Oculocutaneous albinism: an African perspective

Aim: To describe the genetics behind oculocutaneous albinism (OCA), and explore OCA in an African context in terms of the effects on the health and education of individuals with OCA. Methods: A literature-based review was conducted using Pubmed. Searches were restricted to Englishbased publications, focusing on OCA in Africa. Results: The genetics behind OCA and the effects of OCA in terms of visual impairment and skin cancer are explained along with a description of what low vision services and low vision aids are available to those with OCA in Africa. Conclusions: The review concludes with useful advice to those with OCA and those working with or teaching students with OCA.


Introduction
Derived from the Latin word albus meaning 'white', oculocutaneous albinism (OCA) is a relatively rare genetic disorder in which the body does not biosynthesise melanin normally.Melanin is a photo-protective protein whose role in the skin is to absorb ultraviolet (UV) light and prevent damage; without melanin the skin is more prone to sunburn and skin cancer.Lack of melanin results in a triad of signs -pale skin, light hair and pale iris colour -but the consequence of OCA is impaired visual acuity (VA).Visual impairment is caused by the irregular development of the nerve pathways and abnormal retinal development. 1Children present with varying degrees of congenital nystagmus, hypopigmentation of the iris causing iris translumination, reduced pigmentation in the retinal pigment epithelium, foveal hypoplasia, large refractive errors and sometimes reduced colour vision. 2,3The foveal hypoplasia causes the central cones to be spaced out, reducing central VA. 4 Misrouting of the optic nerves from excessive crossing of fibres at the optic chiasm can result in strabismus and reduced stereopsis. 2Photophobia is a common complaint.
The purpose of this review is to describe the genetics behind OCA, and explore OCA in an African context in terms of the effects on the health and education of individuals with OCA.The outcome of this review will be to provide useful advice to those with OCA and those working with or teaching students with OCA.

Genetics
There are four different types of OCA, which result from a mutation in one of several genes (Table 1). 1,2,4Each of these genes is chemically coded to produce proteins which are involved in the production of melanin.The mutation can result in the reduction of melanin production, or no melanin production. 1 All four types of OCA are autosomal recessive.Therefore if both parents are carriers of the mutated gene there is a 25% chance of them having a child affected with OCA and a 67% chance of their non-affected children being carriers. 2A person with OCA will have non-affected children who all carry the mutated gene, provided the co-parent is not affected or carrying the mutation. 2t is possible to carry out genetic sequence analysis to determine whether a foetus has OCA; a sample for analysis would be obtained by amniocentesis at 16-18 weeks' gestation. 5To genetically distinguish between OCA types 1B, 2 and 3, a sequence analysis of genes coding for tyrosinase, P protein and TRP-1 can be completed; however, this is not routinely available in the UK. 5 In Africa, genetics screening is widely unavailable; in fact there are only four human genetics screening and counselling departments in South Africa that provide services to patients from all over Southern and Central Africa. 6

OCA in the UK
In the UK, OCA is estimated to affect 3716 individuals (1 in 17 000 people). 7 Although the prevalence of skin cancer in the UK for individuals with OCA is unknown, the NHS advises that albinism does not alter life expectancy but does increase the risk of developing skin cancer. 8Children with OCA present early in childhood to UK hospital eye clinics.Although OCA cannot be cured, in the UK children and adults will be provided with glasses or contact lenses if a refractive error is present and with low vision aids in the form of large-print books, magnifiers, telescopes and electronic vision enhancement systems (EVES) (CCTV, tablets and smart phones). 8There has been some discussion on whether a tenotomy and re-attachment of the horizontal eye muscles can help reduce nystagmus amplitude and thus improve VA, but the NICE guidelines advise that there is currently insufficient evidence on its efficacy. 8hose with OCA remain under the care of the ophthalmologist/orthoptist during their childhood so that their vision can be monitored; and then under the care of their optometrist for refractive correction and sunglasses/ tinted lenses to help with photophobia for the rest of their life.Individuals in the UK diagnosed with OCA have access to genetic counselling with a geneticist and can be referred to a dermatologist for assessment of their skin and advice regarding skin protection creams available on prescription. 8There are a number of UK charities which provide information and peer support to those affected by OCA or the parents of children diagnosed with OCA. 8 These charities include The Albinism Fellowship (www.albinism.org.uk),National Blind Children's Society (www.nbcs.org.uk) and Nystagmus Network (www.nystagmusnet.org). 8

