Evaluation of a Tangential Map-Based Nomogram for Intrastromal Corneal Ring Segments' Implantation in Keratoconus: One Year Results.

Moataz Faiz Elsawy,Adel Galal Zaky,Mahmoud Tawfik Khalafallah,Abdelrahman Elsebaey Sarhan

doi:10.1155/2020/3983508

Abstract

Purpose To evaluate a new tangential map-based nomogram versus the axial map-based nomogram for ICRS in keratoconus. Methods A prospective case series study including 64 eyes of 64 patients who underwent ICRS implantation. Cone location was determined for each eye with two maps: the axial and the tangential. Appropriate ring selection was determined using two surgical nomograms: axial map-based and tangential map-based. Visual, refractive, and topographic outcomes were assessed before, as well as at 3, 6, and 12 months after ICRS implantation. Results The cone location, and consequently the ring selection, was significantly different in the two nomograms with a “centralization tendency” in the tangential map. In the axial group, UDVA and CDVA improved from 0.12 ± 0.04 and 0.24 ± 0.08 to 0.28 ± 0.08 and 0.4 ± 0.1, respectively. Similarly, MRSE substantially decreased from −6.7 ± 3.3 to −1.2 ± 1.1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1D at 12 months after the procedure. In the tangential group, UDVA and CDVA improved from 0.09 ± 0.06 and 0.2 ± 0.1 to 0.5 ± 0.2 and 0.7 ± 0.2, respectively. MRSE substantially decreased from −4.9 ± 1P=0.01∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months, P=0.01∗. Similarly, the gain in the CDVA was 0.4 and 0.15 in the tangential and axial groups, respectively, at 12 months, Conclusion The tangential map-based nomogram attained better visual and refractive outcomes at 1 year. In addition, the cone location was significantly different between both maps with a centralization tendency in the tangential one.

Highlights

Keratoconus (KC) is a bilateral, progressive, noninflammatory disease of the cornea which often leads to high myopia and astigmatism which impair the acuity and quality of vision
Intrastromal corneal ring segments (ICRS) enriched the armamentarium for KC, with promising results in topographic regularity and uncorrected distant visual acuity (UDVA), raising the hopes to reduce the need for keratoplasty [5, 6]
Appropriate ring selection depends on the cone location and/or asymmetry, spherical error, astigmatism, Q value, and corneal topography; no nomogram is agreed upon [7]

Summary

Introduction

Keratoconus (KC) is a bilateral, progressive, noninflammatory disease of the cornea which often leads to high myopia and astigmatism which impair the acuity and quality of vision. It has an estimated prevalence of approximately 1 in 2000 and an incidence between 50 and 230 per 100,000 [1, 2]. Appropriate ring selection depends on the cone location and/or asymmetry, spherical error, astigmatism, Q value, and corneal topography; no nomogram is agreed upon [7]. All of these parameters are measured objectively with standard techniques. In contrast, is neither agreed for its definition nor its Journal of Ophthalmology

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Results

Conclusion