CT Orbit Report: Squint and Lengthening of Right Medial Rectus
Surgical correction of the right medial rectus muscle is the best management option for squint with lengthening of the right medial rectus muscle, as this represents a mechanical restriction requiring anatomical correction to improve ocular alignment and prevent diplopia. 1
Radiological Findings
- Right medial rectus muscle lengthening
- Associated squint (esotropia)
- No evidence of orbital trauma, thyroid eye disease, or other orbital pathology
Clinical Implications
Differential Diagnosis
The lengthening of the right medial rectus muscle with squint may represent:
- Myopic strabismus fixus
- Sagging eye syndrome
- Divergence insufficiency
- Post-traumatic medial rectus lengthening
- Congenital anomaly of the medial rectus
Functional Impact
- Esotropia (inward deviation of the eye)
- Potential diplopia (double vision)
- Restricted abduction (outward movement)
- Possible abnormal head positioning to compensate
Management Algorithm
1. Initial Assessment
- Perform forced duction testing to confirm restriction
- Measure the angle of deviation in primary position and all gazes
- Evaluate convergence amplitudes at near
- Rule out other causes (thyroid eye disease, orbital trauma, 6th nerve palsy)
2. Non-Surgical Options
- For mild, occasional symptoms:
- Observation if patient is opposed to intervention
- Fresnel or ground-in prisms for small to moderate deviations
- Note: Prism correction may need to increase over time 1
3. Surgical Intervention
- Primary approach: Medial rectus recession with potential lateral rectus resection 1
- Surgical planning considerations:
- Typically requires greater surgical dose than standard tables indicate
- Consider adjustable sutures with target of 2-4 prism diopters exophoria
- Assess for mechanical restriction with forced duction testing
- If significant restriction exists, consider wider spreading of the muscle during recession
4. Surgical Techniques
For standard medial rectus lengthening:
- Unilateral or bilateral medial rectus recession
- Potential ipsilateral lateral rectus resection
- Consider adjustable suture technique for optimal results 1
For complex cases with significant restriction:
- Consider muscle union procedures if associated with high myopia
- The Yokoyama procedure may be indicated (suture union of superior rectus and lateral rectus) 1
5. Post-Surgical Management
- Monitor for potential consecutive exotropia
- Consider small residual prism correction if needed
- Watch for lower lid retraction as potential complication
Important Caveats
- Surgery should be delayed until measurements are stable for at least 4-6 months if there is active inflammation 2
- Vertical strabismus surgery has a lower success rate (66%) compared to horizontal strabismus surgery (84%) 2
- Risk of "pulled-in-two syndrome" (muscle rupture during surgery) is higher with inflamed or fibrotic muscles 2
- Fusional exercises have not proven beneficial for treatment of divergence insufficiency 1
- Surgical success rates are generally favorable for horizontal muscle surgery 1
Special Considerations
- If bifid (split) medial rectus is discovered intraoperatively, surgical plan may need modification with asymmetric recession of the muscle heads 3
- If the medial rectus appears detached or severely damaged, prognosis may be poorer and specialized reconstruction techniques may be needed 4
- Careful preoperative imaging assessment is essential to rule out other orbital pathologies that may mimic or contribute to the presentation