Medial Rectus Muscle Advancement in Consecutive Exotropia

Abstract

Purpose: Consecutive exotropia is a frequent consequence of surgery for convergent strabismus that may develop at differing rates postoperatively. Several surgical options on horizontal recti have been proposed, but none report a clearly standardized amount of surgery. The present study provides further results of the medial rectus muscle advancement. Methods: Twenty-eight patients, age ranged from 6-55 years, who had undergone unilateral or bilateral medial rectus advancement to the physiological insertion, with or without contemporary unilateral lateral rectus muscle recession, were included in the study. Factors leading to the onset of consecutive exotropia were analyzed. Results: After 2-3 years, the overall mean angle reduction was 21.3 prismatic diopters (PD) for distance and 22.8 PD for near, with an effectiveness on near vision lower than expected. Only in the 7 cases with a preoperatively larger exotropia at near (of at least 10 PD), the reduction was 17.0 PD for distance and 24.6 PD for near. In unilateral medial rectus muscle advancement, the mean reduction was 14.3 PD for distance and 16.3 PD for near; in bilateral advancement it was 25.8 PD and 25.2 PD respectively. Conclusion: Medial rectus advancement is preferable to other options, especially in cases with convergence deficit, if no excess of divergence or limitation of bulb rotation is present, for which a lateral rectus muscle recession is indicated. Unilateral and bilateral surgeries are useful for exotropia of about 15 PD and 25 PD respectively. The effectiveness depends weakly or not at all on the amount of the previously executed recession.

Consecutive Exotropia after Convergent Strabismus Surgery—Surgical Treatment

“…In our study the advancement exceeds the original insertion of the muscles by maximum 2 mm in only 2 cases when angle of deviation was bigger than 55 PD. We performed an unilateral surgery on an amblyopic eye, especially in cases with unilateral amblyopia and literature data also support that most of surgeons approved this approach [5]. According to some author a major effect is expected if a further advancement is performed [5] but in our patients we have noticed the development of an eyelid fissure narrowing after large amount of advancement.…”

“…This deviation occurs according to Von Noorden between 2% -8% [1] while other studies found an incidence ranged from 4% to 27% [2] [3]. This surgical complication can develop immediately after surgery or many years and even decades later [4] [5], some risk factors causing its development have been reported by ophthalmologist like high hyperopia, amblyopia, vertical deviation, A and V patterns, nystagmus, large medial rectus recessions, restriction of adduction, multiple surgeries, and developmental delay, the failure to evaluate the patient condition preoperatively [2] [3] [5]- [8].…”

“…On the contrary, some surgeons assume that surgery on previously operated muscles is unpredictable and recommend recession of the LR muscles [8]. But, all authors accept that the decision regarding the surgical procedure to be taken involves an assessment of the type and amount of previous surgery and the presence of limitation of adduction (sometimes to the presence of scar traction) or convergence insufficiency [5]. It was established that, large recessions, exceeding 5 mm of the MRM can produce consecutive exotropia associated with limitation of adduction; large resections of the lateral rectus muscle can cause in contrary a limitation of abduction.…”

“…It was established that, large recessions, exceeding 5 mm of the MRM can produce consecutive exotropia associated with limitation of adduction; large resections of the lateral rectus muscle can cause in contrary a limitation of abduction. Usually recession is indicated for patients with consecutive exotropia with limited adduction after bilateral MRM recession, or in cases that underwent unilateral MRM recession/LRM resection surgery [5]. For patients with divergence excess or exotropia with normal MRM function a bilateral LRM recession is indicated, but it should be avoided in patients with limitation of adduction [5].…”

“…Usually recession is indicated for patients with consecutive exotropia with limited adduction after bilateral MRM recession, or in cases that underwent unilateral MRM recession/LRM resection surgery [5]. For patients with divergence excess or exotropia with normal MRM function a bilateral LRM recession is indicated, but it should be avoided in patients with limitation of adduction [5]. But one thing is actual concerning consecutive exotropia-it requires special attention of the orthoptist and surgeons, due to the difficulties in pre-operative assessment, in planning and even performing the surgery [4].…”