Contrast sensitivity function in patients with beta-thalassemia major

Investigation of the color discrimination ability using the Farnsworth-Munsell 100-hue test and structural changes by SS-OCT in patients with transfusion-dependent beta-thalassemia

AIM

This study aimed to examine the color discrimination ability of patients with transfusion-dependent beta-thalassemia (TDβ-T) in detail using the Farnsworth Munsell (FM) 100-hue test and to evaluate structural changes by swept source-optical coherence tomography (SS-OCT).

MATERIAL AND METHODS

This prospective, sectional study included 40 patients (79 eyes) with TDβ-T and 21 controls (42 eyes). The volunteers underwent a detailed ophthalmological examination and SS-OCT (DRI-OCT, Triton) imaging. Excluded were those with congenital color vision defects detected with the Ishihara pseudoisochromatic test. The patients' color vision was examined using the FM 100-hue test. The total error score (TES), the blue-yellow local error score (b-y LES), and the red-green local error score (r-g LES) were calculated. p <0.05 was considered significant.

RESULTS

The mean age was 30.34±6.94 years in the patient group and 32.26±6.43 years in the control group (p = 0.078). The patient group had a significantly lower hemoglobin level (9.25±0.87 g/dL vs. 14±1.79 g/dL, p <0.001) and a significantly higher ferritin level (2665.56±2658.05 μg/L vs. 52.87±69.59 μg/L, p<0.001) compared to the control group. The mean TES, b-y LES, and r-g LES were higher in the patients than in the controls (64.84±30.18 vs. 28.45±16.55, p<0.001, 34.21±17.54 vs. 15.67±10.07, p <0.001, and 29.32±15.72 vs. 12.12±7.94, p<0.001, respectively). The patients had a higher b-y LES than r-g LES (34.21±17.54 vs. 29.32±15.72, p = 0.015). Choroidal thickness was lower in the patients than in the controls (284.34±63.55 µm vs. 324.98±88.05 µm, p = 0.043).

CONCLUSION

We found that the color discrimination ability of the patients with TDβ-T was reduced in both the r-g and b-y color axes compared to the controls, and their color discrimination ability in the b-y color axis was more affected than in the r-g axis.

Burden of ocular abnormalities in patients with beta thalassaemia: a cross-sectional study

INTRODUCTION

In Pakistan, the reported carrier rate of thalassaemia is estimated to be 5%-8% with 5000 new patients diagnosed every year. Several known systemic complications of beta thalassaemia major have been studied, but no studies are conducted to assess ocular complications among these patients from our population.

METHODS

It was a cross-sectional study design conducted at three private and public sector centres in Pakistan. We recruited 203, 11-17 years old children with beta thalassaemia major in our study. Frequency of overall ocular complications such as retinal pigment epithelium degeneration, visual field defects, increased retinal vascular tortuosity, lenticular opacities, anterior segment abnormality, etc among beta thalassaemia patients were verified by an ophthalmologist.

RESULTS

On univariate analysis male gender (prevalence ratio (PR): 1.023 (0.903 to 1.160), OGTT levels (PR: 0.99 (0.978 to 1.003) and serum calcium levels (PR: 0.716 (0.616 to 0.936)) were significantly associated with ocular complications. However, on multivariable analysis after adjusting for covariates we observed that the prevalence of ocular complications was 88% higher in males as compared with females. Moreover, with every one unit increase in serum calcium levels the prevalence of ocular complications were decreased by 24%.

CONCLUSION

Our study results showed that the frequency of ocular complications in beta thalassaemia children was 22.7%. Male gender was a risk factor for ocular complications among children with beta thalassaemia. However, high calcium levels among these patients were found to be protective for ocular complications.

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

BACKGROUND

The aim of this study is to evaluate eye structures and function in patients receiving iron chelating therapy and to assess whether a correlation exists between the onset of ocular alterations and the intake of iron chelating drugs.