OCA in Africa
The total population of individuals with OCA in Africa is unknown and the incidence of OCA will vary both between countries and within regions.In Tanzania, the OCA population is estimated at 31 345 (1 in 1429 people), which is nearly 8.5 times the UK OCA population. 9Zimbabwe has an OCA population similar to the UK, estimated at 3050 (1 in 4000-5000 people), but its total population is a quarter of the UK's. 9In South Africa's Venda region the incidence is 1 in 1970; two clans with the same number of individuals with OCA have an incidence of 1 in 825 people in the Vhatavhatsindi clan but 1 in 3107 people in the Vhalaudzi clan. 9he higher incidence in the Vhatavhatsindi clan is attributed to them living in a relatively isolated and inaccessible area with a restricted gene pool, which leads to a high level of intra-community breeding. 9n comparison with Western countries, OCA in Africa has significant health consequences.In Tanzania half the albino population will develop advanced skin cancer between 20 and 30 years of age, with less than 2% of albino children in Tanzania living to be 40 years of age. 71][12] Late presentation with advanced skin cancer and lack of therapeutic facilities such as radiotherapy and chemotherapy result in early mortality. 10In one study men were affected with skin cancer more than women, which the authors suggested was because men tended to work outdoors, 10 but in other studies an equal proportion of affected men and women were reported. 11,12In a retrospective study of 64 patients with OCA who had skin cancer treated in a hospital in Tanzania over a 9-year period, 83% of those presenting were 21-40 years old and 81% presented with tumours more than 5 cm in diameter; the duration of the illness was a median 24 months. 10In this hospital, where surgery was the only treatment option available, surgical site infection was the most common complication (55% of the 20 cases with complications), and there was a mortality rate of 6%. 10 The authors found a reoccurrence rate of 30% and reported that this was as a consequence of delayed presentation and failure to complete treatment. 10A 2-year retrospective review of hospital charts in a Nigerian hospital reported that 20 albinos presented with on average 1.9 lesions but that 70% of the patients did not complete their treatment or were lost to follow-up, despite half of these patients needing radiotherapy. 11The Nigerian authors concluded that skin cancer was the major cause of morbidity among individuals with OCA in Africa and that poverty and under-education resulted in late presentation. 11n a special school for the visually impaired in South Africa, attended by 112 children with OCA, focus group interviews found that although the children knew 'creams' should be used on their skin, they did not understand the term SPF and as a result the application of sunscreen lotions was only 37.8%. 3There was an insufficient supply of sunscreen lotions and the cost and access to the lotions made it prohibitive for them to use sunscreen. 3Death from skin cancer is the most serious and likely consequence of OCA in Africa; poor supply and high costs of skin protection creams and undereducation of those affected by OCA and their communities is resulting in advanced multiple skin lesions.Better education regarding skin protection is the primary preventative measure.
In a secondary school survey of 38 albino children living in South Africa, 74% did not know what caused albinism, with 79% reporting that their parents had never explained albinism to them. 13In a Zimbabwe study of 138 children with OCA, only 10.9% of the students understood that OCA was an inherited condition; in fact 50.7% pupils stated they had no idea why their skin was pale. 14This shows a high level of under-education regarding this condition.This high level of undereducation regarding OCA was also reported following a WHO albinism pilot survey of 12 African countries, which found that people with OCA did not fully understand their condition. 15lack, yet white, people in parts of Africa have been shunned because of having albinism.OCA is coupled with stigma and superstitions; recently there have been 100 albinos murdered in Tanzania and their body parts sold on the black market. 16OCA can cause extreme light sensitivity, which contributes to the physical and social exclusion of individuals with OCA. 13 In fact the South African school survey reported that 86% of the children with OCA felt they had fewer friends. 13In conclusion, it appears that individuals with OCA in Africa must deal with more than just their visual impairment and potential health concerns from skin cancer.Not only must they cope with stigma and discrimination from within their communities due to the under-education of what causes OCA, but also the possibility of harm because of mythology that wealth can be generated from selling albino body parts and the poor legal structures in dealing with the resultant murders.

