CAIRS rings: biological intracorneal segments that flatten advanced keratoconus and help avoid a transplant

Warsaw · Krakow · Vienna · Zurich

CAIRS (Corneal Allogenic Intrastromal Ring Segments) are segments made of human corneal tissue, implanted into a channel created by a femtosecond laser within the patient’s own cornea. They flatten the cone, reduce irregular astigmatism, and restore contact lens tolerance or good vision with glasses. Unlike plastic rings, they integrate with the tissue. SwissLaser offers the only structured CAIRS pathway for patients from Poland: qualification and follow-ups in Warsaw or Krakow, procedure at our center in Vienna. Why Vienna? In Poland, CAIRS is classified as a corneal tissue transplant and cannot be performed in a private clinic – which is why the procedure itself is carried out in Austria.

CAIRS in brief

What it is: arc-shaped segments of acellular donor corneal tissue (KeraNatural), 90–340 degrees long, implanted into the corneal stroma at a depth of approximately 70–80% of its thickness. The method was described by Dr. Soosan Jacob in 2018; in Europe, it is performed by a dozen centers.
For whom: advanced keratoconus (stage II–IV), intolerance to hard contact lenses, peripheral scars, cornea too thin or too steep for crosslinking alone. Condition: clear corneal center and thickness of at least 300–350 µm at the implantation site.
Effect: Kmax flattening by an average of 4–7 D, improvement in uncorrected and corrected visual acuity by 2–4 lines, better contact lens tolerance. The effect increases over 3–6 months. If necessary, segments can be removed or replaced.
Price and pathway: 16,000 PLN per eye, including coordination of the procedure in Vienna, ATOS femtosecond laser, tissue from a certified bank, and follow-ups in Poland. Qualification with tomography 400 PLN. Price list and installments.
Safety: donor cell-free tissue does not cause rejection; the risk of displacement and extrusion, typical for PMMA rings, is negligible with CAIRS. The procedure takes about 30 minutes, under topical anesthesia.

SwissLaser in numbers: crosslinking since 2007, method learned from Prof. Theo Seiler in Zurich · over 25,000 refractive procedures by the chief surgeon · MS-39 and Anterion tomography · one team in Warsaw, Krakow, Vienna, and Zurich · Google: 4,8 (Warsaw) and 5,0 (Krakow)

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Preliminary Eligibility Assessment

CAIRS rings — shortest answers

How does CAIRS differ from Intacs and Keraring? In material and safety profile. Intacs and Keraring are hard plastic, which remains a foreign body in the cornea and in a few percent of cases displaces or extrudes.
Must CAIRS take place in Vienna? Currently, yes. The procedure using human tissue requires a certified tissue bank and infrastructure, which we have at our Vienna center.
How much does CAIRS cost and are installments available? 16,000 PLN per eye with tissue, laser, procedure in Vienna, and follow-ups in Poland. Qualification 400 PLN. Installments through Santander Consumer Bank; NFZ (National Health Fund) does not finance this method.
Does CAIRS replace crosslinking? No, these methods complement each other. CAIRS improves corneal shape, crosslinking stops the disease. For progressive keratoconus, we combine them: first CAIRS, after 1–3 months CXL in Poland to stabilize the new shape. For stable keratoconus, CAIRS alone is sufficient.
Can my body reject CAIRS? No. The segments are free of donor cells, so the immune system has nothing to recognize as foreign. Rejection has not been described in publications. Over time, the patient’s own corneal cells populate them.

What are CAIRS rings and how do they work

Intracorneal segments work mechanically: placed in the peripheral part of the stroma, they add volume to the cornea outside the cone and “pull” its center, flattening the apex. The longer and thicker the segment, and the closer to the center, the greater the flattening effect. Classic rings (Intacs, Keraring, Ferrara) are made of polymethyl methacrylate, i.e., hard plastic. CAIRS is the same idea made from the material the cornea is built from.

The tissue comes from a certified tissue bank (KeraNatural, ready-made, sterile segments), is free of donor cells, so the immune system does not recognize it as foreign. Over time, the patient’s own corneal cells populate the segment. This allows it to be placed deeper and closer to the center than plastic, achieving greater flattening with less risk.

