<p>Asymmetric Thickness Intracorneal Ring Segments for Keratoconus</p>

Abstract

Purpose To describe the anatomical and functional results of the implantation of asymmetric thickness intracorneal ring segments (AS-ICRS) in eyes with keratoconus and asymmetric/irregular astigmatism (type 2 – Duck – and type 3 – Snowman – phenotypes, Fernandez-Vega/Alfonso morphologic Keratoconus classification). Materials and Methods Retrospective observational study including 19 consecutive patients (21 eyes) with keratoconus who underwent manual implantation of the Keraring ® Asymmetric ICRS (AS). Analysis included demographic and clinical data and Pentacam (Oculus ® ) measurements: topographic astigmatism; topographic flat meridian (K1), steepest meridian (K2) and the maximum keratometric point (Kmax); total root mean square (RMS) and high order RMS (HOA) aberrations and comatic Zernike coefficients (Z3 1 ;Z3 −1 ) at 0º and 90º meridians. Results Overall mean age was 35.3±11.7 years and median follow-up was 7.1 months (range 6–12). At the end of follow-up, a significant improvement from baseline was achieved in both UDVA (0.24±0.22; p=0.017) and CDVA (0.21±0.17; p<0.001). Regarding topographic measurements, the greatest decrease was observed in K2 (2.76±1.9D; p<0.001) and astigmatism (1.97±1.5; p<0.001). Aberrometry analysis showed a reduction of 1.27±3.2µm in the total RMS (p=0.085), 0.24±0.9µm in HOA (p=0.227) and 0.78±0.5 (p<0.001) in the 90º component of comatic aberration. The procedure effects in the CDVA, topographic and aberrometric parameters were higher in type 2 cones without statistical significance (p>0.05 in all). Conclusion Implantation of the Keraring ® Asymmetric ICRS in keratoconus with asymmetric/irregular astigmatism allowed an improvement of several clinical, topographic and aberrometric parameters, with clinical efficacy and safety, with a tendency to a greater effect in the type 2 cones.

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

“…[ 1 2 3 4 5 6 7 8 9 10 11 ] However, many topographical characteristics make customization of intrastromal segments more desirable. [ 24 25 26 27 28 29 30 31 ] In this case series, we created tapered segments for patients with pericentral or paracentral decentered cones who showed gradation of keratometric values with one side being steeper than the other. We attempted to do this by varying the volume of tissue implanted in different zones – adding more volume where greater flattening was required and less where less flattening was required.…”

“…Asymmetric synthetic ICRS have previously been reported to regularize the corneal shape and result in appreciable visual improvement in patients with a significant difference between corneal topographic and comatic axes. [ 25 26 27 28 29 30 31 ] These asymmetric segments are available as fixed combinations of arc length, diameter, thickness variation, width variation, and in clockwise and anti-clockwise versions. Moreover, the thickness changes at a uniform rate from one end to the other, without varying stretches of uniform thickness as we were able to do in the case of CAIRS.…”

Clinical Outcomes of a New Type of Continuous Intrastromal Corneal Ring for Treatment of Keratoconus

“…12 First, ring segments were extensively studied for treatment of low to moderate myopia, 13,14 but, later, their indication for usage was redirected toward ectatic corneal diseases such as keratoconus, 15 and they are now considered a mainstay part of keratoconus treatment, delaying the need for keratoplasty or removing it altogether for some patients. 16,17 Recently, Daxer proposed a new kind of continuous corneal ring (MyoRing) along with a new method of implantation. This method consists of creating a corneal pocket in deep stroma using a microkeratome.…”

Asymmetric Intrastromal Corneal Ring Segments with Progressive Base Width and Thickness for Keratoconus: Evaluation of Efficacy and Analysis of Epithelial Remodeling

“…The thickness or width of these segments varies so as to treat the keratoconus heterogeneously, targeting certain areas of the cornea, according to the phenotype. Asymmetric ICRS implantation has resulted in good visual, refractive and topographic outcomes, with a particularly large decrease in coma-like aberration [ 6 , 9 , 12 , 13 , 14 , 15 ].…”