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      Characterization of Retinal Thickness in Individuals with Albinism: Baseline Data for a Black South African Population

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          Abstract

          Introduction

          The central retina is responsible for several visual functions and continues to develop postnatally. In albinism, which is a genetic disorder characterized by impaired melanin biosynthesis, the development of the central retina is prematurely arrested and results in foveal hypoplasia. Retinal thickness measurements can be determined non-invasively using optical coherence tomography systems. This article reports on the retinal thickness measurements of individuals with albinism in South Africa to aid in the assessment and management of affected individuals.

          Methods

          The study used a comparative research design and included 60 individuals (30 albinism and 30 controls) aged from 10 to 30 years who accessed the eye clinic at a tertiary institution in KwaZulu-Natal, South Africa. The Optovue iVue100 optical coherence tomographer was used to measure retinal thickness in the nine Early Treatment Diabetic Retinopathy Study (ETDRS) sectors including the central foveal, parafoveal and perifoveal regions. Study data were analysed using descriptive and inferential statistics.

          Results

          The mean central foveal thickness was significantly higher in individuals with albinism compared with controls (289 µm versus 239 µm, p < 0.001). In contrast, control participants showed thicker retinal thickness measurements in the other ETDRS sectors (p < 0.001). The nasal and temporal quadrants were thickest and thinnest, respectively, in the parafoveal and perifoveal regions for the albinism and control groups.

          Conclusion

          Individuals with albinism, aged from 10 to 30 years, have higher central foveal thickness but thinner retinal thickness measurements in the parafoveal and perifoveal regions. Optometric personnel should consider these measurements when assessing individuals with albinism with foveal retinal diseases.

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          Most cited references35

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          Race- and sex-related differences in retinal thickness and foveal pit morphology.

          To examine sex- and race-associated differences in macular thickness and foveal pit morphology by using spectral-domain optical coherence tomography (SD-OCT). One hundred eighty eyes of 90 healthy patients (43 women, 47 men) underwent retinal imaging with spectral-domain OCT. The lateral scale of each macular volume scan was corrected for individual differences in axial length by ocular biometry. From these corrected volumes, Early Treatment Diabetic Retinopathy Study (ETDRS) grids of retinal thickness were generated and compared between the groups. Foveal morphology was measured with previously described algorithms. Compared with the Caucasians, the Africans and African Americans had reduced central subfield thickness. Central subfield thickness was also reduced in the women compared with the men, although the women also showed significant thinning in parafoveal regions. There was no difference between the sexes in foveal pit morphology; however, the Africans/African Americans had significantly deeper and broader foveal pits than the Caucasians. Previous studies have reported race- and sex-associated differences in macular thickness, and the inference has been that these differences represent similar anatomic features. However, the data on pit morphology collected in the present study reveal an important and significant variation. Between the sexes, the differences are due to global variability in retinal thickness, whereas the variation in thickness observed between the races appears to be driven by differences in foveal pit morphology. These differences have important implications for the use of SD-OCT in detecting and diagnosing retinal disease.
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            Relationship between foveal cone specialization and pit morphology in albinism.

            Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism.
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              Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity?

              To characterize and grade the spectrum of foveal hypoplasia based on different stages of arrested development of the fovea. Grading was performed using morphologic findings obtained by ultra high-resolution spectral-domain optical coherence tomography. Best-corrected visual acuity (BCVA) was calculated for different grades. Observational case series. Sixty-nine patients with foveal hypoplasia (albinism, n = 34; PAX6 mutations, n = 10; isolated cases, n = 14; achromatopsia, n = 11) and 65 control subjects were examined. A 7×7-mm retinal area was sampled using a 3-dimensional scanning protocol (743×75, A scans×B scans) with ultra high-resolution spectral-domain optical coherence tomography (SOCT Copernicus HR; 3-μm axial resolution). Gross morphologic abnormalities were documented. B-scans at the fovea were segmented using a longitudinal reflectivity profile. Logarithm of the minimum angle of resolution BCVA was obtained. Grading was based on presence or absence of foveal pit and widening of the outer nuclear layer (ONL) and outer segment (OS) at the fovea. Quantitative measurements were obtained for comparing atypical foveal hypoplasia in achromatopsia. Best-corrected visual acuity was compared with the grade of foveal hypoplasia. Four grades of foveal hypoplasia were distinguished: grade 1, shallow foveal pit, presence of ONL widening, presence of OS lengthening; grade 2, grade 1 but absence of foveal pit; grade 3, grade 2 but absence of OS lengthening; grade 4, grade 3 but absence of ONL widening. There was significant difference in visual acuity (VA) associated with each grade (P<0.0001). Grade 1 was associated with the best VA (median VA, 0.2), whereas grades 2, 3, and 4 were associated with progressively poorer VA with a median VA of 0.44, 0.60, and 0.78, respectively. The atypical features seen with foveal hypoplasia associated with achromatopsia were characterized by decreased retinal and ONL thickness and deeper foveal depth. A structural grading system for foveal hypoplasia was developed based on the stage at which foveal development was arrested, which helps to provide a prognostic indicator for VA and is applicable in a range of disorders associated with foveal hypoplasia. Atypical foveal hypoplasia in achromatopsia shows different characteristics. The author(s) have no proprietary or commercial interest in any materials discussed in this article. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                Clin Optom (Auckl)
                Clin Optom (Auckl)
                opto
                Clinical Optometry
                Dove
                1179-2752
                20 January 2021
                2021
                : 13
                : 15-22
                Affiliations
                [1 ]Discipline of Optometry, School of Health Sciences, University of KwaZulu-Natal , Durban X54001, South Africa
                Author notes
                Correspondence: Nishanee Rampersad Discipline of Optometry, School of Health Sciences, University of KwaZulu-Natal , Westville Campus, Private Bag, DurbanX54001, South AfricaTel +27 31 260 7562Fax +27 31 260 7666 Email rampersadn@ukzn.ac.za
                Author information
                http://orcid.org/0000-0001-5477-5205
                http://orcid.org/0000-0002-2074-0589
                http://orcid.org/0000-0001-5175-4580
                http://orcid.org/0000-0001-7813-7566
                http://orcid.org/0000-0001-7756-3774
                http://orcid.org/0000-0003-2028-1711
                http://orcid.org/0000-0002-6873-5375
                Article
                273141
                10.2147/OPTO.S273141
                7829131
                33505177
                26e9ecb5-7f0f-416c-addb-614951d79591
                © 2021 Pillay et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                History
                : 04 September 2020
                : 03 November 2020
                Page count
                Figures: 1, Tables: 4, References: 35, Pages: 8
                Categories
                Original Research

                albinism,fovea,foveal hypoplasia,optical coherence tomography,retinal thickness

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