Visual Development During the Second Decade of Life in Albinism.

PURPOSE: To evaluate change in best corrected visual acuity (BCVA) during the second decade of life and the effects of albinism type and extraocular muscle surgery on BCVA in children with albinism. METHODS: In this retrospective longitudinal study, 41 patients with albinism with clinic visits recording binocular BCVA at least once between the ages of 10 and 13 years (visit A) and again between the ages of 17 and 20 years (visit B) were included. Type of albinism, age at each visit, and interval eye muscle surgeries were recorded for each patient. RESULTS: Forty (98%) patients showed BCVA improvement or stability between visits A and B. There was no significant effect of interval extraocular muscle surgery on BCVA. Those carrying either a clinically presumed or moleculary confirmed diagnosis of oculocutaneous albinism types 1B and 2 had the best visual outcomes, consistent with previous studies. CONCLUSIONS: In the majority of patients with albinism, significant improvement in BCVA occurs during the second decade of life. Extraocular muscle surgery was not a significant factor in BCVA improvement in albinism. Overall, the assessments support the finding of improvement of visual acuity in children with albinism at earlier ages and provide new information beneficial in predicting visual outcomes in the second decade of life. [J Pediatr Ophthalmol Strabismus. 2018;55(4):254-259.].

A novel iris transillumination grading scale allowing flexible assessment with quantitative image analysis and visual matching.

PURPOSE: To develop a sensitive scale of iris transillumination suitable for clinical and research use, with the capability of either quantitative analysis or visual matching of images. METHODS: Iris transillumination photographic images were used from 70 study subjects with ocular or oculocutaneous albinism. Subjects represented a broad range of ocular pigmentation. A subset of images was subjected to image analysis and ranking by both expert and nonexpert reviewers. Quantitative ordering of images was compared with ordering by visual inspection. Images were binned to establish an 8-point scale. Ranking consistency was evaluated using the Kendall rank correlation coefficient (Kendall's tau). Visual ranking results were assessed using Kendall's coefficient of concordance (Kendall's W) analysis. RESULTS: There was a high degree of correlation among the image analysis, expert-based and non-expert-based image rankings. Pairwise comparisons of the quantitative ranking with each reviewer generated an average Kendall's tau of 0.83 ± 0.04 (SD). Inter-rater correlation was also high with Kendall's W of 0.96, 0.95, and 0.95 for nonexpert, expert, and all reviewers, respectively. CONCLUSIONS: The current standard for assessing iris transillumination is expert assessment of clinical exam findings. We adapted an image-analysis technique to generate quantitative transillumination values. Quantitative ranking was shown to be highly similar to a ranking produced by both expert and nonexpert reviewers. This finding suggests that the image characteristics used to quantify iris transillumination do not require expert interpretation. Inter-rater rankings were also highly similar, suggesting that varied methods of transillumination ranking are robust in terms of producing reproducible results.

[Oculocutaneous and ocular albinism]. / Okulokutaner und okulärer Albinismus.

Albinism can be divided into oculocutaneous albinism (OCA) and ocular albinism (OA). In the differential diagnostics these can be distinguished from rarer syndromes with partial albinism, which are frequently associated with susceptibility to infections and neurological symptoms. The OCA is an autosomal recessive inherited disease of melanin biosynthesis, which leads to complete or partial loss of melanin in the skin, hair follicles and eyes. Of the seven currently known subtypes (OCA 1-7), four are well-characterized (OCA 1-4). These are based on gene mutations, which code for tyrosinase, a key enzyme in melanin synthesis and for further proteins. These play an important role in the catalytic activity of tyrosinase and the structure and function of melanosomes. In the presence of these subtypes, the clinical symptoms and the course of the disease show a pronounced variability, especially in the type and extent of pigmentation of the skin and hair as well as the severity of eye involvement, which makes the phenotypic classification difficult. Treatment priorities are a consistent protection from UV light for prophylaxis against skin cancer and regular preventive investigations. The ocular alterations typical for albinism necessitate timely diagnostics and care by institutions specialized in ophthalmology. Novel strategies for systemic treatment of subtypes of albinism are in preclinical testing. The OA without skin involvement shows X­linked inheritance, is much rarer and is characterized by reduced pigmentation of the retina and iris, nystagmus and macular hypoplasia, sometimes with substantial loss of visual acuity. The typical ocular symptoms of OA can be manifested to a varying extent in all forms of OCA.

