Cornea — a progressive disease
Keratoconus: diagnosis and management
Keratoconus is a progressive deformation of the cornea that most often appears in adolescence or in young adults. When detected early, it can today be stabilised with cross-linking and corrected by several techniques adapted to the stage of progression. Here is an overview of the full pathway, from screening to corneal transplant if needed.
What is keratoconus?
Keratoconus is a progressive corneal disease in which the cornea thins and deforms into a cone shape, hence its name. This deformation alters the path of light rays and causes irregular astigmatism, progressive myopia and blurred vision that cannot be corrected by standard glasses in the advanced stages.
The disease typically affects adolescents or young adults (between 15 and 30 years of age), with maximal progression in the first years, followed by a gradual slowing. Keratoconus is bilateral in the majority of cases, but often asymmetrical: one eye is more affected than the other. Its prevalence is estimated at between 1 case in 2,000 and 1 case in 400 according to recent studies, with an apparently higher frequency thanks to improved topographic screening tools.
Without management, progressive keratoconus can lead to severe visual loss and, in advanced forms, to the need for a corneal transplant. The good news is that the treatment pathway has been transformed since 2003 with the arrival of cross-linking, which in most cases makes it possible to stabilise the disease before it reaches this stage.
Symptoms and warning signs
Symptoms evolve with the stage of the disease. In early forms, the patient may simply notice:
- A progressive decline in vision, corrected less and less well by glasses
- Frequent changes of prescription at the ophthalmologist (unstable prescriptions)
- Astigmatism that increases rapidly and unusually
- Increased discomfort in light (photophobia), halos around light sources
- Fluctuating blurred vision, sometimes with double images in a single eye (monocular diplopia)
In more advanced forms, vision can no longer be corrected by standard glasses. Patients are then fitted with rigid gas-permeable contact lenses or scleral lenses, which smooth the irregular corneal surface and restore usable vision.
Risk factors and profiles to monitor
The origin of keratoconus is multifactorial, combining genetic predisposition and environmental factors. The main elements to look for during the consultation:
- Chronic eye rubbing — this is the most important mechanical factor, and the easiest to correct. Patients who regularly rub their eyes (out of habit, tiredness or allergy) inflict repeated microtraumas on the cornea. Stopping eye rubbing is the very first therapeutic measure, even before any procedure.
- Allergic background (atopy) — allergic rhinitis, eczema, asthma, chronic allergic conjunctivitis. Allergy sustains rubbing and surface inflammation.
- Family history — a first-degree relative who is affected significantly multiplies the risk. Family screening is recommended.
- Trisomy 21, Marfan, Ehlers-Danlos and Down syndromes — classic associations in the literature.
- Prolonged wear of poorly fitted contact lenses — a debated factor, but one that warrants particular vigilance in chronic wearers.
A young short-sighted patient whose correction increases quickly, or whose astigmatism changes by several dioptres from one year to the next, should undergo systematic topographic examination. It is often in these profiles that early keratoconus is detected.
Screening at the office
The diagnosis of keratoconus today rests on corneal topography, which maps the curvature of the cornea in a few seconds and detects deformations invisible to the standard clinical examination. At the Cachan office, I use the Sirius (CSO) topographer, which combines a Placido analysis of the anterior surface with Scheimpflug imaging of the posterior surface and of pachymetry.
The key parameters analysed
- Maximum keratometry (Kmax) — the curvature value at the most bulging point. A rising Kmax is a major criterion of progression.
- Minimum pachymetry — corneal thickness at the thinnest point. Progressive thinning strongly supports the diagnosis.
- Posterior elevation — often the first detectable sign, even before the anterior surface is deformed.
- Asymmetry analysis — derived indices (I-S index, BAD, etc.) that quantify the suspicion of early or subclinical keratoconus.
The work-up is completed by a slit-lamp biomicroscopic examination (looking for a Fleischer ring, Vogt striae, scarring), and by corneal OCT to analyse localised pachymetry and document the stromal structure.
Key point — Screening before refractive surgery
Every candidate for refractive surgery (LASIK, PKR, SMILE) undergoes systematic topographic screening for keratoconus at the Cachan office. A subclinical or forme fruste keratoconus contraindicates LASIK (risk of post-operative ectasia) and points towards surface techniques such as PKR, or even towards postponing surgery. This screening is non-negotiable in my pre-operative protocol.
