The gift of sight is often taken for granted, yet it plays a crucial role in our interaction with the world. For children, it is the window to life, playing a crucial role in their learning and development. However, for some children, vision challenges begin at birth or develop early in life. These are mostly due to genetic reasons.

Genetic eye disorders are conditions caused by inherited mutations in specific genes that influence the structure and function of the eyes. Early diagnosis and intervention can significantly improve outcomes, making awareness and understanding essential for parents and caregivers.

This article delves into the topic of genetic eye disorders, exploring their causes, symptoms, treatments, and the importance of early intervention.

Understanding Genetic Eye Disorders

Genetic eye disorders result from mutations in one or more genes passed from parents to children. These mutations can lead to a wide range of vision problems, including abnormalities in eye structure, development, or function. While some conditions are relatively common, others fall into the category of rare genetic eye diseases, affecting only a small percentage of individuals.

Genetic eye conditions may be inherited in various ways:

• Autosomal Dominant: Only one copy of the mutated gene is needed for the disorder to manifest.
• Autosomal Recessive: Both parents must pass on a copy of the mutated gene for the condition to develop.
• X-linked: The mutation is located on the X chromosome, affecting males more frequently.

A List of Hereditary Eye Diseases

Here’s a closer look at some hereditary eye diseases that commonly affect children:

1. Stargardt Disease

This is the most common form of inherited macular degeneration, caused by ABCA4 mutation. It typically presents in childhood or adolescence. Stargardt disease primarily affects the macula, responsible for sharp, central vision needed for activities like reading and recognising faces.

Symptoms of this disease include:

• Progressive loss of central vision
• Difficulty adapting to low light (night blindness)
• Distortion of straight lines or blurry spots in the visual field

There’s no cure for this disease yet, but clinical trials are exploring gene therapy and retinal implants. Using sunglasses to protect the eyes from UV light may slow disease progression. Low vision aids can help maximise remaining vision.

2. Congenital Cataracts

Yes, cataracts can develop in children too. Congenital cataracts are opacities in the lens present at birth or during early childhood, often caused by mutations in genes like CRYAA or CRYBB2. If untreated, congenital cataracts can lead to amblyopia (lazy eye) or permanent vision loss.

The following symptoms are commonly faced by children suffering from congenital cataracts:

• Cloudy or blurry vision
• Difficulty focusing or seeing in low light
• Eye misalignment (strabismus) in severe cases.

The most common treatment option for congenital cataracts includes early surgical removal of the cataract. Prescription glasses or contact lenses are provided after surgery. Parents will need to take their children for regular follow-up to monitor vision development.

You can read our article on paediatric cataracts to learn more about this condition.

3. Retinitis Pigmentosa (RP)

Retinitis pigmentosa is a group of genetic disorders that lead to the gradual degeneration of the retina’s photoreceptor cells. This is one of the hereditary eye disease that causes blindness over time. It can be inherited in autosomal dominant, autosomal recessive, or X-linked patterns.

Night blindness (often the first symptom), tunnel vision due to the loss of peripheral vision and difficulties adjusting to changes in light are some of the common symptoms of retinitis pigmentosa.

Vitamin A supplementation (under medical guidance) may slow the progression of the disease. Research on gene therapy and retinal implants offers hope. Mobility training and assistive technologies can improve quality of life to a great extent.

4. Leber Congenital Amaurosis (LCA)

LCA is a severe retinal dystrophy present from birth or early infancy, caused by mutations in one of more than 20 known genes. It is one of the most severe hereditary eye diseases, often leading to significant vision impairment early in life.

Common symptoms of LCA include:

• Poor vision or blindness in infancy.
• Abnormal eye movements (nystagmus).
• Sensitivity to light (photophobia).

LCA is usually managed by:

• Gene therapy: Luxturna, the first FDA-approved gene therapy, is available for RPE65 mutation-associated LCA.
• Supportive measures like low-vision aids and therapy for developmental support.

5. Aniridia

Aniridia is a rare genetic condition characterised by the partial or complete absence of the iris, caused by mutations in the PAX6 gene. It affects the eye’s ability to control light entering the pupil, often requiring lifelong management.

Sensitivity to light (photophobia), poor visual acuity, increased risk of glaucoma, cataracts, or retinal detachment are the most common symptoms of aniridia. The most common management technique includes using tinted glasses or contact lenses to reduce glare. Regular monitoring is required for associated conditions like glaucoma.

6. Choroideremia

Choroideremia is an X-linked genetic disorder affecting the choroid, retina, and retinal pigment epithelium, primarily in males. The progressive degeneration typically results in complete blindness in late adulthood.

Common symptoms include:

• Night blindness in early stages.
• Gradual loss of peripheral vision leads to tunnel vision.
• Central vision is often preserved until later stages.

At present, there is no current cure for this condition, but ongoing gene therapy research looks promising. Low vision aids and mobility training are essential for adapting to vision loss.

Rare Genetic Eye Diseases

Let us now take a look at a few notable rare genetic eye diseases, their causes, symptoms, and current management options. Rare genetic eye diseases are uncommon conditions caused by mutations in specific genes, leading to severe visual impairments. Despite being less common, these conditions are challenging for affected individuals and their families.

1. Peter’s Anomaly

Peter’s anomaly is a congenital defect affecting the cornea, caused by mutations in genes like PAX6 or PITX2. This condition can severely affect vision from birth, requiring early and aggressive treatment. It is characterised by corneal opacity and adhesions between the iris and cornea.

