What is Albinism?

Albinism is a rare genetic condition where a person lacks pigmentation in their eyes and often in their hair and skin. People with albinism have a reduced amount of a pigment called melanin in the iris, which is the coloured part of the eye, and in the retina, the light-sensitive tissue at the back of the eye.

Melanin and the products used to make it are important for healthy eye development. Without them, the retina and optic nerve (which sends visual information from the retina to the brain) may not develop properly.

It is estimated that 1 in 5,000 to 1 in 15,000 people in Sub-Saharan Africa are affected by albinism. In Europe and North America, it affects approximately 1 in 17,000 to 20,000 people. People with albinism usually have poor eyesight from birth.

Although this sight loss is permanent, it does not worsen over time. Rapid involuntary eye movements (nystagmus), crossed eyes (strabismus) and increased sensitivity to light (photophobia) are also common.

What are the different types of albinism?

There are two main types of albinism:

• Oculocutaneous albinism (OCA) – the most common type, affecting affects the skin, hair and eyes. OCA is caused by faults in one of eight genes, OCA1 to OCA8 and causes decreased pigment in the skin, hair and eyes.
• Ocular albinism (OA) – a rarer type that affects the eyes, but not the skin and hair. It’s much less common than OCA. The most common type is ocular albinism type 1 (OA1). This is also known as X-linked ocular albinism or Nettleship-Falls ocular albinism. Estimates suggest it affects at least one in every 60,000 males in the UK. While females can also be affected, it is extremely rare.

Other forms of ocular albinism are much rarer and may be associated with additional signs and symptoms, such as hearing loss. These are usually syndromes and include Hermansky-Pudlak syndrome, Chediak-Higashi syndrome and Griscelli syndrome. In some cases, the genetic cause of the condition is often unknown. All types of albinism can have negative effects on a person’s sight.

What are the causes of oculocutaneous albinism?

The OCA genes (OCA1 to OCA8) mainly affect the enzymes the body uses to generate melanin or other important molecules in the melanin synthesis pathway.

Some of the genes (such as OCA1 and OCA3) are related to the coding or control of these enzymes.

Other genes (such as OCA2) appear to be related to changing the acidity of the environment in which the enzymes operate. In fact, understanding the normal function of these genes has greatly enhanced our understanding of the complex and sophisticated way our body controls pigmentation. There are likely to be more genes and mechanisms that are yet to be discovered in the not too distant future.

How is oculocutaneous inherited?

All oculocutaneous albinism (except that associated with syndromes) is inherited in an autosomal recessive manner. This means that the genes are not carried on the sex chromosomes and that both parents must carry the trait for it to be passed on to their children.

What are the causes of ocular albinism?

Ocular albinism type 1 is caused by faults in the GPR143 gene located on the X chromosome. This gene provides instructions for making a protein that plays a role in the pigmentation of the skin and eyes.

It helps control the growth of cellular structures called melanosomes, which produce and store a pigment called melanin that gives skin, hair, and eyes their colour. In the retina, this pigment also plays an important role in healthy vision.

Most faults in the GPR143 gene alter the size or shape of the GPR143 protein. Many of these genetic changes either prevent the protein from reaching the melanosomes – or else stop it from working properly. As a result, the melanosomes in the skin and the retina can grow abnormally large.

However, researchers don’t currently understand how these enlarged melanosomes lead to vision loss and other eye problems in people with ocular albinism.

How is ocular albinism inherited?

Ocular albinism type 1 is inherited as an X-linked recessive genetic condition. As it is passed on in an autosomal recessive pattern, this would normally mean a child has to get two copies of the faulty gene – one from each parent – to get the condition.

However, the pattern of inheritance is slightly different in this type of ocular albinism as it is caused by a faulty gene on the X chromosome, one of the two sex chromosomes.

As ocular albinism type 1 is passed on in an X-linked inheritance pattern, it affects boys and girls differently. Males only have one X chromosome, which means that having one faulty copy of the GPR143 gene in each cell is enough to cause symptoms of ocular albinism.

