Customized corneal allogenic intrastromal ring segments (CAIRS) for keratoconus with decentered asymmetric cone

Abstract

Corneal allogenic intrastromal ring segments (CAIRS) refer to the intracorneal placement of fresh, unprocessed, processed, preserved, or packaged allogenic rings/segments of any type/length. We described uniform-thickness CAIRS previously. We now describe a new technique of customized CAIRS to personalize the flattening effect as per individual topography. A prospective interventional case series of patients with pericentral/ paracentral decentered cones and gradation of keratometry with one side steeper than the other was conducted. Individually customized tapered CAIRS with variable volume, arc length, taper length, and gradient of taper were implanted. In total, 32 eyes of 29 patients with at least 1-year follow-up were included. Special double-bladed trephines and a CAIRS customizer template allowed the creation of individually customized CAIRS. Mean uncorrected distance visual acuity (UDVA) and spectacle-corrected distance visual acuity improved from 0.22 to 0.47 (P = 0.000) and from 0.76 to 0.89 (P = 0.001), respectively. Significant improvement was seen in K1, K2, Km, Kmax, topographic astigmatism, Q-value, sphere, cylinder, spherical equivalent, Root Mean Square (RMS), Higher Order Aberrations (HOA), and vertical coma (P < 0.01, 0.05). There was no significant change in the width or height of CAIRS between 1 month and last visit on anterior-segment optical coherence tomography. Five eyes continued to remain at the same UDVA, 27 eyes had at least 2 lines, and 13 eyes had at least 3 or more lines improvement in UDVA. The maximum improvement in UDVA was 7 lines. A significant difference in flattening was obtained at different zones across the tapered CAIRS. Thus, differential flattening was achieved across the cone based on the customization plan. Personalized customization was possible for each cornea, unlike limited models of progressive-thickness synthetic segments. Allogenic nature, greater customizability, efficacy, and absent need for large inventories are advantages compared to synthetic segments.

Keratoconus: imaging modalities and management

“…The technique known as CAIRS was first performed in 2015 [ 16 ] . CAIRS involves the placement of ring segments made of allogeneic tissue into the cornea.…”

“…CAIRS involves the placement of ring segments made of allogeneic tissue into the cornea. These segments can be sourced from fresh, unprocessed, processed, preserved, or packaged tissue [ 16 ] . This procedure is becoming increasingly common because of its ability to produce refractive and topographic effects similar to, but with a wider range than, synthetic ICRS.…”

“…This procedure is becoming increasingly common because of its ability to produce refractive and topographic effects similar to, but with a wider range than, synthetic ICRS. Additionally, the allogeneic nature of the segments reduces the risk of complications such as overlying melting, necrosis, intrusion, extrusion, and migration [ 16 ] .…”

Bowman Layer Marking for Correct Placement of Corneal Allogeneic Intrastromal Ring Segments

“…CAIRS are becoming more widely adopted around the world [4][5][6][7][8][9] as a treatment for keratoconus and other corneal ectasias. It can be implanted in the form of segments or FIGURE 1.…”

Tissue addition keratoplasty in keratoconus: Trends and concerns

“…Tissue addition keratoplasty procedures involving human donor corneal tissue include intrastromal keratoplasty (ISLK),[ 4 ] Bowman layer transplantation,[ 5 6 ] corneal allogenic intrastromal ring segment (CAIRS) implantation,[ 6 7 8 ] and femtosecond intrastromal lenticular implantation (FILI). [ 9 ] Studies report the use of stromal small-incision lenticule extraction (SMILE) lenticules or donor corneal lenticules fashioned with automated microkeratome cut or fashioned with femtosecond laser-aided dissection.…”