Abstract
Abstract: :
Purpose: To test the hypothesis that the rod photoresponse is altered by high dose deferoxamine (DFO). While thalessemics on chronic low dose DFO chelation therapy remain free of toxicity for years, high dose DFO may cause retinal toxicity. The mechanism for the DFO retinal toxicity is unknown. Methods: Iron overload of vital organs necessitated use of high dose DFO in a 28-year old woman with ß-thalessemia major, who had been managed with chronic transfusion and low dose DFO. After 5 weeks on high dose DFO, she developed severe visual complaints. DFO was discontinued after thorough evaluation of retinal and visual function including electroretinography. Her course was monitored for 4 years after discontinuing the high dose DFO. ERG responses to full-field stimuli were obtained in conditions that permitted derivation of rod photoresponse characteristics. Results: Rod cell sensitivity and the saturated amplitude of the rod cell response remained compromised, and never recovered to pre-treatment levels. Despite this, over the course of 2 years, extensive, dense scotomata vanished and dark-adapted visual sensitivity returned to normal. The ERG post-receptoral response parameters also gradually returned to normal. Conclusions: Irrevesible rod dysfunction was sustained, possibly through compromise of rod inner segment or pigment epithelial processes. Fortunately, visual deficits were largely reversible.
Keywords: electroretinography: clinical • electrophysiology: clinical • retina