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Nonsurgical option available for long-standing or sensory strabismus in adults
With Botox, improvements in the position of the eye can be seen even after the initial 3-month paresis has worn off.
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Case No. 1: Mr. Smith is a 50-year-old man who presents to the adult motility clinic with the complaint of new-onset horizontal binocular double vision. On exam, he has an esotropia that increases in left gaze and resolves in right gaze. He also has abduction deficit on the left side.
Case No. 2: Mrs. Brown is a 50-year-old woman who presents to the adult motility clinic with the complaint that her right eye drifts in. She denies ever having double vision and says that she has never been able to see the effect of a 3-D movie. Her eye has been drifting in for as long as she can remember, becoming more noticeable in adulthood. She is having more difficulty making eye contact and describes that people never know if she is looking at them in conversation. On exam, she has comitant esotropia with full extraocular movements in each eye.
Case No. 3: Mr. Ford is a 50-year-old man who presents to the adult motility clinic with the complaint of his right eye drifting out since he suffered a penetrating injury to his right eye 10 years prior. His vision was reduced to hand motion in the affected eye, and his eye has slowly drifted out over the past few years. He denies diplopia but complains of difficulty making eye contact and is very self-conscious of his eye misalignment.
In the above scenarios, Mr. Smith’s case describes paralytic strabismus, Mrs. Brown’s case describes uncorrected childhood strabismus, and Mr. Ford’s case describes sensory strabismus. The varying presentations depend on the timing of onset of the ocular misalignment and the potential for binocularity.
Lea Ann Lope
In the case of paralytic strabismus, the onset occurred after visual maturation with an acute disruption of the binocular system, therefore resulting in diplopia. Surgical correction of the strabismus restores the ocular alignment and stereoacuity. In the case of uncorrected childhood strabismus, the onset occurred before visual maturation with suppression of the misaligned eye. It is unlikely that even if these patients undergo surgical correction of their strabismus as an adult that they will ever have the potential for binocularity postoperatively. In the case of sensory strabismus, the misalignment occurred as a result of decreased vision in the affected eye with a subsequent decreased ability or inability to use both eyes together.
Uncorrected childhood strabismus, sensory strabismus
Patients with long-standing strabismus, often since childhood, that either was never corrected or was corrected and now recurred, and patients with sensory strabismus make up a large proportion of my adult strabismus population. All too often I have heard the same story from this subset of patients: that they were told nothing could be done to treat their ocular misalignment, that their insurance would not cover a cosmetic procedure because no functional benefit would come of it, and that they would have double vision if their eye alignment was fully corrected. Patients with long-standing strabismus, despite not commonly having double vision, long for correction of the misalignment of their eyes.
It is well-documented in the medical literature that strabismus carries several social stigmas. These psychosocial aspects of strabismus include poor self-confidence, decreased ability to make eye contact, difficulty securing employment and difficulty with interpersonal relationships. After strabismus surgery, an improvement in all these aspects has been reported.
The correction of long-standing strabismus without double vision is considered reconstructive, not cosmetic. Due to the known psychosocial aspects of strabismus, eye muscle surgery to reconstruct the ocular alignment to its normal position is covered by most insurance companies.
Treatment options
Treatment options for patients not complaining of double vision are limited. Prismatic correction in spectacles does not apply to these patients because the prisms do not actually change the position of the eye but help to alleviate double vision. Patients without double vision would not see a benefit from prismatic correction. Traditional eye muscle surgery has been the mainstay treatment for these patients, and it is performed just as it is for patients with double vision. The angle of misalignment is measured in the office and then translated to millimeters of extraocular muscle weakening or strengthening.
During the office exam, I look for suggestions of anomalous retinal correspondence, a situation in which a patient may acquire diplopia postoperatively due to the new ocular alignment. I began using Botox (onabotulinumtoxinA, Allergan) injections of the extraocular muscles as a diagnostic tool to determine if the patient would have diplopia once the angle of misalignment was changed. If the patient does not complain of double vision during the 3-month duration of action of the Botox, then I know it is prudent to proceed with the eye muscle surgery to correct the deviation in its entirety. This diagnostic use of Botox has been reported for use in the investigation of postoperative diplopia and fusion potential, and to differentiate between a partial and complete sixth cranial nerve palsy.
Patients without the potential for binocular vision do not have a drive postoperatively to keep the eyes aligned. Therefore, they must understand the risk of strabismus recurrence after surgery. Because of the risk of recurrence and the potential need for additional eye muscle surgery in the future, I have added therapeutic Botox injections of the extraocular muscles to my armamentarium of treatment. This procedure does not carry the risks of surgery; it can be done in the office setting with electromyographic-guided assistance or under anesthesia for patients who are more tentative.
Extraocular muscle injections
The use of Botox to treat strabismus has been well-reported in the medical literature for congenital esotropia and strabismus associated with cerebral palsy and to augment traditional eye muscle surgery. It also may play a role in adult patients with long-standing strabismus or sensory strabismus who desire an improvement in the position of the eye. Botox, which can be injected directly into the muscle through a needle electrode with electromyographic guidance, interferes with the release of acetylcholine at the neuromuscular junctions and temporarily inhibits muscle contraction. Its effects occur within days of the injection, and the temporary paresis of the injected muscle lasts approximately 5 to 8 weeks after injection. An injection between 2.5 units and 7.5 units is enough to produce the temporary paresis.
Long-lasting lengthening effects of the muscle can occur after the temporary pharmacologic muscle paresis has worn off, due to changes in the length-tension curves of the muscle and the muscle composition. We therefore can see an improvement in the position of the eye even after the initial paresis has worn off. One injection may be enough to improve the alignment to a point at which a patient is happy with the new alignment, or it may require multiple injections to reach this point. Long-term follow-up is needed to support this. Because the end goal in this population of patients is improvement in the physical appearance of the ocular alignment and not resolution of diplopia, an outcome of “improved” but not “perfect” is often sufficient. Botox may provide an alternative to surgical correction of treatment of long-standing and sensory strabismus.
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For more information:
Lea Ann Lope, DO, can be reached at Children’s Hospital of Pittsburgh, Children’s Hospital Drive, 45th and Penn Avenue, CHP Faculty Pavilion, Suite 5000, Pittsburgh, PA 15201; 412-692-9896; email: lopel@upmc.edu.Disclosure: Lope has no relevant financial disclosures.