Megalocornea

What is megalocornea?

Megalocornea is a rare eye disease that causes oversized corneas, the part of your eyes that lets in light. It also causes the fluid-filled space between your cornea and iris (the colored area of your eye) to become deeper than normal.

Megalocornea is a congenital (from birth) condition. Healthcare providers usually diagnose the condition in early childhood. Megalocornea usually causes mild vision issues, but it’s not progressive — it doesn’t typically worsen over time. It’s the opposite of microcornea, which features an unusually small cornea.

Megalocornea is often associated with other conditions, including connective tissue diseases such as Marfan syndrome. When this occurs, megalocornea may put your child at risk for cataracts and other eye issues. Diagnosing megalocornea early is important so your provider can keep checking on your child’s eyes and vision.

Your healthcare provider may refer to megalocornea as:

• Anterior megalophthalmos.
• Congenital anterior megalophthalmia.
• Isolated congenital megalocornea.
• Macrocornea.
• MGC1 or MGCN.
• X-linked megalocornea.

How does megalocornea affect the eyes?

Megalocornea usually affects both eyes, in two ways:

• Diameter of your cornea (side-to-side measurement) grows larger than it should (more than 13 millimeters).
• Front section of your eye where clear, watery fluid flows in and out (anterior chamber) becomes deeper than normal.

Who does megalocornea affect?

Most people who get megalocornea are assigned male at birth (AMAB). More than 90% of megalocornea cases are due to an X-linked chromosome abnormality, which affects people who are AMAB.

Megalocornea is rare. Researchers don’t know how many people are born with the condition, though they believe it’s underdiagnosed.

What are the types of megalocornea?

There are two main types of megalocornea:

• Isolated, primary or simple megalocornea affects only your cornea.
• Anterior megalophthalmos is associated with an underlying disease and can affect other parts of your child’s eyes or body.

What causes megalocornea?

Megalocornea occurs due to a genetic change (mutation) in the CHRDL1 gene, which happens during fetal development. CHRDL1 helps control eye development. Researchers suspect this mutation causes a part of your eye (optic cup) to grow larger than it should.

What are the symptoms of megalocornea?

Many people born with megalocornea don’t have symptoms. Others may experience:

• Gradual vision changes or blurred vision due to astigmatism.
• Light sensitivity (photophobia).
• Mild nearsightedness (myopia).

In some cases, your child may develop:

• Cataracts.
• Coloboma.
• Dislocated lens (ectopia lentis) or shaking lens (phacondonesis).
• Glaucoma.
• Larger-than-normal ring (ciliary body band) around their lens.
• Low vision.
• Retinal detachment (detached retina).

How is megalocornea diagnosed?

Healthcare providers typically diagnose megalocornea in early childhood. Eye care specialists (ophthalmologists) detect megalocornea with an eye exam and genetic testing. Accurate diagnosis is important to rule out glaucoma and other conditions and to guide treatment.

Your healthcare provider may use other exams, including:

• Glaucoma tests.
• Gonioscopy.
• Optical coherence tomography (OCT).
• Tonometry.
• Ultrasound.
• Vitreal index calculation to measure the gel-like fluid in your eye (vitreous).

Is there a cure for megalocornea?

Megalocornea doesn’t have a cure, but treatment can help protect your child’s vision, address underlying conditions and prevent complications. Early diagnosis enables your healthcare provider to give your child the care they need.

Your healthcare provider may refer you to a pediatric ophthalmologist. If your child has an underlying medical condition, they may need to see other specialists as well.

What are treatments for megalocornea?

In many cases, megalocornea doesn’t require treatment. Most people with megalocornea have normal vision and fluid pressure (intraocular pressure). Your child’s healthcare provider may recommend “watchful waiting,” where they regularly check your child’s eye health for any changes.

Your child may need treatment to manage symptoms or other underlying conditions. Nonsurgical treatment may involve:

• Medication, such as eye drops.
• Vision aids (eyeglasses or specially fitted contact lenses).

Surgical treatments include:

• Cataract surgery or surgery to treat glaucoma.
• Photorefractive keratectomy (PRK) eye surgery to treat nearsightedness or astigmatism.

How can I reduce my child’s risk of developing megalocornea?

There isn’t anything you can do to avoid developing megalocornea. But you can take measures to protect your eyes.

You or your child can avoid damage to your cornea by wearing protective eyewear when you do:

• Cleaning with bleach or other chemicals.
• Outdoor work such as lawn mowing.
• Repairs that involve power tools, hammering or painting.
• Sports such as baseball or hockey.

If your child wears contact lenses, follow cleaning and disinfecting instructions to prevent an eye or cornea infection. Keep appointments with your eye specialist and follow treatment guidelines to avoid complications and preserve your child’s vision.

What can I expect if my child has megalocornea?

Most children with megalocornea develop and maintain good vision, while others can manage symptoms with vision aids or corrective procedures.

The outlook for children with associated disorders depends on the disease and its severity. If symptoms get worse, talk to your healthcare provider about the best options to protect your child’s eyes and health.

When should I seek care for megalocornea?

Early diagnosis of megalocornea is important so your child can receive effective care. Alert your healthcare provider if your child experiences discomfort, pain or vision changes.

Your provider can offer treatment options to give your child relief and protect their sight.

Regular follow-up care is important to treat underlying conditions and avoid complications, such as cataracts or glaucoma.

A note from Cleveland Clinic

Megalocornea is a rare condition that causes an oversized cornea, the part of your eye that helps you focus and see clearly. The good news is that most people don’t experience symptoms. Others find that corrective eyewear helps preserve sight and avoid complications. With regular eye exams, your child should be able to see clearly — and live life to the fullest.