Evaluating the Clinical Effectiveness of Medial Rectus Local Anaesthetic Injections for the Treatment of Near Exotropia
Rahul Dwivedi, BSc(Hons), MBChB; Ian B. Marsh, FRCOphth
Aintree University Hospital
Introduction: Earlier studies demonstrate injecting local anaesthetic (LA) into extraocular muscles disrupts their structure, encourages remodelling whilst increasing their strength and stiffness.1 This study evaluates the clinical effectiveness of LA injections to the medial rectus (MR) muscle of patients with near exotropia.
Methods: Retrospective case-note study of patients with symptomatic near exotropia who underwent LA injections to their MR muscles between October 2014-May 2017. Data analysed via Microsoft Excel; T-Test statistical analysis performed(P<0.01 significant). Patient age, pre-operative angle of deviation in prism dioptres(PD), post-operative angle(PD), mean reduction of angle(PD), improvement of diplopia, post-operative follow-up period, further management and complications evaluated.
Results: 10 eyes of 8 patients. Mean age=34.9 years. All patients underwent injection of their MR with 5ml Marcain 0.5%. Mean pre-operative angle of deviation=11.2PD. Mean post-operative angle=7.70PD (P=0.009). Mean reduction in angle=3.50PD (P=0.0004). 62.5%(5 patients)=improvement of diplopia. 50%(4 patients)=further procedures. 2 patients=LA to contralateral MR. 1 patient=ipsilateral MR resection/LR recession(adjustable suture). 1 patient=ipsilateral LR botox+repeat MR LA. Mean post-operative follow-up=3.7 months. No complications.
Discussion: Injecting LA into the MR of patients with near exotropia achieves a reasonable reduction in the angle of deviation that is statistically significant. Nearly two-thirds of the patient sample experienced improvement of diplopia and half required further management. There were no complications.
Conclusion: Although achieving statistically significant results with regards to reducing angles of deviation, injecting LA into MR of near exotropia patients produces a modest clinical response for reducing diplopia. It is a safe procedure that may be a useful initial and/or adjunctive treatment option for these patients.
References: 1. Scott AB1, Miller JM, Shieh KR. Treating Strabismus by injecting the agonist muscle with bupivacaine and the antagonist with botulinum toxin. Trans Am Ophthalmol Soc 2009 Dec; 107: 104-9.