Ocular toxicity of desferrioxamine: light microscopic histochemical and ultrastructural findings

The Impact of Systemic Medications on Retinal Function

This study will provide a thorough review of systemic (and select intravitreal) medications, along with illicit drugs that are capable of causing various patterns of retinal toxicity. The diagnosis is established by taking a thorough medication and drug history, and then by pattern recognition of the clinical retinal changes and multimodal imaging features. Examples of all of these types of toxicity will be thoroughly reviewed, including agents that cause retinal pigment epithelial disruption (hydroxychloroquine, thioridazine, pentosan polysulfate sodium, dideoxyinosine), retinal vascular occlusion (quinine, oral contraceptives), cystoid macular edema/retinal edema (nicotinic acid, sulfa-containing medications, taxels, glitazones), crystalline deposition (tamoxifen, canthaxanthin, methoxyflurane), uveitis, miscellaneous, and subjective visual symptoms (digoxin, sildenafil). The impact of newer chemotherapeutics and immunotherapeutics (tyrosine kinase inhibitor, mitogen-activated protein kinase kinase, checkpoint, anaplastic lymphoma kinase, extracellular signal-regulated kinase inhibitors, and others), will also be thoroughly reviewed. The mechanism of action will be explored in detail when known. When applicable, preventive measures will be discussed, and treatment will be reviewed. Illicit drugs (cannabinoids, cocaine, heroin, methamphetamine, alkyl nitrite), will also be reviewed in terms of the potential impact on retinal function.

HIF2α activation and mitochondrial deficit due to iron chelation cause retinal atrophy

Iron accumulation causes cell death and disrupts tissue functions, which necessitates chelation therapy to reduce iron overload. However, clinical utilization of deferoxamine (DFO), an iron chelator, has been documented to give rise to systemic adverse effects, including ocular toxicity. This study provided the pathogenic and molecular basis for DFO-related retinopathy and identified retinal pigment epithelium (RPE) as the target tissue in DFO-related retinopathy. Our modeling demonstrated the susceptibility of RPE to DFO compared with the neuroretina. Intriguingly, we established upregulation of hypoxia inducible factor (HIF) 2α and mitochondrial deficit as the most prominent pathogenesis underlying the RPE atrophy. Moreover, suppressing hyperactivity of HIF2α and preserving mitochondrial dysfunction by α-ketoglutarate (AKG) protects the RPE against lesions both in vitro and in vivo. This supported our observation that AKG supplementation alleviates visual impairment in a patient undergoing DFO-chelation therapy. Overall, our study established a significant role of iron deficiency in initiating DFO-related RPE atrophy. Inhibiting HIF2α and rescuing mitochondrial function by AKG protect RPE cells and can potentially ameliorate patients' visual function.

Vitelliform maculopathy: Diverse etiologies originating from one common pathway

Vitelliform lesions (VLs) are associated with a wide array of macular disorders but are the result of one common pathway: retinal pigment epithelium (RPE) impairment and phagocytic dysfunction. VLs are defined by the accumulation of yellowish subretinal material. In the era of multimodal advanced retinal imaging, VLs can be further characterized by subretinal hyperreflectivity with optical coherence tomography and hyperautofluorescence with fundus autofluorescence. VLs can be the result of genetic or acquired retinal diseases. In younger patients, VLs usually occur in the setting of Best disease. Additional genetic causes of VL include pattern dystrophy or adult-onset vitelliform macular dystrophy. In older patients, acquired VLs can be associated with a broad spectrum of etiologies, including tractional, paraneoplastic, toxic, and degenerative disorders. The main cause of visual morbidity in eyes with VLs is the onset of macular atrophy and macular neovascularization. Histopathological studies have provided new insights into the location, nature, and lifecycle of the vitelliform material comprised of melanosomes, lipofuscin, melanolipofuscin, and outer segment debris located between the RPE and photoreceptor layer. Impaired phagocytosis by the RPE cells is the unifying pathway leading to VL development. We discuss and summarize the nature, pathogenesis, multimodal imaging characteristics, etiologies, and natural course of vitelliform maculopathies.

Evaluation of Optical Coherence Tomography Findings and Choroidal Thickness in Beta-Thalassemia Major Patients Using Chelation Therapy

Objectives

This study aims to analyze the posterior segment of the eye in children with thalassemia major (TM) treated with chelation therapy.

Methods

Forty-four patients diagnosed with TM and 44 age- and gender-matched participants without systemic diseases were included in this cross-sectional comparative study. A complete ophthalmologic examination, including visual acuity and fundus examination, was performed on all participants. The study and control groups' optic coherence tomography (OCT) evaluation was performed with a spectral domain featured OCT device. Central macular thickness (CMT), macular volume, ganglion cell complex (GCC) thickness, retinal nerve fiber layer (RNFL) thickness, subfoveal choroidal thickness (CT), CT at 1 mm temporal to the fovea, CT at 1 mm nasal to the fovea, CT at the 1 mm temporal to the optic nerve head, and CT at the 1 mm nasal to the optic nerve head were compared between the study and control groups.

Results

The mean ages for the study group and for the control group were 15.2±6.2 and 14.2±4.9 years, respectively. The mean subfoveal CT was 287.73±47.04 µm in the TM group and 312.66±39.95 µm in the control group (p=0.014). CT at the nasal to the fovea and temporal to the optic nerve head was thinner in the TM group than in the healthy group. The mean CMT, macular volume, GCC thickness, and RNFL thickness of the study and the control groups were similar. No significant difference was found between the patients with and without deferoxamine therapy concerning macular thickness, GCC thickness, and macular and peripapillary CT.

Conclusion

Our results suggested that subfoveal, perifoveal, and peripapillary CTs were significantly thinner in children with TM than the control group. The use of deferoxamine did not cause a further reduction in CT.

PATTERN DYSTROPHY-LIKE CHANGES ASSOCIATED WITH A VERY HIGH SERUM FERRITIN LEVEL IN β-THALASSEMIA MAJOR

PURPOSE

To report a rare case of pattern dystrophy-like retinal changes in a young β-thalassemia major patient with a very high serum ferritin level.

