Contrast Sensitivity in Patients with Beta-Thalassemia Major and Sickle Cell Disease Under Regular Transfusions and Treatment with Desferrioxamine

Abstract

Purpose: Evaluation of contrast sensitivity in patients with beta-thalassemia major and sickle cell disease which undergo regular transfusions and chelation therapy with desferrioxamine (DFX).Materials and Methods:We studied contrast sensitivity in 48 eyes (24 patients) with beta-thalassemia major (group A) and in 42 eyes (21 patients) with sickle cell disease (group B), compared to 60 eyes of 30 healthy individuals (control group). Contrast sensitivity was measured using B-VAT II-SG Mentor Video Aquity Tester.Results: We found no statistically significant difference between group A and group B in any spatial frequency, while we found statistically significant differences between group B and control group in all spatial frequencies studied. Between group A and control group we found statistically significant differences in spatial frequencies of 2.3, and 6 cyc/deg.Conclusion: DFX causes retinal alterations that may explain reductions in contrast sensitivity function and justifies regular evaluations that may allow early detection of visual function deterioration.

Comparison of contrast sensitivity in β-thalassemia patients treated by deferoxamine or deferasirox

“…Previous studies have also confirmed similar findings; Gartaganis et al have found that contrast sensitivity function in all beta-thalassemic patients with normal Snellen visual acuity was significantly lower compared to the normal control subjects for all spatial frequencies tested 10 . Spyridon et al also reported reduced contrast sensitivity values in patients with major thalassemia than the values for normal subjects for frequencies of 2, 3 and 6 cpd 11 …”

“…Ocular complications of thalassemia and its therapeutic modalities has been reported by many sources 1, 3, 7, 8. But there are only few studies that evaluate contrast sensitivity in these patients 9, 10, 11. Impaired contrast sensitivity in the presence of normal visual acuity can detect early changes in the visual system of these patients.…”

“…They used the Vector Vision CSV-1000 contrast sensitivity test and conclude that contrast sensitivity function in all β-thalassemia patients was significantly lower than normal subjects 10 . Spyridon et al in 2010 used B-VAT II SG mentor visual acuity tester to measure contrast sensitivity in β-thalassemia major patients and found significant difference between contrast sensitivity of thalassemic and normal subjects in special frequencies of 2, 3, and 6 cycles per degree (cpd) 11 …”

Prochelators triggered by hydrogen peroxide provide hexadentate iron coordination to impede oxidative stress

“…[12] The high dosage required for treatment can lead to deterioration in vision, cardiac health and overall growth. [13, 14] It has been speculated that some of the side effects of chelation therapy may be the result of off-target metal binding by the administered drug that leads to deficiency in other essential metals. [15] While one DFO molecule provides sufficient donor atoms to fill the six coordination sites of iron and form stable non-reactive complexes, it can also bind other metal ions.…”