Topometric Indices And Corneal Densitometry Change After Corneal Refractive Surgery Combined With Simultaneous Collagen Crosslinking

Figures & data

Table 1 Baseline Characteristics Of The Population (Mean ± Standard Deviation (Min–Max))

	All Eyes	PRK Xtra	LASIK Xtra	SMILE Xtra
UCVA (logMAR)	1.47 ± 0.44 (0.6–1.82)	0.68 ± 0.05 (0.6–1.82)	1.55 ± 0.35 (1–1.82)	1.69 ± 0.19 (1.3–1.82)
CDVA (logMAR)	0.02 ± 0.08 (−0.1–0.18)	−0.05 ± 0.06 (−0.1–0)	−0.003 ± 0.09 (−0.1–0.18)	0.05 ± 0.05 (0–0.1)
MRSE (D)	−7.29 ± 3.19 (−12.88–(−2.63)	−3.33 ± 0.56 (−4–(−2.63))	−10.32 ± 2.36 (−12.88–(−6))	−7.17 ± 2.27 (−10.75–(−4.38))
Kmax (D)	46.99 ± 1.27 (45.1–48)	46.96 ± 0.85 (45.5–47.6)	46.99 ± 1.27 (45.1–48)	46.17 ± 2.21 (42–48.5)
Kmean (D)	45.16 ± 1.60 (40.8–47.4)	45.36 ± 0.80 (44.5–46.3)	45.57 ± 1.05 (44.1–46.6)	44.84 ± 2.07 (40.8–47.4)
Corneal astigmatism (D)	1.68 ± 0.81 (0.5–3.6)	1.78 ± 0.98 (1–2.9)	1.84 ± 0.64 (0.9–2.7)	1.54 ± 0.87 (0.5–3.6)
Q-value	−0.31 ± 0.26 (−0.75–0.52)	−0.34 ± 0.07 (−0.43–(−0.25))	−0.16 ± 0.42 (−0.46–0.52)	−0.38 ± 0.17 (−0.75–(−0.24))
Thinnest pachymetry (microns)	518.54 ± 27.26 (476–584)	497.2 ± 25.53 (476–528)	538.29 ± 31.26 (509–584)	515.92 ± 17.92 (476–584)
HOA (rms)	0.27 ± 0.13 (0.07–0.53)	0.17 ± 0.09 (0.07–0.28)	0.23 ± 0.08 (0.15–0.39)	0.35 ± 0.12 (0.15–0.53)
Topographic indices
ISV	21.63 ± 5.27 (14–33)	22.4 ± 7.89 (14–33)	20.43 ± 2.76 (17–26)	22 ± 5.48 (15–31)
IVA	0.14 ± 0.05 (0.07–0.27)	0.14 ± 0.03 (0.11–0.18)	0.12 ± 0.03 (0.07–0.15)	0.16 ± 0.06 (0.1–0.27)
KI	1.04 ± 0.02 (0.99–1.07)	1.03 ± 0.03 (0.99–1.06)	1.05 ± 0.01 (1.03–1.06)	1.04 ± 0.02 (1.02–1.07)
CKI	1.01 ± 0.02 (1–1.1)	1.01 ± 0.01 (1–1.01)	1.01 ± 0.01 (1–1.02)	1.02 ± 0.03 (1–1.1)
IHA	7.47 ± 3.20 (2.7–10.6)	5.84 ± 2.53 (2.1–8.2)	5.84 ± 2.53 (2.1–8.2)	8.52 ± 4.65 (0.5–15.4)
IHD	0.014 ± 0.004 (0.005–0.024)	0.02 ± 0.01 (0.01–0.02)	0.012 ± 0.004 (0.01–0.02)	0.01 ± 0.01 (0.005–0.024)
Rmin	7.25 ± 0.29(6.95–8.04)	7.19 ± 0.13 (7.09–7.41)	7.17 ± 0.21 (7–7.48)	7.33 ± 0.36 (6.95–8.04)
Corneal densitometry (Gray scale unit; GSU)
Anterior
0–2 mm	24.26 ± 1.52 (21.1–27.1)	23.62 ± 1.18 (22.5–25.4)	25.61 ± 1.07 (23.8–27.1)	23.75 ± 1.43 (21.2–25.9)
2–6 mm	21.92 ± 1.78 (18–25.4)	21.5 ± 0.96 (19.8–22.2)	23.53 ± 1.31 (21.8–25 .4)	21.16 ± 1.74 (18–23.7)
6–10 mm	25.3 ± 6.10 (16.3–35.9)	24.1 ± 5.00 (16.3–29.1)	27.6 ± 5.19 (21.9–35.4)	24.46 ± 7.01 (17.7–35.9)
Center
0–2 mm	14.35 ± 0.92 (12.8–16.5)	14.18 ± 0.85 (13.2–15.3)	15.3 ± 0.82 (14.3–16.5)	13.86 ± 0.53 (12.8–14.8)
2–6 mm	13.06 ± 1.21 (11.1–16.2)	12.96 ± 0.84 (11.5–13.5)	14.23 ± 1.31 (13–16.2)	12.43 ± 0.74 (11.1–13.4)
6–10 mm	16.65 ± 5.04 (10.6–26.3)	16.38 ± 4.55 (10.6–21.5)	18.84 ± 4.46 (14.6–25.8)	15.48 ± 5.50 (11.3–26.3)
Posterior
0–2 mm	13.02 ± 1.16 (10.7–15.2)	12.62 ± 0.68 (11.4–13.1)	14.21 ± 0.75 (13.4–15.2)	12.53 ± 1.02 (10.7–14)
2–6 mm	11.94 ± 1.24 (9.8–15.2)	11.6 ± 0.85 (10.1–12.1)	13.19 ± 1.07 (12.2–15.2)	11.35 ± 0.95 (9.8–15.2)
6–10 mm	15.22 ± 4.01 (10.1–24.2)	14.84 ± 3.66 (10.1–19.2)	17.99 ± 4.17 (14.3–24.2)	13.77 ± 3.48 (10.7–20.8)

