Keratoconus Treatment in Turkey: Cross-Linking, Corneal Rings and Transplant in Istanbul

Keratoconus is an eye condition in which the cornea, the clear dome at the front of the eye, gradually thins and bulges forward into a cone shape. Because the cornea does most of the eye's focusing, the cone bends light unevenly, and vision becomes blurred and distorted in a way that glasses correct less and less well. According to the American Academy of Ophthalmology (AAO), keratoconus often starts in the late teens or early twenties and can progress over about 10 to 20 years. It does not cause blindness, as NHS patient information points out, but without treatment it can seriously affect reading, driving and work.

It is also more common than once thought. The figure often quoted is 1 in 700 people (EyeWiki), but a 2017 nationwide study of 4.4 million people in the Netherlands found a prevalence of about 1 in 375, with an average age at diagnosis of 28 and 61% of patients male. EyeWiki notes higher rates in the Middle East, India, China and Australia.

The AAO lists these signs:

• Early stage: mild blurring, slightly distorted vision in which straight lines look bent or wavy, more sensitivity to light and glare, and sometimes redness or swelling of the eye.
• Later stage: more blurring and distortion, increasing short-sightedness and astigmatism, and contact lenses that no longer fit or feel comfortable.

A glasses prescription that keeps changing, especially rising astigmatism in a teenager or young adult, is the classic warning sign. Our free astigmatism test can show you whether your focus is uneven, but only a corneal scan can diagnose keratoconus.

The cause is not fully understood. The AAO and EyeWiki list these risk factors:

• Family history: about 1 in 10 people with keratoconus has a parent with it (AAO).
• Eye rubbing, often linked to eye allergies (atopy, vernal keratoconjunctivitis). EyeWiki describes eye rubbing in genetically predisposed people as a driver of both onset and progression.
• Allergic conditions such as asthma and eczema.
• Some general conditions: Down syndrome, connective-tissue disorders (Marfan and Ehlers-Danlos syndromes), sleep apnoea and hormonal change in pregnancy.

The single most useful thing you can do today is the simplest: stop rubbing your eyes. The AAO warns that rubbing damages thin corneal tissue and makes symptoms worse.

The most widely used grading is the Amsler-Krumeich classification, which places an eye in stage 1 to 4 by its prescription, corneal curvature (K reading), thickness and any scarring:

Criteria as summarised by Khorrami-Nejad et al., Journal of Ophthalmic and Vision Research, 2019. Newer systems such as Belin's ABCD grading add the back surface of the cornea and your corrected vision.

Keratoconus stage 2 is moderate disease with a cornea that is still thicker than 400 µm and free of scarring. That matters because 400 µm is the standard minimum thickness for conventional cross-linking (EyeWiki), so stage 1 and 2 eyes are usually good candidates if they are progressing. Thinner corneas can sometimes still be cross-linked with modified protocols. A stage tells you the shape of the cornea at one moment; whether it is changing is what decides treatment.

Keratoconus usually affects both eyes, but often unevenly. EyeWiki describes most cases as bilateral but asymmetric, and the "better" eye may show only high astigmatism or mild steepening on a scan. So if you have been told you have keratoconus in one eye only, the other eye still needs regular corneal scans, and each eye is treated on its own merits. If one eye is progressing, it can be cross-linked while the other is monitored.

In early keratoconus, glasses or soft contact lenses are often enough. As the cornea becomes more irregular, rigid gas-permeable (RGP) lenses usually give much sharper vision because they replace the uneven cone with a smooth optical surface. EyeWiki notes that most people who can wear hard or gas-permeable lenses see a dramatic improvement. If rigid lenses are uncomfortable, there are other designs: hybrid lenses (a rigid centre with a soft skirt), "piggyback" lenses (a rigid lens over a soft one) and large scleral lenses that rest on the white of the eye and vault over the cornea.

Lenses do not stop keratoconus progressing, which is why a progressing eye is usually cross-linked as well. Contact lenses are fitted by a specialist optometrist; we recommend you keep your lens fitter at home and send us their records.

Keratoconus NHS contact lenses: in the UK, hospital contact lens services fit lenses when there is a medical need, usually when vision cannot be improved enough with glasses but can with contact lenses, and keratoconus is one of the listed conditions. Patients pay a set NHS charge per lens (one NHS trust listed £60.75 in 2023), with exemptions such as being under 16, or 16–18 and in full-time education. You are normally referred through your GP or optometrist to the hospital eye service.

Corneal cross-linking is the only treatment that can stop keratoconus getting worse. Riboflavin (vitamin B2) drops are soaked into the cornea and then activated with a controlled dose of ultraviolet-A light. This creates new bonds (cross-links) between the collagen fibres, stiffening the cornea in the same way it naturally stiffens with age from the thirties onwards. In the UK, NICE guidance says the evidence on standard epithelium-off CXL is adequate in quality and quantity for normal use. The US Food and Drug Administration approved cross-linking in April 2016 (EyeWiki).

How well does it work? NHS patient information reports that cross-linking stops progression in more than 90% of cases, with a large UK eye hospital's own figures since 2013 at about 94% and fewer than 1% needing a repeat treatment. In US trials summarised by EyeWiki, the steepest corneal reading flattened by an average of 1.6D, about a third of patients gained some corrected vision and about 5% lost some. It also reduces the need for transplants: in the Netherlands, about 25% fewer corneal transplants for keratoconus were performed in the three years after CXL was introduced nationally than in the three years before (201 versus 269).

