Can ECO-CAIRS Make Penetrating Keratoplasty Obsolete?

Over the last decade, the number of keratoplasty procedures for corneal ectasia has declined, largely due to the widespread adoption of corneal cross-linking (CXL), which can halt disease progression. Meanwhile, emerging visual rehabilitation techniques such as ECO-CAIRS (eco-corneal allogenic intrastromal ring segments) may further reduce the need for keratoplasty by improving corneal shape and visual function, according to Emilio Torres-Netto MD, PhD, who practices at the ELZA Institute in Switzerland.

The journey towards ECO-CAIRS for corneal ectasia began only recently, but its progress has been remarkably swift. From the first polymethylmethacrylate (PMMA) corneal ring implantations, the search for greater biocompatibility reached a turning point in 2018 with Dr Soosan Jacob’s introduction of CAIRS and Dr Shady Awwad’s subsequent use of femtosecond laser for graft preparation. Since then, ongoing refinement has led ELZA Institute specialists to study increasingly sophisticated techniques to facilitate the implantation process.

In 2022, the team started with femto-CAIRS, which presented challenges. “We were left with some important questions: How [can we] make their insertion easier? How [can we] insert more volume? And because we are adding biological tissue from a donor, how [can we] avoid rejection or infection?” Dr Torres-Netto said.

These questions prompted the team to investigate ultra-high-fluence cross-linking as a means of stiffening the donor tissue before implantation, ultimately resulting in ECO-CAIRS. One important advantage of the technique is tissue hydration. Conventional CAIRS segments are implanted in a relatively dehydrated state and can rapidly rehydrate upon contact with the tear film, causing them to swell, which can make insertion more difficult. With ECO-CAIRS, ultra-high-fluence cross-linking at 30 J/cm² modifies and stiffens the donor tissue, rather than the patient’s cornea, while allowing more controlled rehydration.

When asked whether penetrating keratoplasty for keratoconus will be obsolete by 2040, Dr Torres-Netto said the answer is “almost yes.” Advances in cross-linking and visual rehabilitation such as ECO-CAIRS now allow to stabilise the disease, improve corneal shape and visual function, and avoid transplantation in most patients. A key prerequisite, however, is early diagnosis. Access to screening, follow-up, and treatment varies considerably between countries and healthcare settings, which inevitably influences how often patients present with advanced disease.

Dr Torres-Netto witnessed this shift in his own practice. “Fifteen years ago, we were performing keratoplasty for keratoconus quite often. Over the past decade, however, the number has fallen dramatically. Today, only a very small proportion of our patients ultimately require either DALK or penetrating keratoplasty.” For Dr Torres-Netto, this reflects a fundamental change in keratoconus management: from replacing the cornea to preserving, stabilising, and increasingly rehabilitating the patient’s own cornea.

ECO-CAIRS is one of several treatment options for keratoconus and can be particularly useful in highly asymmetric corneas, improving corneal regularity and visual function while potentially helping selected patients avoid keratoplasty. The allogenic segments are relatively easy to implant, customisable, and may offer advantages in biocompatibility and long-term extrusion compared with rigid PMMA rings.

Elastography studies Dr Torres-Netto presented also suggest that CAIRS and rigid segments interact differently with corneal biomechanics. These differences may be relevant for astigmatism correction, suggesting that nomograms developed for rigid segments may not directly apply to CAIRS, although further studies are needed.

Ongoing studies are expected to further expand the possibilities for patients with keratoconus. “We are continuing our work on cell viability, cell culture, ultrastructure, and biomechanics, with more data expected over the coming year,” Dr Torres-Netto concluded.

Emilio Torres-Netto MD, PhD, FEBO, FWCRS is an expert cornea, cataract, and refractive surgeon practicing at The ELZA Institute in Zurich, Switzerland.