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J. S. Baath, W. C. Lam, M. Kirby; Deferoxamine Ocular Toxicity: Incidence and Outcome in a Paediatric Population. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3702.
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Deferoxamine (DFO) is a chelating agent used widely for the treatment of transfusional hemochromatosis. The described ocular side-effects of DFO have included symptoms such as blurriness, field constriction, and colour vision dysfunction, and objective findings such as pigmentary retinopathy and decreased responses on ERG. Many institutions have adopted an ophthalmic screening protocol for patients on DFO despite little information regarding the rate of ocular toxicity. Our study aimed to determine the incidence of DFO toxicity at a major paediatric hospital that uses regular ophthalmic screening for all DFO patients.
An REB approved retrospective case series of all patients treated with DFO for transfusional hemochromatosis at The Hospital for Sick Children (HSC) in Toronto, Canada between 1995 and 2005 inclusive. The regular protocol for DFO patients at HSC includes receiving ophthalmic screening exam at baseline with yearly follow-up. Data collected from charts included demographics, medical history, non-ocular side-effects of DFO, age at start of DFO, age at first ophthalmic exam, number of ophthalmic exams, and detailed information regarding the ophthalmic follow-up of any patient that developed DFO ocular toxicity.
A total of 84 patients received regular DFO treatment for transfusional hemochromatosis related to long-term hypertransfusion. 70 (83.3%) had Beta Thalassemia Major, 10 (11.9%) had E Beta Thalassemia, and 4 (4.8%) had Alpha Thalassemia. The average age of the patients at the time of this analysis was 12.6 years (SD 5.6 years) and average age at start of DFO was 6.0 years (SD 3.4 years). 17 (20.2%) patients developed bone toxicity from DFO and 1 (1.2%) developed auditory toxicity. A total of 421 ophthalmic screening examinations were performed for an average of 5.0 exams per patient. DFO related ocular toxicity was found in only 1 (1.2%) patient. This patient developed central blurriness, retinal pigmentary changes on examination, and decreased central responses on ERG. Symptoms improved after 3 days of stopping DFO and the patient has achieved normal clinical and ERG follow-up for three years after restarting a lower dose of DFO.
In this large paediatric centre, DFO related ocular toxicity has been a rare and mild finding. Although the rate of toxicity is low, regular ophthalmic screening may still be justifiable as early detection of retinal toxicity may lead to optimization of the DFO dose and thus prevention of long-term visual sequelae.
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