TITLE: Clinical Observations
of Pharmaceutical, Physical and Visual Evidence of
Presumed
Extraocular Myositis and
Tendonitis.
AUTHOR:
David F. Sucher O.D.
El Cerrito, CA
Figures 3
Charts 1
Tables 3
Photos 2
Published in the AOA Journal
January 2002 pages 39-50.
Abstract
Purpose:
This study examines data from
pharmaceutical, physical and visual tests that support the possible diagnosis of
presumed extraocular myositis and tendonitis (PEM-T).
Methods:
The
presence of ocular pain derived from inflamed extraocular musculature and
tendons in sixty subjects with PEM-T was detected by palpating their globes near
the eye muscle insertions. The pain sensations were subjectively rated and
recorded. Because the sensation of pain elicited by such palpation was most
often unilateral, the study compares the affected side with pain to the side
that exhibits vision disturbance during the Turville Infinity Binocular Balance
(TIB) test. Lastly, an anti-inflammatory ophthalmic pharmaceutical was used to
see if the pain could be resolved. Saline
was used as a control. The subjects evaluated their pain after one and ten
minutes of the saline drop. The remaining subjects who still had pain after the
saline drops were given one of two topical steroids, a hydrophilic or a
lipophilic derivative of prednisolone. Again,
the subjects rated and recorded their pain after one, ten and sixty minutes.
Results:
Of sixty subjects who had headaches
and associated painful areas on their globes, fifty-eight observed the monocular
blur effect (MBE) on the same side as these palpable sore spots.
Of the sixty subjects with such sore areas, ten individuals were relieved
with a saline drop. Of the remaining fifty subjects, twenty-five received a drop
of lipophilic, prednisolone acetate and twenty-five received a drop of
hydrophilic, prednisolone sodium phosphate. Of the fifty subjects from these two
groups, forty-three had a significant reduction of their palpable pain
sensations; the data indicates that there was little difference in response
between the two formulations of prednisolone.
Conclusion:
The corroboration of results from pharmaceutical, physical and visual tests
supports the diagnosis of PEM-T.
Key words:
eyestrain, orbital tenderness, digital palpation, extraocular myositis,
extraocular tendonitis, hydrophilic steroid, lipophilic steroid, Turville
Infinity Binocular Balance test, monocular blur effect.
Introduction
Extraocular myositis and tendonitis are acute and/or chronic inflammations of the extraocular eye muscles and tendons and their sheaths (fascia). If these tissues are inflamed, then, it would seem likely that they may elicit pain upon eye movement and when palpated with the fingertip. There have been reports of trochleitis with superior oblique myositis in patients who report exquisite point tenderness of the globe which is aggravated by eye movement.1 Achy and sore eye muscles are commonly reported with viral influenza. Echographic findings have indicated single and unilateral extraocular muscle hypertrophy in sixty-eight percent of patients with idiopathic orbital myositis.2 Although some of these unilateral findings could be explained by Grave's disease and restrictive myopathies, a significant number could not be explained.
It is feasible that inflammation of the eye muscles might also occur as a result of them being overworked, since it is generally accepted that over-exercising and straining any striate muscle can lead to its fatigue and eventual inflammation.3 In binocular difficulties, eyes with a tendency for a divergent posture overwork the medial recti and the expected, associated inflammation would be nasal. For eyes with a tendency for a convergent posture, the lateral recti work harder and the sore areas might be felt temporally. Because one attribute of inflammation is pain, inflammation of muscles, including the eye muscles, are noticeable to touch, and the degree of sensitivity is often proportional to the amount of inflammation. Palpating for pain is a well-accepted method for ascertaining diagnosis of a medical condition.4 Touching, feeling and palpating a painful elbow or knee is an easy way to assess the exact location and amount of pain defining the problem and ruling out other causes.
The pain from inflamed muscles and tendons can radiate along nerve pathways and evolve into a tension headache.4 There is ample literature associating binocular visual problems with tension headache.5-9 Because our technological age challenges binocular vision with a multitude of near tasks, often performed under artificial light, headache is now recognized as a modern problem and frequency is increasing with computer use.10 Computer users make repetitive vertical eye movements when looking from keyboard to monitor. These vertical eye movements are longer and more rigorous than compared to operating a typewriter.
