Sir,
The article titled, “Large exotropia after retrobulbar anesthesia,” by Kim and Kim[1] is well-written and a very rare and an interesting one. I commend the authors for the workup of the case and its management.
An observation made is that lateral rectus alone is affected in both the eyes. Due to similarity, though asymmetry, of affection, a question, whether the muscle and the individual are susceptible to myotoxicity, is raised. Direct injection into the muscle is another possibility which can be ruled out if the extraocular movements were tested after inserting the needle and before injecting the anesthetic.
Myotoxicity either due to injection of anesthetic into the muscle or its proximity causes degeneration followed by regeneration of muscles in a span of 3–4 weeks as shown by some studies[2,3] whereas permanent restriction was reported in a few cases.[4,5] In the present case, there was progressive deterioration of contracture of lateral recti which is a rare phenomenon.
The right eye was operated first followed by the left. Was there any restriction of movements noted in the gap of 1 month? It is also not clear, exotropia was observed after how many days following surgery. This information provided by the authors may help practitioners to anticipate and correlate the condition. Histologically, there is the appearance of macrophages within the muscle fibers which phagocytose fragmented cytoplasm, seen as early as 14 hours.[2] The role of inhibitors of macrophage recruitment to the site of inflammation has to be elucidated in future. At molecular level, increased intracellular Ca2+ appears to be a necessary element in myotoxicity.[3] Hence, intervention at molecular level may open doors to such myotoxicity.
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References
- 1.Kim CH, Kim US. Large exotropia after retrobulbar anesthesia. Indian J Ophthalmol. 2016;64:91–2. doi: 10.4103/0301-4738.178148. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Benoit PW, Belt WD. Destruction and regeneration of skeletal muscle after treatment with a local anaesthetic, bupivacaine (Marcaine) J Anat. 1970;107(Pt 3):547–56. [PMC free article] [PubMed] [Google Scholar]
- 3.Zink W, Graf BM. Local anesthetic myotoxicity. Reg Anesth Pain Med. 2004;29:333–40. doi: 10.1016/j.rapm.2004.02.008. [DOI] [PubMed] [Google Scholar]
- 4.Rainin EA, Carlson BM. Postoperative diplopia and ptosis. A clinical hypothesis based on the myotoxicity of local anesthetics. Arch Ophthalmol. 1985;103:1337–9. doi: 10.1001/archopht.1985.01050090089038. [DOI] [PubMed] [Google Scholar]
- 5.Capó H, Roth E, Johnson T, Muñoz M, Siatkowski RM. Vertical strabismus after cataract surgery. Ophthalmology. 1996;103:918–21. doi: 10.1016/s0161-6420(96)30587-3. [DOI] [PubMed] [Google Scholar]