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Abstract

An electroretinographic (ERG) study was undertaken to test the hypothesis that scotopic retinal function is altered in transfused thalassemics on chronic Deferoxamine (DFO). ERG a- and b-wave responses and dark adapted visual thresholds were obtained from 11 patients with beta-thalassemia major, ages 7 to 38 (median 17) years. A quantitative model of the activation of phototransduction was fitted to the a-waves to estimate the gain of the transduction processes and the saturated amplitude of the rod photoresponse. From b-wave stimulus/response functions. the saturated b-wave amplitude and an index of b-wave sensitivity (log sigma ) were calculated. The patients' data were compared to those of normal subjects. The relations of the ERG parameters to age. average ferritin level, and duration of transfusion without DFO as well as other clinical parameters were examined. Longitudinal measures of b-wave responses and dark adapted visual thresholds. available for nine of the patients, were examined for significant change over time. For all patients both the gain and saturated amplitude of the rod response are normal. In two patients log sigma is below the 99% prediction interval for normal. One has low scotopic visual sensitivity. The duration of transfusion therapy unprotected by DFO chelation therapy was correlated with log a. These results suggest iron accumulation rather than DFO toxicity underlies scotopic dysfunction in older thalassemics. some of whom may have had extended periods of transfusion without the protection of chelation. Thus, monitoring of retinal function is recommended in such patients.

Macular vitelliform lesion in desferrioxamine-related retinopathy

“…To our knowledge, only a single report demonstrated the presence of a similar vitelliform-appearing macular lesion in a patient with desferrioxamine toxicity [14]. Although electrophysiologic testing can be useful in demonstrating photoreceptor and retinal pigment epithelial cell dysfunction in patients with desferrioxamine toxicity, these tests are not specific and variable results have been reported [9,15,16]. Our patient's full-field ERG showed normal cone and rod responses.…”

Retinal abnormalities in β-thalassemia major

“…The iron overload caused by the transfusion therapy and the iron chelator-induced toxicity both increase the need for thalassemic patients to undergo regular ophthalmic evaluations. 9 ; 31 ; 56 ; 57 …”

“…40 ; 50 ; 53 ; 64 ; 76 ; 80 ; 91 ; 92 ; 98 Furthermore, monitoring of retinal function with ERG has been useful in β-TM patients who have nine or more years of transfusions unprotected by iron chelation therapy. 57 …”

“…They concluded that iron might have damaged rods when the patients became iron overloaded. 57 Moreover, they concluded that iron chelation therapy protected against iron induced retinal damage. 10 ; 16 ; 19 ; 57 Both Genead et al and Pan et al, presented case-reports of DFO-induced retinopathy and demonstrated no clinical alterations in ERG findings.…”

“…57 Moreover, they concluded that iron chelation therapy protected against iron induced retinal damage. 10 ; 16 ; 19 ; 57 Both Genead et al and Pan et al, presented case-reports of DFO-induced retinopathy and demonstrated no clinical alterations in ERG findings. 40 ; 71 Interestingly, Simons et al, demonstrated ERG and EOG alterations in a β-TM patient who was noncompliant with DFO chelation therapy.…”