METHODS

Observational case report of a β-thalassemia major patient with bilateral pattern dystrophy-like retinal changes.

RESULTS

An 18-year-old man experienced blurring of vision in both eyes. Patient had a very high serum ferritin level and had a history of using various iron-chelating drugs. Funduscopy revealed bilateral widespread retinal pigment epithelium changes with macular involvement, which resembled pattern dystrophy-like changes. Fundus autofluorescence imaging showed extensive area of decreased autofluorescence signal interspersed with increased autofluorescence signals, whereas optical coherence tomography demonstrated macular retinal pigment epithelium thinning and interdigitation zone disruption corresponding to retinal pigment epithelium damage and atrophy.

CONCLUSION

Pattern dystrophy-like changes should be considered as a possible manifestation of retinal changes in patients with β-thalassemia major. Iron overload, which is indicated by a very high serum ferritin level, might have a role in the formation of this rare retinal manifestation in β-thalassemia major.

Optical coherence tomography findings in patients with transfusion-dependent β-thalassemia

BACKGROUND

Structural ophthalmologic findings have been reported in patients with β-thalassemia due to chronic anemia, iron overload, and iron chelation therapy toxicity in few previous studies. We aimed to investigate structural ocular findings and their relationship with hematological parameters in patients with transfusion-dependent β-thalassemia (TDT).

METHODS

In this cross-sectional study, from January 2018 to January 2019, 39 patients with TDT over the age of 18 participated. Multicolor fundus imaging, optical coherence tomography (OCT), and blue light fundus autofluorescence imaging were performed for all patients and 27 age- and sex-matched controls.

RESULTS

The mean age of patients was 28.6 ± 6.2 years. The central macular thickness and macular thicknesses in all quadrants were significantly thinner in patients than controls (P<0.05). None of the retinal nerve fiber layer (RNFL) measurements were significantly different between TDT patients and controls. There was a significantly negative correlation between hemoglobin with central macula thickness (r=-0.439, P=0.005). All measurements of macular subfield thickness were insignificantly thinner in patients with diabetes mellitus (DM) compared to the non-DM subgroup.

CONCLUSIONS

Macular thickness was significantly thinner in central macula and entire quadrants in TDT patients compared to healthy individuals; however, all RNFL measurement thicknesses were comparable between the two groups. Close monitoring of TDT patients by periodic ophthalmologic examinations with more focus on diabetic patients, patients with severe anemia and iron overload should be warranted.

[Effects of systemic drugs on the development of drug-induced retinopathy]

This article reviews information on possible adverse events occurring in the organ of vision - in particular, the retina - after using systemic drugs, discusses the drugs that lead to drug-induced retinopathy most often, and describes histomorphological changes and modern understanding of the pathogenesis of damage to retinal structures.

Visual electrophysiology in the assessment of toxicity and deficiency states affecting the visual system

Visual disturbance or visual failure due to toxicity of an ingested substance or a severe nutritional deficiency can present significant challenges for diagnosis and management, for instance, where an adverse reaction to a prescribed medicine is suspected. Objective assessment of visual function is important, particularly where structural changes in the retina or optic nerve have not yet occurred, as there may be a window of opportunity to mitigate or reverse visual loss. This paper reviews a number of clinical presentations where visual electrophysiological assessment has an important role in early diagnosis or management alongside clinical assessment and ocular imaging modalities. We highlight the importance of vitamin A deficiency as an easily detected marker for severe combined micronutrient deficiency.

Retinal and Choriocapillaris Vascular Changes in Patients Affected by Different Clinical Phenotypes of β-Thalassemia: An Optical Coherence Tomography Angiography Study

Simple Summary

β-thalassemia represents a hematological disorder that determines anomalous hemolysis and ineffective erythropoiesis. The patients, undergoing regular lifelong blood transfusion, show an iron overload in the tissues that requires an iron chelation therapy. Both iron accumulation and iron-chelating agents cause ocular manifestations, such as retinal pigment epithelial (RPE) degeneration, RPE mottling, cataract, optic neuropathy and retinal venous tortuosity. In this cross-sectional study, we described the retinal and choriocapillaris microvascular changes in different clinical phenotypes of β-thalassemia that may reflect a tissue hypoxia status and oxidative damages.

Abstract

In this cross-sectional study we assessed the vascular alterations in retinal and choriocapillaris perfusion in patients affected by β-thalassemia, by means of optical coherence tomography angiography (OCTA). A total of 124 eyes of 62 patients (mean age 44.74 ± 5.79 years old) affected by β-thalassemia (transfusion dependent thalassemia (TDT), non-transfusion dependent thalassemia (NTDT) and minor) were compared to 40 eyes of twenty healthy subjects. We evaluated the vessel density (VD) in superficial capillary plexus, deep capillary plexus, radial peripapillary capillary, choriocapillaris and the foveal avascular zone area. The TDT group showed a statistically significant reduction in retinal and choriocapillaris VD respect to controls and the other groups (p < 0.05). No statistically significant difference was found in OCTA parameters between β-thalassemia minor and controls. The NTDT group showed a significant reduction in VD in deep capillary plexus respect to controls and β-thalassemia minor. Significant negative correlations were shown in TDT group between foveal avascular zone and hemoglobin (r = −0.437, p = 0.044) and between ferritin levels and VD of choriocapillaris (r = −0.431, p = 0.038). The OCTA parameters provided a deeper understanding on retinal and choriocapillaris vascular impairment affected by tissue hypoxia levels and the oxidative stress in different clinical phenotypes of the β-thalassemia.

