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PubMed2003

The clinical features of albinism and their correlation with visual evoked potentials.

AIM: To investigate the relation between the clinical and electrophysiological abnormalities of patients undergoing visual evoked potential investigation for albinism. METHODS: 40 subjects with a probable or possible clinical diagnosis of albinism underwent pattern appearance and/or flash visual evoked potential (VEP) examination. The VEP findings are correlated with the clinical features of albinism determined by clinical examination and orthoptic assessment. RESULTS: The majority of patients with clinical evidence of albinism showed a contralateral predominance in the VEPs. There was close correlation between the clinical signs of albinism and the degree of contralateral VEP predominance. This manifested as an interhemispheric latency asymmetry to monocular pattern appearance stimulation but amplitude asymmetry to flash stimulation. The strongest correlation for pattern appearance interhemispheric latency difference was with foveal hypoplasia (rho = 0.58; p = 0.0003) followed by nystagmus (rho = 0.48; p = 0.0027) and iris transillumination (rho = 0.33; p = 0.039). The VEP abnormalities were of greater magnitude in those patients with most features of albinism. Several patients with apparently mild disorders of ocular pigmentation had small but significantly abnormal VEP latency asymmetries. CONCLUSION: There is a strong association between the magnitude of the interhemispheric latency asymmetry of the pattern appearance VEP, and of amplitude asymmetry of the flash VEP, with the clinical signs of albinism. The data are consistent with a spectrum of abnormalities in albinism involving both clinical expression and electrophysiological misrouting, which is wider than previously recognised.

Adolescent↗
PubMed2005

Comparison of clinical findings in pediatric patients with albinism and different amplitudes of nystagmus.

INTRODUCTION: Visual acuity in albinism can vary and is difficult to predict. We undertook this study to investigate whether patients with albinism with absent or minimal nystagmus have better visual acuity and ocular alignment than patients with albinism and obvious nystagmus. METHODS: Our retrospective chart review of 38 pediatric patients with albinism yielded 16 patients with absent or minimal nystagmus and 22 patients with obvious nystagmus. RESULTS: Patients with albinism and absent or minimal nystagmus had best-corrected visual acuities ranging from 20/20 to 20/50, with a mean visual acuity of 20/33. Those patients with albinism and obvious nystagmus had best-corrected visual acuities ranging from 20/30 to 20/200, with a mean visual acuity of 20/80. Visual acuity was significantly better in the group with absent or minimal nystagmus (P < 0.001). Of the 16 patients with absent or minimal nystagmus, 6 were orthophoric and 10 had a strabismic deviation of 12 prism diopters (PD) or less. None of these patients required strabismus surgery. Of the 22 patients with nystagmus, 16 were orthophoric, 1 had a horizontal deviation of less than 12 PD, and 5 had larger angle horizontal deviations ranging from 20 to 50 PD. CONCLUSION: Our findings suggest that pediatric albinism patients with absent or minimal nystagmus can be expected to demonstrate better visual acuity and are less likely to show a strabismic deviation of greater than 12 PD compared with those with obvious nystagmus (P = 0.0003).

Adolescent↗
PubMed2003

Hopi Indians, "cultural" selection, and albinism.

The incidence of albinism in Hopi Indians has been estimated as approximately 1 in 200 individuals. It has been suggested that "cultural" selection as the result of a mating advantage of males with albinism has been important in the maintenance of this high incidence. To examine this hypothesis quantitatively, a model that includes male-mating advantage, mutation, and viability selection is analyzed. In order to play an important role in the maintenance of the high incidence of albinism, the necessary mating advantage of males with albinism appears unrealistically high. However, if the extent of viability selection against individuals with albinism is not as large as previously assumed, the necessary amount of mating advantage is not as high. Other related aspects are also discussed here, such as the type of albinism in Hopi Indians and its impact, the conditions for a polymorphism with male-mating advantage and viability selection, and the time necessary to change the incidence of albinism either by the relaxation or institution of male-mating advantage.

Albinism↗
PubMed1994

Ophthalmic features of minimal pigment oculocutaneous albinism.