Sequence analysis of tyrosinase gene in ocular and oculocutaneous albinism patients: introducing three novel mutations.

PURPOSE: Albinism is a heterogeneous genetic disorder of melanin synthesis that results in hypopigmented eyes (in patients with ocular albinism) or hair, skin, and eyes (in individuals with oculocutaneous albinism). It is associated with decreased visual acuity, nystagmus, strabismus, and photophobia. The tyrosinase gene is known to be involved in both oculocutaneous albinism and autosomal recessive ocular albinism. In this study, we aimed to screen the mutations in the TYR gene in the nonsyndromic OCA and autosomal recessive ocular albinism patients from Iran. METHODS: The tyrosinase gene was examined in 23 unrelated patients with autosomal recessive ocular albinism or nonsyndromic OCA using DNA sequencing and bioinformatics analysis. RESULTS: TYR gene mutations were identified in 14 (app. 60%) albinism patients. CONCLUSIONS: We found 10 mutations, 3 of which were novel. No mutation was found in our ocular albinism patients, but one of them was heterozygous for the p.R402Q polymorphism.

Mutational analysis of oculocutaneous albinism: a compact review.

Oculocutaneous albinism (OCA) is an autosomal recessive disorder caused by either complete lack of or a reduction of melanin biosynthesis in the melanocytes. The OCA1A is the most severe type with a complete lack of melanin production throughout life, while the milder forms OCA1B, OCA2, OCA3, and OCA4 show some pigment accumulation over time. Mutations in TYR, OCA2, TYRP1, and SLC45A2 are mainly responsible for causing oculocutaneous albinism. Recently, two new genes SLC24A5 and C10orf11 are identified that are responsible to cause OCA6 and OCA7, respectively. Also a locus has been mapped to the human chromosome 4q24 region which is responsible for genetic cause of OCA5. In this paper, we summarized the clinical and molecular features of OCA genes. Further, we reviewed the screening of pathological mutations of OCA genes and its molecular mechanism of the protein upon mutation by in silico approach. We also reviewed TYR (T373K, N371Y, M370T, and P313R), OCA2 (R305W), TYRP1 (R326H and R356Q) mutations and their structural consequences at molecular level. It is observed that the pathological genetic mutations and their structural and functional significance of OCA genes will aid in development of personalized medicine for albinism patients.

Structural grading of foveal hypoplasia using spectral-domain optical coherence tomography a predictor of visual acuity?

PURPOSE: 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. DESIGN: Observational case series. PARTICIPANTS AND CONTROLS: 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. METHODS: 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. MAIN OUTCOME MEASURES: 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. RESULTS: 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. CONCLUSIONS: 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. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Oculocutaneous albinism type 1A: a case report.

The term, oculocutaneous albinism (OCA), describes a group of inherited disorders of melanin biosynthesis that exhibits congenital hypopigmentation of ocular and cutaneous tissues. The clinical spectrum of OCA ranges from a complete lack of melanin pigmentation to mildly hypopigmented forms. OCA1A is the most severe type with a complete lack of melanin production throughout life; the milder forms OCA1B, OCA2, OCA3 and OCA4 show some pigment accumulation over time. Clinical manifestations include various degrees of congenital nystagmus, iris hypopigmentation and translucency, reduced pigmentation of the retinal pigment epithelium, foveal hypoplasia, reduced visual acuity and refractive errors, color vision impairment, and prominent photophobia. All four types of OCA are inherited as autosomal recessive disorders. At least four genes are responsible for the different types of the disease (TYR, OCA2, TYRP1, and MATP). Diagnosis is based on clinical findings of hypopigmentation of the skin and hair in addition to the characteristic ocular symptoms. Herein we present a case with OCA1A.

Comprehensive analysis of oculocutaneous albinism among non-Hispanic caucasians shows that OCA1 is the most prevalent OCA type.