Desferrioxamine-Related Pseudo-Vitelliform Dystrophy and the Effect of Anti-Vascular Endothelial Growth Factor

We report a case of a 72-year-old female who developed bilateral pseudo-vitelliform dystrophy after taking desferrioxamine for the treatment of chronic iron overload. The patient then developed a right superior hemiretinal vein occlusion associated with intraretinal fluid in the right eye and was treated with monthly intravitreal aflibercept injections for 3 months followed by as required treatment. In addition to the intraretinal fluid responding to anti-VEGF treatment, there was a reduction in the size of the pseudo-vitelliform subfoveal deposit height, which was not seen in the untreated eye. Our case of an uncommon presentation of desferrioxamine-related maculopathy associated with a vein occlusion and the changes associated with intravitreal anti-VEGF treatment may help with the potential hypotheses of the pathophysiology of desferrioxamine-related pseudo-vitelliform retinal lesions and help with the potential future treatments of the condition.

Drug-induced maculopathy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of drug-induced maculopathies including their clinical presentations, diagnostic findings, and treatment options. With the increasing pace of development and arrival of drugs to the market, this review aims to inform retina specialists of relevant side effects that may be encountered in a clinical practice setting.

RECENT FINDINGS

The major themes visited in this article focus on relevant findings of drugs that cause pigmentary and crystalline maculopathy, photoreceptor dysfunction, cystoid macular edema, central serous choroidopathy, uveitis, and vascular damage.

SUMMARY

The current review reports updated findings and discusses the pathophysiologic mechanisms, presentations, and treatments of drug-induced maculopathies.

New thiazolidinones reduce iron overload in mouse models of hereditary hemochromatosis and β-thalassemia

Genetic iron-overload disorders, mainly hereditary hemochromatosis and untransfused β-thalassemia, affect a large population worldwide. The primary etiology of iron overload in these diseases is insufficient production of hepcidin by the liver, leading to excessive intestinal iron absorption and iron efflux from macrophages. Hepcidin agonists would therefore be expected to ameliorate iron overload in hereditary hemochromatosis and β-thalassemia. In the current study, we screened our synthetic library of 210 thiazolidinone compounds and identified three thiazolidinone compounds, 93, 156 and 165, which stimulated hepatic hepcidin production. In a hemochromatosis mouse model with hemochromatosis deficiency, the three compounds prevented the development of iron overload and elicited iron redistribution from the liver to the spleen. Moreover, these compounds also greatly ameliorated iron overload and mitigated ineffective erythropoiesis in β-thalassemic mice. Compounds 93, 156 and 165 acted by promoting SMAD1/5/8 signaling through differentially repressing ERK1/2 phosphorylation and decreasing transmembrane protease serine 6 activity. Additionally, compounds 93, 156 and 165 targeted erythroid regulators to strengthen hepcidin expression. Therefore, our hepcidin agonists induced hepcidin expression synergistically through a direct action on hepatocytes via SMAD1/5/8 signaling and an indirect action via eythroid cells. By increasing hepcidin production, thiazolidinone compounds may provide a useful alternative for the treatment of iron-overload disorders.

Pattern dystrophies in patients treated with deferoxamine: report of two cases and review of the literature

Background

Deferoxamine (DFO) is one of the most commonly used chelation treatments for transfusional hemosiderosis. Pattern dystrophies constitute a distinct entity of retinal disorders that has been occasionally identified in association with deferoxamine.

Case presentation

We report two cases of bilateral macular pattern dystrophy in transfusion dependent patients undergoing chronic chelation therapy with deferoxamine due to thalassemias. Our patients were evaluated with multimodal imaging and the results are presented. Both patients had normal cone and rod responses in the full-field electroretinogram and continued the prescribed chelation therapy, after hematology consult. The patients were followed up every 3 months for 2 and 4 years respectively for possible deterioration. Their best corrected visual acuity remained stable with no anatomic change on Optical Coherence Tomography findings.

Conclusion

Multimodal imaging of our patients allowed a better evaluation and possibly earlier detection of the DFO-related changes. Screening and close follow up of patients under chronic chelating therapy is important in order to promptly diagnose and manage possible toxicity either with discontinuation of the offending agent or dose modification.

Deferoxamine therapy for intracerebral hemorrhage: A systematic review

Intracerebral hemorrhage (ICH) is a significant cause of morbidity and mortality worldwide. Several recent controlled trials have reported that deferoxamine (DFX) therapy appears to be effective for ICH. The aim of this study was to perform a systematic review of DFX therapy for ICH patients and evaluate the efficacy and safety of DFX therapy for ICH patients. We searched Medline, Embase, the Cochrane Database of Systematic Reviews, clinicaltrials.gov, all Chinese databases and the reference lists of all included studies and review articles. We then performed a systematic review of studies involving the administration of DFX following ICH. Only two studies were included, a prospective, randomized clinical trial and a prospective,observational cohort study with concurrent groups. Qualitative analysis of each study revealed one randomized controlled trial of moderate quality with a moderate risk of bias and one observational cohort study of moderate quality with a moderate risk of bias. DFX may be an effective treatment for edema in patients with ICH. However, due to the small number of trials and small sample sizes of these trials, insufficient evidence exists to determine the effect of DFX on neurologic outcomes after ICH and the safety of this intervention. Further investigation is required before DFX can become a routine treatment for ICH.

CORRELATION BETWEEN SUBFOVEAL CHOROIDAL THICKNESS AND FOVEAL THICKNESS IN THALASSEMIC PATIENTS

PURPOSE

To assess the impact of two iron chelation modalities in thalassemic patients on foveal and subfoveal choroidal thickness.

METHODS

The study included 60 β-thalassemia major patients. They included 30 patients on oral deferasirox after a period of subcutaneous deferoxamine (Group 2) and 30 patients on subcutaneous deferoxamine (Group 3). Thirty age- and sex-matched healthy children were included as a control group (Group 1). All participants underwent a complete ophthalmologic evaluation and Spectral Domain Optical Coherence Tomography.

