Cylinder Axis Agreement: Unexpected Scenarios

BACKGROUND: The purpose of this retrospective study was to evaluate cylinder axis agreement between manifest refraction (MR), cycloplegic refraction (CR), Allegro Oculyzer ІІ and Allegro Topolyzer-Vario. METHODS: We included 82 patients (32 males and 50 females, 28.1 ± 8.7 years old), with 156 eyes scheduled for wavefront optimized laser refractive surgery, photorefractive keratectomy (PRK) in 50 eyes and laser-assisted in situ keratomileusis (LASIK) in 106 eyes, for correction of simple, myopic, hyperopic or mixed astigmatism. Cylinder axis was determined under manifest and cycloplegic refractions and using Allegro Occulyzer ІІ and Allegro Topolyzer-Vario platforms. Cylinder axis agreement was assessed by intraclass correlation coefficient, Pearson correlation coefficient and by the method described by Bland and Altman. RESULTS: Intraclass correlation coefficient and Pearson correlation coefficient showed statistically significant cylinder axis agreement between manifest refraction, cycloplegic refraction, Allegro Oculyzer ІІ and Allegro Topolyzer-Vario (p <0.001). Despite statistically significant cylinder axis agreement between the four measuring tools, 4 of 156 eyes (2.5%) showed unexpected discrepancy between Allegro Oculyzer ІІ and Allegro Topolyzer-Vario cylinder axis. CONCLUSION: Although cylinder axis shows statistically significant agreement between manifest refraction, cycloplegic refraction, Allegro Oculyzer ІІ and Allegro Topolyzer-Vario, unexpected discrepancies occur.