Oculocutaneous albinism (OCA) is a genetically heterogeneous group of disorders characterized by absent or reduced pigmentation of the skin, hair, and eyes. In humans, four genes have been associated with "classical" OCA and another 12 genes with syndromic forms of OCA. To assess the prevalence of different forms of OCA and different gene mutations among non-Hispanic Caucasian patients, we performed DNA sequence analysis of the four genes associated with "classical" OCA (TYR, OCA2, TYRP1, SLC45A2), the two principal genes associated with syndromic OCA (HPS1, HPS4), and a candidate OCA gene (SILV), in 121 unrelated, unselected non-Hispanic/Latino Caucasian patients carrying the clinical diagnosis of OCA. We identified apparent pathologic TYR gene mutations in 69% of patients, OCA2 mutations in 18%, SLC45A2 mutations in 6%, and no apparent pathological mutations in 7% of patients. We found no mutations of TYRP1, HPS1, HPS4, or SILV in any patients. Although we observed a diversity of mutations for each gene, a relatively small number of different mutant alleles account for a majority of the total. This study demonstrates that, contrary to long-held clinical lore, OCA1, not OCA2, is by far the most frequent cause of OCA among Caucasian patients.

[Phenotype of the visual system in oculocutaneous and ocular albinism]. / Phänotyp des visuellen Systems bei okulokutanem und okulärem Albinismus.

In spite of albinism being one of the visual impairments which has been known for over a century, it has only been known for a few decades that albinism is correlated to severe cerebral morphological developmental alterations. The increasing knowledge about the role of melanin in the development and orientation of cerebral neurons not only renders more insight into albinism, but also a greater insight in the physiological neuronal and cerebral development in man. Concerning the morphological and visual phenotype there are new clinical findings which enlarge the known spectrum of albinism. In a representative group of 506 persons with oculocutaneous and ocular albinism who are in care at the Department of Ophthalmology at the University of Saarland (UKS), we present a staging of morphological findings of the iris, retinal pigment epithelium and macula, and of the optic nerve head which has been in use for 10 years. Albinism may present with a remarkably mild ocular phenotype and a near to normal functional phenotype. We present correlations between molecular genetic types of albinism, ocular phenotype and visual function. Of great importance concerning later visual acuity is the dysplasia of the optic nerve head (ONH), which is a frequent finding in albinism. The appearance of the ONH should always be included in any clinical description of an albinism patient. It is highly possible that due to a moderate phenotype there are still many patients who have not been diagnosed yet. Visual acuity of 30/20 to 20/20 and no nystagmus do not rule out albinism. In addition, when performing albino VEPs in phenotypically normal children with infantile strabismus, small ONHs, but normal visual acuity and no nystagmus, the classical atypical chiasmal crossing is sometimes found. Therefore, the number of persons having undiagnosed albinism is probably quite high, perhaps there even is a very broad transition zone from normal to albinotic.

Diagnóstico laboratorial do albinismo oculocutâneo / Laboratory diagnosis of oculocutaneous albinism

OBJETIVO: Avaliar os métodos laboratoriais dos diferentes tipos de albinismo oculocutâneo (OCA 1 e OCA 2) de forma descritiva e analisar sua eficiência. MATERIAL E MÉTODO: O teste do bulbo capilar é um método químico usado para distinguir as duas formas, no entanto recentemente teve sua eficácia como teste padrão contestada. O avanço da biologia molecular permite a análise das mutações que causam o distúrbio e a sua localização gênica. CONCLUSÃO: O teste do bulbo é seguro apenas para o diagnóstico do OCA 1A, podendo ser usado como complemento de um método mais apurado. A análise molecular fornece um diagnóstico definitivo, permitindo distinguir OCA 1 de OCA 2, pois as mutações afetam genes em cromossomos diferentes.

OBJECTIVES: To evaluate the laboratories methods of the oculocutaneous albinism (OCA 1and OCA 2) of descriptive form and to analyze its results. METHODS: The hair bulb test is a chemical method used to distinguish the two forms, however, recently had its effectiveness as an standard test contested. The advance of molecular biology allows the analysis of the mutations that cause the disturb and its genic location. CONCLUSIONS: The bulb test is secure only for the diagnosis of OCA 1A, being able to be used as complement of a more refined method. The molecular analysis supplies a diagnostic definitive allowing to distinguish OCA 1 from OCA 2, because the mutations affect genes in different chromosomes.

[A new form of Oculocutaneous albinism, OCA4].

Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). OCA4 was firstly reported in a Turkish OCA patient. The gene responsible for OCA4 is the human homologue of the mouse underwhite (uw) gene, which encodes the mem-brane-associated transporter protein (MATP). MATP gene is located on chromosome 5p13.3 and is divided into 7 exons and 6 introns. MATP gene is transcriptionally modulated by MITF, and encodes a protein of 530 amino acids. There are at least 18 pathologic mutations and 8 non-pathologic polymorphisms have been found.