The stages of progression
Keratoconus is classically staged according to the Amsler-Krumeich classification, which takes into account keratometry, refraction, pachymetry and the presence of scarring. Without going into technical detail, in practice we distinguish:
- Early or forme fruste keratoconus — vision still correctable by glasses or soft contact lenses, topography already abnormal. This is the ideal stage to intervene if progression is confirmed.
- Moderate keratoconus — significant astigmatism, vision corrected with rigid or scleral lenses. Topography shows a clear deformation.
- Advanced keratoconus — marked thinning, possible corneal scarring, decreasing lens tolerance. The discussion turns to intracorneal rings, or even corneal transplant.
- End-stage keratoconus — a very thin cornea, central scarring, sometimes a history of hydrops (an acute episode of corneal oedema due to rupture of Descemet’s membrane). Corneal transplant becomes the main option.
Progression is assessed by repeating topography over time: a Kmax increase of more than 1 dioptre in a year, measurable thinning, or a drop in corrected visual acuity are all criteria that point towards active treatment rather than simple monitoring.
Step-by-step management
Keratoconus treatment follows a progressive logic, adapted to the stage, the rate of progression and the patient’s age. The primary objective is always to stop the progression; visual restoration comes in a second phase, after stabilisation.
Keratoconus — Comparator
Keratoconus: cross-linking, rings or transplant?
Keratoconus progressively deforms the cornea. Depending on the stage and progression, three main options exist — from simple stabilisation to replacing the cornea. They often complement one another.
| Criterion | Cross-linkingCXL — stabilisesisolated · click to close | Ringsintracornealisolated · click to close | Transplantof the corneaisolated · click to close |
|---|---|---|---|
| Objective | Stabilise: stop the progression (does not correct vision). | Regularise the cornea: better vision and lens tolerance. | Replace a cornea that is too deformed or opacified. |
| When / stage | Progressive keratoconus, early to moderate. | Mild to moderate forms, cornea still clear. | Severe forms, as a last resort. |
| Principle / procedure | Vitamin B2 + UV: strengthens the collagen (cross-linking). | Two segments slid into the thickness of the cornea. | The cornea is replaced by a graft (full thickness or deep layers). |
| Recovery | A few days of discomfort (like PKR). | Quick, a few days. | Long — several months to a year, sutures to remove. |
| Reversibility | Permanent (lasting strengthening). | Reversible (removable or exchangeable). | Permanent. |
| Main risks | Transient corneal haze, infection (rare). | Displacement / extrusion (rare), partial effect. | Graft rejection, residual astigmatism, prolonged follow-up. |
| Recommended if… | your keratoconus is progressing and the aim is to stop it as early as possible. | your cornea is still clear and the aim is to improve vision without a transplant. | the other options are no longer enough: the cornea is too damaged. |
Tip: hover over a row to follow it, click a column header to isolate it, or choose what matters most to you.
These approaches are often complementary: we stabilise first (cross-linking), regularise if needed (rings), and a transplant remains reserved for the most advanced forms. Properly fitted contact lenses also remain a cornerstone of correction.
Educational diagram — Dr Moïse Tourabaly, ophthalmologist. For information purposes only, this does not replace medical advice: only an examination determines the technique suited to your eye.
Step 0 — Stopping eye rubbing and optical correction
This is the first prescription, and often the most important. The patient must absolutely stop all eye rubbing, even occasional. Any associated ocular allergies are treated actively (antihistamines, short-course topical corticosteroids, avoidance of identified allergens) to remove the cause of the rubbing. A patient who continues to rub their eyes mechanically worsens their keratoconus, regardless of the quality of any other treatment undertaken.
Optical correction is adapted to the stage: glasses for as long as they allow usable vision, then rigid gas-permeable lenses or scleral lenses for more advanced forms. These lenses do not stabilise the disease, but they restore functional vision by smoothing the irregular surface.
Keratoconus — Lens comparator
Contact lenses for keratoconus: soft, rigid or scleral?