Symptoms of Peter’s anomaly include:

• Cloudy cornea leads to poor vision or blindness.
• Eye malformations, including small or misshapen eyes (microphthalmia).
• Secondary complications such as glaucoma.

Peter’s anomaly is usually treated through surgical intervention, such as corneal transplantation, which can restore clarity in vision. If glaucoma or cataract is identified, then those need to be treated. Post-surgery and other treatment, the child will be monitored regularly to manage complications.

2. Usher Syndrome

Usher syndrome is a rare genetic disorder characterised by a combination of hearing loss and progressive vision loss due to retinitis pigmentosa. It is caused by mutations in several genes, including MYO7A and USH2A. Usher syndrome significantly affects both sensory modalities, making everyday tasks challenging.

Some of the common symptoms are:

• Progressive loss of night vision and peripheral vision.
• Hearing impairment or deafness from birth.
• Possible issues with balance in some cases.

Usher syndrome is usually managed by providing hearing aids or cochlear implants for hearing loss. Children are also given mobility training for vision impairment. Ongoing research into gene therapy offers hope for potential treatment in the future.

3. Achromatopsia

Achromatopsia is a rare hereditary condition caused by mutations in CNGA3, CNGB3, or other related genes. It affects the cone cells in the retina, which are responsible for colour perception and daylight vision.

Complete colour blindness (inability to perceive any colour), extreme light sensitivity (photophobia) and poor central vision and visual acuity are common symptoms of this condition. Management options include using tinted lenses or sunglasses to reduce light sensitivity and assistive tools to enhance contrast and improve vision.

4. Leber Hereditary Optic Neuropathy (LHON)

LHON is a mitochondrial genetic disorder caused by mutations in the mitochondrial DNA (MTND1, MTND4, MTND6 genes). It leads to rapid central vision loss, typically during young adulthood. LHON rarely affects females and typically results in permanent central vision loss.

Common symptoms of LHON include:

• Sudden, painless loss of central vision in one eye, often followed by the other eye.
• Difficulty with tasks requiring sharp vision, such as reading or recognizing faces.
• Peripheral vision remains intact.

No definitive treatment is available yet for LHON, but certain supplements like odobenine may slow disease progression in some cases. Genetic counselling is recommended for families.

Diagnosing Genetic Eye Disorders

Accurate diagnosis is crucial for effective management of any disease, including genetic eye disorders. Accurate and early diagnosis can make a huge difference in the prognosis and progression of these diseases.

Several tools and methods are employed to identify these disorders:

• Genetic Testing: Identifies mutations in specific genes responsible for eye conditions.
• Ophthalmic Examination: Includes tests like visual acuity assessment, slit-lamp examination, and retinal imaging.
• Electroretinography (ERG): Measures the electrical response of the retina to light stimuli.
• Family History Analysis: Understanding the hereditary pattern helps determine the likelihood of genetic transmission.

Genetic Eye Disease Treatment Options

While there is no universal cure for most genetic eye disorders, advancements in medicine and technology have made significant strides in treatment:

• Gene Therapy: Luxturna, the first FDA-approved gene therapy for inherited retinal disease, targets mutations in the RPE65 gene (associated with LCA). Promising research on gene-editing techniques such as CRISPR aims to correct genetic mutations.
• Low Vision Aids: Devices such as magnifiers, screen readers, and braille resources improve daily living for individuals with vision impairment.
• Surgical Interventions: For conditions such as congenital cataracts or glaucoma, early surgery can prevent further complications.
• Medication: Retinoids and other drugs are being explored to slow the progression of conditions such as Stargardt disease and RP.
• Vision Therapy: Tailored exercises and techniques can help maximise remaining vision and improve functional outcomes.

Managing and Supporting Children with Genetic Eye Disorders

Parenting a child with a genetic eye disorder may not be easy. However, a proactive approach can make a huge difference. Early diagnosis and treatment are critical to preventing or minimising vision loss. Work with teachers and schools to create an Individualised Education Plan tailored to the child’s needs.

Counselling can help children and families cope with the emotional impact of vision impairment. Providing the child with access to tools such as screen readers, voice-command devices, and accessible learning materials can also help your child cope with the condition.

Sources:

• https://eyesurgeryguide.org/hereditary-eye-diseases-a-comprehensive-list/
• https://www.optometrists.org/childrens-vision/guide-to-pediatric-eye-conditions/a-guide-to-childrens-eye-diseases/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC8122153/
• https://lumberton.refocuseyedoctors.com/managing-genetic-eye-conditions-in-children/
• https://my.clevelandclinic.org/health/diseases/24298-stargardt-disease
• https://www.verywellhealth.com/congenital-cataracts-vision-loss-babies-children-4173482
• https://www.webmd.com/eye-health/what-is-retinitis-pigmentosa
• https://my.clevelandclinic.org/health/diseases/lebers-congenital-amaurosis
• https://www.verywellhealth.com/aniridia
• https://my.clevelandclinic.org/health/diseases/choroideremia
• https://www.allaboutvision.com/conditions/cornea/peters-anomaly/
• https://my.clevelandclinic.org/health/diseases/usher-syndrome
• https://my.clevelandclinic.org/health/diseases/achromatopsia
• https://my.clevelandclinic.org/health/diseases/leber-hereditary-optic-neuropathy-lhon