Binocular fixation error or misalignment, also known as fixation disparity, can be measured utilizing the monocular blur effect (MBE). 11,12 If the TIB test was conducted in only one direction of gaze, finding the monocular blur effect might be difficult; however, by moving the head and aiming the eyes in different directions, the blur can vary. The variation in the blur makes the observation of the monocular blur effect easier. Although the decrease in visual acuity from parafoveal viewing eye of the non-fixating eye (lagging eye) during binocular vision is small and does not drop in lines of acuity, the subject can easily report the quality of their sight diminishing.11, 12 A crisp 20/20 is qualitatively better than a washed out 20/20. To rule out optical disturbances and to verify that the monocular blur effect is a result of errant binocular vision, the other centrally fixating eye is covered to allow the parafoveally-viewing eye to regain central fixation. When this is done, improvement of visual acuity can be observed. The variation of the monocular blur seems to implicate a peripheral or non-comitant origin for the error. Ogle and others are adamant that most binocular errors are comitant with a central origin. 13, 14 Subjectively, subjects report more visual discomfort when viewing objects or print in the direction of gaze that has the greatest monocular blur effect; this might be interpreted as the direction of view with the greatest muscular effort. 15
The Turville Infinity Binocular Balance Test is not only useful in discovering the MBE, but it is instrumental in determining the amount of prism needed to reduce fixation error. Prism lenses can be held over the eyes to reduce fixation error and thereby eliminate the monocular blur. Application of prism in spectacles relieves eyestrain and associated headache.9 Other methods of measuring binocular error utilize anaglyphic and Polaroid filters, but placing a filter over the eyes contaminates the testing. The TIB allows the observer to view in free space, not inside a phoropter or inside any other mechanical device. Having a mechanical device, such as the phoropter, near to the eyes can easily contaminate testing due to the variable effects of proximal or psychic convergence as well as to Bell’s phenomenon which causes divergence drift from the darkening of the vision inside the phoropter.16 The TIB test utilizes peripheral binocular fusion locks at the same time each eye sees independently. Morgan17 found that that application of vertical prism to align the uneven images during the TIB test was extremely accurate in correcting vertical fixation disparity directly. The TIB test is not as useful in measuring horizontal fixation disparity directly, although some authors have redesigned the test to measure horizontal fixation disparity.18 Horizontal fixation error can be determined by adding horizontal prism in ½ diopter increments during the TIB test until the monocular blur clears. The prism lens is held over either eye for a few seconds to insure that the improved blur is not transient.
In the author's clinical experience, patients observe the pain elicited from the globe upon palpation to be reduced with topical corticosteroids. Injections and oral use of steroids have been used to quell idiopathic orbital myositis2. The author’s preliminary clinical evaluations showed that other possible pharmaceutical agents, such as non-steroidal anti-inflammatory drugs and anesthetic drugs, were not as effective as the steroids. Also, from clinical experience, the topical steroids seemed to work more quickly to quell the pain from presumed extraocular myositis and tendonitis. Although the classical effects of glucocorticoids are slowly performed through intracellular receptors that modulate gene transcription, recent evidence has shown that steroids can have a rapid non-genomic response in neuronal membranes.19 This direct-acting response can occur in seconds; whereas, a genomic one might take hours. The anesthetic effect of topical steroids has been reported to significantly abate post-tonsillectomy pain.20 The steroid action is so fast that the use of a steroid may possibly be appropriate as not only a diagnostic test, but also as a treatment modality.
One explanation for this non-classical action of steroids is offered by Cutrer and Moskowitz who found that certain neurosteroids could act to bind and modulate GABA receptors that are inhibitory receptors in the peripheral and central nervous systems, which modulate trigeminal nociceptive neurons enervating the meninges. 21 Interestingly, in this regard, intranasal steroids have also been reported to reduce peripheral nociceptive reactivity.22
Methods
Sixty patients who suffered at least two headaches a month and who had detectable, palpable tender areas on the globes of their eyes were selected from a clinical population. No bifocal wearers were accepted in this study. There were 42 females and 18 males and ages ranged from 18 to 45. (Chart 1) All patients were informed that they were subjects in a study and informed consent agreements were gathered. All subjects were examined for pathological entities that are associated with global tenderness, the most obvious being an infection or lid inflammation. None of the patients were hyperemic and their general health was good. Of interest, although computer use was not a criterion for participation, only eighteen subjects did not use a computer on a regular basis.
