Colour contrast sensitivity and electrophysiological abnormalities in patients undergoing long term desferrioxamine treatment

Purpose To describe the spectrum of colour contrast sensitivity and electrophysiological abnormalities in patients undergoing long term desferrioxamine (DFO) treatment for systemic iron overload in blood transfusion-dependent anaemias. Methods Thirty five patients on long term DFO treatment with abnormal colour contrast sensitivity and/or abnormal retinal electrophysiology examined in the Electrophysiology Department at Moorfields Eye Hospital were included in this study. They underwent visual acuity testing, colour contrast sensitivity and International-standard electrophysiological evaluation including pattern and full-field electroretinography (PERG and FFERG). In most patients follow up investigation also included recording of ocular symptoms, fundus morphology and DFO treatment (dose and route of administration). Results Most patients manifested colour contrast threshold elevation, mainly along the tritan axis and also pattern ERG abnormalities as an indication of macular dysfunction. Full-field ERG abnormalities, when present, were consistent with generalised photoreceptor dysfunction involving rods only, cones only, or both rods and cones. In some patients these abnormalities were partly reversible following cessation or reduction of DFO treatment. Conclusion When DFO retinal toxicity occurs, it can present with a wide range of electrophysiological abnormalities, including macular and/or generalised retinal dysfunction. Early colour vision abnormalities usually involve the S-cone-driven pathway. Colour contrast sensitivity and electrophysiological evaluation may be used to detect DFO retinal toxicity and monitor recovery, providing an essential aid to the management of the patient.