At some point, you probably would have come across a person who had strikingly unusual white skin, light-colored hair (of eyebrows and eyelashes too), and bluish eyes. This distinctly light shade of the hair, skin, and eyes in people is caused by an absence of the coloring pigment, melanin.
This condition is termed ‘Albinism’, and the people who have it are called ‘Albinos’.
Albinism does not cause any pain by itself, but it can make a person vulnerable to other health complications such as sunburn or skin cancer, which are painful and distressing.
Albinism is a genetic condition and is more prevalent in people of Sub-Saharan African descent. In the US, it affects approximately 1 in every 20,000 people whereas, in the rest of the world, it can be as high as 1 in 3,000.
You may already be familiar with this condition, however, the lesser-known fact is that Albinism is accompanied by several visual defects. The extent of visual deficit varies among the types of Albinism.
Its two main types are:
Oculocutaneous albinism affects the eyes, skin, and hair, whereas ocular albinism only affects the eyes.
You may think, how does it affect your vision? And what causes it?
To find out, let’s take a brief overview of how different types of Albinism affect the eyes and their prevalence.
‘Oculo’ means eyes and ‘cutaneous’ means skin, hence this condition affects the eyes, skin, and hair of a person.
Oculocutaneous albinism (OCA) is hereditary, and it is caused by the mutation of several genes that control the production of color pigment (melanin) within our bodies. The mutation of these genes disrupts the process of melanin development such that a person’s body has a less than average amount present for the normal coloration of hair, skin, and eyes.
All individuals with OCA can have varying amounts of skin, hair, and iris pigment depending on the type of gene mutation. But several visual problems are common among all types, which are explained below:
You may have wondered, what gives us our unique eye color? ‘Iris’ is the part of the eye containing the color pigment, which gives us a beautiful and distinct eye color. In people with OA1, both the iris and retina have little to no pigment, which results in a blue color of the eyes.
Normally, the greater the amount of melanin (color pigment) is present in the iris, the darker the eye color will be, and vice versa. People with the most pigment have black color, and others have a lighter shade, such as brown, green, grey, or blue. The absence of melanin in OA1 results in blue irises. Due to a lack of melanin, the blood vessels in the eyes can become more visible in certain lighting, hence giving the eye a pinkish or red appearance.
Foveal hypoplasia refers to the underdevelopment of the iris and cornea. This leads a person to experience blurry vision, diminished ability of color perception and depth perception, and poor visual quality.
Nystagmus refers to involuntary, rapid, and repetitive eye movements. People with OA1 have difficulty with uncontrolled eye movement, which may be side to side, up and down, or in a circular motion. This usually affects both eyes.
In a healthy pair of eyes, six muscles control eye movement and point both eyes in the same direction. In contrast to this, eyes with OA1 do not sync together. When you look at a certain object, instead of focusing both eyes on that object, one eye gets turned in a direction different from the other. This condition is also known as crossed eyes.
Nyctalopia is the term used for diminished night vision. In other words, people with nyctalopia cannot see properly in a dimly lit or dark surrounding. People who have oculocutaneous albinism tend to have difficulty seeing at night and need assistive devices to help them see.
Photophobia is sensitivity to bright lights. People with eye problems usually experience discomfort in very bright lighting. Sometimes this discomfort can be too much and further reduce a person’s ability to see clear images.
What Do People With Oculocutaneous Albinism Look Like?
People with OCA have a small amount of melanin present in skin and hair, in contrast to a complete absence of this pigment. It gives them a very fair skin tone, with freckles or moles on the face.
They usually have colors ranging from a pale blonde to golden tone, or strawberry blonde hair and blue eyes. Some people who have a greater amount of melanin may even have brown hair.
Ocular albinism, in contrast to Oculocutaneous Albinism, only affects the eyes.
It is an X-linked recessive disease, so it mostly only occurs in males and is very rare in females. Although the vision loss due to this disease is permanent, it is not progressive.
Ocular Albinism Type-1 (OA1)
Ocular Albinism Type 1 is also known as Nettleship-Falls syndrome. It is the most commonly occurring type of Ocular albinism. A person born with Ocular Albinism has normal skin and hair but has to endure the same visual difficulties as in OCA. These include strabismus, hypoplasia, hypopigmentation, and weak color perception.
Ocular Albinism Type-2 (OA2)
Ocular Albinism Type-2 is also called the Forsius-Eriksson syndrome. In addition to the visual defects that occur in OA1, people with OA2 also have pronounced problems with night vision (nyctalopia) and colored vision.
However, this is a relatively rare condition. The prevalence of X-linked ocular albinism is estimated to be 1 male in 20,000 people.
Causes of Oculocutaneous Albinism and Ocular Albinism
Melanin is the color pigment that is present in our skin, hair, and eyes. There are several genes responsible for synthesizing proteins, which in turn produce this pigment in our body. When an abnormal mutation occurs in one of these genes, it disrupts the melanin production, thereby causing Albinism. The types of albinism differ based on which gene undergoes mutation.
Both oculocutaneous albinism and ocular albinism are hereditary diseases. Oculocutaneous albinism is an autosomal recessive condition, meaning a person inherits two copies of a mutated gene — one from each parent.
In contrast to this, Ocular albinism is an X-linked recessive disease, meaning that it can be passed down from a mother who carries a mutated X gene to her son. This disease almost exclusively affects men, because they only have a single copy of the X chromosome, whereas women have two copies of the X chromosome.
Prevalence Of Ocular Albinism
As mentioned above, Ocular Albinism only affects males. Women may be carriers for it but have symptoms in rare cases.
The most common form of this disorder, ocular albinism type 1, affects at least 1 in 60,000 males in the US.
Since albinism is a group of genetic disorders, it can not be cured. At best, these eye conditions can be managed effectively by taking precautionary measures and preventing eyesight from worsening. Avoiding unnecessary sun exposure, wearing dark shades, using spectacles (for near or farsightedness), and other low-vision aids for vision correction can immensely help in carrying out daily routine tasks while also managing Oculocutaneous albinism and Ocular albinism.