Physical evidence that might indicate PEM-T was searched for by detecting soreness on the globe of the eye approximately near eye muscle insertions. The examiner began by palpating the globes gently with the fingertip underneath the supraorbital bone while the eyes looked in extreme down gaze. (Photo 1) This procedure was performed around the entire globe so that all muscles could be evaluated for pain. All palpations occur on top of the lid to avoid direct contact with the bulbar conjunctiva. Patients reported if there was a noticeable sensitivity or pain sensation when palpated in such a manner. They reported in which eye(s) the pain was present and subjectively evaluated the sensitivity on a scale of 0-4, where zero indicated no tender spots; one, a slight sensation; two, noticeable tenderness; three, very noticeable; four, very noticeable with headache.
Assessment of the binocular status of the patients was accomplished utilizing the Turville Infinity Balance test, which measures fixation disparity by means of monocular blur caused by parafoveal viewing of the "lagging" eye. Reading showed that uni-ocular components of fixation disparity are not equal, but rather unequal with one eye with central fixation and the other eccentric fixation, "the lagging eye".23 The TIB test method has been previously described and used to associate the monocular blur effect with headache.11 The TIB is eloquently praised by Meredith Morgan as the one of most natural, accurate and reliable tests of fixation disparity.17 All subjects were tested for the monocular blur effect with their best corrected, habitual Rx in place. They observed 20/60 letters during the TIB test in up gaze and down gaze and reported if the monocular blur effect was present and, if so, on which side it was present. The monocular blur effect is confirmed and distinguished from optical effects by covering the good eye, or the non-blurred eye, and observing improvement in visual acuity of the blurred eye when binocular vision suspended. If the blur is due to a binocular problem such as fixation disparity, the blur will clear. If the blur is due to an optical distortion, the visual acuity will not improve when viewed monocular. The side that demonstrates the monocular blur effect was recorded and compared to the side that had the tender sensations on the globe. A chi square statistical analysis was made to determine the significance of correlation between global tenderness and monocular blur.(Table 3)
Further confirmation of the possible existence of PEM-T is made by means of pharmaceutical testing. The use of ophthalmic steroids was chosen to determine if the pain from PEM-T could be reduced. Future studies might indicate greater understanding of other pharmaceutical usage for PEM-T. Of clinical value, two derivatives of prednisolone, the water-based phosphate preserved with benzalkonium chloride and the lipid-based acetate also preserved with benzalkonium chloride were compared for effectiveness. A saline preserved with benzalkonium chloride was used as a control substance.
All subjects, after assessing and rating the soreness on palpation of their eyes, were given a single drop of normal saline in the eye with the tender spot. Then, in one minute and again after ten minutes the eye was palpated and soreness rated. If the tender spot was still present after another ten minutes, a single drop of either prednisolone sodium phosphate 1/8% or prednisolone acetate 1% was administered. Digital palpation was done one minute later, at ten minutes and at sixty minutes. Twenty-five subjects received prednisolone acetate and twenty-five subjects received prednisolone sodium phosphate.
Subjects evaluated their tender spots. They reported in which eye(s) the pain was present and subjectively evaluated the sensitivity on a scale of 0-4, where zero indicated no tender spots; one, a slight sensation; two, noticeable tenderness; three, very noticeable; four, very noticeable with head pain. Evaluations of tender spots were done after each instillation at the specified timed intervals and recorded. All sixty subjects initially reported either a rating of two or higher to qualify as subjects. An improvement of two levels was arbitrarily selected as an indicator of pain relief.
Although care was taken to insure proper informed consent about participating in this study, at no time were the subjects' responses cued; the examiners avoided suggestive language. The saline and prednisolone bottles were purposely chosen to look identical. Before the instillation of the second prednisolone drop, the subject was only told that another drop of the first solution was going in their eye. The drops, which were kept at room temperature, were administered in the upper fornix near the inflamed area.(Photo 2) After each drop, the subjects were asked to evaluate their tender spot(s). The results are a collection of subjective responses of pain sensation elicited by the application of a small amount of pressure on the globe approximately near the eye muscle insertions.