When glasses are no longer enough, contact lenses correct vision by compensating for the irregularity of the cornea. Three families, from the most comfortable to the most effective on advanced forms.
| Criterion | Softmild formsisolated · click to close | RigidRGPisolated · click to close | Hybridrigid centre + soft skirtisolated · click to close | Sclerallarge diameterisolated · click to close |
|---|---|---|---|---|
| Principle | Conform to the cornea: immediate comfort, correct mild forms. | Create a regular optical surface over the cornea (tear film). | A rigid centre (sharp optics) surrounded by a soft skirt (comfort). | Large diameter: rest on the white of the eye, vaulting over the cornea (tear reservoir). |
| Comfort | High from the outset. | Adaptation needed (foreign-body feeling at first). | Good: the comfort of soft, the optics of rigid. | Comfortable (they do not touch the cornea), more technical to fit. |
| Visual quality | Acceptable on mild forms. | Excellent — the reference on an irregular cornea. | Excellent — central rigid optics. | Excellent, even on advanced forms. |
| Suitable stage | Mild. | Mild to moderate. | Mild to moderate. | Moderate to advanced, or intolerance to rigid lenses. |
| Handling | Easy. | Easy (small size). | Moderate. | Fitting with a saline reservoir, learning curve. |
| Price / coverage | €€ — regular replacement. | € — durable (1 to 2 years); keratoconus coverage (LPP). | €€€ — annual replacement. | €€€ — custom-made, durable; keratoconus coverage (LPP). |
| Recommended if… | your keratoconus is mild and you want immediate comfort. | you are looking for the best vision and can tolerate the adaptation. | you want the optics of rigid with more comfort. | your cornea is very deformed or rigid lenses are poorly tolerated. |
Tip: hover over a row to follow it, click a column header to isolate it, or choose what matters most to you.
Contact lenses do not cure keratoconus but often provide the best vision by regularising the cornea. The choice is made by trial, during specialised fitting: we move from soft to rigid or hybrid, then to scleral lenses as the cornea deforms.
Educational diagram — Dr Moïse Tourabaly, ophthalmologist. For information purposes only, this does not replace medical advice: only an examination determines the technique suited to your eye.
Step 1 — Corneal cross-linking (CXL) at Clinique Victor Hugo
Corneal cross-linking is the reference technique for stabilising a progressive keratoconus. First described in 2003 by Wollensak and Spoerl in Dresden (Wollensak et al., Am J Ophthalmol, 2003), the principle is to create covalent bridges between the collagen fibres of the corneal stroma, in order to strengthen the biomechanical resistance of the cornea and stop the progression.
In practice, the procedure takes place at Clinique Victor Hugo, on an outpatient basis, under topical anaesthesia. After debridement of the central corneal epithelium (Dresden protocol, epi-off, a well-established reference), a riboflavin solution (vitamin B2) is instilled for about twenty minutes, then the cornea is exposed to ultraviolet A light for a few minutes at controlled power. The photoreaction induces the stabilising covalent bridges.
The long-term results are now well documented. The Italian Siena Eye Cross Study (Caporossi et al., Am J Ophthalmol, 2010) showed stabilisation of keratometry with a mean follow-up of more than 4 years, and 10-year data confirm the durability of the benefit in the majority of cases. Cross-linking has significantly reduced the number of corneal transplants needed in countries that adopted it early.
What cross-linking does not do: it does not improve vision, it stabilises it. A slight flattening of the cornea is sometimes observed over time, but that is not the aim of the procedure. When visual improvement is sought after stabilisation, we move on to the next step.
Step 2 — Topography-guided PKR on the Teneo platform with the OCTAVIUS module
Once the keratoconus has been stabilised by cross-linking, a surface remodelling by topography-guided PKR may be proposed to improve vision in patients whose refraction remains disabling despite optical corrections. The principle is to sculpt the anterior surface of the cornea with the excimer laser, guided by the eye’s personalised topography, in order to regularise the surface and smooth out part of the irregular astigmatism.
At Clinique Victor Hugo I use the Teneo laser platform (Bausch + Lomb) combined with the OCTAVIUS analysis module, which allows personalised treatment planning from the patient’s corneal imaging. Topography-guided PKR does not aim at full correction of the refraction as in standard refractive surgery: the objective is to regularise the surface, to improve visual quality, lens tolerance, or to make spectacle correction more effective.
This approach combining cross-linking then topography-guided PKR, often grouped under the term CXL plus in the literature, has transformed the management of progressive keratoconus by offering, beyond stabilisation, a real visual gain in a majority of selected patients.
Step 3 — Intracorneal rings
When the keratoconus is more advanced, when lens tolerance becomes insufficient, and when topography-guided PKR is not enough, the placement of intracorneal rings may be proposed. These are small semicircular segments made of biocompatible material, inserted into the thickness of the cornea using a femtosecond laser that creates a precise peripheral tunnel.
