What Causes Keratoconus? Genes, Rubbing and Inflammation

Keratoconus is a progressive, inflammatory eye condition in which the normally round cornea becomes thin and gradually bulges outward into a cone-shaped cornea. This change in corneal shape affects how light enters the eye, leading to blurry or distorted vision. But why does it happen to some people and not others? This guide looks at what actually causes keratoconus: the genes you inherit, the inflammation on the surface of your eye, and the eye rubbing that so often ties the two together.

The cornea’s primary role is to focus light onto the retina for clear vision. When the corneal tissue weakens and thins, it loses its regular dome shape. Understanding why that weakening occurs is essential for predicting disease progression, protecting future vision, and in some people it may stop keratoconus taking hold at all.

What Causes Keratoconus?

Keratoconus was long described as a condition with no clear cause. Modern research tells a different story: keratoconus is an inflammatory condition, driven by a combination of genetic susceptibility and chronic inflammation at the ocular surface. In most patients, several of these factors act together to weaken the corneal collagen structure.

• Vigorous eye rubbing, often linked to allergies or irritation, which accelerates corneal thinning.
• Chronic eye inflammation, including allergic eye disease and atopy, affecting the corneal surface.
• Family history of keratoconus or other corneal conditions.
• Genetic conditions such as Down syndrome and connective tissue disorders.
• Hormonal changes during puberty or pregnancy that impact corneal thickness. There’s a full guide to keratoconus and pregnancy.
• Chronic irritation from poorly fitted contact lenses has been proposed as a contributing factor, though the evidence for this is weaker than for rubbing and allergy.

Eye Rubbing: The Biggest Modifiable Cause

If there is one message to take from this page, it is this: stop rubbing your eyes. Vigorous, habitual eye rubbing is the strongest modifiable risk factor for keratoconus. Rubbing does two things at once. It physically stresses and distorts the thin corneal tissue, and it floods the ocular surface with inflammatory mediators that break down collagen. In a genetically susceptible eye, that combination is exactly what drives the cornea to thin and bulge.

Many patients rub without realising it, particularly at night, on waking, or during allergy season. Identifying and breaking the habit is one of the most powerful interventions we have.

Allergies, Atopy and Inflammation

Keratoconus is strongly associated with allergic conditions such as hay fever, eczema, asthma and allergic conjunctivitis. Itchy eyes lead to rubbing, and the allergic response itself raises the level of inflammatory enzymes in the tear film that degrade corneal collagen. This is a key reason keratoconus is understood as an inflammatory condition rather than a simple structural one. Treating the itch, with lubricants, antihistamines or anti-inflammatory drops where appropriate, removes both the trigger to rub and part of the inflammatory load on the cornea.

Genetics and Family History

Keratoconus runs in families. Having a parent or sibling with the condition significantly increases your risk, and it is more common in certain genetic conditions, including Down syndrome and some connective tissue disorders. No single keratoconus gene has been identified; instead, many genes appear to contribute a background susceptibility. That susceptibility usually needs an environmental push, most often rubbing and inflammation, before keratoconus develops. If keratoconus runs in your family, regular corneal imaging for children and teenagers is strongly recommended.

Who Gets Keratoconus and When?

Keratoconus affects people of all ages, but it typically begins during the teenage years or early adulthood, and it tends to progress fastest in young patients while the cornea is still biologically active. Males are affected slightly more often than females, and the condition is more common in people with allergic or atopic disease and in those with a family history. Hormonal surges during puberty and pregnancy can also accelerate changes in corneal thickness and shape, which is why these life stages deserve closer monitoring.

Symptoms of Keratoconus

The common early signs are blurry or distorted vision that glasses cannot fully correct, increasing sensitivity to light and glare, frequent prescription changes, and halos or ghosting around lights at night. For the full picture of symptoms, stages and how the condition is managed, see our dedicated keratoconus page.

How Keratoconus Is Diagnosed

Keratoconus is diagnosed with specialised corneal imaging that can detect the condition long before vision changes become obvious; read how corneal topography and tomography are changing the way we detect keratoconus.

How Keratoconus Is Treated

Treatment depends on the stage of the disease, from glasses and specialty contact lenses in early keratoconus through to surgical options for advanced disease. Corneal cross-linking strengthens the cornea and halts progression, while CAIRS can reshape the cornea and improve vision in suitable patients. For a complete overview of every option, including transplant surgery for severe cases, visit our keratoconus page.

Preventing and Managing Keratoconus Progression

Because the main driver of keratoconus is inflammation, much of it triggered by eye rubbing, genuinely reducing the risk is possible in a way it is not for many other eye conditions. Avoiding vigorous eye rubbing is the simplest and most effective preventive measure. Regular eye check-ups, especially for those with a family history of keratoconus, are essential for detecting early changes in corneal thickness and shape.

Managing the allergies and irritation that cause itchy eyes, wearing well-fitted corrective lenses, and protecting the eyes from trauma all reduce the inflammatory load on the cornea and the risk of further thinning. In cases of progressive keratoconus, treatments such as corneal cross-linking offer a way to stabilise the cornea and preserve visual acuity.

Patients diagnosed early have the best chance of preserving their vision. By controlling the causes you can control, stopping the rubbing, treating the inflammation, and monitoring closely if keratoconus runs in your family, most people with keratoconus can achieve long-term eye health and stable vision.