Keratoconus Cross-Linking Surgery

Written and edited by the Smart Laser Eye Center Editorial Staff · Medically reviewed by Dr. Alim Huseynov, MD and Prof. Dr. Levent Alimgil, MD · Last updated: 10 September 2026

Keratoconus Cross-Linking

Especially, Keratoconus Disease causes blurry vision of the cornea, which develops in the shape of an outward cone, and may cause sensitivity to light and glare. Usually affects both eyes, but often affects one eye more than the other. Also, it usually begins to affect people between the ages of 10 and 25. Additionally, the condition may progress slowly for 10 years or more. However, the development of keratoconus usually slows down and stops after the age of 35. Also, Keratoconus Cross-Linking Surgery very effective treatment of Keratoconus disease.

In the early stages of keratoconus, you can correct vision problems with glasses or soft contact lenses. You may then need to continue treatment with other types of lenses, such as rigid, permeable contact lenses or scleral lenses. If there is no treatment and your condition progresses to an advanced stage, you may need a corneal transplant.

Treatment Method

Cross-linking surgery is performing to increase the biomechanical stability and stiffness of the cornea in order to prevent the progression of keratoconus. Technically, in the center of the eye, with a diameter of approximately 6-7 mm, the epithelium, which is the top layer of the cornea, is strip and 0.1% Riboflavin solution (also known as vitamin B₂ as Riboflavin content) to be drip into the eye, ultraviolet-A radiation light at a wavelength of 370 nm is apply in accordance with a certain procedure.

It is done with the application by the doctor. Ultraviolet-A radiation light activates Riboflavin, leading to the formation of collagen bonds between collagen fibrils and corneal stroma and an intense healing process in the anterior stroma. More importantly, This technique should not be apply to patients with a central corneal thickness of less than 400 microns, as it may cause a risk of toxic reactions in the endothelium, the innermost layer of the cornea.

Laser Eye Treatment

According to the condition of the cornea and eye structure, in patients with keratoconus whose progression has stopped after the age of 35, first Smart Laser Eye surgery and immediately after cross-linking surgery can be perform and the patient can get rid of his glasses or lenses. Keratoconus Patients are treat under the Sensitive Profile Patient Program.

ICL (Intraocular) Phakic lenses can be a very effective solution in the treatment of eye defects in patients who have had Cross-Linking treatment in Keratoconus Disease and whose development of Keratoconus disease has stopped. Click for information about ICL (Intraocular Lens)…

These treatments can be offer in addition to the above vision correction options, depending on the patient’s condition.

Symptoms

Although keratoconus is of varying severity, it typically affects both eyes and has well-known signs and symptoms, although there is no clear consensus on the signs and symptoms associated with early keratoconus. And these findings can be detect with a state-of-the-art corneal tomography device. The early stages of the disease are often referred to as subclinical or form-fruste keratoconus, but there are no unified criteria for the use of these two terms.

Subclinical keratoconus is typically a reference to one eye with normal corneal hourglass findings and topographic signs of keratoconus (or questionable topographic findings) in the other eye with keratoconus.

The signs and symptoms of keratoconus may change as the disease progresses.

• Blurred or distorted vision.
• Increased sensitivity to bright light and glare, which can cause problems when driving at night.
• The need for frequent changes in eyeglass prescriptions.
• Sudden worsening or blurred vision.

When to see a doctor

If your eyesight is deteriorating rapidly due to astigmatism, you should definitely call our hospital and see your ophthalmologist. During routine eye examinations in our hospital, especially keratoconus symptoms are analyze and keratoconus risk is determined.

Causes of the Disease

Although the cause cannot be determine exactly, among the causes of the disease in medical research; It has been determined that genetic and environmental factors from the family are caused by asthma, eczema, allergies, intense eye rubbing. Keratoconus most often appears with no family history at all, but a minority of patients do have an affected relative, and having a close relative with keratoconus raises your own risk — which is why it is worth screening siblings and children.