RESULTS

Age, gender, intraocular pressure, best-corrected visual acuity, and refraction were not statistically different between the three studied groups. Ferritin level, pretransfusion hemoglobin, serum iron, and duration of thalassemia were not statistically different between the two thalassemic groups. Foveal thickness in Group 1 (225.15 ± 17.35 μm) was statistically higher than in Group 2 (210.53 ± 21.73 μm) (P < 0.001) and Group 3 (200.15 ± 7.34 μm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P = 0.001). Subfoveal choroidal thickness in Group 1 (279.70 ± 32.54 μm) was statistically higher than in Group 2 (255.80 ± 19.20 μm) (P < 0.001) and Group 3 (248.28 ± 20.43 μm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P < 0.05).

CONCLUSION

Thalassemic patients can develop a significant decrease in foveal thickness because of the inevitable use of chelation therapy. Deferoxamine as a chelating agent can affect foveal thickness more than the oral form (deferasirox).

Pseudovitelliform maculopathy associated with deferoxamine toxicity: multimodal imaging and electrophysiology of a rare entity

Deferoxamine is a commonly used chelating agent for secondary hemochromatosis. We report a rare retinal manifestation of deferoxamine toxicity in a 68-year-old man and provide supporting multimodal imaging and electrophysiology. The patient had iron overload related to transfusion-dependent myelodysplastic syndrome and developed a pseudovitelliform macular lesion related to deferoxamine toxicity. We also describe for the first time the worsening of this maculopathy on deferasirox, an alternative chelating agent. Macular pseudovitelliform lesion is a unique manifestation of deferoxamine toxicity that can be mistaken for pattern dystrophy. It is important to recognize this manifestation, because discontinuation of the offending agent may halt or reverse the toxicity.

Safety profiles of iron chelators in young patients with haemoglobinopathies

BACKGROUND

This review describes the safety of deferoxamine (DFO), deferiprone (DFP), deferasirox (DFX) and combined therapy in young patients less than 25 yr of age with haemoglobinopathies.

METHODS

Searches in electronic literature databases were performed. Studies reporting adverse events associated with iron chelation therapy were included. Study and reporting quality was assessed using AHRQ Risk of Bias Assessment Tool and McMaster Quality Assessment Scale of Harms. Prospective clinical studies were pooled in a random-effects meta-analysis of proportions.

RESULTS

Safety data of 2040 patients from 34 studies were included. Ninety-two case reports of 246 patients were identified. DFX (937 patients) and DFP (667 patients) possess the largest published safety evidence. Fewer studies on combination regimens are available. Increased transaminases were seen in all regimens (3.9-31.3%) and gastrointestinal disorders with DFP and DFX (3.7-18.4% and 5.8-18.8%, respectively). Therapy discontinuations due to adverse events were low (0-4.1%). Reporting quality was selective and poor in most of the studies.

CONCLUSION

Iron chelation therapy is generally safe in young patients, and published data correspond to summary of product characteristics. Each iron chelation regimen has its specific safety risks. DFO seems not to be associated with serious adverse effects in recommended doses. In DFP and DFX, rare, but serious, adverse reactions can occur. Data on combined therapy are scarce, but it seems equally safe compared to monotherapy.

β-Thalassemia and ocular implications: a systematic review

Background

Beta-thalassemia is a severe genetic blood disorder caused by a mutation in the gene encoding for the beta chains of hemoglobin. Individuals with beta-thalassemia major require regular lifelong Red Blood Cell transfusions to survive. Ocular involvement is quite common and may have serious implications.

Methods

Extensive review of observational studies on beta-thalassemia, to determine the prevalence and spectrum of ocular abnormalities, by clinical examination and multimodal imaging, and to investigate risk factors for their development.

Results

Frequency of ocular involvement differs among various studies (41.3–85 %, three studies). Ocular findings in beta-thalassemia may correlate to the disease itself, iron overload or the chelating agents used. Beta-thalassemia ocular manifestations include ocular surface disease, as demonstrated by tear function parameters (two studies). Lens opacities are present in 9.3–44 % (five studies). Lenticular opacities and RPE degeneration correlated positively with use of desferrioxamine and deferriprone respectively (two studies). Ocular fundus abnormalities characteristic of pseudoxanthoma elasticum (PXE), including peau d’orange, angioid streaks, pattern dystrophy-like changes, and optic disc drusen are a consistent finding in seven studies. Patients with PXE-like fundus changes were older than patients without these fundus changes (two studies). Age (two studies) and splenectomy (one study) had the strongest association with presence of PXE-like fundus changes. Increased retinal vascular tortuosity independently of the PXE-like fundus changes was found in 11–17.9 % (three studies), which was associated with aspartate amino transferase, hemoglobin and ferritin levels (two studies). Fundus autofluorescence and electrophysiological testing (ERG and EOG) may indicate initial stages or more widespread injury than is suggested by fundus examination (two studies).

Conclusions

Beta-thalassemia may present with various signs, both structural and functional. Pseudoxanthoma elasticum like fundus changes are a frequent finding in patients with b-thalassemia. These changes increase with duration or severity of the disease. Retinal vascular tortuosity may be an additional disease manifestation related to the severity and duration of anemia and independent of the PXE-like syndrome. Patients with long-standing disease need regular ophthalmic checkups because they are at risk of developing PXE-like fundus changes and potentially of subsequent choroidal neovascularization.

Targeting iron-mediated retinal degeneration by local delivery of transferrin

Iron is essential for retinal function but contributes to oxidative stress-mediated degeneration. Iron retinal homeostasis is highly regulated and transferrin (Tf), a potent iron chelator, is endogenously secreted by retinal cells. In this study, therapeutic potential of a local Tf delivery was evaluated in animal models of retinal degeneration. After intravitreal injection, Tf spread rapidly within the retina and accumulated in photoreceptors and retinal pigment epithelium, before reaching the blood circulation. Tf injected in the vitreous prior and, to a lesser extent, after light-induced retinal degeneration, efficiently protected the retina histology and function. We found an association between Tf treatment and the modulation of iron homeostasis resulting in a decrease of iron content and oxidative stress marker. The immunomodulation function of Tf could be seen through a reduction in macrophage/microglial activation as well as modulated inflammation responses. In a mouse model of hemochromatosis, Tf had the capacity to clear abnormal iron accumulation from retinas. And in the slow P23H rat model of retinal degeneration, a sustained release of Tf in the vitreous via non-viral gene therapy efficently slowed-down the photoreceptors death and preserved their function. These results clearly demonstrate the synergistic neuroprotective roles of Tf against retinal degeneration and allow identify Tf as an innovative and not toxic therapy for retinal diseases associated with oxidative stress.

