“As always, if you do feel that you may have a problem with your eye health or vision, please visit your optometrist for an eye health check.”

Six Rare Eye Conditions | Rare disease day 2019

Today is rare disease day, so we thought we would highlight some of the rarest eye conditions. You may have heard of some of the more common eye conditions such as Cataracts, Glaucoma or Age-related Macular Degeneration (AMD), but have you heard of Retinoblastoma or Microphthalmia? Let’s dive a bit deeper and look at some of the rarest eye conditions…


Anophthalmia is a rare eye disorder, which is often known as ‘no eye’. It is estimated to affect 1 in 250,000 people. Anophthalmia is where one, or both, eyes don’t grow whilst the foetus is developing in the womb.

Some babies have anophthalmia or microphthalmia because of a change in their genes or chromosomes. Anophthalmia and microphthalmia can also be caused by taking certain medicines, during pregnancy.

Anophthalmia can be diagnosed from an ultrasound scan. If both eyes are affected, then this will result in blindness. If just one eye if effected, it will not necessarily result in low vision if the other eye has good vision, but they may struggle with depth perception.
People who have Anophthalmia will usually have ‘conformers’ which are a plastic, clear shapers placed inside the eye socket to help, to encourage growth and development of the facial and eye socket structure.


Microphthalmia, more commonly known as ‘small eye’, is very similar to Anophthalmia. It is more common than Anophthalmia, but still rare with it occurring in roughly 1 in 10,000 people. With microphthalmia, one or both eyeballs are abnormally small, which leads to reduced vision and in some cases, can result in significant vision loss. The condition also occurs while developing in the womb and just like anophthalmia, and there are no conclusive causes at the moment.
A prosthetic eye can be moulded around the existing eye to give a more natural shape and look.
People who have microphthalmia will need to see an optometrist more often, to monitor for other conditions, such as cataracts..


Just like the two rare eye conditions previously mentioned, Coloboma is linked to gene changes during early pregnancy.  A coloboma occurs in approximately 1 in 10,000 people, although this may be slightly higher due to some individuals being undiagnosed.

A coloboma is a space in part of the eye, which happens when the structures are under developed. It can affect many different parts of the eye such as the iris, the lens, the retina, the network of blood vessels and the optic nerve. If the iris (the coloured part of the eye) is affected, then it might leave a ‘key-hole’ shape in the pupil.
Each case of coloboma has different impacts on the individual’s vision. It can range from being sensitive to bright lights, to it effecting central vision.
There is currently no treatment for coloboma, if a child is living with this rare condition they will be monitored regularly on their visual development and be prescribed glasses and sunglasses to help with the sensitivity to light.

Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a rare disorder which involves the breakdown and loss of cells in the retina. Retinitis Pigmentosa is regarded as a rare condition. There are currently no official statistics, it is estimated that 1 in 4,000 people worldwide have it!

The retina is the tissue at the back of the eye which is light-sensitive and contains photoreceptors (cells which are needed first to process sight).
In the early onset of RP, the photoreceptors will start to breakdown and cause night blindness and a gradual loss of vision. As RP progresses, it will cause more vision loss centrally.

Children and adults who develop RP may benefit from a special lens which can magnify central vision. A National Eye Institute sponsored clinical trial showed that a daily dose of vitamin A slowed the progressions of the condition in adults. Another treatment is an artificial device called the Argus II, which is showing promise in restoring some vision to people in the late stages of RP. The Argus II functions as the lost photoreceptor cells.


Retinoblastoma is a rare form of eye cancer, which mostly affects children under the age of 5. It is estimated that retinoblastoma makes up 2% of all cancers in children before the age of 15. 1 in 4 of those children will have the rare condition in both eyes. Retinoblastoma is cancer of the retina. In the early stages of development, the retina is formed very quickly, but retinoblastoma is formed when the cells continue to grow beyond usual development which form a cancer.

40% of all retinoblastoma cases are caused by a faulty gene, but the other 60% of cases have no known cause. One of the symptoms of retinoblastoma is a white reflection in the pupil which may be more obvious on a photograph. This symptom is often confused with a cataract or retinal detachment. Treatment includes, but is not limited to, laser treatment, cryotherapy (freezing), chemotherapy and surgery.

Fortunately, 9 out of 10 cases are detected early and successfully treated. If it does spread, it can be slightly more difficult to treat, but it is usually identified before it reaches that stage.

Behçet’s disease

Behçet’s disease is a very rare condition, which is poorly understood. It is believed that fewer than 1 in 100,000 people in northern European countries are affected by Behçet’s disease. It is more common in Middle Eastern, Far Eastern and Mediterranean countries.

Behçet’s disease results in the inflammation of blood vessels. Some of the symptoms include mouth ulcers, painful eyes and blurred vision. It is believed to be an autoinflammatory condition, when the immune system attacks the blood vessels accidentally. Although it is not clear what triggers the condition, genes and environmental factors are thought to initiate it.

Thankfully, these conditions are very rare, and there continues to be ongoing medical research into developing a greater understanding of these conditions. As always, if you do feel that you may have a problem with your eye health or vision, please visit your optometrist for an eye health check. You can find a local optician by clicking here.

“As always, if you do feel that you may have a problem with your eye health or vision, please visit your optometrist for an eye health check.”

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