In a recent article in Ocular Surgery News, titled Experts explore CAIRS through landmarks that shaped its evolution, Prof. Farhad Hafezi MD, PhD, FARVO, and Dr. Emilio Torres-Netto, MD, PhD, FWCRS joined Dr. Soosan Jacob MS, FRCS, DNB and Prof. Damien Gatinel, MD, PhD in outlining the clinical and scientific trajectory of Corneal Allogenic Intrastromal Ring Segments (CAIRS)—a biological alternative to synthetic ring segments for treating keratoconus, invented by Dr. Jacob.
Surgical Innovation and Clinical Translation: Jacob on the Origins and Adaptability of CAIRS
Dr. Jacob, who first described the CAIRS technique in 2018, was instrumental in moving the concept from theory into clinical practice. In the article, she described CAIRS as “very versatile,” underscoring its adaptability across a wide range of keratoconus severities and its relevance in settings where synthetic implants are contraindicated or unavailable. Jacob emphasized that CAIRS offers a biological solution to a biomechanical problem, particularly in patients with thin or irregular corneas that would not tolerate rigid synthetic devices.
She also highlighted CAIRS’ accessibility in resource-limited environments, pointing out that allogenic donor tissue can often be sourced locally and processed without the manufacturing constraints associated with synthetic ICRS. “We are seeing its utility not just in complex tertiary centers,” she noted, “but also in regions where keratoconus is prevalent and options are limited.”
Importantly, Jacob has continued to refine the technique’s surgical workflow, including the use of femtosecond laser channels for depth control, as well as strategies for customizing ring arc lengths and positions based on individual corneal topography. This flexibility, she noted, is critical for personalizing treatment in a disease that presents with wide anatomical variation.
Her work laid the foundation for subsequent innovations such as ECO-CAIRS and Femto-CAIRS, which further enhance reproducibility and biomechanical predictability. Together with collaborators like Hafezi and Torres-Netto, Jacob has helped to establish CAIRS as a scalable, customizable, and physiologically sound approach to keratoconus management—capable of filling the therapeutic gap between conventional CXL and corneal transplantation.
The Biomechanical Argument: Hafezi’s Perspective
Prof. Farhad Hafezi framed CAIRS within a larger biomechanical logic model that underpins much of his research in keratoconus. “The synthetic rings can work very well in many cases,” he acknowledged, “but in a fragile, 350-μm cornea that is biomechanically weak, the stiffness of PMMA may not be compatible.” This comment encapsulates a central concern in ectatic disease: that a rigid implant in a compromised cornea may exacerbate mechanical stress rather than mitigate it.
Hafezi emphasized that allogenic ring segments, composed of human corneal collagen, offer a more biomechanically and optically coherent solution. Unlike synthetic implants, CAIRS integrate into the host stroma with less disparity in elasticity, shape memory, and refractive index. This physiological match may reduce complications such as segment migration, melt, or extrusion, particularly in severely thinned or irregular corneas.
Crucially, he also addressed surgical control. When pre-treated with ultra high-fluence cross-linking (ECO-CAIRS), the allogenic segments become stiffer and more manageable during surgery. “You can shape the rings before implantation,” he explained, “and once inside the cornea, they hold that shape. This gives the surgeon predictability and mechanical stability, two things we haven’t always had with synthetic rings.”
Hafezi also positioned CAIRS within a rehabilitative, rather than merely stabilizing, framework. At the ELZA Institute, CAIRS are used not just to arrest ectasia, but to restore a more regular corneal geometry in preparation for secondary interventions, such as toric IOL implantation. In this way, CAIRS becomes a structural platform within a multistage therapeutic pathway, enabling refractive rehabilitation even in corneas that previously would have progressed to transplantation.
His perspective aligns with a broader shift in keratoconus care—from reactive to proactive, from one-off procedures to staged strategies—in which CAIRS and adjunctive technologies like PACE and high-resolution elastography are integrated into personalized treatment plans.
Surgical Refinement: Torres-Netto on Technique
Dr. Emilio Torres-Netto, a key figure in the clinical development of CAIRS at the ELZA Institute, emphasized the importance of standardization and reproducibility to facilitate broader clinical adoption. “This is not a ‘feel your way through it’ procedure,” he explained. “We now have precise nomograms, defined centration points, and reproducible depth settings using femtosecond lasers.” His comments highlighted how the technique has progressed from early conceptual stages into a structured, protocol-based intervention.
He also discussed the value of pairing CAIRS with high-fluence cross-linking (ECO-CAIRS) prior to implantation. Pre-stiffening the ring segments, he noted, makes them “easier to insert and position accurately,” reducing surgical time and improving intraoperative control. This pre-treatment also minimizes the risk of segment deformation or unexpected biomechanical response after implantation.
Importantly, Dr. Torres-Netto underscored patient selection criteria, stressing that CAIRS is not a universal solution, but rather a targeted option for patients with advanced, non-scarring keratoconus, particularly where synthetic ICRS or standard CXL would be insufficient or inappropriate. In these cases, CAIRS offers mechanical support without tissue removal, preserving stromal architecture while enabling further refractive rehabilitation.
In the broader surgical strategy at ELZA, CAIRS is frequently used in combination with topography-guided, customized epithelium-on CXL (PACE), or followed by toric IOL implantation for visual rehabilitation. “It’s not a standalone technique—it’s part of a staged, multimodal approach to restoring structure and vision,” Torres-Netto explained.
Biomechanical context: Gatinel’s take
Prof. Damien Gatinel provided a crucial biomechanical lens through which to understand the rationale for CAIRS. He emphasized that the mechanical mismatch between rigid synthetic rings and biomechanically weakened corneas may undermine the very stability that ring implantation seeks to achieve. “A stiff ring in a weak cornea is like placing a metal rod in jelly,” he explained, underscoring how PMMA-based implants can distort force distribution in severely ectatic corneas. Gatinel’s insights reinforce the idea that biomechanical compatibility—not just shape or placement—is fundamental to long-term success. By more closely matching the viscoelastic properties of native corneal tissue, allogenic ring segments may offer a more physiological means of reshaping and supporting the cornea in advanced keratoconus.
Together, the experts agree that CAIRS represents a meaningful advance in keratoconus surgery, particularly as new tools and protocols make the technique more reproducible and globally accessible.
Read the full article on Ocular Surgery News here.