Retinal abnormalities in β-thalassemia major

Patients with beta (β)-thalassemia (β-TM: β-thalassemia major, β-TI: β-thalassemia intermedia) have a variety of complications that may affect all organs, including the eye. Ocular abnormalities include retinal pigment epithelial degeneration, angioid streaks, venous tortuosity, night blindness, visual field defects, decreased visual acuity, color vision abnormalities, and acute visual loss. Patients with β-thalassemia major are transfusion dependent and require iron chelation therapy to survive. Retinal degeneration may result from either retinal iron accumulation from transfusion-induced iron overload or retinal toxicity induced by iron chelation therapy. Some who were never treated with iron chelation therapy exhibited retinopathy, and others receiving iron chelation therapy had chelator-induced retinopathy. We will focus on retinal abnormalities present in individuals with β-thalassemia major viewed in light of new findings on the mechanisms and manifestations of retinal iron toxicity.

Multimodal imaging in a case of deferoxamine-induced maculopathy

PURPOSE

To report a case of deferoxamine-induced maculopathy and present the use of multimodal retinal imaging to study this disease entity.

METHODS

This is an observational case report of one patient. Multimodal imaging with fundus autofluorescence, infrared imaging, and spectral domain optical coherence tomography was used to investigate the macular changes induced by deferoxamine toxicity.

RESULTS

A 53-year-old man with history of β-thalassemia presented with decreased vision in both eyes 1 month after initiating deferoxamine therapy. Infrared imaging showed areas of increased stippled infrared intensity through the macula. Fundus autofluorescence revealed diffuse areas of stippled hyperautofluorescence and hypoautofluorescence. Spectral domain optical coherence tomography changes included disruption of the ellipsoid zone, attenuation of the photoreceptors, and deposits within the retinal pigment epithelium.

CONCLUSION

A case of deferoxamine-induced maculopathy was described and the use of multimodal retinal imaging to study this disease entity was presented.

Functional and Structural Abnormalities in Deferoxamine Retinopathy: A Review of the Literature

Deferoxamine mesylate (DFO) is the most commonly used iron-chelating agent to treat transfusion-related hemosiderosis. Despite the clear advantages for the use of DFO, numerous DFO-related systemic toxicities have been reported in the literature, as well as sight-threatening ocular toxicity involving the retinal pigment epithelium (RPE). The damage to the RPE can lead to visual field defects, color-vision defects, abnormal electrophysiological tests, and permanent visual deterioration. The purpose of this review is to provide an updated summary of the ocular findings, including both functional and structural abnormalities, in DFO-treated patients. In particular, we pay particular attention to analyzing results of multimodal technologies for retinal imaging, which help ophthalmologists in the early diagnosis and correct management of DFO retinopathy. Fundus autofluorescence, for example, is not only useful for screening patients at high-risk of DFO retinopathy, but is also a prerequisite for identify specific high-risk patterns of RPE changes that are relevant for the prognosis of the disease. In addition, optical coherence tomography may have a clinical usefulness in detecting extent and location of different retinal changes in DFO retinopathy. Finally, this review wants to underline the need for universally approved guidelines for screening and followup of this particular disease.

Multimodal imaging in deferoxamine retinopathy

PURPOSE

To describe macular lesions in patients with deferoxamine (DFO) retinopathy, and to follow their clinical course using multimodal imaging.

METHODS

The authors retrospectively reviewed charts and multimodal imaging of 20 patients with β-thalassemia diagnosed with DFO retinopathy (40 eyes) after a minimum of 10 years of DFO treatment. Imaging included fundus photography, near-infrared reflectance and fundus autofluorescence imaging on confocal laser scanning ophthalmoscope, and spectral domain optical coherence tomography.

RESULTS

Mean age of the 20 patients was 45 years, and mean duration of subcutaneous DFO therapy was 32 years (range, 20-52 years). Ten patients (50%) showed different types of pattern dystrophy-like fundus changes, including butterfly shaped-like (n = 3), fundus flavimaculatus-like (n = 3), fundus pulverulentus-like (n = 3), and vitelliform-like (n = 1) changes. Ten patients (50%) presented only minimal changes in the macula; these patients were significantly younger than patients presenting other patterns (P = 0.023). Confocal laser scanning ophthalmoscope and spectral domain optical coherence tomography showed that these abnormalities were more diverse and widespread than expected by ophthalmoscopy. Abnormal fundus autofluorescence and/or near-infrared reflectance signals corresponded to accumulation of material located within the outer retina or in the Bruch membrane-retinal pigment epithelium (RPE) complex on spectral domain optical coherence tomography. Follow-up examinations during a 40-month period revealed progressive development of RPE atrophy in areas of pattern dystrophy-like changes.

CONCLUSION

DFO retinopathy included a variety of pattern dystrophy-like changes or minimal changes affecting the RPE-Bruch membrane-photoreceptor complex. Multimodal imaging demonstrated that fundus changes were more diverse and widespread than expected from ophthalmoscopy. Consistently with previous histologic description of DFO retinopathy, multimodal imaging confirmed that photoreceptor outer-derived retinoids, various fluorophores, and RPE displacement or clumping are involved in DFO retinopathy, finally leading to frank RPE atrophy in most cases of pattern dystrophy-like changes.

Deferoxamine retinopathy: spectral domain-optical coherence tomography findings

BACKGROUND

To describe the spectral domain optical coherence tomography (SD-OCT) findings of a patient who developed pigmentary retinopathy following high-dose deferoxamine administration.

