Rod and rod mediated function in patients with beta-thalassemia major

Ocular abnormalities in beta thalassemia patients: prevalence, impact, and management strategies

BACKGROUND

Beta thalassemia (β-thalassemia) is a hereditary disease caused by defective globin synthesis and can be classified into three categories of minor (β-TMi), intermedia (β-TI), and major (β-TM) thalassemia. The aim of our study is to investigate the effects of β-thalassemia and its treatment methods on different parts of the eye and how early-diagnostic methods of ocular complications in this disorder would prevent further ocular complications in these patients by immediate treatment and diet change.

METHODS

We developed a search strategy using a combination of the words Beta thalassemia, Ocular abnormalities, Iron overload, chelation therapy to identify all articles from PubMed, Web of Science, Scopus, and Google Scholar up to December 2018. To find more articles and to ensure that databases were thoroughly searched, the reference lists of selected articles were also reviewed.

RESULTS

Complications such as retinopathy, crystalline lens opacification, color vision deficiency, nyctalopia, depressed visual field, reduced visual acuity, reduced contrast sensitivity, amplitude reduction in a-wave and b-wave in Electroretinography (ERG), and decrease in the Arden ratio in Electrooculography (EOG) have all been reported in β-thalassemia patients undergoing chelation therapy.

CONCLUSION

Ocular problems due to β-thalassemia may be a result of anemia, iron overload in the body tissue, side effects of iron chelators, and the complications of orbital bone marrow expansion.

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.

Electrophysiological assessment for early detection of retinal dysfunction in β-thalassemia major patients

PURPOSE

The purpose of this study was to assess the role of various diagnostic tests in early detection of retinal changes in β-thalassemia major patients.

METHODS

Thirty-eight visually asymptomatic β-thalassemia major patients receiving regular blood transfusions and iron-chelation therapy with deferoxamine (group A, n = 13), deferasirox (group B, n = 11) or deferoxamine with deferiprone (group C, n = 14) and fourteen age- and sex- matched healthy individuals were included in the study. All participants underwent ophthalmoscopy, full-field electroretinography (ERG), visual evoked potentials (VEP), multifocal electroretinography (mfERG), fundus autofluorescence (FAF) imaging and optical coherence tomography (OCT) scans.

RESULTS

Retinal pigment epithelium changes were present in two cases. Scotopic ERG demonstrated decreased a-wave amplitude in groups A, B and C (p = 0.03, p = 0.002 and p = 0.002, respectively) and decreased b-wave amplitude in groups B and C (p = 0.002 and p = 0.01, respectively) compared to controls. Photopic ERG showed delayed b-wave latency in groups A and C (p = 0.03 and p = 0.03, respectively) ERG maximal combined response and VEP response did not differ between groups. MfERG showed reduced retinal response density in ring 1 in groups A, B, C (p < 0.001, p < 0.001, p = 0.001, respectively) and ring 2 in group B (p = 0.02) and delayed latency in ring 5 in groups A and B (p = 0.04 and p = 0.04, respectively). Abnormal FAF images appeared in three cases and OCT abnormalities in one case, whereas no changes were observed in controls (p = 0.55 and p = 1.00, respectively).

CONCLUSIONS

Full-field ERG and mfERG are more sensitive tools for detecting early retinal changes in β-thalassemia patients compared with ophthalmoscopy, VEP, FAF imaging and OCT scans.

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.

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.

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.

Macular vitelliform lesion in desferrioxamine-related retinopathy

To report a case of a macular vitelliform lesion associated with desferrioxamine treatment. Ocular, electrophysiological, psychophysical, perimetric, fluorescein angiographic, fundus autofluorescence, and spectral-domain OCT examinations were obtained on a 45-year-old Caucasian woman with thalassemia major treated with blood transfusions and desferrioxamine. The patient was observed to have a vitelliform macular lesion in the right eye with a hypopigmented macular lesion and retinal pigment mottling in the left. At the most recent follow-up visit, best-corrected visual acuity was 20/70 in the right eye and 20/25 in left. Full-field electroretinogram (ERG) testing showed normal cone and rod responses. Mild localized elevations of rod psychophysical thresholds were found. A vitelliform macular lesion can develop in patients treated with desferrioxamine. Some such patients may not show diffuse photoreceptor cell functional loss as determined by electrophysiological testing.

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.

Retinal toxicity during pegylated alpha-interferon therapy for chronic hepatitis C: a multifocal electroretinogram investigation

BACKGROUND

Ocular side-effects in the form of retinal ischaemia and haemorrhages have been reported in patients undergoing standard alpha-interferon therapy.

AIM

To assess the ocular impact of therapy with sustained release pegylated alpha-2a interferon (Pegasys) for chronic hepatitis C.

METHODS

Ten patients receiving Pegasys and ribavirin and 10 healthy volunteers were recruited. Patients underwent full ophthalmic investigations and multifocal electroretinogram testing at baseline, at regular intervals during treatment and post-treatment. The multifocal electroretinogram maps retinal function. Responses were compared with sequential recordings from healthy volunteers.

RESULTS

All patients had normal clinical ophthalmic investigations at baseline. During therapy a single patient experienced central visual disturbance lasting 24 h with no prolonged ill effect. No other patient was aware of any change in vision. Fundal abnormalities appeared in five patients during treatment. The multifocal electroretinogram showed reductions in retinal function in five patients. Nine of 10 patients exhibited abnormalities on at least one multifocal electroretinogram or fundoscopic investigation.

CONCLUSIONS

Subclinical retinal toxicity during anti-viral therapy with pegylated alpha-interferon and ribavirin was frequent in this study and it suggests that patients should be warned of this risk and monitored during therapy.