Education of children with OCA in Africa
A questionnaire study of 38 albino children (aged 11-16 years) attending a special school for the visually impaired in South Africa found that 95% had received an eye test and 18% were wearing spectacles. 13The school adapted for the children by allowing them to walk up to the blackboard to read and by using a mobile blackboard; the children also had access to CCTV, magnifiers and large-print books. 13n a second school survey by the same author in Zimbabwe, where the subjects were recruited from all the primary and secondary mainstream schools in 5 of the 9 districts in Zimbabwe, 138 pupils completed a questionnaire and interview. 14In this survey, 95.6% of the children reported the inability to see the blackboard or their school books.This resulted in delay in completing their school work and making mistakes. 14ccess to health care was different for the Zimbabwe children; only 45.7% had received an eye test with 24.6% wearing spectacles.Classroom adaptations for the children in the Zimbabwe group showed that 94.2% sat at the front of the classroom, they used large-print books, were allowed additional time to complete their work, they had their own books rather than sharing with classmates and they were given extra tuition. 14However, 70% felt that no special provision was made for them in their schools. 14None of the children reported using CCTV or magnifiers.
Interestingly, 84% of the South African children felt they had equal or greater intelligence than normally pigmented people and yet 87% of the children felt that children with OCA should be educated in a special school for their primary education and 74% for their secondary education. 13The children would appear to be unaware that education through a special school rather than the local mainstream schools would contribute further to their social exclusion in the community.

