How Do Cairs Segment Length And Thickness Influence Optical And Keratometric Outcomes In Keratoconus?
Published 2026 - 44th Congress of the ESCRS
Reference: FP30.11 | Type: Free paper | DOI: 10.82333/8sd8-m577
Authors: Dilan Colak Arici* 1 , Dr Metin Suleymanzade 2 , Dr Ugur Tunc 3 , A/Prof. Burcu Yakut 4 , Dr Fatma Feyza Nur Keskin Perk 5 , Dr Sepideh Lotfi 2 , Prof. Dr Aylin Kilic 6
1Ophthalmology Department,Beyoglu Eye Training and Research Hospital,Istanbul,Türkiye, 2Ophthalmology Department,Biruni University,Istanbul,Türkiye, 3Ophthalmology Department,Medipol University,Istanbul,Türkiye, 4Ophthalmology Department,Haseki Training and Research Hospital,Istanbul,Türkiye, 5Ophthalmology Department,Cam and Sakura City Hospital,Istanbul,Türkiye, 6Ophthalmology,Swiss Vision Group,Istanbul,Türkiye
Purpose
To evaluate the impact of corneal allogenic intrastromal ring segment (CAIRS) geometric characteristics—specifically segment length and thickness—on postoperative visual, refractive, keratometric outcomes in keratoconus.
Setting
The study conducted at Swiss Vision Eye Clinic.
Methods
This retrospective study included 40 eyes of 40 patients with keratoconus who underwent CAIRS implantation. Segment arc length, width, and height were recorded, and implant volume was calculated. Postoperative changes were analyzed for visual acuity (UCVA and CDVA; expressed as post–pre logMAR differences), refractive parameters (spherical equivalent, sphere, cylinder), keratometric values (K1, K2, Kmean, Kmax). Correlations between geometric parameters and clinical changes were assessed using Spearman’s rank analysis.
Results
Mean postoperative change was −0.59±0.43 logMAR for UCVA and −0.42±0.41 logMAR for CDVA. Greater arc length was significantly associated with spherical reduction (r=0.354, p<0.05), SE change (r=0.364, p<0.05), and Kmean change (r=0.441, p<0.01). Segment thickness demonstrated significant correlation with CDVA improvement (r=0.433, p<0.01) and K2 change (r=0.341, p<0.05), but did not directly correlate with refractive cylinder change (p>0.05). Implant volume showed strong correlations with K1 change (r=0.513, p<0.01), K2 change (r=0.584, p<0.01), and Kmean change (r=0.513, p<0.01). Kmax and refractive cylinder changes did not demonstrate significant correlation with segment geometry (p>0.05).
Conclusions
CAIRS geometry exerts distinct biomechanical effects on postoperative outcomes. Segment length predominantly determines spherical refractive change, whereas segment thickness and implant volume primarily drive keratometric remodeling. Although refractive astigmatism does not directly correlate with geometric parameters, the significant association between segment thickness and CDVA improvement suggests enhanced corneal regularization rather than a purely refractive cylinder effect. These objective findings support geometry-based customization of CAIRS and may guide the development of a more precise, individualized nomogram for keratoconus management.