Lucas SEM, Burdon KP. Genetic and Environmental Risk Factors for Keratoconus. Annu Rev Vis Sci. 2020;6:25-46. doi:10.1146/annurev-vision-121219-081723

Risk factors

These factors can increase your chances of developing keratoconus:

• Having a family history of keratoconus
• rub your eyes vigorously
• Having certain conditions such as retinitis pigmentosa, Down syndrome, Ehlers-Danlos syndrome, hay fever, and asthma

Complications

In some cases, your cornea can swell rapidly, causing a sudden decrease in vision and scarring of the cornea. This is cause by a condition where the inner lining of your cornea breaks down, allowing fluid to enter the cornea (hydrops). The swelling usually goes away on its own, but a scar may form that affects your vision.

Advanced keratoconus can cause injury to your cornea, especially where the cone is most prominent. An injured cornea causes worsening vision problems and may require corneal transplant surgery.

Diagnosis

To diagnose keratoconus, our ophthalmologist will review your medical and family history and perform an eye exam. He or she may do other tests to determine more details about the shape of your cornea. Tests to diagnose keratoconus include:

Eye breakout. In this test, your eye doctor uses special equipment that measures your eyes to check for vision problems. He may ask you to look at a device with different lenses to help you determine which combination gives you the sharpest vision. He or she may also use a retinoscope to evaluate your eyes.

Examination with a bio-microscope (Slit-Lamp). In this test, your doctor directs a vertical beam of light to the surface of your eye and uses a low-power microscope to view your eye. It evaluates the shape of your cornea and looks for other potential problems with your eye.

Keratometry Test

In this test, your eye doctor focuses a circle of light on your cornea and measures the reflection to determine the basic shape of your cornea.

Computerized corneal mapping

Special photographic tests such as corneal tomography and corneal topography record images to create a detailed shape map of your cornea. A corneal CT can also measure the thickness of your cornea. Corneal tomography can detect early signs of keratoconus before the disease appears during examination with the Bio-Microscope.

Treatment options in keratoconus: cross-linking, CAIRS and ring segments

Keratoconus treatment answers two separate questions, and the two should not be confused. The first is whether the disease can be stopped from progressing; the second is whether the quality of vision can be improved. Corneal cross-linking answers the first question, and intrastromal ring procedures answer the second. For that reason the two are usually not alternatives to one another but consecutive steps of the same plan.

The first question: is the disease progressing?

Progression is not established from a single measurement. According to the current international consensus, at least two of the following three findings must be documented together: steepening of the anterior corneal surface (an increase of 1.0 D or more in Kmax within 12 months), steepening of the posterior surface, and thinning of the cornea. A single topography taken at the first visit is therefore rarely sufficient; consecutive measurements on the same device are required.

Below the age of 18 the situation is different. Because the disease can progress considerably faster in children and adolescents, cross-linking is not delayed in this group. Conversely, prophylactic cross-linking of an adult eye that shows no documented progression is not supported by current evidence.

Gomes JAP, Tan D, Rapuano CJ, et al. Global consensus on keratoconus and ectatic diseases. Cornea. 2015;34(4):359-69. doi:10.1097/ICO.0000000000000408

Cross-linking: which protocol, and at which corneal thickness?

Corneal cross-linking stiffens the cornea by combining riboflavin with ultraviolet-A light. Its purpose is not to correct vision but to arrest progression. In the original Dresden series, 23 eyes with progressive keratoconus were treated at 3 mW/cm² for 30 minutes; progression was halted in every eye, and in 70 per cent of them maximum keratometry regressed by a mean of 2.01 D. Which protocol may be applied is decided by corneal thickness:

• 400 µm and above — the conventional (Dresden) protocol at 3 mW/cm² for 30 minutes, or an accelerated protocol at 9 mW/cm² for 10 minutes. Both deliver the same total dose of 5.4 J/cm².
• 320–399 µm — thickness is temporarily raised with hypo-osmolar riboflavin or with a contact lens-assisted technique, and 400 µm is confirmed intraoperatively before the ultraviolet phase is started.
• Below 320 µm — cross-linking is not performed. Other options are evaluated in these eyes.

