to produce symptoms for 30
minutes or thereabouts and thereafter caused dizziness and nausea. In
these patients, Eckardt et al. (1943) found abnormal electromyograms
from the muscles of the scalp and neck.
It is
impossible to state dogmatically that errors of refraction or abnormal
motility are the basic factors in the production of ocular headache even
when correction of these errors provides relief. Some persons with only
slight errors of refraction or slight muscle imbalance cease to complain
of headache when a properly prescribed prescription has been given;
others with more pronounced error do not complain of headache and may
even prefer to go without glasses although their visual acuity is
improved by wearing them. This apparent contradiction has been explained
by the theory that those individuals with slight errors are constantly
trying to overcome their disability, thereby accounting for tiring and
strain of the ciliary muscle, while those with greater errors are said
not to make such efforts and thus escape ciliary muscle strain. Although
this theory may explain some patients with headaches and associated
hyperopia, it certainly does not explain all cases. Some observers
stress the extracranial nature of eyestrain and believe that muscle
function is the particularly important factor. Such observers indict the
extraocular muscles and the so-called accessory muscles of accommodation
that are situated in the eyebrows and forehead as being responsible for
"traction"' upon "epicranial aponeuroses," leading
to headaches that are primarily occipital. Gordon (1934) supported the
idea that ocular headaches arise in extracranial structures.
It
should be obvious that the true causes of "ocular" headaches
are not known, but experience has taught that correction of refractive
errors and of motor imbalance are often curative whether the origin of
the trouble is refractive, extracranial, or intracranial.
Mention
is made here of features of eyestrain headaches in order that
non-ophthalmologists may be better able to identify cases in which
eyestrain is a probable factor.
Ocular
headache usually commences as a sensation of heaviness that gradually
becomes more acute. Some such headaches are described as dull, others as
bursting, sharp, throbbing, etc. Gordon (1934) and others have suggested
that headaches occurring in patients with uncorrected hyperopia have a
different location than those occurring in patients with uncorrected
astigmatism, while headaches that develop because of ocular muscle
imbalance have yet a different location than those caused by uncorrected
refractive errors. We doubt that such localizations have value. As a
general rule, headaches arising from eyestrain cause discomfort around
or behind the eyes that often spreads to involve the forehead and
temples, but may extend even to the posterior occiput. Except for
frontal headaches and ``tired sensation'' in the eyes, headaches
associated with eyestrain are rarely localized with any degree of
exactness by the patient.
A
careful history will usually enable the examiner to determine whether
the headache is due to eyestrain or whether other factors are involved.
The typical eyestrain headache develops after the eyes have been used.
It usually appears some hours after their use and gradually increases in
severity if continued efforts are made to go on with the work at hand.
When the headache is described as present on awakening, one should
immediately inquire whether it is also present before retiring at night
and whether it ever awakens the individual during the night. If a
headache is absent on retiring but is present on awakening, or if a
headache awakens a patient from a sound sleep, it is not caused
by eyestrain.
If a
patient states that his or her headaches occur only after use of the
eyes, it is important to determine whether this is the rule, for
headaches that are separated by long periods of relief are unlikely to
be associated with eyestrain.
Finally,
headaches associated with eyestrain are virtually never associated with
other systemic symptoms, such as nausea and vomiting. Thus, when
headaches are not clearly associated with use of the eyes, when they
awaken the patient at night, and/or when they are spaced far apart, it
is highly unlikely that the eyes are responsible, and inquiry regarding
other possible factors should be made. In some cases, organic causes of
headache will become obvious. In other individuals, the headaches will
appear to be psychogenic in nature (Derby, 1930). Such individuals
usually have good visual acuity and vividly describe such unlikely
situations as: (1) the inability to even glance at print without the
immediate onset of severe pain in the eyes; (2) the inability to drive
because of the resultant headaches; (3) the necessity for resting their
eyes, etc. These patients may be impossible to help.
There
are very few children below school age who complain of headaches from
eyestrain. In young children of school age and in adolescents, headaches
may allow the individual to escape from school work or may serve as an
excuse for poor performance, particularly when the child has performed
well in the past. In older individuals, headaches may serve as a similar
escape or excuse with respect to their performance at work. Adults who
are in the age of presbyopia complain of ocular discomfort, but rarely
of genuine headaches. Their eyes tire and print becomes blurred.
The
examination of the eyes that follows after a meticulous history has been
obtained does not require elaboration here.
The
prescribing of lenses, including prismatic corrections for horizontal,
and particularly for vertical, imbalance, depends upon conclusions based
primarily on the history and secondarily on findings during the
examination. Prescribing lenses for the relief of headache simply
because a minor refractive error or ocular motility disturbance exists
is likely to be unproductive unless the history and examination have
pointed to eyestrain as a factor. On the other hand, it is good practice
to correct these abnormalities if the history and examination suggest
the possibility of eyestrain. In such circumstances, it is often useful
to fit the patient with the appropriate correction in a trial frame and
then have the patient sit in the waiting room with the trial frame in
place. Often such patients will state that they can immediately discern
an improvement in their condition, and the lenses can be prescribed with
some confidence. In other instances, the patients will use the lenses
for awhile and then bitterly complain that they continue to experience
discomfort. In such cases, glasses may still be prescribed but with much
less enthusiasm. In such individuals, a frank discussion of the problem
and the role of corrective lenses is appropriate management. Cooperation
and mutual understanding by the patient and the ophthalmologist are
usually all that is necessary in such instances.
In
patients with significant anisometropia, the relief of eyestrain
headaches by the use of spectacle or contact lenses designed to equalize
differences in retinal image size has received a great deal of
attention. Our experience with such lenses suggests that they rarely
accomplish the purpose for which they are prescribed. Many of these
patients have psychogenic headaches, and although the lenses may
profoundly reduce differences in image size, their headaches continue
unabated.
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