METHODS

A prospective cohort study was performed. Eighty-eight patients, composed of children and adults with thalassemia major (TM) who are taking or had taken iron chelating drugs (deferoxamine, deferiprone or deferasirox), have been initially enrolled in the study. The final sample featured 80 patients, including 18 children and 62 adults. These subjects received an eye examination to evaluate intraocular pressure (IOP), best corrected visual acuity (BCVA), the presence of refractive defects, cornea, anterior chamber, lens, fundus oculi, visual field and mean retinal nerve fiber layer (RNFL) thickness. Logistic regression model analysis was performed in order to assess any correlation. In addition, a literature search regarding the relation between iron chelating drugs and ocular adverse events was carried out to compare the results obtained with the evidence in the literature.

RESULTS

Logistic regression did not report a significant correlation between the intake of iron chelating drugs and the onset of anterior ocular segment alterations, lens opacities, retinal diseases, optical neuropathies, astigmatism, visual field and RNFL thickness defects. Logistic regression returned a statistically significant correlation between myopia and iron chelation therapy (p-value 0.04; OR 1.05) and also between presbyopia and total duration of therapy with deferoxamine (p-value 0.03; OR 1.21). Although intraocular pressure levels remained within the normal range, a significant correlation with the length of deferoxamine therapy has been found (p-value 0.002; association coefficient -0.12). A negative correlation between deferiprone and presbyopia has also been observed.

CONCLUSION

Iron chelation therapy is not associated with severe visual function alterations. Limitation of deferoxamine treatment can help prevent ocular complications. Deferiprone and/or deferasirox may be preferable, especially in patients over age 40 years.

Novel retinal findings in β-thalassemia major: older age and higher ferritin level as the risk factors

PURPOSE

To investigate retinal changes in β-thalassemia major patients and identify their association with systemic risk factors.

METHODS

In this prospective study, 120 β-thalassemia major patients received complete ophthalmic examinations (best-corrected visual acuity, contrast sensitivity, color vision, and indirect ophthalmoscopy) and retinal imaging using color fundus photography and fundus autofluorescence imaging. Patients were grouped according to the presence of thalassemia-related retinal changes. The association between systemic risk factors (age, type and duration of iron chelator use, history of splenectomy, hemoglobin level, and ferritin level) and thalassemia-related retinal changes was investigated using logistic regression analysis.

RESULTS

Thalassemia-related retinal changes were identified in 36.7% of patients. Several distinct retinal changes were observed, including retinal refractile bodies in 10% of patients and retinal hemorrhage in 5.8% of patients. Fundus autofluorescence imaging showed abnormal patterns in 36.3% of patients with thalassemia-related retinal changes and 18.4% of patients without thalassemia-related retinal changes. Age (odds ratio [OR] = 1.10, 95% confidence interval [CI] 1.03-1.18) and ferritin level (OR 1.16, 95% CI 1.01-1.33) were associated with thalassemia-related retinal changes.

CONCLUSION

Novel retinal changes were observed in β-thalassemia major patients. This study identified older age and higher ferritin level as risk factors for thalassemia-related retinal changes.

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.

Ophthalmic Evaluation in Beta-Thalassemia

OBJECTIVES

To determine the association of ocular manifestations in beta-thalassemia with the patient's age, blood transfusion requirements, average serum ferritin and dose and duration of iron chelation therapy.

METHODS

Sixty multi-transfused beta thalassemia patients of 12 to 18 y of age on chelation therapy were included in this cross-sectional analysis. Structural and functional evaluation of the retina was done using Optical coherence tomography (OCT) and Electroretinography (ERG), including flash ERG and Pattern ERG (PERG). Routine ophthalmic examination and B scan of the eye was also done. Flash ERG a-waves and b-waves were recorded, however only a-wave amplitude was evaluated. Pattern ERG n35, n95 and p50 waves were recorded and p50 wave amplitude was evaluated. The a-wave on flash and p50 on pattern waves represent retinal photoreceptor epithelium (RPE) photoreceptor response, which is mainly affected in beta-thalassemia.

RESULTS

Ocular changes were detected in 38.3% and a significant correlation was noted with increase in age (p = 0.045) but not with serum ferritin, transfusion requirements or chelation therapy. Refractive errors were found in 14 cases (23%), such as myopia with astigmatism in 13 (21.7%) and only myopia in 6 subjects (10%). OCT abnormality was noted in 1 patient (1.7%) who had thinning of central retina; right eye 132 μm and left eye 146 μm (n > 200 μm). Abnormalities were noted in a-wave amplitude on flash ERG in 20% of cases, while reduced p50 amplitude on PERG was noted in 15%.