Data and
Results
On a scale of zero to four, a subjective sensation of pain needed to improve two levels in order to consider the drop effective. A pain sensation of three, very noticeable, would have to come down to a rating of one before the drop qualified as giving relief. Twenty-seven of the sixty subjects experienced temporary relief within the first minute with the saline drop, but only ten subjects had the effect last greater than ten minutes. (Figure 1) Of the remaining fifty subjects, twenty-five received the prednisolone acetate and twenty-five prednisolone sodium phosphate. Forty-three experienced significant relief of pain within ten minutes. Subsequently, thirty-nine of these forty-three treated subjects felt prolonged relief sixty minutes after the drug instillation (Figure 2) Both corticosteroids had a combined 78% positive result , 14% had no effect and 8% only experienced temporary relief. The saline had a 16% positive result, although 45% had a temporary positive effect within the first minute.
This clinical study shows a significant effect of both the prednisolone acetate and the prednisolone sodium phosphate on the resolution of eye pain from presumed extraocular myositis and tendonitis. The effect of the ophthalmic drop was statistically significant (Tables 1 and 2); the subjective responses after the instillations included many positive comments, such as "oh, that feels so much better." The comparison of prednisolone acetate and prednisolone sodium phosphate showed nearly equal results. Of the twenty-five subjects who received prednisolone sodium phosphate, twenty-two experienced reduction in soreness after ten minutes and twenty had a prolonged effect sixty minutes following the instillation. Of the twenty-five subjects who received the prednisolone acetate, twenty one experienced significant resolution of pain after ten minutes and nineteen maintained the effect sixty minutes later. (Figure 3)
Of sixty subjects who reported having tender areas around the globes, fifty-eight had a corresponding monocular blur effect (MBE) on the same side. This represents a statistically significant correlation (Table 3) There were thirteen subjects with tender spots on both eyes, but ten of these subjects admitted that one side had much greater pain; therefore, fifty-seven subjects had more noticeable tender sensations on one side. Three subjects had equal pain sensation on both eyes. Only two subjects had no monocular blur effect and, interestingly, these subjects did not have a positive response to the steroid drops.
Discovering
pain sensations
In this study tender areas on the eyeball of sixty subjects were identified by means of digital palpation. Detecting such pain in these areas of the eye can indicate a sore muscle-tendon, although not all palpable eye sensations are necessarily derived from myositis and tendonitis. A painful eye can mean any infectious or non-infectious, local or systemic, inflammation of any part of the eye. However, the eye sensations from palpated areas of the globe in pathological cases are often hyper acute and associated with other signs and symptoms. In this study subjects who felt these sore areas around their eyes when touched were carefully examined including a dilated fundus examination to rule out other possible causes of pain in the eye.
Palpation of the globe by the fingertip is not difficult, but should be performed as near the insertions of the eye muscles as possible. (Photo 1) The examiner may use specific sites around the globe or palpate the entire capsule circularly with the tip of a finger on top of the eyelid as the subject looks in extreme gazes. Digital palpation can also be self-administered in the same manner. The subject, then, evaluates the intensity of the pain. Many individuals when suffering viral influenza will notice that their eyes are achy and feel sore when moved. 24 This can represent a pathological form of extraocular myositis and tendonitis and is part of a disease process. From the author’s clinical experience, the pain associated with PEM-T derived from eyestrain and possible binocular deficits tends to be more specific and reappear in the same place. While both types of myositis and tendonitis have acute phases, the author has observed that presumed extraocular myositis and tendonitis can be chronic with varying intensities of eye pain possibly coming and going for weeks or longer depending on the use of the eyes and possibly associated with chronic daily headache.9 As presumed extraocular myositis and tendonitis is studied more, the association with chronic headache may become more clearly understood.
Reactions to touching these tender areas around the eye varied from mild irritation to extreme sensitivity. Subjects who returned reported that these tender areas were most sensitive after using their eyes in a strenuous manner and when experiencing headache. In the study most subjects had noticeable to very noticeable tender spots and after instillation of the prednisolone felt no pain or slight pain sensation. Subjects at level four had not only significant reduction in pain sensations on the globe, but also reported withdrawal of the headache in three of the four subjects with an initial rating for soreness of four.