PURPOSE: The purpose of this study is to describe the heterogeneous phenotype of individuals with an unusual type of albinism--minimal pigment oculocutaneous albinism. METHODS: Nine patients with minimal pigment oculocutaneous albinism were identified and followed for up to 11 years. The criteria were the presence of oculocutaneous albinism in association with low hairbulb tyrosinase activity in the patient and disparate activity in the parents with one parent having normal activity and the other having low tyrosinase activity. Changes in skin, hair, and ocular pigment were followed as the patients matured. As a measure of ocular pigment, iris transillumination and macular transparency were graded according to a previously published scheme. RESULTS: Patients were born with white scalp hair and skin, and nystagmus developed. Visual acuity was reduced to 20/50 to 20/200 for the group, but in one patient vision improved with maturity. Irides were blue. In seven patients, iris pigment developed, which was detected by transillumination with slit-lamp biomicroscopy, including the one patient with improved visual acuity. All patients had foveal hypoplasia, and melanin pigment in the fundi could not be detected by clinical examination. Visual acuity in the group did not correlate directly with the presence or development of iris transillumination or macular transparency. The pedigrees were consistent with an autosomal recessive inheritance pattern. CONCLUSION: This unique type of oculocutaneous albinism has heterogeneous clinical features. Minimal pigment oculocutaneous albinism appears to represent a new type of tyrosinase-related oculocutaneous albinism (OCA1MP).

Adolescent↗
PubMed2004

Subnormal visual acuity (SVAS) and albinism in Mexican 12-13-year-old children.

BACKGROUND: In a previous study the vision of 1046 12-13-year-olds in Sweden was examined. Of those 67 had some kind of visual disturbances and in 20 no obvious cause was found. In this group, defined as children with subnormal visual acuity syndromes (SVAS), albinism was shown to be a major cause to the visual dysfunction giving a prevalence of about 1%. This is about 100 times higher than previous figures. Albinism can therefore be the cause in many cases of unexplained low visual acuity, at least in Sweden. Subnormal visual acuity is usually found in 2-4% in a pediatric population and is often called 'amblyopia'. The Swedish study showed that in many cases 'amblyopia' should be replaced by 'SVAS' and further investigation. The present Mexican study was designed identically to the Swedish study. The objective was to describe the distribution of visual acuity and the prevalence of ocular disorders, including incidence of subnormal visual acuity (SVAS) and the occurrence of albinism in a Mexican population of 12-13-year-olds. SUBJECTS AND METHODS: Altogether 1035 children, 12-13 years of age, were examined. A total number of 344 children were referred to the university pediatric eye clinic for further examination. 272 of these had simple refractive errors, 59 were diagnosed with an ophthalmological disorder and 13 children could not be pathologically classified. These were referred to a second ophthalmological examination, including VEP (Visual Evoked Potential) recordings. VEP reveals an asymmetric (right vs. left) cortical response after monocular stimulation in albinism. RESULTS: No child showed iris translucency or any other typical albinoic sign. VEP was recorded from 11 children. Three children showed an asymmetric VEP and were classified as albinos. The VEP response was normal in 8 of the children. CONCLUSIONS: The results indicate that albinism is common in Mexico, although not as common as in a similar Swedish population. A prevalence of albinism of approximately 0.3% was found in the Mexican population, compared to approximately 1% in the Swedish study group. The number of albinos was much higher in both study groups than to be expected from previous estimates. The difference between the Swedish and the Mexican figures may be explained by the general difference in pigmentation between Sweden and Mexico and thus probably by the subsequent lower number of commonly occurring albino foci in the Mexican heritage. It is emphasised that in investigations of children with SVAS, also in countries with a generally high pigmentation level, electro-physiological examinations are important, to be able to reveal albinism, but also to exclude or verify other conditions in the SVAS group, for example neurometabolic conditions.

Adolescent↗
PubMed1990

Red or rufous albinism in southern Africa.

Red or rufous albinism is a rare type of oculocutaneous albinism described, but not as yet fully investigated, in Africa and New Guinea. Twelve rufous albino subjects from 10 families participated in this preliminary study. The prevalence of rufous albinism was found to be approximately one in 8,580 among school children in the negroid population. The combination of the unusual red skin colour, ginger to reddish hair colour, low susceptibility to sun damage, and minimal visual problems, in affected individuals, suggested that they form a group which is distinct from the brown and other types of albinism. The mode of inheritance was found to be recessive. Tyrosinase assays showed that rufous albinos are tyrosinase positive and on electron microscopy studies normal melanosomes and melanocytes were observed in hair bulbs and skin. Visual evoked potential testing did not show the gross decussation abnormalities of the optic pathway detected in other types of albinism. Rufous albinism might be at one end of the spectrum of types of oculocutaneous albinism and, because affected people have such mild symptoms, their inclusion in this group might be debatable.

