Ophthalmology · Cornea
Keratoconus, in 3D
Cross-linking and intrastromal segments, explained on a three-dimensional model. The cornea provides two thirds of the eye’s focusing power: when its shape changes, the image is distorted.
Chapter 01
Five layers in half a millimetre
The cornea is about 0.5 mm thick at the centre. From the outside in:
1/3 Epithelium — the surface; it renews within days.
Chapter 02
When the stroma loses strength
The collagen fibres weaken: the cornea thins and bulges forward, usually below the centre. Irregular astigmatism appears, which glasses cannot fully correct.
Treatment 1 · Halting progression
Cross-linking (CXL)
It strengthens the collagen so the cornea stops deforming. With anaesthetic drops, in under an hour:
1/4 The central epithelium is removed.
Treatment 2 · Improving the shape
Intrastromal segments
Biocompatible arcs, about two tenths of a millimetre, placed within the stroma itself. Invisible from outside, unfelt and reversible:
1/3 A femtosecond-laser tunnel at about three quarters of the depth.
CXL + segments
Often, both
One halts progression and the other improves the shape: they are often combined. Neither cures keratoconus; many patients continue with glasses or contact lenses, with a cornea that no longer worsens.
Schematic model for information purposes: the corneal layers and cross-linking bonds are exaggerated so they can be seen. It does not replace an individual assessment by your ophthalmologist.
Assessing the cornea early matters
Keratoconus usually begins in adolescence and can progress for years. Regular corneal imaging detects progression in time; stopping eye rubbing is the single most important habit change.
To learn more: Guide: keratoconus · Keratoconus and cross-linking assessment in Madrid
Also in 3D: refractive surgery · Also in 3D: the cataract, seen from the inside
Schematic model for information purposes: the corneal layers and cross-linking bonds are exaggerated so they can be seen. It does not replace an individual assessment by your ophthalmologist.
Authorship, medical review and sources
- Author and medical reviewer
- Dr. Francisco Javier Abellán Martínez
- Ophthalmologist · Medical registration no. 282880215
- The same specialist currently authors and medically reviews the content; this is not presented as an independent external review.
- Last medically reviewed
Sources consulted (2)
- Corneal collagen cross-linking for keratoconus and keratectasia (HTG319) (Opens in a new tab)National Institute for Health and Care Excellence (NICE)
- Corneal cross-linking: indications, procedure and follow-up (Opens in a new tab)Moorfields Eye Hospital NHS Foundation Trust
General educational content. It does not replace an individual assessment, diagnosis or personalised instructions from your healthcare team.
How these guides are written and reviewed