Use of
Pharmaceutical Agents
Besides demonstrating that tender and painful areas exist on the eye, this
study demonstrates that prednisolone seems to relieve these pain sensations. The
use of a saline drop as a control was practical. With it, no allergic reactions
occurred. There was very little recovery time after the instillation of saline
so that sequential use of the other pharmaceutical agents could be done. If the
pain sensation persisted beyond ten minutes after the instillation of the saline
drop, then one drop of prednisolone sodium phosphate 1/8% or prednisolone
acetate 1% was added and pain sensation was again checked in the specified timed
intervals.
Almost half of
the individuals experienced a reduction in tenderness with the saline drop
within the first minute although that number dropped quickly thereafter.
Nonetheless, ten of sixty subjects had prolonged relief with the saline drop.
The saline drop may actually soothe extraocular inflamed tissues and have a
therapeutic effect for a short period of time. Relief from the saline drop,
while clearly present, was much less than the effect of the drop of prednisolone:
16% saline effect compared to 78% prednisolone effect. Statistical analysis
shows a significant relationship between the use of prednisolone and reduction
of pain emanating from the eye. (Tables 1 and 2)
There were no adverse reactions to
the use of a single drop of prednisolone acetate or prednisolone sodium
phosphate except for a few slight sting reactions. Some patients were aware that
the acetate drop was different than the saline drop since prednisolone acetate1%
being a suspension had to be shaken vigorously. It also fogged vision and left a
milky white residue. Some subjects could taste the prednisolone acetate.
However, the solution of prednisolone sodium phosphate 1/8% looked and felt like
the saline drop and subjects receiving this drop had a similar reduction in pain
sensation as subjects receiving a drop of prednisolone acetate.
This observation made from a comparison of results of the two kinds of prednisolone shows that both produce cessation of the pain.(Figure 3) There was no appreciable difference in efficacy between the phosphate and acetate forms of prednisolone. Even though many practitioners consider Pred Forte the gold standard for the treatment of iritis and uveitis, in this study its lipophilic properties gave it no advantage over the hydrophilic derivative of prednisolone. The hydrophilic sodium phosphate, even at a low concentration, was equal in patient response to pain reduction for both the short and long term response periods. It is possible to surmise, then, that the external myo-tendinous tissues and neuronal membranes are easily accessible by either the lipophilic and hydrophilic derivatives of prednisolone. Lipophilic derivatives of ophthalmic steroids can penetrate the corneal epithelium and can subsequently increase intraocular pressure and cause cataract with prolonged use. 25 The hydrophilic derivatives penetrate the cornea poorly and produce fewer deleterious side effects. This knowledge could help to make judicious choices for therapy.
If pharmaceutical resolution of the pain demonstrates the quelling of inflammation, then, the question arises: from where does the inflammation come and why is it predominantly on one side? The coincidence of the unilateral presentation of tender spots with the unilateral presentation of the monocular blur in the MBE is interesting. Previous studies have indicated that the MBE almost always varies in different directions of gaze, a probable result of eye muscle imbalance.11 If this assertion is true, then the association of the tender areas on the globes with an eye muscle error is more understandable. If an eye muscle is involved, then inflammation of that muscle and its tendon is also more likely to occur.
Visual Tests:
Because fusion
is a powerful reflex, the eye muscles are compelled to keep the eyes aligned.26
It is possible that eye muscle imbalances can disrupt the alignment of the eyes
in their effort to maintain clear and comfortable binocular vision.27
Muscular compensation for these misalignments consequently strain and fatigue
the eye muscles themselves.28 It
is reasonable to assume that if the eye muscles are overworked, they can become
more inflamed and more sensitive to the touch depending on the amount of time
the eyes are used and the degree of the imbalance. Knowledge about the binocular
error helps us to understand what causes the strain and where it may be posited.28
The Turville Infinity Balance test is a vision test known to detect eye muscle imbalance.29 Eye muscle imbalance can cause one eye to lose fixation with a corresponding decrease in monocular visual acuity. 11 A significant number of subjects had the monocular blur occur on the same eye that could feel pain with digital palpation of the globe. Of the sixty subjects the MBE occurred on the same side as the tender areas in 58 subjects.