CONCLUSIONS

A significant correlation was noted between ocular findings and increase in age, but not with serum ferritin, transfusion requirements or chelation therapy. ERG appears to be a promising tool for screening patients with beta-thalassemia and can serve as a follow-up test for evaluating retinal function.

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.

Ocular refractive and biometric characteristics in patients with thalassaemia major

BACKGROUND

Thalassaemia major is associated with characteristic findings in craniofacial bony structures and thereby may render abnormal bony orbit and subsequently distinctive ocular biometry. The purpose of the present study was to evaluate the ocular refractive and biometric characteristics in patients with thalassaemia major.

METHODS

This case-controlled study comprised 94 eyes of 47 patients with thalassaemia major and 88 eyes of 44 age- and sex-matched healthy control subjects. All participants had a complete ocular examination including slitlamp biomicroscopy, fundoscopy, ocular biometry, keratometry, refraction and analysis using Fourier transformation.

RESULTS

There were no significant differences in spherical equivalent (p = 0.66) and total astigmatism (p = 0.83) between groups. Mean uncorrected vision and visual acuities (logMar) were similar (p = 0.32 and p = 0.71, respectively). Compared with controls, thalassaemic patients had a shorter axial length (23.01 ± 0.12 [SEM] mm versus 23.46 ± 0.12 mm, p = 0.035), thicker crystalline lens (4.01 ± 0.11 mm versus 3.87 ± 0.1 mm, p = 0.046) and steeper average keratometry (44.02 ± 0.24 D versus 43.44 ± 0.24, p = 0.03). Fifty-seven per cent of thalassaemic patients had against-the-rule astigmatism (total), while 64.6 per cent of controls showed a with-the-rule pattern (p < 0.05). These patterns were also found for corneal astigmatism. The magnitudes of total, corneal and lenticular astigmatism were similar among groups. Regression analysis showed significant correlation between corneal (J0 and J45) and total (J0 and J45) astigmatism. The correlations were less prominent between lenticular and total J0 and J45. The mean intraocular pressure was 14.68 ± 0.27 mmHg and 13.3 ± 0.26 mmHg in the thalassaemia and control groups, respectively (p < 0.001). Six eyes (12.8 per cent) of four patients in the thalassaemia group had posterior subcapsular cataract, while the condition had not been observed in controls (p = 0.049).

CONCLUSIONS

Shorter axial length, thicker lens, steeper corneal curvature and more against-the-rule pattern were characteristic findings in patients with thalassaemia major.

Alterations in conjunctival cytology and tear film dysfunction in patients with beta-thalassemia

PURPOSE

Patients with beta-thalassemia (beta-tha) represent a group with lifelong transfusion-dependent anemias. This study aimed to describe the conjunctival changes and tear film parameters in these patients.

METHODS

A total of 52 patients (104 eyes) with beta-tha major and 22 normal control subjects (44 eyes) were studied during 1999 through 2000. Tear film break-up time (BUT), Schirmer test, rose Bengal staining, and cytologic evaluation of the conjunctival epithelium were performed in all subjects. The Papanicolaou and May-Grümwald-Giemsa staining procedures were performed on all smears. Patients and control subjects were compared for tear function parameters and conjunctival changes.

RESULTS

The BUT, Schirmer test, and rose Bengal staining values were significantly lower (P < 0.001) in beta-tha patients than in control subjects. Keratinized cells were observed in conjunctival samples in 41% of patients, with a decrease in the number of goblet cells per slide in 64% of patients. In 9% of beta-tha patients, there were a slightly greater number of inflammatory cells than in control eyes.

CONCLUSION

Ocular surface disorder of these patients was characterized by goblet cell loss and conjunctival squamous metaplasia. Our findings were correlated positively with the variable age. Epithelial damage by toxic reaction and disorder of tear quality and quantity are implicated as important factors in the pathogenesis of the ocular surface disease in beta-tha patients.