Adolescent↗
PubMed2002

A sociological study of children with albinism at a special school in the Limpopo province.

This article maintains that it is the social context, as much as, and sometimes more than the physical condition, that largely structures and limits the lives of people with albinism. It deals with albinism from a sociological, rather than a medical perspective. Viewed as such the problems experiencing by affected people stem primarily not from their physical differences but from the way others respond to those differences and from the social and physical environments they have to cope with. The article is based on a study of 32 children with albinism from a special school in the Limpopo province. Educational, health and social problems, attitude and perceptions about albinism were tested by way of structured interviews. The data reveal an acute lack of information about the causes and consequences of albinism. It projects it as a condition still deeply immersed in myths and superstition resulting in the stigmatizing and rejection of affected people. It also discloses a physical environment which is preventing rather than supporting people with albinism from reaching their potential. It calls for a reorientation in dealing with albinism--away from just medical intervention to treating it as a social construct requiring a holistic approach.

Africa South of the Sahara↗
PubMed1997

Albinism: an update and review of the literature.

BACKGROUND: Albinism can be a diagnostic challenge to the optometrist, with ocular albinism the entity most likely to be overlooked or misdiagnosed. Albinism should be suspect in a child with nystagmus. METHODS: Albinism is best diagnosed by electron microscopy of skin or hair bulbs. Measuring the flash visually evoked response (VER) is the best way to confirm the abnormal decussation of the optic nerve fibers. Transillumination of the iris can be performed to see if it lacks pigment on its posterior surface. Optometrists should also be alert for nystagmus, strabismus, lack of stereopsis, and poor fusional capacity. Most people with albinism have photophobia and reduced acuity, and many have defective hearing. RESULTS: This review describes the various kinds of albinism and summarizes associated ocular manifestations with pertinent forms of the disorder. CONCLUSIONS: Optometrists are responsible for detection of albinism and provision of optical aids and related advice to afflicted patients. These patients also need appropriate counselling and genetic studies of family members.

Albinism, Oculocutaneous↗
PubMed2001

Stereopsis in patients with albinism: clinical correlates.

PURPOSE: A hallmark of albinism is excessive decussation of retinostriate projections at the optic chiasm. This misprojection might lead to abnormalities in the retinal correspondence and may account for the usual absence of stereovision. We report on 2 groups of patients with albinism who have either fine or gross stereopsis and compare the clinical findings of these groups to other patients with albinism with similar visual acuities but no stereopsis. METHODS: A retrospective chart review of patients with albinism was used to segregate those with a letter visual acuity of 20/100 or better in one eye, assessment of stereopsis, and strabismus < or = 10 PD. Forty-five patients were identified. Albinism type, best-corrected visual acuity, motility, Titmus vectograph stereoacuity, iris and macula transparency grades, and the presence or absence of both melanin and an annular reflex in the macula were tabulated. A comparison of the clinical characteristics of the groups with and without stereopsis was made. RESULTS: Those albino subjects who demonstrated stereopsis had better visual acuity, less iris transillumination, more frequent presence of melanin in the macula, less nystagmus, and less marked foveal hypoplasia than the albino subjects without stereopsis. No nystagmus was clinically detected in 5 patients with fine stereopsis. All these differences were statistically significant. Macular transparency grade was not significantly different between the groups. CONCLUSIONS: Patients with albinism who demonstrate stereopsis tend to have better visual acuity, more iris pigment, and more melanin pigment in the macula than their counterparts without stereopsis.

Adolescent↗
PubMed1991

Variable expression of vision in sibs with albinism.

Oculocutaneous albinism is defined by the presence of cutaneous and ocular hypopigmentation, the latter associated with nystagmus, iris transillumination, reduced retinal pigment, foveal hypoplasia, and misrouting of the optic fibers at the chiasm. The visual acuity is variable but almost always reduced. We report on two brothers with oculocutaneous albinism and markedly different visual acuity. One brother has a visual acuity of 20/100, while the second has similar cutaneous pigmentation and visual acuity of 20/20 and had not previously been recognized as having oculocutaneous albinism. Both brothers have foveal hypoplasia and misrouting of the optic fibers at the chiasm. Biochemical analysis suggests that this is a tyrosinase-related type of oculocutaneous albinism. This study demonstrates that careful observation of foveal development in relatives with normal vision is necessary to detect all individuals with albinism in a family. A suspected diagnosis of albinism may be confirmed when the visual-evoked potentials show excessive decussation of the optic fibers at the chiasm.