Feature	CAIRS (human tissue)	Intacs, Keraring (PMMA)	Corneal transplant (DALK, PK)
Material	acellular donor corneal tissue	hard polymer (plastic)	full or layered donor cornea
Biocompatibility	integrates with the cornea, no rejection	permanent foreign body	risk of rejection 10–20% (PK), lower with DALK
Risk of displacement, extrusion	negligible	3–10% in long-term observations	not applicable
Reversibility	yes, segment can be removed or replaced	yes	no
Recovery	days to weeks	days to weeks	12–18 months, sutures
Steroid drops	several weeks	several weeks	months or years
Application	advanced keratoconus with clear central cornea	moderate keratoconus	central scars, very thin cornea

More about the mechanics of segments in the articles how intracorneal rings work and CAIRS: allogenic intracorneal rings.

For whom CAIRS: indications and limits of the method

CAIRS is not a method for every keratoconus. It is a step between crosslinking and transplant, for patients for whom merely stopping the disease is not enough to see well.

Advanced keratoconus (Kmax 52–65 D) with a clear corneal center and thickness of 300–350 µm in the implantation zone.
Intolerance to hard or scleral contact lenses or inability to fit them stably.
Cornea too thin or too steep for crosslinking alone: CAIRS first regularizes the shape, and CXL after 1–3 months stabilizes it.
High irregular astigmatism and asymmetry (inferior cone): the segment is placed where the cornea is steepest.
Patients qualified for transplant who want to avoid or postpone it.
Ectasia after LASIK and keratoconus after failed PMMA rings (after their removal).

When CAIRS will not help

dense scars in the corneal center, after previous hydrops with scarring of the visual axis
corneal thickness below 300 µm at the planned channel site
active inflammation, severe dry eye syndrome without treatment
expectation of full vision without glasses: CAIRS improves quality and regularity, the remaining refractive error is corrected later with an ICL lens or glasses

How CAIRS treatment proceeds: qualification in Poland, procedure in Vienna, follow-ups in Poland

The procedure using human tissue is subject to regulations that, in practice, require a certified tissue bank and infrastructure, which we have at our center in Vienna. Everything else takes place in Warsaw or Krakow.

Qualification in Warsaw or Krakow

Icon: corneal tomography – qualification examination

MS-39, Anterion tomography, assessment of corneal thickness and transparency, simulation of segment placement. Decision whether CAIRS is the right stage and whether to combine it with crosslinking. 400 PLN, approximately 90 minutes.

Procedure in Vienna (approx. 30 minutes)

Topical anesthesia. Schwind ATOS femtosecond laser with cyclorotation compensation creates a channel at the planned depth and axis, without a blade. The KeraNatural segment is inserted into the channel and positioned. Our Polish-speaking coordinator assists with travel and accommodation arrangements; usually 2 nights in Vienna.

First Days

Follow-up the next day in Vienna, return to Poland. Mild discomfort, foreign body sensation, blurred vision for several days. Antibiotic and steroid drops for 2–4 weeks.

Follow-ups in Poland and subsequent stages

Icon: follow-up visits after the procedure

After one week, one month, three months, and six months in Warsaw or Krakow, each time with tomography. After 1–3 months, crosslinking, if planned; after one year of stability, correction of the remaining refractive error with an ICL lens, glasses, or contact lenses.

Recovery

Days 1–3: discomfort, photophobia, blurred vision; office work possible from day 3–5.
Weeks 1–4: gradual improvement in corneal regularity; avoid rubbing the eye, swimming pool, and contact sports.
Months 1–6: effect increases, tomography documents flattening; selection of new glasses or contact lenses after 3 months.
Permanently: annual tomographic follow-up; segments remain in the cornea, no replacement required.

CAIRS results and safety according to publications and our experience

Corneal flattening: in Dr. Jacob’s series (2018, 24 eyes), Kmax decreased by an average of approximately 5 D, and uncorrected visual acuity improved in all patients; subsequent publications (2021–2024) confirm flattening by 4–7 D.
Visual acuity: improvement in best corrected visual acuity by an average of 2–3 lines; in some patients, return to spectacle correction instead of scleral lenses.
Tissue rejection: not described in publications; segments are acellular.
Complications: segment displacement below 2%, transient edema or opacity around the segment, rarely repositioning required. Infection below 1%.
Reversibility: segment can be removed; the cornea largely returns to its initial state.