For fathers with OA1, all of his daughters will become carriers, and his sons will not have albinism and will not be carriers. As females have two copies of the X chromosome, a woman with only one faulty copy of the GPR143 gene will usually be unaffected. However, each of her sons will have a one in two chance of having ocular albinism – and each of her daughters has a one in two chance of becoming a carrier.

How does albinism affect vision?

Albinism affects the retina and the optic nerve, leading to vision impairment. People with albinism will have an underdeveloped area in the centre of their retina called the fovea, which is responsible for sharp vision.

As a result of this foveal hypoplasia, the eye cannot process sharply focused images, resulting in blurred vision that can impact their ability to carry out everyday activities such as reading, driving or recognising faces. The optic nerve fibres of people with ocular albinism do not follow the usual routes to the brain, which affects their ability to correctly interpret the light that enters the eye into images.

These sight problems are present at birth and cannot be fully corrected to normal even with glasses or contact lenses. However, they will not worsen over time. People with albinism often have problems with movements of their eyes.

They usually have nystagmus meaning that the eyes move constantly, usually back and forth horizontally. They also often have strabismus where the two eyes look in different directions.

People with albinism may also adopt a head posture to hold their eyes in the position where nystagmus is the most quiet. People with albinism often have a problem with glare because of reduced pigmentation in the eyes. Despite all these visual problems, people with albinism usually can read reasonably well but will often need larger print text to help with reading.

What are the symptoms of ocular albinism?

People with ocular albinism may have the following eye problems:

• Reduced visual acuity – due to refractive errors, such as extreme nearsightedness or farsightedness or astigmatism.
• Poor depth perception – difficulties in seeing things in three dimensions and with judging how far away an object is.
• Nystagmus – rapid back-and-forth eye movements, causing reduced vision. Photophobia – where the eyes are sensitive to bright light and glare.
• Strabismus – where the eyes point in different directions or appear to be crossed.

How is albinism diagnosed?

An ophthalmologist may carry out several different tests to diagnose albinism. These may include:

• Clinical examinations – to look for nystagmus, strabismus or photophobia.
• Family history – to find out if any other family members are affected.
• Examination of the iris – to look for signs of reduced pigmentation.
• Retinal examination – to see if they have foveal dysplasia.
• Visual function tests – however, reduced visual acuity may not be noticeable until the child is old enough to recognise objects.
• Genetic testing – a blood test to identify faults in the GPR143 gene may be used to confirm a diagnosis. This can also help inform accurate genetic counselling for other family members.

How is albinism treated?

While albinism is currently incurable, there are several resources and support that can help improve the lives of people living with the condition. These include:

• Corrective eyewear – as a child gets older, it’s likely they will usually need to wear glasses or contact lenses to help improve their vision. They should have their eyes tested every year to make sure they have the right prescription.
• Low-vision aids – people may benefit from vision aids such as large-print or high-contrast books and printed materials, handheld magnifying lenses, large computer screens, or speech-to-text conversion software.
• Sun protection – wearing sunglasses, tinted glasses or a hat with a wide brim outdoors can help relieve sensitivity to light.
• Surgery – an operation that involves dividing and then reattaching some of the eye muscles, may sometimes be an option for nystagmus.

Latest research into albinism

Research into albinism has largely focused on understanding the underlying genetic mechanisms and identifying potential therapeutic targets. Scientists are also exploring novel treatment strategies, including gene therapy or pharmacological interventions aimed at correcting the underlying causes of the condition. These developments hold promise for improving the management and quality of life for people with ocular albinism.

Where can I get help?

There are several organisations dedicated to helping people with albinism and nystagmus:

• Global Albinism Alliance - https://albinismalliance.org/en/
• Albinism Fellowship - https://www.albinism.org.uk/
• Nystagmus Network UK - https://nystagmusnetwork.org/