Vector Analysis of Astigmatism in Keratoconic Eyes After Combined Intrastromal Corneal Ring Segments Implantation and Collagen Cross-Linking
Authors Abozaid MA, Abdalla A
Received 10 December 2019
Accepted for publication 23 January 2020
Published 20 February 2020 Volume 2020:14 Pages 473—480
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 2
Editor who approved publication: Dr Scott Fraser
Mortada Ahmed Abozaid,1 Abdelsalam Abdalla2
1Faculty of Medicine, Sohag University, Sohag, Egypt; 2Faculty of Medicine, Assiut University, Assiut, Egypt
Correspondence: Mortada Ahmed Abozaid
Ophthalmology Department, Faculty of Medicine, Sohag University, Sohag, Egypt
Tel +20 932 309 244
Fax +20 932 325 531
Purpose: To analyze astigmatic changes after intrastromal corneal ring segments (ICRSs) implantation accompanied by corneal collagen cross-linking (CXL) in keratoconic eyes using the Alpins vectorial method.
Patients and Methods: Twenty-eight eyes of 18 patients with keratoconus were included in this retrospective non-comparative study. All patients had combined femtosecond laser-assisted Keraring implantation and CXL, and completed at least 2 years of follow-up. Both manifest and corneal astigmatic changes were analyzed using the Alpins vectorial parameters based on 3 vectors; target induced astigmatism (TIA), surgically induced astigmatism (SIA) and difference vector (DV).
Results: Regarding analysis of manifest astigmatism, the TIA arithmetic mean was 5.22 D while the vector mean was 3.13 D Ax 173. The SIA arithmetic mean was 5.41 D while the vector mean was 2.38 D Ax 173. The DV arithmetic mean was 2.10 D while the vector mean was 0.75 D Ax 175. Regarding analysis of corneal astigmatism, the TIA arithmetic mean was 5.22 D while the vector mean was 3.13 D Ax 173. The SIA arithmetic mean was 5.23 D while the vector mean was 1.8 D Ax 12. The DV arithmetic mean was 4.28 D while the vector mean was 2.04 D Ax 157.
Conclusion: Vector analysis of manifest and corneal astigmatism in keratoconic eyes with previous ICRS and CXL reveals more accuracy and predictability of manifest refraction in calculating SIA.
Keywords: Alpins method, astigmatic correction in keratoconus, kerarings, vector analysis
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