CASE PRESENTATION

A 34-year-old man with thalassemia major complained of nyctalopia and decreased vision following high-dose intravenous deferoxamine to treat systemic iron overload. Fundus examination revealed multiple discrete hypo-pigmented lesions at the posterior pole and mid-peripheral retina. Recovery was partial following cessation of desferrioxamine six weeks later. A follow-up SD-OCT showed multiple accumulated hyper-reflective deposits primarily in the choroid, retina pigment epithelium (RPE), and inner segment and outer segment (IS/OS) junction.

CONCLUSION

Deferoxamine retinopathy primarily targets the RPE-Bruch membrane-photoreceptor complex, extending from the peri-fovea to the peripheral retina with foveola sparing. An SD-OCT examination can serve as a simple, noninvasive tool for early detection and long-term follow-up.

Potential clinical applications of chelating drugs in diseases targeting transferrin-bound iron and other metals

INTRODUCTION

Iron is essential for normal, neoplasmic and microbial cells. Transferrin (Tf) is responsible for iron transport and its interactions with chelators are of physiological and toxicological importance and could lead to new therapeutic applications.

AREAS COVERED

Differential interactions of Tf with chelators such as deferiprone (L1) could be used to modify toxicity and disease pathways in relation to iron and other metal metabolism. Iron mobilization by L1 could achieve normal body iron stores in thalassemia patients. Iron mobilization from the reticuloendothelial system by L1 and exchange with Tf could be used to increase the production of hemoglobin in the anemia of chronic disease. Iron accumulation is pathogenic in neurodegenerative, acute kidney and other diseases and could be removed by L1 with therapeutic implications. Deprivation of iron from neoplasmic and microbial cells by chelators could increase the prospect of improved treatments in cancer and infectious diseases. Other applications include metal detoxification and inhibition of oxidative stress-related conditions.

EXPERT OPINION

Specific mechanisms apply in the interactions of chelators with Tf, which could be used in the design of targeted therapeutic strategies in many conditions. In each case specific chelator protocols have to be designed for achieving optimum therapeutic activity.

Retinal and cochlear toxicity of drugs: new insights into mechanisms and detection

PURPOSE OF REVIEW

Various medications can modify the physiology of retinal and cochlear neurons and lead to major, sometime permanent, sensory loss. A better knowledge of pathogenic mechanisms and the establishment of relevant monitoring protocols are necessary to prevent permanent sensory impairment. In this article, we review main systemic medications associated with direct neuronal toxicity on the retina and cochlea, their putative pathogenic mechanisms, when identified, as well as current recommendations, when available, for monitoring protocols.

RECENT FINDINGS

Pathogenic mechanisms and cellular target of retinotoxic drugs are often not well characterized but a better knowledge of the course of visual defect has recently helped in defining more relevant monitoring protocols especially for antimalarials and vigabatrin. Mechanisms of ototoxicity have recently been better defined, from inner ear entry with the use of fluorescent tracers to evidence for the role of oxidative stress and program cell death pathways.

SUMMARY

Experimental and clinical studies have elucidated some of the pathogenic mechanisms, courses and risk factors of retinal toxicity and ototoxicity, which have led to establishment of relevant monitoring protocols. Further studies are, however, warranted to better understand cellular pathways leading to degeneration. These would help to build more efficient preventive intervention and may also contribute to understanding of other degenerative processes such as genetic disorders.

Correlation of fundus autofluorescence, spectral-domain optical coherence tomography, and microperimetry in late deferoxamine maculopathy

PURPOSE

To describe long-term functional and morphologic retinal changes by deferoxamine, a chelating agent used to treat systemic iron overload.

METHODS

Ophthalmologic examination of acute deferoxamine maculopathy and follow-up of 5 years, using ophthalmologic examination, fluorescence angiography, electrophysiology, color vision testing, fundus image-correlated microperimetry, time-domain and spectral-domain optical coherence tomographies. The patient is a 53-year old woman who presented with acute visual deterioration to 20/50 in the right eye, 20/60 in the left eye, and reduced color vision. She had been treated with deferoxamine for 6 months. The diagnosis of deferoxamine maculopathy was made, and the drug discontinued immediately.

RESULTS

After 5 months, visual acuity was 20/25 bilaterally, but mottling of the retinal pigment epithelium (RPE) had developed. Five years later, visual acuity was 20/20 in both eyes. Fundus autofluorescence showed progressively clumped hyper- and hypofluorescence with larger areas of total RPE atrophy in the left eye. Spectral-domain optical coherence tomography visualized areas of RPE thickening, photoreceptor outer segment elongation, outer retinal tubulation, and outer retinal and RPE atrophy. Fundus image-correlated microperimetry showed relative central scotomas at the beginning, some of which recovered to normal light sensitivity, while others deteriorated to absolute scotomas.

CONCLUSION

Although visual acuity had recovered after cessation of deferoxamine, functional and morphologic residues remained, which included disturbed color vision, central microscotomas, and progressive RPE and outer retinal degeneration.

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

Prochelators are agents that have little affinity for metal ions until they undergo a chemical conversion. Three new aryl boronate prochelators are presented that are responsive to hydrogen peroxide to provide hexadentate ligands for chelating metal ions. TRENBSIM (tris[(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzylidene)-2-aminoethyl]amine), TRENBSAM (tris[(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)-2-aminoethyl]amine), and TB (tris[(2-boronic acid-benzyl)2-aminoethyl]amine) convert to TRENSIM (tris[(salicylideneamino)ethyl]amine), TRENSAM (tris[(2-hydroxybenzoyl)-2-aminoethyl]amine), and TS (tris[2-hydroxybenzyl)2-aminoethyl]amine), respectively. The prochelators were characterized by (11)B NMR, and the structures of TRENBSAM, TRENBSIM, and the Fe(III) complex of TS were determined by X-ray crystallography. Of the three prochelator/chelator pairs, TB/TS was identified as the most promising for biological applications, as they prevent iron and copper-induced hydroxyl radical generation in an in vitro assay. TB has negligible interactions with metal ions, whereas TS has apparent binding constants (log K') at pH 7.4 of 15.87 for Cu(II), 9.67 Zn(II) and 14.42 for Fe(III). Up to 1 mMTB was nontoxic to retinal pigment epithelial cells, whereas 10 μM TS induced cell death. TS protected cells against H(2)O(2)-induced death, but only within a 1-10 μM range. TB, on the other hand, had a much broader window of protection, suggesting that it may be a useful agent for preventing metal-promoted oxidative damage.