Use of low vision aids for OCA
Although the impact on VA is variable, the majority of albinos living in the UK will eventually be registered as either visually impaired or severely visually impaired.Low vision aids are prescribed based on the quality of VA and the goals of the individual.There are advantages and limitations to all low vision aids; however, in Africa the concerning limitations are availability and cost.At the Kwale District Eye Centre in Kenya, funding towards the costs of treatment is obtained from a number of charities including Eyes for East Africa, Sightsavers International, CBM International (formerly known as Christian Blind Mission) and individual donations.
OCA is associated with hypermetropia, myopia and astigmatism; correction of refractive errors with spectacles will optimise VA although not correct it to normal levels.Photophobia is helped by dark-tinted glasses; however, there is a further reduction in VA with dark lenses.A hat with a brim is helpful for reducing glare and photophobia, and has the advantage of skin protection for the face and head.
EVES provide maximum magnification through real image magnification; they allow the user to change the size, contrast and brightness of the material according to their needs.The devices allow a better working distance for near and intermediate tasks, an increased field of view, and in the UK would be the mainstay for visually impaired individuals in education and workplace environments.However, these devices are expensive to purchase, install and maintain and they require battery or electrical power sources, something still beyond most individuals with OCA living in Africa.
Telescopes can be used for near, intermediate and distance viewing.Telescopes can be hand-held or spectacle-mounted to be hands free, and come in various sizes and shapes.Telescopes are ideally suited for shortterm viewing, such as reading signs or a blackboard, and for locating a distant object.Telescopes can be used as binocular or monocular devices, and this is particularly useful for individuals with nystagmus, as the amplitude of the nystagmus increases with monocular viewing.Unfortunately, telescopes are still costly, have a reduced field of view and have limited magnification available; they can also be cosmetically unacceptable to many people.However, in my own personal experience with school children in Kenya, telescopes are welcomed; once the child and school teacher is given adequate training, they maximise the child's ability to view the blackboard, allowing them to keep up with their classmates.
For near magnification, individuals with OCA in Africa have two options available to them: hand and stand magnifiers.Hand magnifiers are the most common type of optical aid, as they are easily available and inexpensive.They have a wide range of magnification powers available up to Â12 (http://www.eschenbach.com/products-hand-held-magnifiers.htm).The aids are portable, allowing for use at home as well as at school.They are discreet and therefore more cosmetically acceptable to most people.They are available with illumination systems but this requires batteries or electrical power sources and increases the cost of purchasing and using the appliance.Unfortunately, hand magnifiers have disadvantages.Because they are handheld only one hand is free, which limits manual tasks.They can be tiring to hold, and the correct working distance must be found and maintained; incorrect positioning affects the power, and accommodation will also alter the power.Also, as the magnification power of the device increases, there is a decrease in the field of view.
Stand magnifiers have a magnifying lens attached to some form of stand so that the magnifier sits on the page being viewed.The major advantages of the stand magnifier over the hand magnifier are that the correct working distance is always maintained and the hands are left free; in fact some have a high stand to allow the child to write in the books underneath the stand or the teacher to point to a word.The lens has good lightgathering properties, although illuminated stand magnifiers require batteries or electrical power sources.As with hand magnifiers they come in a wide range of powers up to Â12.5 (http://www.eschenbach.com/products-stand-magnifiers.htm).For children, stand magnifiers are useful for stabilising the effects of accommodation.However, stand magnifiers are more expensive than hand magnifiers, they are bulky and less portable, they are cosmetically more noticeable than a small hand magnifier and have a smaller field of view compared with a hand magnifier.
A unique study which documented the use of low vision appliances with blind East African school children found that after an accurate refraction 9.1% of students had no actual visual impairment, 21.7% were visually impaired and 69.2% were severely visually impaired or blind. 17Of the 50 students who required low vision aids, 21 students found stand magnifiers easiest to use (range +20D to +76D), with only 2 students preferring a hand magnifier of Â6 power; 19 students required only high reading adds (+6D to +20D) and 8 students preferred hyperoculars (+24D to +48D). 17The researchers visited 5 blind schools in Kenya and Uganda in the mid-1990s and discovered that no low vision services or low vision aids were available in any of these schools for the blind.However, with more voluntary ophthalmic charities now working in Africa this situation may have improved.The authors reported that many of the teachers in these schools were visually impaired or blind themselves and as a result 57% of students with low vision were being taught through braille only despite 79% being capable of reading N5-N8 print. 17This study highlighted the need for accurate refraction and access to glasses among the low vision population, as more than 50% of the group had a spherical or astigmatic refractive error greater than 2D and, as highlighted earlier, 9.1% did not have any visual impairment when glasses were prescribed and did not need to be educated in a school for the blind. 17The authors concluded that in Africa it was easy to purchase or grind glass with powers up to +28D to make inexpensive lower powered magnifiers, and that these magnifiers along with accurate refractions and dispensed glasses would provide a cost-effective treatment to help the visually impaired read.They advised that when low vision aids were dispensed support, training and follow-up would be required, especially for children, and that higher powered aids would require additional supervision. 17w vision assessment of a school-aged child with OCA in Africa At the Kwale District Eye Centre, a teacher is employed who has been trained in children's eye health, visual development and low vision by the resident ophthalmologist and the visiting eye professionals who visit the centre for short periods.From his continual active learning about low vision and its management the teacher now works as a low vision therapist at the eye centre and as a visiting teacher for visually impaired children.This an invaluable role linking health and education to children, where in many situations it may be impossible for the children and their families to travel the long distances to the nearest eye centre.
When assessing a child with OCA it is important to identify the problems encountered by the child at home and in school; the child and parents' understanding of OCA, particularly regarding the cause of the albinism; and the effect on both their VA and skin.It is important to meet with the school principal and teacher to establish their attitudes towards OCA, and when necessary educate them diplomatically on the causes and consequences of OCA and how they can maximise the child's ability to see and study in their school.Once the child is assessed and the low vision appliance obtained which matches his or her needs, the child and teacher should be trained on how to use the appliance.The child should then be reviewed at a later date in the school to ensure that the appliance is being correctly used to maximise the child's VA.

Table 1 .
Summary of the classification of OCA types