The rings act like an internal splint: they flatten and recentre the cone, which reduces the irregular astigmatism and improves corrected visual acuity. The procedure is reversible — the rings can be removed or repositioned if needed — which is an important advantage in a progressive pathway.
Intracorneal rings are placed at Clinique Victor Hugo, on an outpatient basis, under topical anaesthesia. Several models exist on the market, each with its own indications according to the topography of the cone, its location and the corneal thickness. The choice of model and the number of rings (one or two) is made from the topographic work-up and the pre-operative planning.
Step 4 — Corneal transplant (DALK or PK)
When keratoconus reaches an end stage — a very thin cornea, central scarring, total intolerance to contact lenses, a history of hydrops with sequelae — a corneal transplant becomes the main option. I perform these transplants at Clinique Sainte-Geneviève (Paris 14), the facility where all of my major intraocular surgery takes place. I am affiliated with the Banque Française des Yeux (BFY), which guarantees the traceability, quality and health safety of the grafts used.
Two techniques exist:
- Deep anterior lamellar keratoplasty (DALK) — this is my first-line technique in advanced keratoconus without endothelial involvement. Only the anterior part of the patient’s cornea is replaced (epithelium and stroma), preserving the patient’s own Descemet’s membrane and endothelium. This preservation is a major advantage: it very substantially reduces the risk of endothelial rejection and improves the long-term survival of the graft.
- Penetrating keratoplasty (PK) — replacement of the entire corneal thickness. I reserve it for cases where DALK is not feasible, in particular in the event of intraoperative perforation of Descemet’s membrane (intraoperative conversion required) or in the event of a history of hydrops with a Descemet scar, which makes lamellar dissection technically risky.
The long-term data are favourable. A recent French study conducted at the Quinze-Vingts Hospital (Borderie et al., Br J Ophthalmol, 2023) reports, on 502 eyes operated on for keratoconus, a graft survival of 96.7% at 10 years and 95.6% at 20 years, with a very significant mean visual improvement. DALK shows better preservation of endothelial cell density and a lower risk of ocular hypertension than PK, which argues for its preference whenever the anatomy allows.
Acute hydrops — this is an acute episode of corneal oedema, linked to a rupture of Descemet’s membrane in advanced keratoconus. When a patient presents as an emergency with acute hydrops, I perform compressive sutures at Clinique Sainte-Geneviève to reappose Descemet’s membrane and accelerate the resorption of the oedema, before later considering definitive surgical management.
Dr Tourabaly’s view
“Keratoconus is a disease where an early diagnosis radically changes the prognosis. In the majority of cases, a young patient detected early, in whom eye rubbing is stopped and who is promptly referred for cross-linking when indicated, will never need a corneal transplant in their lifetime. Covering the whole pathway — from topographic screening to lamellar transplantation if needed — allows me to support each patient over time, with a continuity of follow-up that makes a real difference.”
Patient pathway
The management of keratoconus is organised around three technical facilities:
- Cachan office (94) — consultations, Sirius topographic screening, follow-up of progression. Phone: 01 45 47 08 11.
- Clinique Laser Victor Hugo (Paris 16) — corneal cross-linking, topography-guided PKR (Teneo platform + OCTAVIUS), placement of intracorneal rings.
- Clinique Sainte-Geneviève (Paris 14) — DALK and PK corneal transplants, management of acute hydrops. Affiliation with the Banque Française des Yeux.
Consultation appointments can be booked directly on Doctolib. The first visit includes a complete examination, a Sirius topography (screening or confirmation), corneal OCT and a discussion of the treatment plan adapted to the stage and the rate of progression. Follow-up is then scheduled according to progression — control topographies at regular intervals, a possible decision for cross-linking, then post-operative follow-up if a procedure is performed.
Frequently asked questions
Book an appointment for a keratoconus assessment
Sources
- Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet-A-induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol. 2003;135(5):620-627. PMID: 12719068
- Caporossi A, Mazzotta C, Baiocchi S, Caporossi T. Long-term results of riboflavin ultraviolet A corneal collagen cross-linking for keratoconus in Italy: the Siena Eye Cross Study. Am J Ophthalmol. 2010;149(4):585-593. PMID: 20138607
- Borderie VM, Georgeon C, Sandali O, Bouheraoua N. Long-term outcomes of deep anterior lamellar versus penetrating keratoplasty for keratoconus. Br J Ophthalmol. 2023. PMID: 37890880
This article is for information purposes. A personalised ophthalmological opinion remains essential for any treatment decision.