For me, CAIRS is the biggest change in the treatment of advanced keratoconus since crosslinking. Instead of plastic, we implant tissue that the cornea is made of, and we can place it where the effect is greatest. Many patients who were told that only a transplant remained are now offered a different path.
Dr. med. Victor Derhartunian, FEBO, FWCRS, one of the few surgeons in Europe performing CAIRS

Am I eligible for CAIRS?

Green light

stage II–IV keratoconus with a clear corneal center
corneal thickness of 300–350 µm in the implantation zone
intolerance to hard contact lenses or unsatisfactory vision with lenses
keratoconus too advanced for crosslinking alone
age from approximately 16 years, any age in adults

Yellow light

peripheral scars: position relative to the planned channel is decisive
previous hydrops without central scar
previous PMMA rings: usually removed, and CAIRS implanted after 3 months
severe dry eye syndrome: treatment first

Red light

dense central scars in the visual axis: lamellar transplant (DALK)
thickness below 300 µm
active inflammation or infection

Do you have corneal maps from another center? Send them via online preliminary qualification, and we will tell you if CAIRS is an option before you come for an examination.

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Preliminary Eligibility Assessment

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How much does CAIRS cost and what does the price include

CAIRS (KeraNatural): 16,000 PLN per eye.
Included in the price: tissue from a certified bank, ATOS femtosecond laser, procedure and next-day follow-up in Vienna, travel coordination, all follow-ups in Poland in the first year.
Not included in the price: qualification with tomography 400 PLN, travel and accommodation in Vienna (we assist with booking), crosslinking if planned as a separate stage (3,600 PLN), subsequent ICL lens (11,000 PLN).
Installments: Santander Consumer Bank; CAIRS is not financed by NFZ.

See full price list

Frequently Asked Questions

Will I see without glasses after CAIRS?

The goal is a regular, stable cornea and avoiding a transplant, not full vision without correction. Most patients see significantly better and return to glasses or more comfortable contact lenses. The remaining refractive error can be corrected after one year with an ICL lens.

Does the CAIRS procedure hurt?

No. It is performed under topical anesthesia and takes about 30 minutes. After the procedure, there is a foreign body sensation, photophobia, and blurred vision for several days, alleviated by drops.

How long is the recovery after CAIRS?

Office work from day 3–5, sports after 2–4 weeks, stable effect after 3–6 months. Follow-ups in Poland after one week, one month, three months, and six months, then annually.

Can CAIRS be removed?

Yes. The segment can be removed or replaced with a different size, and the cornea largely returns to its pre-procedure state. This is an important difference compared to a transplant, which is irreversible.

Is CAIRS performed on teenagers?

Yes, usually from around 16 years of age, when keratoconus is advanced and contact lenses are not tolerated. In younger patients, crosslinking, which stops the disease, is a priority.

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For the curious: CAIRS (corneal allogenic intrastromal ring segments) are allogenic intrastromal segments from donor tissue, implanted into a channel created by a femtosecond laser; the method was described by Soosan Jacob (2015, publication 2018). ICD-10 indication: H18.6 keratoconus, H18.7 corneal ectasia. Unlike synthetic rings (Intacs, Keraring), the tissue is acellular and becomes populated by the patient’s own corneal cells.

Sources

Jacob S, Patel SR, Agarwal A et al. Corneal allogenic intrastromal ring segments (CAIRS) combined with corneal cross-linking for keratoconus. J Refract Surg 2018;34(5):296–303. doi:10.3928/1081597X-20180223-01
Corneal allogenic intrastromal ring segments: a literature review. 2025. PMC11856834
Gomes JAP, Tan D, Rapuano CJ et al. Global consensus on keratoconus and ectatic diseases. Cornea 2015;34(4):359–369. doi:10.1097/ICO.0000000000000408
Raiskup F, Theuring A, Pillunat LE, Spoerl E. Corneal collagen crosslinking with riboflavin and ultraviolet-A light in progressive keratoconus: ten-year results. J Cataract Refract Surg 2015;41(1):41–46. doi:10.1016/j.jcrs.2014.09.033

Where We Perform This Procedure

We perform the procedure in both our clinics – same surgeon, same technology, and same prices. Choose a location to see details, directions, and office hours:

Keratoconus treatment in Warsaw
ul. Kolejowa 1, 01-217 Warsaw · tel. +48 22 120 16 90

Keratoconus treatment in Krakow
ul. Kluczborska 15/U3, 31-271 Krakow · tel. +48 12 383 33 60