Woman referred for gradually progressive esotropia

Jeffrey Chang

Vivek Chaturvedi

A 56-year-old woman was referred to the pediatric ophthalmology and strabismus service at the New England Eye Center for gradually progressive left esotropia with accompanying hypotropia.

The patient stated that the condition began approximately 3 years prior to presentation and that she had never had any problems with eye misalignment earlier in her life. The patient denied any pain or ocular swelling at any time during the course of the progression. She denied any diplopia but has had poor vision for years secondary to very high myopia in both eyes.

Ocular history was significant for pathologic myopia in both eyes and dense nuclear sclerotic cataract in the left eye. The patient had no history of thyroid abnormalities, and medical history was significant only for hypertension and osteoporosis. She denied prior head or ocular trauma. She had no family history of strabismus or amblyopia. The patient’s review of systems was unremarkable.

Examination revealed visual acuity of 20/400 in the right eye and hand motions in the left eye. Current glasses prescription was –16.00 +2.50 × 180 in the right eye and –15.00 +4.00 × 180 in the left eye. IOPs were 16 mm Hg in both eyes, and pupil exam showed no afferent pupillary defect.

Figure 1. Left eye fixed in adduction, infraduction.	Figure 2. Myopic fundus with tilted nerve, temporal crescent and visible choroidal vasculature.
Figure 3. Medially displaced superior rectus and inferiorly displaced lateral rectus. Images: Swanic M, Strominger M

Anterior segment exam was unremarkable except for the presence of a densely brunescent cataract in the left eye that prevented visualization of the fundus. Motility exam revealed a left eye that was fixed in esotropia and hypotropia in all fields of gaze (Figure 1). Forced ductions were performed in the office and revealed restriction of ocular motility in the left eye. Fundus exam of the right eye showed a myopic fundus (Figure 2). An MRI scan was obtained and showed no extraocular muscle thickening, but it did show abnormal muscle pathways of the superior and lateral rectus muscles. The superior rectus was shifted nasally while the lateral rectus had shifted inferiorly (Figure 3). Both globes were markedly enlarged, most likely secondary to myopia. Additional MRI sections revealed superotemporal prolapse of the left globe.

What is your diagnosis?

Motility disturbances

Evaluation of a patient with motility disturbances should include a determination as to whether the problem is restrictive or paralytic. This was attempted with forced ductions, which revealed the restrictive nature of the patient’s disease. After this determination was made, the MRI was ordered, and it revealed abnormal locations of the superior and lateral rectus muscles. These findings coupled with a long-standing history of pathologic myopia made the diagnosis apparent.

Diagnosis

The patient was diagnosed with convergent strabismus fixus secondary to high myopia. This is a rare disorder that commonly presents as a gradually progressive esotropia. Over time, without intervention, patients progress to having an eye that is fixed in adduction and is also noted to have substantial restriction of elevation. This final fixed position of the eye gives it the name strabismus fixus. Many patients will subsequently go on to develop the condition in the opposite eye. Sturm et al presented a case of a patient functionally blind due to this extreme eso/hypo deviation in both eyes that completely hid both of his corneas.

Discussion

Myopic strabismus fixus is thought to be secondary to prolapse of the globe out of the muscle cone. This prolapse has been postulated to be secondary to the enlargement of the eye seen in very high myopia. This prolapse of the globe leads to a shift in the muscle pathways of the superior and lateral rectus muscles, nasally and inferiorly, respectively. It is important to note that the locations of the extraocular muscle insertions are not changed. The shift of the lateral rectus inferiorly is thought to lead to infraduction and decreased abduction ability, while the shift of the superior rectus medially likely causes adduction and decreased elevation ability.

A study by Aoki et al that evaluated 16 patients with acquired esotropia secondary to high myopia with MRI found similar muscle pathway deviations to our patient. They evaluated the muscle pathways and level of globe prolapse and found that patients with greater degrees of prolapse and muscle deviations showed greater motility abnormalities. They also studied patients with high and moderate myopia who did not show any ocular motility problems and found that they had no abnormalities in eye muscle position. Of note, the average axial length of patients with high myopia in their study was 29.9 mm while the average axial length of high myopes with motility problems was 33.9 mm. This suggests that the markedly increased axial lengths may be responsible for the globe prolapse and motility disturbances seen in myopic strabismus fixus.

Management

The optimal surgical correction of myopic strabismus fixus is not yet known. Mild cases have been successfully treated with medial rectus recession with lateral rectus resection. This has not been effective for patients with severe disease, such as our patient. Yamada et al published a surgical procedure involving hemi-transpositions of the superior and lateral rectus muscles with scleral fixation 7 mm from the limbus. They combined this with medial rectus recession and reported good outcomes. Wong et al subsequently published their experience with performing a loop myopexy in which the superior and lateral rectus muscles are looped together in an attempt to restore the more lateral position of the superior rectus combined with the more superior position of the lateral rectus. They had to combine this procedure with medial rectus recession to further improve alignment.

Figure 4. Lateral rectus heads inferiorly.	Figure 5. Superior rectus heads medially.
Figure 6. Improvement in left eye position with remaining esotropia.

Because of our prior experience with the procedure, the patient was scheduled for loop myopexy as described by Wong et al. In the operating room, the lateral rectus muscle pathway was found to be heading inferiorly (Figure 4). As expected, the superior rectus was noted to be heading medially (Figure 5). Both muscles were isolated and looped together with nonabsorbable suture, and the conjunctiva was closed.

On postoperative day 1, a marked improvement was noted in the position of the left eye in primary gaze (Figure 6). The patient was extremely pleased with her eye position. We will re-evaluate the patient in the coming months and may perform medial rectus recession to correct the remaining esotropia in primary position. She will also be evaluated for cataract surgery in the left eye, as her new eye position will greatly facilitate the removal of her densely brunescent cataract.

References:

• Aoki Y, Nishida Y, Hayashi O, et al. Magnetic resonance imaging measurements of extraocular muscle path shift and posterior eyeball prolapse from the muscle cone in acquired esotropia with high myopia. Am J Ophthalmol. 2003;136(3):482-489.
• Godeiro KD, Kirsch D, Tabuse MK, Cronemberger M. Yamada’s surgery for treatment of myopic strabismus fixus. Int Ophthalmol. 2008 June 21. [Epub ahead of print].
• Sturm V, Menke MN, Chaloupka K, Landau K. Surgical treatment of myopic strabismus fixus: a graded approach. Graefes Arch Clin Exp Ophthalmol. 2008;246(9):1323-1329.
• Wong I, Leo SW, Khoo BK. Loop myopexy for treatment of myopic strabismus fixus. J AAPOS. 2005;9(6):589-591.
• Yamada M, Taniguchi S, Muroi T, Satofuka S, Nishina S. Rectus eye muscle paths after surgical correction of convergent strabismus fixus. Am J Ophthalmol. 2002;134(4):630-632.

• Matt Swanic, MD, and Mitchell B. Strominger, MD, can be reached at Tufts Medical Center, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.

• Edited by Jeffrey Chang, MD, and Vivek Chaturvedi, MD. Drs. Chang and Chaturvedi can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.