What it does not do: cross-linking aims to stabilise vision, not to improve it. Some people see a little better a year later as a bonus, but you will usually still need glasses or contact lenses afterwards.

Epithelium-off, accelerated and epithelium-on. In the standard (Dresden) protocol, the thin surface skin of the cornea is removed, riboflavin is applied for about 30 minutes and UV light is given for 30 minutes. Accelerated protocols use a stronger light for a shorter time, for example about 10 minutes. Epithelium-on ("epi-on") cross-linking leaves the surface skin in place, which is more comfortable. NICE (2013) judged the evidence for epi-on and combined "CXL-plus" procedures to be limited, and in October 2025 the FDA approved the first epithelium-on cross-linking drug system (EyeWiki). Doç. Dr. Özer explains which protocol suits your cornea and why.

Who is it for? People whose keratoconus is progressing, usually with a cornea at least 400 µm thick at its thinnest point. NHS patient information notes that CXL is generally not needed after the mid-30s, because keratoconus tends to stop progressing as the cornea stiffens naturally with age; your scans decide, not your age alone.

Corneal rings are two small, curved segments of medical plastic placed in a tunnel deep in the outer cornea, away from the centre of vision. They flatten the cone and move its tip back towards the centre. In a 2016 review in Eye and Vision, Vega-Estrada and Alió report an average flattening of 3–5D, with the best gains in people whose vision was poor before surgery; people who already see well in lenses risk losing some sharpness. Rings suit people with reduced vision who cannot tolerate contact lenses and have a clear central cornea. Possible complications include the segments moving or working their way out, infection, haze and thinning over a segment. A real advantage is that the segments can be removed. Because rings do not stop progression by themselves, they are often combined with cross-linking.

Many people search for corrective eye surgery for keratoconus hoping for LASIK. Standard laser eye surgery thins and weakens the cornea further, so the FDA and the AAO list keratoconus as a reason not to have LASIK. There are safer ways to reduce your dependence on glasses once the cornea is stable:

• Toric ICL (implantable collamer lens): a thin lens placed inside the eye corrects short sight and astigmatism without removing corneal tissue. In a 2015 study of 30 eyes treated with a toric ICL six months after cross-linking, 60% saw 20/30 or better without glasses at one year, and no eye lost two or more lines of corrected vision (Antonios et al.). Prof. Dr. Ahmet Satıcı implants ICLs. ICL / EVO ICL implantable lens →
• Surface laser combined with cross-linking: in selected eyes, a carefully limited topography-guided surface laser is combined with CXL to smooth the cornea. NICE describes the evidence for such combined "CXL-plus" procedures as limited, so this is only for carefully chosen corneas. Laser eye surgery in Turkey / Istanbul →
• Lens or cataract surgery: if you also have a cataract, or are older and want lens replacement, the lens calculation is harder in keratoconus because the corneal readings are less reliable and can lead to a long-sighted "surprise" (EyeWiki). Toric lens implants are recommended only in stable, mild to moderate keratoconus, and you must leave out rigid contact lenses for several weeks before measurements. Lens replacement (RLE / smart lens) in Turkey → · Cataract surgery in Turkey / Istanbul (/en/cataract-surgery-turkey/)

A transplant is considered when the cornea is scarred or too thin and contact lenses no longer give useful vision. Without cross-linking, between 10% and 20% of people with keratoconus eventually need one (Godefrooij et al., 2016). There are two main options:

• DALK (deep anterior lamellar keratoplasty): replaces the front and middle layers and keeps your own inner layer (endothelium), so there is no risk of endothelial rejection. NHS information gives up to 18 months for full visual recovery.
• PK (penetrating keratoplasty): a full-thickness transplant held with stitches, with up to two years for full visual recovery (NHS).

Keratoconus transplants do well. In a 2023 British Journal of Ophthalmology study of 502 eyes, graft survival at 20 years was 97.0% after DALK and 94.9% after PK, and vision improved on average from about 20/378 to about 20/32. The authors concluded that DALK may be the better choice when it is possible, because it preserves more of the eye's own endothelial cells. Partial transplants of the inner layers (DMEK and DSAEK) are used for other corneal diseases rather than for keratoconus itself.

No. Orthokeratology (pronounced or-tho-ker-a-TOL-o-gee, often shortened to ortho-k) uses specially designed rigid contact lenses, worn overnight, to temporarily flatten a healthy cornea so that you can see without glasses during the day (AAO). It is used mainly for short sight, in adults and in children. It does not strengthen the cornea, and the effect wears off when you stop wearing the lenses. Keratoconus needs the opposite: a cornea that is made stronger and kept stable.

Corneal mapping before fitting is used to screen out people with keratoconus or an irregular cornea (Charm, Clinical Optometry, 2017), and a 2026 pilot study described the safety of ortho-k in keratoconus as "largely unexplored and potentially controversial".

Is orthokeratology safe? For suitable eyes and careful wearers, it is an established treatment, but any overnight lens carries a risk of corneal infection (microbial keratitis). A US study estimated 13.9 cases per 10,000 patient-years of wear in children, similar to other overnight contact lenses (Bullimore et al., 2013), and the AAO highlights that children may find lens hygiene harder.

Where to buy orthokeratology lenses (UK and elsewhere): ortho-k lenses are custom-fitted medical devices. They should be fitted and monitored by an optometrist or ophthalmologist after corneal mapping, not bought online. If you have keratoconus, ask your eye specialist before trying any reshaping lens. We do not offer orthokeratology.