Overview

Imagine being born with eyes that see the world through an enlarged window - that is the curious reality of megalocornea, a rare eye condition with a unique story to tell.

Megalocornea, also known as anterior megalophthalmos, X-linked megalocornea, and macrocornea, is a rare eye condition present from birth, predominant among assigned males at birth. It makes the cornea, the clear front part of the eye, larger than usual. Furthermore, this condition also results in a deeper front part of the eye, but eye pressure is normal and does not worsen over time. Cornea thinning often occurs with this condition. It is linked to various eye issues, like Axenfeld-Rieger syndrome, glaucoma. It is also part of many different birth syndromes.

Megalocornea can manifest in two ways:

• Primary Megalocornea which is an isolated condition with only the enlarged cornea
• Anterior Megalophthalmos in association with other eye and systemic problems²

When the iris rubs against the lens and its support structures, it can cause issues like the iris becoming see-through (iris transillumination) and releasing pigments, which might lead to another kind of glaucoma. The lens support can also become weak due to stretching, which may result in the lens moving out of place (ectopia lentis), making the possibility of cataract surgery more complicated (which megalocornea patients might need more often).

Causes and risk factors of megalocornea

Although the cause of megalocornea is not fully understood, according to experts, it is believed to be because the eye's optic cup doesn't grow properly. Megalocornea is a genetic condition that is often passed down through an X-linked recessive pattern due to mutations in specific genes on the X chromosome. In some rare cases, it can be inherited in other ways.

The development of megalocornea involves changes in the early stages of eye development, where the eye shape remains more like a bell for a longer time, causing the front part of the eye to grow too much. This makes the cornea bigger but thinner in the centre.

Symptoms and signs

People born with megalocornea may not have any symptoms. But some might experience:

• Gradual vision changes or blurry vision, often due to astigmatism
• Sensitivity to light (photophobia)
• Mild near-sightedness (myopia)
• Cataracts in severe cases
• Coloboma
• Dislocated lens (ectopia lentis) or a wobbly lens (phacondonesis)
• Glaucoma
• A larger-than-normal ring (ciliary body band) around their lens
• Low vision
• Retinal detachment (detached retina)²

Diagnosis of megalocornea

Megalocornea is usually diagnosed during early childhood by eye specialists (ophthalmologists) through an eye examination and genetic testing. To rule out diseases like glaucoma, as well as, to choose the best course of action, a correct diagnosis is essential.

Diagnostic tests that are conducted include:

• Glaucoma assessments
• Ultrasound imaging
• Optical coherence tomography (OCT)
• Tonometry (measuring eye pressure)
• Gonioscopy (examination of the drainage angle in the eye)
• Calculating the vitreal index to assess the gel-like fluid in the eye (vitreous)^4,5

Treatment and management

The treatment and management of megalocornea involves both medical and surgical interventions, along with genetic testing. Medical interventions may include the use of eye drops and support for vision with the aid of spectacles or contact lenses tailored specifically for an individual. Surgical options such as cataract surgery is another treatment alternative where individual approaches should be considered.¹ Furthermore, with megalocornea there is need for long-term optical correction and frequent monitoring.

Genetic testing can be employed to detect the presence of the gene implicated in megalocornea.² This is essential as babies born with megalocornea may have other genetic problems. Therefore, doctors should guide parents of the option for genetic testing to reach an accurate diagnosis.¹

Differential diagnosis

Here are some other conditions linked to megalocornea:

• Infantile glaucoma: Elevated eye pressure, Descemet's membrane issues
• Keratoglobus and megalophthalmos: Other eye enlargements
• Neuhäuser syndrome: Intellectual disability, seizures, facial features
• Frank-ter haar syndrome: Affects eyes, heart, bones, and facial features
• Buphthalmus: Eye enlargement with glaucoma
• Crouzon syndrome: Cranial suture closure, proptosis, shallow orbits
• Marfan syndrome: Connective tissue disorder
• Albinism: Sometimes linked with the megalocornea
• Ritscher-schinzel syndrome: Ocular, cardiac, and craniofacial anomalies
• Wolfram-like syndrome: Ocular atrophy, diabetes, hearing loss
• Lamellar ichthyosis: Cutaneous disorder with a megalocornea in some cases
• Osteogenesis imperfecta: Collagen-based disease with a rare megalocornea^1,2,5

Research and future directions

Recent progress in genetic research is helping us understand the rare condition better. It might even pave the way for treatments tailored to specific mutations in the future. However, there's still more to learn, especially where there is limited information about how it develops.

This condition is not common and often needs care from a team of specialists, including paediatric and anterior segment eye doctors. By improving how we diagnose and studying more cases with modern methods, along with genetic analysis, we can better understand the megalocornea.²

FAQs

What is the age of onset of the megalocornea?

Megalocornea is present from birth.

Is there a cure for megalocornea?

No cure or treatment for megalocornea's enlarged corneas due to anatomical defect but steps are taken in the right direction to manage symptoms.

What are the complications and impact on vision?

Complications can include dislocation of the lens, the retina detaching, developing cataracts early, and getting secondary glaucoma.

Who is prone to megalocornea?

Megalocornea is often linked to an inheritance pattern where it's passed through the X chromosome, accounting for 90% of cases in males. However, it can also be inherited through other genes, or it may occur spontaneously without any family history.

When should I see a doctor if concerned about megalocornea?

It is important to assess treatment early in the event of megalocornea. If your kid experiences pain, discomfort, or changes in eyesight, inform your doctor who will offer remedies to reduce symptoms and protect your child's vision. Frequent examinations are necessary to treat underlying conditions and avoid consequences like glaucoma or cataracts.

Summary

Megalocornea is a rare eye condition typically present from birth, characterized by abnormally large corneas. It can result from various genetic patterns, with X-linked inheritance being the most common, leading to a higher prevalence in males.

While some individuals with megalocornea may not experience any symptoms, others may have gradual vision changes, light sensitivity, and mild nearsightedness. In more severe cases, additional eye problems such as cataracts, coloboma, or glaucoma may develop.

Early diagnosis is essential for effective care, and treatment options can include monitoring and optical correction. Ongoing research and genetic analysis are providing a better understanding of megalocornea, paving the way for improved management and potential future treatment options. Regular follow-up care is crucial to address the underlying conditions and prevent complications.