The rarest eye diseases

What are rare or minority diseases?

There are diseases that affect very few people. This makes resources for their research and the development of treatments for them much less than those used for the other most common diseases.

They are pathologies that affect a very low percentage of the population. In particular, we are talking about rare or minority diseases when they only affect 5 out of every 10,000 people.

As with all medical specialities in ophthalmology, there are also a number of very rare diseases. They are additions with complicated diagnosis and additions that are usually serious, chronic, progressive and end up disabling those who suffer them for a normal life. Let us see some of them:


This is the total or partial lack of iris. The iris is the eye muscle that acts as the diaphragm of a photo camera. When contracting, it lets very little light pass and when dilate it maximizes the light input. This enables us to adapt our vision to environments with much light or very dark.

Patients with this disease are characterized by having the pupil completely black. They cannot regulate the entry of light which causes them serious disorders in vision. They see with a great deal of difficulty, especially in highly lit environments.

With time they tend to develop cataracts more easily and to present serious retinal injuries that may end in blindness.


These are two opposing diseases. The first is characterised by the inability of people who are suffering from it to see in low-light conditions, while the second has the same problem but in very light environments.

The problem lies in retina cells that lose the ability to react to the presence or absence of light. It can develop gradually or appear from the moment of birth. There are studies that relate it to an accused lack of vitamin A.


It is a hereditary disease that directly affects the macula. Let us remember that the macula is the central point of view of the retina. Which allows us to look at a particular object.

It tends to start developing from adolescence and in a short time it causes a very important loss of vision. We must bear in mind that the fact that we cannot focus on any object makes patients who suffer from it only the peripheral, much more limited and imprecise view of the details.

There is no effective treatment at the moment. Although research and pilot projects are being carried out with some drugs that at least slow down the progress of the disease.


People who suffer from this pathology are unable to see the colours. That is, their life is black and white, or rather grey-scale..

The problem is the absence of a retinal cell – called cone cells – which is specifically responsible for distinguishing colours. Most patients suffer from birth. But it has also been the case that it has emerged after suffering from strong trauma. There is no known priest.