Why does the cornea become a cone?
A weaker cornea, an inherited tendency, and the everyday forces that push it out of shape.
Why the cornea weakens
Part 01 · 01In keratoconus the cornea’s collagen layers are weaker and slip more easily. The weakest area, usually just below the centre, thins and is pushed forward into a cone.
It nearly always affects both eyes, but often unevenly, which is why it is often noticed in one eye first.
When it starts, and how fast it moves
Part 01 · 02Starts young
It usually appears in the teens or early twenties, often first noticed as glasses that need changing more and more often.
Fastest in the young
The younger it starts, the faster it tends to progress, and the more years it has to keep changing.
Slows with age
The cornea naturally stiffens as we get older, so progression usually slows by the thirties and forties. Until then, the aim is to protect your vision.
Inherited tendency, mechanical trigger
Part 01 · 03Keratoconus is best understood as two things working together: a cornea that is prone to weakening, and forces that push on it.
What you’re born with
Often runs in families. Linked with allergy and eczema (atopy). More common in Down syndrome and some connective tissue conditions, and linked to sleep apnoea.
What acts on the cornea
Eye rubbing is the strongest risk factor we can change. Itch from allergy, inflammation and lid disease drives the rubbing. Pressure on the eyes during sleep, such as sleeping face down on your hands, adds to it.
Bottom line: we can’t change your genes, but we can reduce the forces acting on your cornea.
Check the family
Part 01 · 04Because keratoconus runs in families, close relatives (parents, brothers and sisters, and children) should have their corneas checked, even if their vision seems fine.
Early keratoconus can be invisible on a standard eye test. Corneal topography and thickness mapping pick up the change before glasses stop working.
Book a family check →Key takeaways
Part 01- 01A weaker cornea thins and bulges into a cone, causing irregular astigmatism
- 02It starts in the teens or twenties, and moves fastest when it starts young
- 03Genes set the risk; eye rubbing is the biggest factor you can change
Book a keratoconus assessment.
Glasses that keep changing, or a family history of keratoconus? A corneal scan shows where you stand.
General health information only, not personal advice. Everyone’s eyes are different. An optometrist or doctor should examine you before any treatment is decided.