Intravitreal bevacizumab (avastin) for choroidal neovascularization associated with deferoxamine retinopathy

PURPOSE

To report the effect of antivascular endothelial growth factor therapy for choroidal neovascularisation associated with deferoxamine toxicity.

METHOD

In an interventional case report, intravitreal antivascular endothelial growth factor therapy was used for the treatment of a choroidal neovascularization in a patient with deferoxamine retinopathy.

RESULTS

A 54-year-old woman with beta-thalassemia intermedia and known deferoxamine toxicity presented with recent vision loss to the left eye secondary to a choroidal neovascular membrane. Visual acuity had decreased from 20/30 to 20/80 in the left eye. Funduscopic examination and fluorescein angiography revealed diffuse retinal pigment epithelial mottling and a choroidal neovascular membrane. Treatment with three doses of intravitreal bevacizumab led to a good structural outcome and improvement of the visual acuity. The patient later developed a choroidal neovascular membrane in the right eye. Similar treatment with intravitreal bevacizumab also led to a rapid structural resolution of the lesion, albeit with a more modest improvement in the visual acuity.

CONCLUSION

Therapy with intravitreal bevacizumab might be an option for the treatment of choroidal neovascularization in the context of deferoxamine toxicity.

Safety issues of iron chelation therapy in patients with normal range iron stores including thalassaemia, neurodegenerative, renal and infectious diseases

An increased number of thalassaemia patients treated with effective chelation therapy protocols are achieving body iron levels similar to those of normal individuals. Iron chelation therapy has also been recently used in a number of other categories of patients with no excess body iron load such as neurodegenerative, renal and infectious diseases. Chelation therapy in the absence of iron overload in the latter conditions raises many safety issues including chelator overdose toxicity and toxicity related to iron and other essential metal deficiencies. Preliminary preclinical and clinical toxicity evidence suggest that deferoxamine and deferasirox can only be safely used for these non-iron loaded conditions for short-term treatments of a few weeks, whereas deferiprone can be used for longer term treatments of many months. The selection of the chelating drug and appropriate dose protocols for targeting specific organs and conditions is critical for the safety of patients with normal iron stores. Chelation therapy is likely to play a major role as adjuvant, alternative or main therapy in many non-iron loading conditions in the forthcoming years.

Effects on the visual system might contribute to some of the cognitive deficits of cancer chemotherapy-induced 'chemo-fog'

The diminution in certain aspects of cognitive function that is reported to occur in some patients during or after adjuvant cancer chemotherapy is variously known as 'chemo-fog', 'chemo-brain' or other such term. In addition to reported deficits in attention, concentration and other functions, most, if not all, of the studies report deficits involving visual-spatial function or visual memory. Since the visual system is part of the nervous system, it seems reasonable to ask if it is susceptible to some of the deleterious effects produced by adjuvant chemotherapeutic drugs. We propose here the possibility that some portion of the vision-related aspects of the 'chemo-fog' spectrum of cognitive deficits results from a direct action of the adjuvant drugs on the visual system or from drug/drug or site/site interaction between effects on the visual system and other critical brain regions.

Future Chelation Monotherapy and Combination Therapy Strategies in Thalassemia and Other Conditions. Comparison of Deferiprone, Deferoxamine, ICL670, GT56-252, L1NAll and Starch Deferoxamine Polymers

Deferiprone (L1), and appropriate combinations with deferoxamine (DFO), can be used effectively for the treatment of thalassemia and other transfusional iron loading conditions. A number of experimental iron chelators such as deferasirox or ICL670 or Exjade (4-(3,5-bis (2-hydroxyphenyl)-1,2,4-triazol-1-yl)-benzoic acid), deferitrin (4,5-dihydro-2-(2,4-dihydroxyphenyl)-4-methylthiazole-4 (S)-carboxylic acid) or GT56-252, 1-allyl-2-methyl-3-hydroxypyrid-4-one or L1NAll and starch DFO polymers, are under clinical evaluation. ICL670 is the most advanced in development and appears to be effective in reducing liver iron in some patients but is overall ineffective in causing negative iron balance. It is also suspected that it is not effective in cardiac iron removal. Combination therapies using L1, DFO and new iron chelating drugs may cause higher efficacy and lower toxicity by comparison to monotherapies. However, several limitations including the high cost of the new chelating drugs may not facilitate the availability of these new treatments to the vast majority of thalassemia patients, most of whom live in developing countries.

Deferoxamine-related ocular toxicity: incidence and outcome in a pediatric population

PURPOSE

Deferoxamine (DFO) is a chelating agent used widely for the treatment of transfusional hemochromatosis. DFO-related ocular toxicity has been previously reported several times, and many institutions have adopted an ophthalmic screening protocol for patients treated with DFO despite little information regarding the rate of ocular toxicity. Our study aimed to determine the incidence of DFO toxicity at a major pediatric hospital that uses regular ophthalmic screening for all DFO-treated patients.

METHODS

A retrospective case series of all patients treated with DFO for transfusional hemochromatosis at The Hospital for Sick Children (Toronto, Ontario, Canada) between 1995 and 2005 inclusive.

