What are hereditary eye diseases? And what is aniridia as an example?

Hereditary eye diseases are conditions that affect the eye and are passed down through genes from parents to children. These diseases can cause a wide range of vision problems, ranging from mild vision impairment to severe vision loss. The severity and nature of the symptoms vary based on the affected gene and the inheritance pattern of the condition. It is important to have regular eye exams, especially if there is a family history of eye diseases, as some of these conditions may not show obvious symptoms in their early stages but can lead to permanent vision loss if not detected and treated in time [1].

As an example of hereditary eye diseases, we will discuss aniridia, which illustrates the complexity of these conditions and their multiple effects on the eye.

What is aniridia?

Aniridia is a rare genetic disorder affecting the eye, characterized by the partial or total absence of the colored part of the eye, which is the iris, and is usually present from birth and affects both eyes. The pupil may also be abnormal or misshapen [3]. This disorder is not limited only to the iris but can be associated with other eye problems that may be present at birth or develop later in life.

Symptoms and problems associated with aniridia

In addition to the absence of the iris, most people with aniridia suffer from cataracts, which is clouding of the lens of the eye [3]. They also often face involuntary eye movements (nystagmus) and increased sensitivity to light (photophobia). Foveal hypoplasia, which is an underdevelopment of a specific area in the back of the eye, can lead to reduced visual acuity [3].

Other problems that may accompany aniridia include:

• Corneal problems (aniridia-associated keratopathy), which is the clear outer covering of the eye [3].
• High eye pressure (glaucoma), which may develop in late childhood or early adulthood [3].
• Optic nerve hypoplasia, where the structures that carry information from the eye to the brain are underdeveloped [3].

Many of these problems contribute to vision loss that worsens over time, and the severity of symptoms is usually similar in both eyes [3].

Genetic causes of aniridia

Aniridia is usually caused by genetic changes in the PAX6 gene. This gene provides instructions for making a protein involved in the early development of the eyes, brain, spinal cord, and pancreas. Changes in the PAX6 gene lead to the production of a non-functional PAX6 protein, which disrupts eye formation before birth and leads to the signs and symptoms of aniridia [3]. In rare cases, the cause may be changes in other genes that control the activity of the PAX6 gene. Aniridia is inherited in an autosomal dominant pattern, which means that one copy of the altered gene in each cell is sufficient to cause the disorder [3].

Diagnosis and treatment

Early diagnosis through a comprehensive eye examination is crucial for detecting hereditary eye diseases such as aniridia in their early stages. Appropriate treatment can help slow or prevent vision loss [1]. For aniridia, treatment may include managing associated symptoms such as cataracts and glaucoma. This may involve prescribed eye drops, medications, laser therapy, or surgery, depending on the specific case [1]. It is important to note that treatment may slow vision loss but may not restore lost vision [1].

If you experience any sudden changes in vision, such as blurred vision, light flashes, eye pain, double vision, discharge from the eye, or inflammation, you should see an eye care professional immediately [1]. These symptoms may be signs of conditions requiring urgent care.

For more extensive information about hereditary eye diseases, genetic diagnosis, genetic counseling, and treatment options, you can visit Hereditary Eye Diseases: Genetic Diagnosis, Counseling, and Treatment Options (Arabic).

Medical references

• Eye Diseases
• Aniridia