Visual function evaluation of Egyptian beta-thalassemia major patients on long-term desferal therapy

ABSTRACT

The success of the iron chelator desferal [DFO] in the treatment of beta - thalassemia is limited by its lack of bioavailability. Also, high dosage has been associated with toxicity of the eyes, ears and others. To investigate a possible subclinical visual neurotoxicity, 30 Egyptian p-thalassemia major [BTM] patients on long-term, recommended DFO dosage were studied using visual evoked potentials [VEPs] and electroretinogram [ERG]. We also aimed to clarify the relation of the possible abnormalities to various clinical, hematologic and biochemical parameters. Ten healthy age - matched individuals were enrolled as controls. Sixteen/30 [53.3%] patients showed subclinical abnormalities using VEP and/or ERG. Nine/30 [30%] had VEPs abnormalities, 10 [33.3%] had ERG abnormalities and 3 [10%] revealed abnormalities by both methods. An interesting observation was the significant association of abnormal VEP and MALE sex [P=0.0002]. No significant correlation was found between neurophysiologic abnormalities and all data studied as age, frequency of blood transfusion, DFO dosage/ duration, splenectomy, CBC values; S. ferritin, Serum Copper, S. Zinc and S. vitamin E. A single patient could have subclinical DFO-induced visual toxicity using VEP as his "toxicity" index [TI] was high [0.078]. the abnormalities can not be mostly attributed to long-term DFO therapy. Serial visual monitoring [including VEP and ERG] of all BTM patients is warranted. It is worthwhile to compare the long-term toxicity of the oral chelating agents [e.g. L 1 and ICL670] with that of DFO before definite conclusions are drawn on any visual neurotoxicity and its relation with the disease state or drug therapy