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Ophthalmology. Retina May 2024
PubMed: 38739070
DOI: 10.1016/j.oret.2024.04.011 -
Metabolic, Pediatric, and Systemic... 1994Several types of hypopigmentation in humans are called albinism. The phenotype for different types of albinism varies according to the amount of pigment in the hale,... (Review)
Review
Several types of hypopigmentation in humans are called albinism. The phenotype for different types of albinism varies according to the amount of pigment in the hale, skin and iris, the reduction in visual acuity and the degree of nystagmus and strabismus. Cutaneous and ocular melanin pigment can range from complete absence throughout the lifetime of the individual to the development of nearly normal levels, including the ability to tan. Visual acuity ranges from 20/40 to 20/400, and visual development in an affected infant is slower than normal. Foveal hypoplasia and altered routing of the optic nerves are found in all types of albinism and are the most constant feature of this condition. The demonstration of optic track misrouting by visual evoked potential studies provides the critical diagnostic procedure for questionable cases of albinism, and this is the single definitive diagnostic test to confirm a diagnosis of albinism.
Topics: Albinism, Ocular; Albinism, Oculocutaneous; Humans; Monophenol Monooxygenase
PubMed: 8719278
DOI: No ID Found -
Pigment Cell Research Aug 2005Ocular albinism type 1 is an X-linked disorder characterized by severe reduction of visual acuity, retinal hypopigmentation, foveal hypoplasia, optic misrouting and the... (Review)
Review
Ocular albinism type 1 is an X-linked disorder characterized by severe reduction of visual acuity, retinal hypopigmentation, foveal hypoplasia, optic misrouting and the presence of giant melanosomes (macromelanosomes) in skin melanocytes and retinal pigment epithelium. The protein product of the OA1 gene is a pigment cell specific membrane glycoprotein, displaying structural and functional features of G protein-coupled receptors (GPCRs). However, in contrast to all other previously characterized GPCRs, OA1 is not localized to the plasma membrane, but is targeted to intracellular organelles, namely late endosomes/lysosomes and melanosomes. These unique characteristics suggest that OA1 represents the first example described so far of an exclusively intracellular GPCR and regulates melanosome biogenesis by transducing signals from the organelle lumen to the cytosol. These findings support previous hypotheses that GPCR-mediated signaling might also operate at the internal membranes in mammalian cells.
Topics: Albinism, Ocular; Amino Acid Sequence; Animals; Eye Proteins; Humans; Melanosomes; Membrane Glycoproteins; Molecular Sequence Data; Mutation; Pigment Epithelium of Eye; Receptors, G-Protein-Coupled; Sequence Homology, Amino Acid; Signal Transduction
PubMed: 16029416
DOI: 10.1111/j.1600-0749.2005.00240.x -
Optometry and Vision Science : Official... May 2011Albinism is an inherited disorder that affects the melanin biosynthesis pathway, which results in reduced or absent pigment formation. This may lead to increased light...
PURPOSE
Albinism is an inherited disorder that affects the melanin biosynthesis pathway, which results in reduced or absent pigment formation. This may lead to increased light transmission through the iris and more reflected light from the fundus. Both these effects contribute to the occurrence of ocular straylight. One aim of this study is to determine whether and how increased iris transmission and fundus reflection in subjects with albinism contributes to the occurrence of ocular straylight. The other aim is to determine the effect that an iris print-contact lens (CL) could have in terms of reducing the occurrence of ocular straylight.
METHODS
Ocular straylight was quantified by means of the straylight parameter s and measured as a function of angle and wavelength in 17 subjects with different types of albinism, none of whom wore an iris print-CL. The measurements were then repeated with the subjects wearing an iris print-CL to reduce the iris transmission component and thus the occurrence of ocular straylight. The contributions of transmission and reflectance components were estimated for each individual.
RESULT
Straylight level increase varied from normal (s ≈9) to severe (8x). In 15 cases, the reflectance component contributed s >3 to up to s = 17. In eight cases, the transmission component contributed s >3 to up to s = 101. A significant reduction in straylight was observed using an iris print-CL in six subjects with elevated straylight values. In the other 11 subjects with albinism, the iris print-CL had no significant effect on straylight because of the low values of the transmission component.
CONCLUSIONS
This study gives insight into the effects of transmission and reflectance on the total measured straylight occurrence in subjects with albinism. Subjects experiencing increased ocular straylight values may benefit significantly from wearing iris print-CLs because transmission of light through the natural iris may cause a significant increase in straylight.
Topics: Adolescent; Adult; Albinism, Ocular; Albinism, Oculocutaneous; Child; Contact Lenses; Diagnostic Techniques, Ophthalmological; Equipment Design; Female; Fundus Oculi; Humans; Iris; Light; Male; Middle Aged; Optical Phenomena; Scattering, Radiation
PubMed: 21358444
DOI: 10.1097/OPX.0b013e318212071e -
Neuropediatrics Feb 2022The aim of this study was to detail the neurodevelopmental profile of subjects affected by ocular albinism (OA) and to collect data on GPR143 gene analysis.
