Subconjunctival Gentamicin Induction of Extraocular Toxic Muscle Myopathy

Abstract

Subconjunctival injection of commercially available gentamicin, delivered in one of several protocols, caused an acute toxic reaction myopathy of the extraocular muscles. The response began as a small focal infiltrate of polymorphonuclear leukocytes, and as the lesion progressed it assumed a mononuclear cell predominance accompanied by muscle fiber degeneration. The injection of individual components of the commercial preparation (gentamicin, methylparaben, ethylenediaminetetraacetic acid (EDTA) and sodium bisulfite), each at the same concentration as in the parent solution, gave no response except for gentamicin alone. Gentamicin caused acute toxic myopathy when injected away from the muscles and when given as an isotonic solution in saline compared to the hypotonic commercial solution. Solutions at acidic pH not containing gentamicin did not initiate myopathy. Several factors that have been inferred as participating in the toxic response to gentamicin have been eliminated. Gentamicin alone is responsible for the induction of the extraocular muscle myopathy.

Post‐cataract surgery diplopia: aetiology, management and prevention

“…This last category has received much attention recently as a potentially avoidable cause of vertical diplopia. Strabismus of this type has been attributed to bridle‐suture trauma to the superior or inferior rectus muscle, direct needle trauma to muscles or related nerves from the retrobulbar needle, ischaemic injury of the muscle from swelling and haematoma formation and an inflammatory reaction to subconjunctival gentamicin; however, most authors now believe that squint is mediated by the myotoxic effect of the local anaesthetic during the retrobulbar injection . The capacity of commonly used local anaesthetics to permanently damage extraocular muscles is now well established.…”

Persistent diplopia after retrobulbar anesthesia

“…If the muscle involved is the superior There are various opinions about the most comrectus muscle, deviation is increased in the upward gaze monly involved muscle. [3][4][5][6][7][8][9][10][11][12][13][14] In this study, the most comand there is lateral incomitance in which deviation is monly involved muscle was the superior rectus muscle. increased in the upward and lateral gaze and normal Contrary to the common notion that the inferior rectus duction of contralateral eye excludes underaction of the muscle is the 1 most commonly affected by retrobulbar contralateral inferior oblique muscle.…”

“…2 Various optical aberration (optical aniseikonia) because of aphakia or pseudophakia; reversal of ocular dominance; and causative mechanisms have been suggested: damage to extraocular muscles and orbital soft tissues during operacolor/brightness disparity between operated and unoperated eyes. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In this study, we evaluated clinical chartion, either directly or secondary to injury of adjacent acteristics of the patients with diplopia persisting for more than 6 months and analyzed the causative factors. in 14 patients, in 12 patients diplopia was due to overaction of the vertical rectus muscle (Table 2), and in 2 patients the diplopia was due to minimal underaction Case Report of the extraocular muscle.…”

Inferior rectus paresis and medial rectus overaction following retrobulbar anesthesia for cataract surgery

“…The possible mechanisms of damage include direct trauma by the needle or bridle suture, myotoxicity by local anesthetic and subconjunctival gentamicin injection. It is interesting to note that in some cases the paresis may persist whereas in others initial muscle damage may be followed by muscle fibrosis and overaction [1][2][3][4][5][6][7][8][9]. We report one such case, wherein underaction of one of the vertical muscles was associated with overaction of a horizontal muscle.…”