Femtosecond Laser Implantation of a 355-Degree Intrastromal Corneal Ring Segment in Keratoconus: A Three-Year Follow-Up

Table 3

Comparison between preoperative and postoperative sphere, cylinder, and spherical equivalent (SE) measurements.

	Preoperative	12 months postoperative	24 months postoperative	36 months postoperative	value	P1	P2
Sphere
Mean ± S.D.	−9.68 ± 3.08	−6.32 ± 2.37	−7.13 ± 3.09	−7.45 ± 3.2	<0.001	0.004	0.129
Median (range)	−8.75 (−4.25–−16)	−5.75 (−3.5–−12.5)	−7.25 (−3.5–15)	−7.75 (−3.75–−15.5)
Cylinder
Mean ± S.D.	−5.82 ± 1.55	−3.81 ± 0.81	−4.21 ± 1.24	−4.32 ± 1.24	<0.001	0.003	0.198
Median (range)	−6.25 (−3.25–−8.5)	−3.88 (−2–5.5)	−4 (−2–7)	−4 (−2–6.75)
Spherical equivalent SE
Mean ± S.D.	−12.55 ± 3.64	−8.25 ± 2.62	−8.72 ± 3.39	−9.62 ± 3.73	<0.001	0.173	0.009
Median (range)	−12 (−6.12–−19.75)	−7.75 (5–−14.75)	−7.75 (−5–−19.5)	−9.94 (−5–−18.75)

value compared the six repeated measures and was calculated by Friedman’s two-way ANOVA test. P1 compared 12 months postoperative and 24 months postoperative measures and was calculated by Wilcoxon signed-rank test. P1 compared 24 months postoperative and 36 months postoperative measures and was calculated by Wilcoxon signed-rank test. value was calculated by paired samples t test. value <0.05 is statistically significant. SE: spherical equivalent.