AIM
The aim of this study was to detail the neurodevelopmental profile of subjects affected by ocular albinism (OA) and to collect data on GPR143 gene analysis.
DESIGN
The design of the study involves a retrospective longitudinal observational case series.
METHODS
We collected data on the neurodevelopmental profile of 13 children affected by OA from clinical annual assessments conducted for a period of 6 years after the first evaluation. We described visual profile, neuromotor development and neurological examination, cognitive profile, communication and language skills and behavioral characteristics. The GPR143 gene analysis was performed as well.
RESULTS
Children presented a variable combination of ocular and oculomotor disorders unchanged during the follow-up, a deficit in visual acuity and in contrast sensitivity that progressively improved. Abnormalities in pattern visual evoked potential were found. No deficits were detected at neurological examination and neuromotor development except for a mild impairment in hand-eye coordination observed in five cases. A language delay was observed in five cases, two of whom had also a developmental quotient delay at 2 years evolving to a borderline/deficit cognitive level at preschool age, difficulties in adaptive behavior and autistic-like features were found. Mutations in the GPR143 gene were identified in the two patients who presented the most severe clinical phenotype.
CONCLUSION
Children with OA may share, in addition to a variable combination of ocular signs and symptoms, a neurodevelopment impairment regarding mostly the cognitive, communicative, and social area, especially those with GPR143 mutation.
Topics: Albinism, Ocular; Child, Preschool; Evoked Potentials, Visual; Eye Proteins; Humans; Membrane Glycoproteins; Retrospective Studies
PubMed: 34327695
DOI: 10.1055/s-0041-1732430 -
Human Mutation Feb 2002Albinism ocular type 1 (OA1) is an X-linked type of albinism that mainly effects pigment production in the eye, resulting in hypopigmentation of the retina, nystagmus,... (Review)
Review
Albinism ocular type 1 (OA1) is an X-linked type of albinism that mainly effects pigment production in the eye, resulting in hypopigmentation of the retina, nystagmus, strabismus, foveal hypoplasia, abnormal crossing of the optic fibers, and reduced visual acuity. The OA1 gene is located on chromosome Xp22.32 and the coding sequence is divided into nine exons. The protein is an integral transmembrane protein that has weak similarities to G protein-coupled receptors. A total of 25 missense, two nonsense, nine frameshift, and five splicing mutations have been reported in the OA1 gene associated with OA1. There are also several deletions of some or all exons of the OA1 gene with deletions of exon 2 resulting from unequal crossing-over, due to flanking Alu repeats. Mutation and polymorphism data on this gene is available from the International Albinism Center - Albinism Database web site (http://www.cbc.umn.edu/tad).
Topics: Albinism, Ocular; Databases, Nucleic Acid; Exons; Eye Proteins; Humans; Membrane Glycoproteins; Molecular Sequence Data; Mutation; Phenotype; Polymorphism, Genetic; RNA Splice Sites
PubMed: 11793467
DOI: 10.1002/humu.10034 -
Indian Journal of Ophthalmology Mar 2019
Topics: Abnormalities, Multiple; Albinism, Ocular; Coloboma; Female; Fluorescein Angiography; Fundus Oculi; Humans; Iris; Iris Diseases; Rare Diseases; Tomography, Optical Coherence; Young Adult
PubMed: 30777963
DOI: 10.4103/ijo.IJO_1182_18 -
Der Ophthalmologe : Zeitschrift Der... Aug 2007In 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... (Review)
Review
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.
Topics: Albinism, Ocular; Albinism, Oculocutaneous; Genetic Predisposition to Disease; Humans; Optic Nerve Diseases; Vision Disorders
PubMed: 17684749
DOI: 10.1007/s00347-007-1571-4 -
International Ophthalmology Clinics 1992
Review
Topics: Albinism, Ocular; Albinism, Oculocutaneous; Chediak-Higashi Syndrome; Humans; Melanins; Vision Disorders; Visual Pathways
PubMed: 1537658
DOI: 10.1097/00004397-199203210-00015 -
Ophthalmic Surgery, Lasers & Imaging... Aug 2022This case series details macular findings in three female siblings who were found to be carriers of a previously unreported splice mutation in GPR143 (X-linked ocular...
This case series details macular findings in three female siblings who were found to be carriers of a previously unreported splice mutation in GPR143 (X-linked ocular albinism [OA1]). Presumed lyonization is responsible for both the subtle and varied findings in OA1 carriers, even among siblings, and especially in patients with darker skin pigmentation. In this series, we used green-light autofluorescence to reveal subtle subfoveal involvement and used optical coherence tomography angiography to uncover previously unreported narrowing of the foveal avascular zone, consistent with foveal hypoplasia. .
Topics: Albinism, Ocular; Eye Proteins; Female; Humans; Membrane Glycoproteins; Mutation
PubMed: 35951714
DOI: 10.3928/23258160-20220713-03