Sir,
We read with interest the article by Akar et al.1 We would like to make the following observations/queries.
In patients with Duane’s retraction syndrome there is some degree of subnormal and some degree of anomalous innervation of the lateral rectus (LR) muscle. The extent and severity of the two may be variable. Presumably, subnormal innervation may lead to deficient abduction and anomalous innervation may lead to co-contraction with globe retraction, palpebral aperture narrowing, or retraction equivalents like upshoots and downshoots.
In their article the authors describe patients of type 1 Duane syndrome to be with esotropia of 20 pd or more, an AHP larger than 20°, limited abduction, and no significant upshoots or downshoots in the adducted position. There is no objective grading used for the measurement of shoots or palpebral aperture changes. Some of these cases may have had retraction or retraction equivalents (shoots) that were not clinically very apparent.
It has been suggested that vertical rectus transposition (VRT) may worsen retraction and shoots.2, 3 Thus an objective measurement (pre- and postoperative) of palpebral aperture changes and shoots is in order, more so with augmented transposition as in Akar et al.1
Also, the confirmation of absence of anomalous LR innervation pre-operatively is essential. This may be assessed by the Romero-Apis force degeneration test4 or, as suggested by some, by electromyography.5
It has also been suggested by some that prerequisite to VRT should be the elimination of misinnervation of the lateral rectus by a procedure such as periosteal fixation.6
We notice some increase in globe retraction on adduction in Figure 2a; however, it is difficult to comment with only a single photograph. We would like to know from the authors whether they noticed any worsening of retraction or shoots in their patients on follow-up.
In our opinion, VRT in DRS cases should always be performed with the rider that retraction and retraction equivalents may worsen.
References
Akar S, Gokyigit B, Pekel G, Demircan A, Demirok A . Vertical muscle transposition augmented with lateral fixation (Foster) suture for Duane syndrome and sixth nerve palsy. Eye (Lond) 2013; 27: 1188–1195.
Rosenbaum AL . Costenbader lecture. The efficacy of rectus muscle transposition surgery in esotropic Duane syndrome and VI nerve palsy. J AAPOS 2004; 8: 409–419.
Molarte AB, Rosenbaum AL . Vertical rectus muscle transposition surgery for Duane’s syndrome. J Pediatr Ophthalmol Strabismus 1990; 27: 171–177.
Romero-Apis D . Estrabismo. Auroch: Mexico, DF Auroch, 1997 p 156.
Souza-Dias C . Congenital VI nerve palsy is Duane syndrome until disproven. Binocul Vis Strabismus Q 1992; 7: 70.
Sharma P, Tomar R, Menon V, Saxena R, Sharma A . Evaluation of periosteal fixation of lateral rectus and partial VRT for cases of exotropic Duane’s retraction syndrome. Indian J Ophthalmol 2014; 62: 204–208.
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Bhambhwani, V., Pandey, P., Sood, S. et al. Vertical rectus transposition in Duane’s syndrome: does co-contraction worsen?. Eye 29, 839 (2015). https://doi.org/10.1038/eye.2014.309
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DOI: https://doi.org/10.1038/eye.2014.309