The uni-ocular components of fixation disparity may be such that one eye has central fixation and the other eye is off by the entire amount of the fixation disparity.23 If one eye is misaligned, it will lose central fixation and visual targets will be seen slightly off axis in that eye. This fixation error causes a decrease in visual acuity and might explain the phenomenon of blurring during MBE. To confirm that the MBE exists, the non-blurred eye is covered suspending binocular vision and letting the affected eye regain central fixation. If the blur disappears, then it can be assumed that the fixation error trying to maintain fusion is eliminated. Each subject was double checked for MBE in this manner.
If a muscle imbalance contributes to fixation disparity, one would expect that as the imbalance increases in a particular direction of gaze, then, the fixation disparity and the monocular blur would increase in same direction of gaze. The blur in MBE usually varies with the actual binocular fixation error.11, 30 This variability of MBE in different directions of gaze would be difficult to explain other than from the eye muscle difficulty. It is not likely that fusion reflexes mediated by the cortex and sub cortex would vary in the different fields of view. Instead, it is more likely that the mechanical forces holding and pulling the two eyes are not perfectly coordinated and that this uneven distribution causes variable balance and thus variable fixation error. As the strain of fixation increases, the blur gets worse.
The association between the presence of tender spots and eye muscle imbalance which reveals fixation error on the same side as the tender spots supports the contention that eye pain could be the result of strain of the eye muscles. The association of headache and monocular blur effect has been reported.15 Most theoretical studies of binocular vision are performed in a straight ahead gaze and the influences of the eye muscles are often understudied. Understanding the coordination and balance of the eye muscles requires testing in different directions of gaze and comparing horizontal, vertical and cyclotorsional eye movements.11, 31 A majority of binocular studies and clinical testing is performed in straight ahead gaze only and the rationale is that powerful fusion reflexes are controlled by the brain and eye muscles are subservient to these dominating reflexes. Identifying an eye muscle pain associated with an eye muscle imbalance puts greater emphasis on the hypothesis that the anatomical arrangement of the eye muscle insertions could possibly be a source of fusion difficulty and lesser emphasis on a dysfunctional integrative sensory system.
The incidence of PEM-T seems to be more likely in individuals who have imbalanced eye muscles that create an uneven distribution of work and make some muscles work harder. This uneven distribution is detected by the vision tests and the results of these tests correlate significantly with the presence and location of the eye pain. Prism lenses reduce the MBE and alleviate the eye muscle imbalance.11, 15 By so doing, it is possible to surmise that some PEM-T could be avoided.
Diagnosis
of PEM-T
The corroboration of data and the preponderance of evidence help to establish the probability of a diagnosis of presumed extraocular myositis and tendonitis. In the literature, the entire subject of extraocular myositis and tendonitis is limited to infectious, systemic or unknown in origin.32- 36 One form of PEM-T and tendonitis may be defined by the presence of binocular strain and its correlation with the physical evidence of palpable tender areas. The absolution of pain from these sensitive areas with prednisolone might help to confirm the diagnosis of this form of PEM-T.
With a tentative diagnosis of PEM-T, the associated tension headache may be understood as a result of the eyestrain 15 although this is still just an inference. In these cases, the headache is often reported to be physically near the sensitive, painful areas on the globes. The pain is probably signaled by the many trigeminal nerve endings in the muscle or tendon.37 The inflammation of these ocular tissues releases prostaglandin, leukotriene, thromboxane and other immune response biochemicals that cause pain.38 In the author’s private practice, he has found individuals with excellent binocular vision and eye muscle coordination who present with presumed extraocular myositis and tendonitis. In these cases, perhaps the eye muscles are overworked and not necessarily imbalanced. Overuse could possibly produce inflammation of the ocular muscles and tendons fatigued by repetitive eye movements such as from computer use and other tasks.
