Eyeworld

SUMMER 2026 | EYEWORLD | 65 C The distinction between allogenic inlays and synthetic inlays is both biological and biomechanical, Dr. Kiliç said. Synthetic inlays— such as the Keraring (Mediphacos), Intacs, or Ferrara Ring—are made from materials like PMMA or hydrogel polymers. They function by shortening the arc, creating a mechanical spacer effect within the stroma, redistributing tissue tension, and altering corneal curvature, she said. "However, they remain a foreign body, which carries risks of interface haze, extrusion, infection, and long-term material degradation. They do not integrate with the host tissue." She noted that allogenic stromal inlays, by contrast, are composed of human collagen— they are biologically compatible with the host stroma and, over time, integrate into the native extracellular matrix. "This integration means the reshaping effect is maintained by tissue, there is no foreign body inflammatory response, and the biomechanical behavior is far more physiologically appropriate. The cornea essen- tially incorporates the donor tissue as part of its own architecture. This integration is a major theoretical and practical advantage." Best candidates and success rates The ideal candidates, Dr. Kiliç said, are patients with progressive keratoconus or post-refractive ectasia who still have enough clarity to avoid transplantation. Specifically, she noted patients with moderate to advanced keratoconus, cor- rected distance visual acuity that is still compro- mised despite spectacles or contact lenses, and a desire to defer a penetrating or lamellar kera- toplasty are strong candidates. This can also be combined with crosslinking for added stability. Early and mid-term data are encouraging, Dr. Kiliç said, noting that published studies on CAIRS report meaningful improvements in un- corrected and corrected visual acuity, significant reductions in keratometry readings (often 3–6 D of flattening), and improvements in higher or- der aberrations. Patient satisfaction tends to be high as well, she said. In well-selected patients, these procedures appear capable of deferring or potentially avoiding keratoplasty in a meaning- ful proportion of cases. "That said, long-term data beyond 5–7 years remains limited, and we don't yet have robust randomized controlled trials comparing these techniques head-to-head with DALK or PKP," Dr. Kiliç said. "Success is also highly dependent on patient selection—in very advanced ectasia with central scarring, these additive approaches are unlikely to suffice." According to Dr. Kiliç, short-to-medium- term results are genuinely promising—improve- ments in visual acuity, topographic flattening, and reduced dependence on rigid contact lenses are consistently reported. Complications reported in the literature include interface haze (generally mild and transient), partial lenticule displacement in early cases, and suboptimal centration. Unlike synthetic rings, there are lim- ited reports of extrusion of allogenic material to date, which is a meaningful safety advantage. The best candidates are patients with ker- atoconus or ectasia at a stage where some stro- mal reinforcement and reshaping is needed but the cornea still has adequate transparency and thickness, she said. Contraindications include corneas with significant central scarring (which would benefit more from a transplant), active ocular surface disease, significant dry eye, or corneas below the minimum safe residual stro- mal thickness for tunnel creation. The data for the predecessor operation, Intacs, suggested that two-thirds of patients who had these segments implanted got two lines of vision or better on the eye chart, Dr. Parker said, adding that CAIRS is a little better than that. With carefully selected patients, we often are very impressed with the results. It's rare for patients to have CAIRS and end up needing a transplant after that because of dis- appointing visual outcomes. That said, if you're operating on someone who is hand motion, and they're not going to be satisfied with 20/100 vision, you might find yourself doing more interventions, Dr. Parker said. Dr. Jacob generally finds good success with these procedures, although she did note that this is therapeutic refractive surgery, so it can sometimes be hard to define "success" with a specific number or outcome. It's not necessarily like SMILE or LASIK, she said, where you're aiming to get the patient free of glasses. With this, you're aiming for improving quality of vision and not glasses-free vision. CAIRS, she said, can not only help with im- proving the topography and vision but may also possibly play a role in improving biomechanics. 2 To an extent, it can also help with the stabiliza- tion of the disease because of the redistribution continued on page 66

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