This limit is not arbitrary. In a 400 µm cornea saturated with riboflavin the irradiance reaching the inner cell layer of the cornea is approximately 0.18 mW/cm², which is about half of the 0.35 mW/cm² damage threshold measured for endothelial cells. Cross-linking depopulates the stroma of keratocytes to a depth of roughly 300 µm, and that zone repopulates over a period of up to six months. As the cornea thins, the safety margin at the endothelium disappears first, which is precisely why the choice of protocol is tied to thickness.

Wollensak G, Spoerl E, Seiler T. Am J Ophthalmol. 2003;135(5):620-7. doi:10.1016/s0002-9394(02)02220-1 · Spoerl E, Mrochen M, Sliney D, Trokel S, Seiler T. Cornea. 2007;26(4):385-9. doi:10.1097/ICO.0b013e3180334f78

An accelerated protocol is not simply the same treatment delivered faster. In a meta-analysis of 14 randomised controlled trials, the conventional protocol produced greater corneal flattening and a deeper stromal demarcation line, whereas the accelerated protocol caused less reduction in central corneal thickness. No difference was found between the two in uncorrected or corrected visual acuity, spherical equivalent, corneal biomechanical measurements or endothelial cell density. In other words the two protocols are close but not interchangeable, and the choice belongs to the surgeon.

Yeh CY, Chen KC, Chen YJ, Cheng SF. Eur J Ophthalmol. 2025;35(3):785-798. doi:10.1177/11206721241298317

For thin corneas the contact lens-assisted technique has been described in measured terms: in a series of 14 eyes whose minimum thickness after epithelial removal was 377.2 ± 14.5 µm, a riboflavin-soaked soft contact lens raised the functional thickness to 485.1 ± 15.8 µm, a mean gain of 107.9 µm. The stromal demarcation line was measured at 252.9 ± 40.8 µm and no significant endothelial cell loss was recorded.

Jacob S, Kumar DA, Agarwal A, et al. J Refract Surg. 2014;30(6):366-72. doi:10.3928/1081597X-20140523-01

CAIRS: a segment prepared from donor cornea instead of synthetic material

CAIRS stands for Corneal Allogenic Intrastromal Ring Segments. The distinguishing feature of the method is that the segment placed inside the cornea is not synthetic: it is trephined from donated human corneal tissue. The segment is implanted into a channel dissected within the corneal stroma, and by flattening the cone it aims to improve the quality of vision rather than to stop the disease.

Compared with synthetic rings, the most consistently reported difference is that extrusion of the implant and melting of the tissue around it occur markedly less often, because the implanted material has the same structure as the cornea itself. CAIRS has also been applied in thinner corneas than synthetic segments allow; published series report a lower bound in the region of 320–350 µm. Channel depth is generally taken as 35–70 per cent of corneal thickness or as a fixed 200–250 µm, with a segment width of about 1.5 mm. There is no universal nomogram: several groups have published their own.

In the series that introduced the technique, 24 eyes with stage 1 to 4 keratoconus received segments in the 6.5 mm optic zone through femtosecond-dissected channels, followed by accelerated cross-linking, or by the contact lens-assisted variant where the cornea was too thin. Over a mean follow-up of 11.58 ± 3.6 months uncorrected distance visual acuity improved by 2.79 ± 2.65 lines and corrected distance visual acuity by 1.29 ± 1.33 lines; no eye progressed and no segment-induced complication was observed. This was a pilot study, and its authors state plainly that long-term outcomes remain to be determined.

