Long-Term Effects of Iron Chelating Agents on Ocular Function in Patients with Thalassemia Major

Effects of medications on hypoxia-inducible factor in the retina: A review

Hypoxia-inducible factor (HIF) plays a critical role in the mechanisms that allow cells to adapt to various oxygen levels in the environment. Specifically, HIF-1⍺ has shown to be widely involved in cellular repair, survival, and energy metabolism. HIF-1⍺ has also been found in increased levels in cancer cells, highlighting the importance of balance in the hypoxic response. Promoting HIF-1⍺ activity as a potential therapy for degenerative diseases and inhibiting HIF-1⍺ as a therapy for pathologies with overactive cell proliferation are actively being explored. Digoxin and metformin, HIF-1⍺ inhibitors, and deferoxamine and ⍺-ketoglutarate analogues, HIF-1⍺ activators, are being studied for application in age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. However, these same medications have retinal toxicities that must be assessed before implementation of therapeutic care. Herein, we highlight the duality of therapeutic and toxic potential of HIF-1⍺ that must be carefully assessed prior to its clinical application in retinal disorders.

Ocular biometry, anterior chamber morphometry, and their relationship with serum ferritin levels in children with beta thalassemia major

Background

Ocular biometry and anterior segment evaluations are important to determine ocular development and pathological changes, especially in thalassemia patients in Mediterranean countries such as Turkey.

Objectives

The objectives of this study were to compare ocular biometry and anterior segment parameters in children with thalassemia major and healthy controls and to examine the relationship between ferritin levels, anthropometric measurements, and ocular parameters.

Design

This is a prospective case-control study.

Methods

The height, weight, body mass index, and occipitofrontal circumference values of the participants were recorded. Anterior and vitreous chamber depth, lens thickness, axial length, central corneal thickness, anterior chamber volume, iridocorneal angle, pupil diameter, and mean keratometry were measured. Measurements were compared between patients and healthy children, and between patients with ferritin levels above and below 1000 ng/mL.

Results

This study included 40 patients and 45 controls. Height, weight, and body mass index were significantly lower while ferritin level and occipitofrontal circumference were significantly higher in patients compared with the controls (p < 0.001 for all). There were no statistically significant differences in the other ocular parameters (p > 0.05). In comparisons between patients with ferritin levels below (n = 15) and above 1000 ng/mL (n = 25), there were no significant differences in age, height, weight, body mass index, occipitofrontal circumference, or ocular parameters (p > 0.05). Occipitofrontal circumference and mean keratometry value were positively correlated in patients with ferritin levels below 1000 ng/mL (r = 0.573, p = 0.025), while body mass index was negatively correlated with pupil diameter in patients with ferritin levels above 1000 ng/mL (r = -0.469, p = 0.018).

Conclusion

Children with thalassemia showed significant growth retardation and large occipitofrontal circumference but did not differ from controls in terms of biometrics and anterior segment morphology. Our results demonstrated a positive correlation between the occipitofrontal circumference and mean keratometry value in children with ferritin levels below 1000 ng/mL and a negative correlation between body mass index and pupil diameter in children with ferritin levels above 1000 ng/mL.

Iron overload and iron chelating agent exposure in anemia-associated outer retinal degeneration: a case report and review of the literature

Background

Deferoxamine retinopathy is the informally designated term used to describe a characteristic pattern of outer retinal degeneration in iron-overloaded chronic anemia patients who are treated with deferoxamine. We hypothesize that insufficiently treated iron overloading and not only deferoxamine is the cause of the retinal degeneration. Our case report is based on exposure histories of two anemia patients and literature review.

Case presentation

Both anemia patients presented with bilateral visual loss secondary to photoreceptor and retinal pigment epithelium degeneration. Chart review showed that visual loss came after a year-long slow, and rather monotonous rise in plasma ferritin concentrations, with no obvious relation to iron chelator exposure. In one patient, the onset of symptomatic visual loss came after a bout of fever followed by two additional febrile episodes, all accompanied by plasma ferritin spikes. Adjustment of iron chelation therapy did not improve visual function. Experimental studies clearly show that both systemic and intraocular exposure to iron ions can induce retinal degeneration.

Conclusion

The available evidence indicates that retinal degeneration in chronic anemia patients treated by deferoxamine is cause by insufficient iron chelation, not by deferoxamine. The actual role of iron chelating agents may be to promote a long enough survival to allow the slow development of retinal siderosis.