RESULTS

A total of 84 patients received regular DFO treatment for transfusional hemochromatosis related to long-term hypertransfusion. A total of 421 ophthalmic screening examinations were performed (average, 5.0 examinations per patient). DFO-related ocular toxicity was found only in one patient (1.2%). This patient had central blurriness and retinal pigmentary changes shown by examination and decreased central responses shown by electroretinography, but these changes were all found to be completely reversible after a change from intravenous to subcutaneous therapy at a reduced dose.

CONCLUSIONS

In this large pediatric center, DFO-related ocular toxicity has been a rare and mild finding. Regular ophthalmic screening should be carried out for patients receiving high-dose subcutaneous or intravenous therapy, because early detection of retinal toxicity may lead to optimization of the DFO dose and thus prevention of long-term visual sequelae.

Fundus autofluorescence in retinopathy caused by deferoxamine toxicity

PURPOSE

To describe the fundus autofluorescence photographic pattern in a case of deferoxamine retinopathy.

METHODS

Observational case report.

RESULTS

A 91-year-old woman receiving intravenous deferoxamine treatment presented with a history of deteriorating vision in both eyes. Autofluorescence photography revealed well circumscribed areas of hyperautofluorescence that correlated with areas of pigmentation shown by color photography. Deferoxamine retinopathy was diagnosed.

CONCLUSION

Fundus autofluorescence photography is a noninvasive imaging method for early detection of deferoxamine retinopathy and can be used to monitor the status of the macula in patients at risk for this toxicity.

EOG as a monitor of desferrioxamine retinal toxicity

Iron overload caused by blood transfusion-dependent anaemia usually results in lethal cardiac toxicity unless treated by iron-chelation therapy. Chelation therapy with desferrioxamine (DFO) is well established and widely used to remove excess iron. Unfortunately, visual disorders have been recorded after DFO infusion. In this investigation, a 61-year-old Caucasian female received DFO for her autoimmune haemolytic anaemia. Prior to starting with the DFO treatment, her baseline ophthalmic screening and electrooculogram (EOG) were completely normal. Two years later she noticed a grey scotoma in her right eye. Visual acuity in this eye was reduced from 6/5 to 6/9 and funduscopy revealed evidence of non-specific mottling of the retinal pigment epithelium of both retinae. The EOG was flat (106%) in the right eye and subnormal in the left (155%). The lower limit of our EOG Arden Ratio for normal subjects is 180%. After her DFO treatment was stopped, her right visual acuity returned to 6/5, her field tests showed progressive improvement bilaterally and the EOG went back to the normal range. While waiting for splenectomy, the patient was restarted on a lower dose of DFO and EOG measurements were carried out every two (or three) weeks to monitor for DFO toxicity. The EOG varied during this period indicating some deterioration of function in the retinal pigment epithelium. However, normalisation of the EOG values (right = 217%, left = 217%) occurred after splenectomy and cessation of DFO therapy. Her visual function was normal and her visual acuity 6/4 bilateral when she was discharged from our outpatient clinic. On reviewing her history it was apparent that the EOG was the most sensitive indicator of DFO toxicity.

Desferrioxamine related maculopathy: a case report

Desferrioxamine is used for the treatment of chronic iron overload, acute iron poisoning, and certain anaemias. Ocular toxicity secondary to prolonged treatment with desferrioxamine may result in night blindness, visual field constriction, cataract, pigmentary retinopathy and optic neuropathy. To avoid such complications an ophthalmic screening has been suggested for patients taking desferrioxamine. We report an 81-year-old patient who developed irreversible ocular toxicity despite undergoing ophthalmic screening.

Benefits and risks of deferiprone in iron overload in Thalassaemia and other conditions: comparison of epidemiological and therapeutic aspects with deferoxamine

Deferiprone is the only orally active iron-chelating drug to be used therapeutically in conditions of transfusional iron overload. It is an orphan drug designed and developed primarily by academic initiatives for the treatment of iron overload in thalassaemia, which is endemic in the Mediterranean, Middle East and South East Asia and is considered an orphan disease in the European Union and North America. Deferiprone has been used in several other iron or other metal imbalance conditions and has prospects of wider clinical applications. Deferiprone has high affinity for iron and interacts with almost all the iron pools at the molecular, cellular, tissue and organ levels. Doses of 50-120 mg/kg/day appear to be effective in bringing patients to negative iron balance. It increases urinary iron excretion, which mainly depends on the iron load of patients and the dose of the drug. It decreases serum ferritin levels and reduces the liver and heart iron content in the majority of chronically transfused iron loaded patients at doses >80 mg/kg/day. It is metabolised to a glucuronide conjugate and cleared through the urine in the metabolised and a non-metabolised form, usually of a 3 deferiprone: 1 iron complex, which gives the characteristic red colour urine. Peak serum levels of deferiprone are observed within 1 hour of its oral administration and clearance from blood is within 6 hours. There is variation among patients in iron excretion, the metabolism and pharmacokinetics of deferiprone. Deferiprone has been used in more than 7500 patients aged from 2-85 years in >50 countries, in some cases daily for >14 years. All the adverse effects of deferiprone are considered reversible, controllable and manageable. These include agranulocytosis with frequency of about 0.6%, neutropenia 6%, musculoskeletal and joint pains 15%, gastrointestinal complains 6% and zinc deficiency 1%. Discontinuation of the drug is recommended for patients developing agranulocytosis. Deferiprone is of similar therapeutic index to subcutaneous deferoxamine but is more effective in iron removal from the heart, which is the target organ of iron toxicity and mortality in iron-loaded thalassaemia patients. Deferiprone is much less expensive to produce than deferoxamine. Combination therapy of deferoxamine and deferiprone has been used in patients not complying with subcutaneous deferoxamine or experiencing toxicity or not excreting sufficient amounts of iron with use of either drug alone. New oral iron-chelating drugs are being developed, but even if successful these are likely to be more expensive than deferiprone and are not likely to become available in the next 5-8 years. About 25% of treated thalassaemia patients in Europe and more than 50% in India are using deferiprone. For most thalassaemia patients worldwide who are not at present receiving any form of chelation therapy the choice is between deferiprone and fatal iron toxicity.