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Woman presents with late-onset progressive esotropia
The left eye demonstrated an adducted position in primary gaze with restriction on elevation and abduction.
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A 73-year-old woman presented to the New England Eye Center for an evaluation of progressive esotropia of her left eye. She reported that her left eye had been turning inward for the past 40 years but had gotten progressively worse over the past 3 years. She denied any sudden changes in vision or diplopia. She denied having esotropia as a child. She required glasses for myopia in her left eye as a child but denied patching or previous eye surgery.
At the time of consultation, the patient had severe myopic degeneration in the left eye, cataracts in both eyes and blepharitis in both eyes. She was not on ophthalmic medications and had no family members with eye disease.
History
Her medical history was significant for hypercholesterolemia and osteoporosis. Her medications were celecoxib, atorvastatin, vitamin A and cetirizine. Her surgical history was not significant. Her family history was significant only for breast cancer in her mother. She was a former smoker and did not have any history of alcohol abuse.
Examination
The patient’s best corrected visual acuity was 20/25 in the right eye and count fingers at less than 6 inches in the left eye. Manifest refraction was +4.50 –2.00 × 180 in the right eye and –17.00 in the left eye. Pupillary response was normal in both eyes (4 mm to 2.5 mm) with no afferent pupillary defect. Confrontational visual fields and IOP were normal in both eyes.
The extraocular muscle exam is shown in Figure 1. Duction testing was full in the right eye, but the left eye demonstrated a –2 limitation of abduction and a –2 limitation of elevation on abduction. Modified Krimsky test with the patient focused at distance revealed a left esotropia of 40 D and a left hypotropia of 8 D.
Figure 1. Extraocular movement photos demonstrating adducted position of the left eye in primary gaze with restriction on elevation and abduction.
Images: Lee G, Strominger MB
Anterior segment exam showed blepharitis in both eyes, clear corneas, and normal anterior chamber and iris, with 1 to 2+ nuclear sclerotic cataract in the right eye and 1 to 2+ cortical, 3+ nuclear sclerotic and 1+ posterior sclerotic cataract in the left eye.
On posterior segment exam, the patient had posterior vitreous detachments of both eyes but clear media. The optic nerve was normal in the right eye with a cup-to-disc ratio of 0.3, and the left optic nerve had a tilted disc with peripapillary atrophy but a cup-to-disc ratio of 0.3. Fundus exam of the right eye was normal, and the left eye had myopic macular atrophy with retinal pigment epithelial changes. The peripheral retina was otherwise normal.
What is your diagnosis?
Progressive esotropia
The differential diagnosis of late-onset progressive esotropia and hypotropia includes cranial nerve VI palsy, partial cranial nerve III palsy, thyroid eye disease, prior orbital wall fracture with restriction of the extraocular muscles, orbital myositis and convergent strabismus fixus.
By history, the course of the patient’s esotropia was slowly progressive, making an ischemic or paralytic cranial nerve less likely. She denied any history of trauma to the orbit or facial fractures. She had no pain in the eye and no proptosis, which made thyroid eye disease and orbital myositis less likely. MRI of the orbits showed no orbital masses or enhancement or enlargement of the muscles, but it revealed the orientation of the muscles (Figure 2). The left superior rectus had shifted nasally, and the left lateral rectus was shifted inferiorly.
Given her clinical findings and MRI results, the patient was diagnosed with convergent strabismus fixus.
Convergent strabismus fixus is a progressive abnormality of the eye muscles and pulley system, resulting in a fixed eye position in adduction with restriction of abduction. With time, the eye also may develop hypotropia with limitation of elevation. The main finding associated with this abnormality has been moderate to high myopia. Demer et al reported the existence of the connective tissue “pulley” system in the posterior Tenon’s fascia that moves with the eyes and represents the functional origin of the muscles.
Figure 2. Coronal section of MRI of the orbits demonstrating inferotemporal displacement of the lateral rectus muscle (arrow) and nasal displacement of the superior rectus muscle (arrowhead).
Figure 3. Postoperative alignment photos demonstrating small residual esotropia but much improved primary position with improved elevation and abduction.
Orbital imaging studies of eyes with convergent strabismus fixus have demonstrated displacement of the lateral rectus muscle inferotemporally and the superior rectus muscle nasally, with the posterior portion of the elongated myopic eye prolapsing in a superotemporal direction. A hypothesis for the pathophysiology of convergent strabismus fixus is that in highly myopic eyes, the long eye stretches the superior and lateral recti bands, resulting in an initial shift of the lateral rectus muscle inferotemporally, restricting abduction and increasing infraduction. Additionally, the superior rectus muscle shifts nasally, resulting in increased adduction and limitation of elevation with resultant hypotropia. The result is an eye that is pulled into an adducted hypotrophic position with significant restrictions in abduction and elevation.
Mild cases can be treated with medial rectus recession and lateral rectus resection with possible upward displacement and posterior fixation of the lateral rectus muscle. However, because the pulley system is not rectified, these patients may require additional surgeries. Yamada’s technique involves a hemi-transposition of the superior and lateral recti muscles and recession of the medial rectus muscle. While effective, this may result in anterior segment ischemia by operating on three of the recti muscles. More recently, there have been reports of using a loop myopexy of the superior and lateral recti muscles, using either a non-absorbable equatorial stay suture or a silicone band, which are effective and easily reversible, with little risk of compromise of the anterior ciliary circulation. Additional medial rectus recession can be performed if the esotropia is particularly large.
The patient underwent strabismus surgery using a loop myopexy with a non-absorbable suture of the superior and lateral recti muscles shown (Figure 3). The patient had good abduction and elevation ductions of the left eye.