Keratoconus

What is keratoconus?

In a healthy eye, the cornea is smoothly curved, like the surface of a clear watch‑glass. In keratoconus, the cornea gradually becomes thinner and weaker in some areas and starts to bulge forward into a cone shape. This change is called an “ectasia” – a stretching and thinning of the tissue – and it distorts how light focuses on the retina at the back of the eye.​

Key points:​

• It is usually found in both eyes, though one eye may be more affected.
• It often starts in the teenage years or early adulthood and can slowly progress for many years.
• It is one of the most common reasons young people may eventually need a corneal transplant if not managed early.

Because the change is gradual, many people do not realise they have keratoconus at first and simply notice that their glasses prescription keeps changing.​

Symptoms

Symptoms usually develop slowly and can vary from mild to severe depending on how advanced the condition is.​

Common symptoms include:​

• Blurred or distorted vision that is not fully clear with ordinary glasses.
• Ghosting or double images, especially when looking at lights or text.
• Increased sensitivity to bright light and glare – night driving often becomes difficult.
• Halos around lights or starbursts at night.
• Frequent changes to your glasses prescription, often with increasing astigmatism.
• Eye strain, headaches or squinting to try to see more clearly.

In more advanced keratoconus, people may notice:​

• Very blurred, “shadowy” vision in one or both eyes.
• Poor tolerance of normal soft contact lenses.
• Sudden worsening of vision and eye pain if a complication called “acute hydrops” occurs (when fluid enters the cornea because of a small internal tear).

Any rapid change in vision, especially in one eye, should be checked urgently by an eye‑care professional.​

What causes keratoconus?

The exact cause is not fully understood, but keratoconus seems to arise from a combination of genetic and environmental factors.​

Known risk factors and associations include:​

• Family history: around 1 in 10 people with keratoconus have a close relative with the condition.
• Allergy and eye rubbing: hay fever, eczema, asthma or itchy eyes can lead to frequent eye rubbing, which is strongly linked to developing and worsening keratoconus.
• Certain medical conditions: for example, Down syndrome and some connective tissue disorders.
• Ethnicity and environment: the condition appears more common or more severe in some populations and in sunnier climates.

Avoiding vigorous eye rubbing and managing allergies properly are important steps for anyone with keratoconus or a strong family history.​

How is keratoconus diagnosed?

Keratoconus is diagnosed by an eye specialist (optometrist or ophthalmologist) using detailed tests of the cornea.​

Typical assessment includes:​

• History and vision testing: discussion of symptoms, family history and allergies; measuring visual acuity and glasses prescription.
• Slit‑lamp examination: a microscope is used to examine the cornea for thinning, scarring, a cone shape or stress lines.
• Corneal topography or tomography: special scanners map the shape and thickness of the cornea in detail, often detecting keratoconus before it is visible with standard examination.
• Pachymetry: measuring corneal thickness.

These tests help determine the stage of keratoconus (mild, moderate or advanced) and whether it is still progressing, which is crucial for choosing treatment.​

Treatment goals

Treatment has two main goals:​

1. Improve vision – by correcting the irregular focus of the eye.
2. Slow or stop progression – to reduce the risk of severe distortion, scarring and the need for a transplant.

The right approach depends on your age, how advanced the condition is, and whether recent tests show that it is still getting worse.​

Vision correction options

Glasses and soft contact lenses

In the very early stages, standard glasses or soft contact lenses may correct vision well enough. However, as the cornea becomes more irregular, these often do not give sharp, stable vision.​

Rigid gas‑permeable (RGP) lenses

Rigid (hard) contact lenses are a key treatment for many people with keratoconus.​

They work by:​

• Providing a smooth front surface that “masks” the cone‑shaped cornea underneath.
• Allowing light to focus more evenly, giving much clearer vision than glasses in many cases.

They need careful fitting by an expert and regular checks. Some people need time to get used to the feel of them, but many wear them successfully for years.​

Scleral and hybrid lenses

For more advanced or irregular corneas, larger lenses may be used:​

• Scleral lenses: large rigid lenses that rest on the white of the eye (sclera) and vault over the cornea, filled with fluid; often very comfortable and can give excellent vision.
• Hybrid lenses: a rigid centre with a soft edge, combining clarity with improved comfort.

These lenses need specialist fitting but can transform vision for people who struggle with standard lenses.​

Corneal collagen cross‑linking (CXL)

Corneal collagen cross‑linking is a minimally invasive procedure designed to strengthen the cornea and stop keratoconus from getting worse.​

How it works:​

• Vitamin B2 (riboflavin) eye drops are applied to the cornea.
• A carefully controlled ultraviolet (UV‑A) light is shone onto the cornea for a set time.
• This creates extra “cross‑links” between collagen fibres, making the cornea stiffer and more stable.

Key points:​

• The main aim is to halt or slow progression, not necessarily to remove the need for glasses or contact lenses.
• Some people see a modest flattening of the cone and improvement in vision over time.
• It is most effective when done early, especially in younger patients whose keratoconus is still progressing.

Different techniques (such as “epi‑off” and “epi‑on” cross‑linking) are used depending on the individual eye and the centre’s protocol.​

Surgical options for advanced keratoconus

If vision is still poor despite specialised lenses, or if scarring is severe, surgical options may be considered.​

These include:​

• Intrastromal corneal ring segments (ICRS, e.g. INTACS, Kerarings): tiny plastic arcs inserted into the cornea to reshape and flatten it. They can improve glasses or contact lens vision in selected patients.
• Deep anterior lamellar keratoplasty (DALK): a partial‑thickness corneal transplant where the front layers are replaced but the inner layer is kept, reducing some risks compared with full transplants.
• Penetrating keratoplasty (full‑thickness transplant): used when scarring or thinning is very advanced; the central cornea is replaced with donor tissue.

Even after surgical procedures, many people still use glasses or contact lenses for the clearest vision, but the overall shape and strength of the cornea are improved.​

Living with keratoconus

Keratoconus can be emotionally challenging, especially when it affects young people’s study, work, driving and sport. However, understanding the condition and having a clear plan helps a lot.​

Helpful habits:​

• Avoid rubbing your eyes – this is one of the most important things you can do.
• Treat allergies and itchy eyes promptly with the help of your doctor.
• Attend regular follow‑up visits and repeat corneal scans as recommended.
• Use contact lenses as instructed and keep them clean and well‑fitted.
• Ask about support groups or counselling if you feel overwhelmed – many people find it reassuring to talk to others with the same condition.

With early diagnosis, cross‑linking where appropriate, and modern lens or surgical options, most people with keratoconus can work, drive and live normal, active lives.​