Adolescent↗
PubMed2004

Positive angle kappa in albinism.

BACKGROUND: Albinism is an inherited disorder of deficient melanin production. There is a high prevalence of strabismus in patients with albinism. We investigated the prevalence of a positive angle kappa in patients with albinism and report its effect on assessment of binocular alignment. METHODS: We retrospectively reviewed the charts of 207 consecutive patients with the diagnosis of albinism seen at the University of Minnesota between 1984 and 2002. Angle kappa and alignment using prism and alternate-cover test (PACT) and Krimsky measurements were recorded. RESULTS: In 99.6% of our patients with albinism, angle kappa was noted to be positive. The mean difference between PACT and Krimsky measurements was 17.11 prism diopters in the more exotropic (or less esotropic) direction per Krimsky test. Because of the high prevalence of a positive angle kappa, esodeviations often appeared less and exodeviations appeared greater than when measured using PACT. CONCLUSIONS: Positive angle kappa can be considered another clinical feature of albinism. Consideration should be given to the effect of positive angle kappa on alignment as observed by Krimsky measurement when planning extraocular muscle surgery, particularly when preoperative sensory testing suggests binocular potential.

Albinism, Oculocutaneous↗
PubMed2004

Positive angle kappa: a sign of albinism in patients with congenital nystagmus.

PURPOSE: To determine whether the association of positive angle kappa and congenital nystagmus is a distinguishing feature of albinism. DESIGN: Observational case series. METHODS: Prospective examination of the location of the corneal light reflex in patients with albinism and idiopathic congenital nystagmus. RESULTS: A positive angle kappa in at least one eye was noted in 20/21 (95%) patients with albinism versus 4/12 (33%) patients with congenital nystagmus (P =.0003, Fisher exact test). A positive angle kappa in both eyes was noted in 15/21 (71.4%) patients with albinism versus 2/12 (16.6%) patients with idiopathic congenital nystagmus (P =.0039, Fisher exact test). CONCLUSION: A positive angle kappa in patients with congenital nystagmus is associated with albinism. The pathophysiology of the positive angle kappa may relate to the anomalous decussation of optic axons that characterizes the albinotic visual system.

Adolescent↗
PubMed1998

Unilateral alpha reactivity: an electroencephalographic finding in albinism.

Persons with various forms of albinism frequently have misrouting of their optic nerve fibers. Visual evoked potential (VEP) studies can confirm this because monocular stimulation tends to result in asymmetrical rather than symmetrical occipital response. This type of decussation abnormality is associated only with albinism. In the electroencephalogram (EEG) of normal subjects, unilateral eye opening or closing does not affect the frequency, reactivity, regulation, and symmetry of alpha rhythm. In contrast, in our study, 6 of 19 persons with oculocutaneous and ocular albinism responded to unilateral eye opening with contralateral disappearance or significant attenuation of their alpha rhythm. The most likely explanation of this phenomenon is that the visual pathway misrouting is complete or nearly complete in some children with albinism so that one rather than both occipital lobes receive visual information from each eye. This type of alpha behavior, like VEP studies, supports the diagnosis of albinism, and such testing can be easily performed during a routine EEG recording.

Adolescent↗
PubMed1990

Albinism and Hermansky-Pudlak syndrome in Puerto Rico.

Five types of oculocutaneous albinism and two types of ocular albinism were found among 349 Puerto Rican albinos. The most prevalent type of albinism was the Hermansky-Pudlak syndrome (HPS). HPS was observed in five of every six albinos in Puerto Rico. The prevalence of HPS was highest in the northwestern quarter of the island, affecting approximately one in 1,800 persons, and approximately one in 22 are carriers of the gene. HPS is an autosomal recessively inherited triad of a tyrosinase-positive type of albinism, a hemorrhagic diathesis due to storage pool deficient platelets and accumulation of ceroid in tissues. The pigmentary phenotype of HPS albinos resembled that of any other type of oculocutaneous or ocular albinism. The most reliable method of diagnosing HPS is by a deficiency of platelet dense bodies observed by electron microscopy. The accumulation of ceroid in the tissues is associated with fibrotic restrictive lung disease and granulomatous enteropathic disease. The enteropathic disorder resembles Crohn's disease and with few exceptions, had its onset after 13 years of age. The major causes of death were fibrotic restrictive pulmonary disease, hemorrhagic episodes and sequelae of granulomatous enteropathic disease. Menometrorrhagia was common in women with HPS. No immune deficiency was found in HPS patients. The majority of patients with HPS had visual acuities of 20/200 or worse and consequently were legally blind. Albinos of all types, including HPS, lacked binocular vision due to nearly complete crossing of the optic tracts.