[Mutations and polymorphisms of the P gene associated with oculocutaneous albinism type II].

Oculocutaneous albinism typeII(OCA2), the most common type of albinism, is an autosomal recessive disorder. It is caused by mutations in the P gene, which is located on chromosome 15q11.1-q12 and divided into 24 exons and 23 introns. P gene codes for 838-amino-acid integral membrane protein with 12 putative transmembrane domains, but the exact function is not clear yet. There are at least 60 pathologic mutations and 43 non-pathologic polymorphisms have been found. Pathologic mutations include missense mutations, nonsense mutations, frameshift mutations and splice-sit mutations. But unlike TYR gene, most of P gene mutations are located on the C-terminal and don' t cluster in defined regions. It is difficult to define the pathologic mutations since many non-pathologic polymorphisms also lie in exons. Some non-pathologic missense mutations may be associated with phenotypic variation in normally pigmented individuals and need to further study.

P gene mutations associated with oculocutaneous albinism type II (OCA2).

Oculocutaneous albinism type II (OCA2) is the most common form of albinism in humans. OCA2 has been previously associated with mutations of the P gene, the human homologue to the murine pink-eyed dilution gene. The P gene encodes a 110 kDa protein containing 12 potential membrane spanning domains and is associated with melanosomal membranes. The specific function of the P protein is currently unknown but is thought to be involved in tyrosinase processing and transport. We report nine novel mutations in the P gene associated with OCA2. These include two missense mutations, c.1938A>C (p.Ile646Val) and c.1556T>C (p.Val519Ala); one nonsense mutation c.612G>A (p.Trp204X); five frameshift mutations: c.2372_2373delTC, c.1555delG, c.1938_1939insC, c.2050delT, and c.1045_1046delAT; and a splice site mutation c.1951+1G>A. We also report 12 novel polymorphisms including one amino acid substitution, c.2365_2366GC>CA (p.Ala789Glu). At present, there is no functional assay to determine if a mutation is truly pathogenic. The presence of numerous polymorphisms of the P gene in the coding region, several of which result in amino acid substitutions, makes molecular diagnosis problematic. To ensure accurate molecular diagnosis, further mutational analysis will be necessary to produce a comprehensive list of mutations associated with OCA2. This information will also help define the critical functional domains of the P protein. Mutations associated with OCA2 can be found in the Albinism Database (http://albinismdb.med.umn.edu).

Color vision in patients with the Hermansky-Pudlak syndrome.

PURPOSE: To study color vision in patients with oculocutaneous albinism (OCA) METHODS: We evaluated color vision in 42 patients with OCA using the HRR color plates. Sixty seven percent of the patients had the Hermansky-Pudlak syndrome (HPS), diagnosed genetically or clinically. The remaining patients had unknown mutations leading to OCA. RESULTS: 47.6 % of patients of OCA of all types included had a color vision defect. Of these, 55% were female and 45% were male patients. 50% of patients with the HPS (all types) had a color vision deficit. 42.9% of patients with OCA of unknown type had color weakness. 57.1% had normal color vision. CONCLUSIONS: Results suggest that many patients with OCA and the HPS have a mild red-green color perception deficiency that is not a sex linked trait. The prevalence of color vision deficits in our study population increased with decreasing visual acuity.

Color vision in patients with the Hermansky-Pudlak syndrome

PURPOSE: To study color vision in patients with oculocutaneous albinism (OCA) METHODS: We evaluated color vision in 42 patients with OCA using the HRR color plates. Sixty seven percent of the patients had the Hermansky-Pudlak syndrome (HPS), diagnosed genetically or clinically. The remaining patients had unknown mutations leading to OCA. RESULTS: 47.6 of patients of OCA of all types included had a color vision defect. Of these, 55 were female and 45 were male patients. 50 of patients with the HPS (all types) had a color vision deficit. 42.9 of patients with OCA of unknown type had color weakness. 57.1 had normal color vision. CONCLUSIONS: Results suggest that many patients with OCA and the HPS have a mild red-green color perception deficiency that is not a sex linked trait. The prevalence of color vision deficits in our study population increased with decreasing visual acuity