In certain situations, the discovery of presumed extraocular myositis and tendonitis as a pharmacologically treatable clinical entity might benefit individuals who struggle to maintain comfort in a work environment. Today's business world embraces new worker health problems. The industrial age brought the assembly line and repetitive stress injury. The computer age has brought us carpal tunnel syndrome and wrist injuries from repetitive keystroking. The recognition of PEM-T as another casualty of the computer age might help to explain computer vision syndrome with associated symptoms of eye strain, headache, photosensitivity, dizziness, nausea, irritated eyes, red eyes, twitching and double vision. 39, 40 PEM-T could be dubbed equivalently ocular "carpal tunnel syndrome" caused by the repetitive motion of the eyes moving from keyboard or reference material to the computer screen many times a day. These repetitive vertical eye movements could exhaust the muscle fibers and inflame the tendons leading to PEM-T.
The trigeminal neuron output or the pain signal releases into the cerebral blood supply metabolic neuroproteins which are known to cause vasodilatation of the arterial walls and are considered responsible for some vascular headache.41 Although PEM-T is classified as tension headache, it could also contribute to the development of migraine.8, 42 Further studies need to be conducted to determine the association of headache with PEM-T. The ophthalmic steroid seems to quickly reach extraocular sites and somehow interact with acetylcholine receptors, the nociceptive receptors or the opioid receptors and acts as an anesthetic providing quick relief of pain. Quelling these inflamed extraocular tissues possibly removes a cause of tension headache. Prednisolone drops obviously do not ameliorate all headaches. However, any reduction of headache with the prednisolone drop would seem to implicate the eye muscles and tendons as possible sources of the pain.
Not only is pain elicited from the inflammation from PEM-T, but the heat of the inflammation is also possibly problematic. It is possible that the warming of the eye from PEM-T contributes to dry-eye syndrome.43, 44 Although this was not examined in this study, this possible effect deserves consideration since the diagnosis of PEM-T should be considered an anterior segment disorder. The redness of the inflammation can sometimes be seen near the muscle insertions. The swelling of the tissues from the inflammation should also be contemplated as it could contribute to the site sensitivity, and, perhaps, compression forces might affect other parts of the eye. This also should be studied.
Conclusion
The results of the data suggest that there is a correlation between monocular blur, a measure of fixation disparity, and eye pain. All sixty subjects with tender spots exhibited variable monocular blur during binocular viewing on the same eye except in two cases. This association was shown to be statistically significant. Prednisolone was also shown to mollify the soreness. All sixty subjects initially received a saline drop and while ten of the sixty subjects had improvement, thirty-nine of the remaining fifty subjects had a noticeable reduction of pain with either prednisolone acetate 1% or prednisolone sodium phosphate 1/8%. This result indicates that the areas eliciting the pain sensations could be soothed by either the lipophilic or hydrophilic derivatives of the steroid. The results were statistically significant with important clinical implications.
The study purports that presumed extraocular myositis and tendonitis might exist as a clinical entity. The study concluded that asthenopia from acute PEM-T when interfering with work or otherwise disabling could possibly be treated with prednisolone. Use of only one or two drops of steroids per incident would probably not greatly aggravate a herpes epithelial keratitis 45 ( such an infection would present quite differently to the clinician). However, patients must certainly be advised to return to clinic if pain is not resolved promptly. Also, there remains the danger of long term use of even limited use of steroids.25 The hydrophilic derivative would probably be the steroid of choice, because it was shown to be as effective as the lipophilic form and is known to have fewer long term side effects. However, regular visits to the eye doctor would be recommended to rule out a steroid response. As well, it would be advisable to limit the quantity of the drug prescribed to the patient.
More importantly, the use of steroids should be limited to acute episodes of PEM-T. Every effort should be made by the clinician to treat the underlying cause(s) of PEM-T so that both chronic and acute PEM-T will not occur. Prism lenses and other ophthalmic lenses, vision therapy and management are courses of action that can avert the progression of PEM-T. Prism lenses can be particularly useful in “balancing” an eye muscle imbalance and neutralizing an associated heterophoria. Often, eliminating the eye muscle imbalance eliminates the headaches.5, 6, 15 However, uncomfortable patients are appreciative of the steroid drops as they can break the cycle of inflammation and provide immediate relief. Such relief does vary. The author has noted from personal observation that for some the effect lasts days and weeks and for others, who quickly return to demanding vision tasks at work, the relief may be only hours.
The diagnosis and treatment of PEM-T may help clinicians differentiate it from other clinical entities and may help toward the understanding of eyestrain, an ever-growing problem in our computerized world.