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A 77 year old man with diplopia
Digital Journal of Ophthalmology 2004
Volume 10, Number 11
November 19, 2004
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| Diagnosis and Discussion | The diagnosis of right inferior rectus muscle injury with secondary fibrosis and restriction was made and the patient underwent an inferior rectus recession on an adjustable suture.
Persistent binocular diplopia is a rare complication of cataract extraction and is estimated to occur in 0.2 to 0.3% of cases [1,2]. The diplopia is thought to be the result of trauma to one or more extra-ocular muscles, either directly through needle trauma or bridle sutures or indirectly through the myotoxic effect of local anaesthetic [3-6]. The myotoxicity of local anaesthetics (lignocaine, mepivacaine and bupivacaine) have been clearly illustrated in experimental studies on rats, primates and humans [7,8]. In all cases the histological findings supported destruction of virtually all muscle fibres in the infiltrated muscles. Carlson et al found minimal muscle regeneration in the human study and suggests the patients advanced age as a contributory factor for increased fibrosis. The inferior rectus muscle was affected in up to 80% of all cases [2, 9-12]. Muscle injury can cause paresis, over action or contracture. Contracture or fibrosis follows an initial period of paresis but, as this case demonstrates, patients do not present during the paretic phase, as they only become symptomatic weeks or months after the surgery. It has been suggested that left eyes are more commonly involved as right-handed professionals who may have difficulty with access to the left eye give most of the anaesthetic blocks [2,13]. MR or CT imaging techniques has shown segmental thickening or enlargement of the inferior rectus muscle in patients with restriction following cataract extraction [9,14].
There is consensus in the literature regarding the treatment of these cases with the vast majority of authors suggesting recession of the restricted muscle using an adjustable suture technique if the diplopia cannot be controlled with prisms. The results appear to be extremely good with most patients achieving fusion after surgery with or without prisms.
A sub-tenon’s or topical local anaesthetic technique has been suggested to reduce the risk of this complication although there have been case reports implicating sub-tenon’s anaesthesia in strabismus following cataract extraction [15,16].
In conclusion, diplopia following cataract extraction is a rare complication but all patients should be told about the possibility of postoperative diplopia and strabismus. The vast majority of cataract surgery is performed in an elderly population, which may reduce the chances of regeneration of the affected muscle with an increase in subsequent fibrosis and contracture.
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