Albinism, Ocular↗
PubMed1994

Albinism and the associated ocular defects.

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.

Albinism, Ocular↗
PubMedDate not supplied

Albinism.

Albinism is the term applied to a heterogeneous group of genetically determined disorders characterized by hypopigmentation and affecting the eyes. After describing the clinical features of albinism in general, the authors discuss the various forms of oculocutaneous albinism, ocular albinism, and albinoidism that are of interest to the ophthalmologist. Emphasis is placed on the ocular features of each form. The visual pathway abnormalities and the clinical management of albinism are discussed.

Albinism↗
PubMed2006

Spectrum of foveal development in albinism detected with optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) has shown the absence of a foveal depression in an individual with oculocutaneous albinism, type 1 (OCA1) and best-corrected visual acuity (BCVA) of 20/400. However, the presence of an annular light reflex in the macula has been noted with indirect ophthalmoscopy in other patients with albinism who have better vision. We studied macular architecture in albinism with OCT when binocular BCVA was > or = 20/60 and compared this to detection of foveal development with binocular indirect ophthalmoscopy. METHODS: Eleven patients with albinism and BCVA > or = 20/60 were recruited for OCT. Average central macular thickness was recorded. Presence of an oval annular reflex was determined with binocular indirect ophthalmoscopy. RESULTS: Mean binocular BCVA was 20/39 (range: 20/20 to 20/50). Twelve eyes had a rudimentary annular reflex detected with ophthalmoscopy. OCT was reliable in 20 of 22 eyes. A foveal depression was identified with OCT in four eyes. Mean macular thickness for these four eyes was 233 microm (+/- 22.5 microm). We found a weak inverse correlation between BCVA (logMAR) and thickness (r = -0.21). CONCLUSIONS: OCT shows the spectrum of foveal development in albinism, from complete absence of development to a central depression corresponding to a rudimentary annular reflex detected with ophthalmoscopy. The reduced rate of detection of foveal development with OCT compared with ophthalmoscopy is likely related to poor fixation in patients with nystagmus.

Adolescent↗
PubMed2000

Comparison of techniques for detecting visually evoked potential asymmetry in albinism.

PURPOSE: We compared techniques for analyzing visually evoked potential (VEP) asymmetry in children with albinism to find one that could be used effectively and efficiently. METHOD: Subjects included 21 child volunteers, ages 10 months to 6 years (control group) and 21 children with albinism, ages 2 months to 6 years (albinism group). Five-channel flash VEP was performed on all subjects. Electrodes were positioned at Oz, O1, O2, O3, and O4 (10/20 system). Data were analyzed by use of techniques previously described. These included inspection of the VEP waveforms, measurement of hemispheric waveform parameters, calculation of an asymmetry index, and use of a bipolar derivation between left and right hemispheric responses (interhemispheric difference potential). In addition, we quantified the interhemispheric difference potential by use of Pearson's correlation coefficient. Measurements of sensitivity and specificity determined the success of the 5 analysis paradigms. The accuracy of each paradigm represented the ability to classify the data according to volunteer or albinism group and is derived from both sensitivity and specificity measures. RESULTS: Measurement of hemispheric differences in VEP waveform parameters was the least sensitive measure method for detecting multichannel VEP asymmetry in albinism. Comparison of left and right eye interhemispheric difference potential increased accuracy to 67%. Nonquantitative inspection of waveform demonstrated an accuracy of 76%. The asymmetry index and Pearson's correlate measure yielded accuracy rates of 79% and 83%, respectively. CONCLUSION: The efficiency and capability of Pearson's correlate measure in quantifying interhemispheric difference potentials to detect albinotic misrouting makes this a useful and practical technique in a pediatric clinic.

Albinism↗