Jacob S, Patel SR, Agarwal A, et al. J Refract Surg. 2018;34(5):296-303. doi:10.3928/1081597X-20180223-01

ICRS: synthetic intrastromal corneal ring segments

ICRS are synthetic segments implanted inside the cornea. They flatten the cone, reduce irregular astigmatism and in most cases improve what the eye can achieve with spectacles or a contact lens. The thickness of the segment, the arc length and the position of implantation are selected according to corneal topography, the location of the cone and the astigmatism to be corrected.

One point deserves emphasis here: planning depends on the brand of segment used. Every manufacturer publishes its own nomogram and its own optic zone — some segments are designed for a 5.0 to 6.0 mm optic zone, others for a fixed 5.0 mm, and others again for diameters of 6.7 to 8.2 mm. A segment plan therefore cannot be produced before the brand has been decided. Channel depth is typically dissected at 75 to 80 per cent of corneal thickness, and the entry incision is placed on the steep meridian.

Vega-Estrada A, Alio JL. Eye Vis (Lond). 2016;3:8. doi:10.1186/s40662-016-0040-z

Sequencing: which treatment comes first?

• In progressive keratoconus the ring procedure and cross-linking are most often performed in the same session.
• In a cornea that has already been cross-linked, the flattening effect of a segment is reduced, because the tissue has been stiffened. The sequence therefore has to be planned from the outset rather than decided later.
• Where Kmax exceeds 70 D, or where there is scarring in the centre of the cornea, the contribution of segments and cross-linking is limited; in these eyes corneal transplantation (DALK or penetrating keratoplasty) comes into consideration.
• At least 6 to 12 months of documented stability is expected before the residual refraction is addressed. In suitable eyes an intraocular lens (phakic ICL) may then be evaluated.

Which of these options is appropriate for your eye is decided by your surgeon, after all of the measurements have been evaluated together.

How many items does one keratoconus assessment require?

In keratoconus the decision does not rest on a single map. It rests on a data set whose items check one another. For two eyes, the items that have to be collected, read and compared are distributed as follows:

Most of these items are ones the surgeon already knows. The difficult part is not knowing them; it is interrogating every one of them, in the same order, without exception, in every case. At the end of a busy day, a single line skipped is a far more realistic risk than a gap in knowledge.

What RLES AI screens in this plan

Our clinic uses RLES AI®, a clinical decision support system developed for refractive and corneal surgical planning, as a second pass over the keratoconus assessment. It does not replace the examination; it makes sure that what is knowable is not overlooked.

• Keratoconus and ectasia screening — tomographic indices are read together. Indices that are mathematically dependent on one another are not counted as separate pieces of evidence, which reduces both false alarms and false reassurance.
• Contact lens-induced surface change — lens wear can temporarily distort corneal shape. Where that pattern is present the measurements are treated as unreliable and the plan is not finalised until consecutive, mutually consistent maps are obtained.
• Ocular surface and dry eye — untreated dry eye both distorts the measurement and increases symptoms, so the surface is stabilised first.
• Intraocular pressure and anterior chamber angle — the angle value on the preoperative tomography is read in every case, and a narrow angle is referred for separate assessment.

Beyond screening, the software checks whether the intended plan is compatible with the measurements of that particular cornea:

• Tissue safety engine — the thickness that will remain after treatment is calculated and compared with the safety floors.
• Keratoconus-specific checks — the progression criteria (anterior and posterior steepening, thinning) are compared across consecutive measurements; for cross-linking the thinnest corneal thickness is checked against the protocol thresholds above, and a ring plan is verified against the nomogram of the specific segment selected.
• Preconditions for complications — medication history and chronic disease questions are worked through in the same order in every case.

What this screening gives you

The benefit is this: the decision is made by your surgeon, but it is on record that every one of these items was asked before the decision was taken. If an item was not asked or not measured, the report names it as not reported rather than leaving it blank. No missing item is quietly counted as normal.

The software does not make a diagnosis, does not decide on surgery and does not guarantee an outcome. Detailed information about the system is available at rlesai.com.

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