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Scleral buckling is still the most common procedure to repair a rhematogenous retinal detachment. Acute or chronic infection of scleral explant is rare but well recognised serious postoperative complication threatening the eye and jeopardising the retinal attachment and visual outcome. They may present acutely as painful red eye with purulent discharge or chronically with extrusion of the explants. The reported incidence varies between 0.5% and 5.6%.1 Surgical technique, different synthetic materials of scleral explants, duration of surgery, size, and position of buckle affect the rate of infection.
In the largest retrospective review of 757 patients with episcleral buckle for rhegmatogenous retinal detachment, Roldan-Pallares and associates had reported 1.3% patients requiring removal of the implant with the commonest seen in silicone sponge (9%) and the least common encountered in hydrogel implant (1.3%).2
Smiddy et al have studied 45 cases of scleral buckling infection and identified coagulase negative staphylococci being the most common isolates (17 of 33 positive cultures), and the others include Staphylococcus aureus, Bacillus, and Mycobacterium.1Corynebacterium pseudotuberculosis is a rare zoonosis and, apart from its rare description in human lymphadentitis, it has not been reported in the ophthalmology literature. The isolates from the scleral buckle infection of our case was susceptible to penicillin and vancomycin. The treatment regimen and possible sources of the infection have been explored.
A 63 year old white man presented with 8 week history of dull ache over his left eye coupled with mucopurulent discharge. He had received an uneventful scleral buckling surgery with encircling silicone rubber band, 5 mm radial hydrogel episcleral sponge, and cryopexy for his left eye retinal detachment 8 years earlier. On examination, the visual acuity was 20/20 in his right eye and 20/50 in his left. Examination revealed exposed hydrogel scleral buckle with surrounding conjunctival oedema and hyperaemia (fig 1). Fundus examination showed a clear view and an attached retina with good buckle support. There was no feature of erosion and the chorioretinal adhesion from previous retinal cryopexy looked adequate. An infected buckle was diagnosed and the removal of buckle was arranged. Intraoperatively, the hydrogel buckle was noticed to be decomposed into a mess and it had to be removed in pieces. The scleral bed was irrigated with copious gentamicin solution. Gram smear of the specimen showed Gram positive bacilli and culture grew Corynebacterium pseudotuberculosis, which was sensitive to penicillin and vancomycin but resistant to erythromycin. One week of systemic ampicillin and cloxacillin together with 4 weeks of topical penicillin and vancomycin were prescribed. The conjunctival wound healed without sequelae and the retina remained attached. Upon inquiry, he did not have any history of trauma or gross contamination over the ocular surface. There was no recent travel history within 6 months from buckle exposure. He had constant contact with animals, as a dog was kept as a pet at home.
A hydrogel episcleral implant is the most resistant material to be infected in buckling surgery.2 This peculiar clinical and bacteriological pattern may be related to the intricate physiochemical and biocompability characteristics of hydrogel. The low infective incidence of hydrogel implant was believed to be because of the lack of dead spaces and probable antibiotic absorption and depot effect.3 However, observations related to the fragility, swelling, and fragmentation of the hydrogel material with time were made since the first report in 1997 and the dead spaces created could possibly contribute to delayed episcleral implant infection years after surgery.2,4–6
Corynebacterium pseudotuberculosis is a veteran infection and throughout the literature only 25 cases have been reported in humans and 22 of them have been reviewed.7 Exposure is usually occupational especially with a history of contact with sheep. The sheep farming industries within New Zealand and Australia are particularly involved. Infected humans generally presented with lymphadenitis, abscess, and constitutional symptoms.
Animal acquired infection was deemed as the most probable source of infection in our patient since he had a contact history with domestic animals, but otherwise no gross ocular soiling or contaminations was noted. Just like other human infection, the presentation of scleral buckling infection is closely related to the virulence and infective dose of the offending organisms. Our case may represent the first human ocular Corynebacterium pseudotuberculosis infection involving a scleral buckle after retinal reattachment operation.
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