Abbreviations: CDVA, corrected distance visual acuity; CKI, central keratoconus index; D, diopter; HOA, higher-order aberration; IHA, index of height asymmetry; IHD, index of height decentration; ISV, index of surface variance; IVA, index of vertical asymmetry; KI, keratoconus index; Kmax, maximum keratometry value; Kmean, mean keratometry value; MRSE, manifest refraction spherical equivalent; Rmin, minimum radius of curvature; rms, root mean square; UCVA, uncorrected visual acuity.

Table 2 Clinical Measures In Each Visit (Mean ± Standard Deviation)

	Day 0	Month 1	Month 3	Month 6
UCVA (logMAR)	1.47 ± 0.44	0.02 ± 0.12*	0 ± 0.07*	0.04 ± 0.11*
CDVA (logMAR)	0.02 ± 0.08	−0.04 ± 0.06*	−0.01 ± 0.06	−0.01 ± 0.03
MRSE (D)	−7.29 ± 3.19	−0.35 ± 0.87*	−0.37 ± 0.65*	−0.39 ± 0.87*
Kmax (D)	46.57 ± 1.75	45.52 ± 1.40*	45.33 ± 1.64*	45.23 ± 1.42*
Kmean (D)	45.16 ± 1.60	40.19 ± 2.78*	39.46 ± 3.05*	38.51 ± 2.57*
Corneal astigmatism (D)	1.68 ± 0.81	0.76 ± 0.48*	1.00 ± 0.47*	0.90 ± 0.36*
Q-value	−0.31 ± 0.26	0.55 ± 0.75*	0.84 ± 0.61*	1.02 ± 0.52*
Thinnest pachymetry (microns)	518.54 ± 27.26	418.05 ± 46.23*	417.21 ± 32.79*	415.56 ± 10.77*
HOA (rms)	0.27 ± 0.13	0.53 ± 0.23*	0.53 ± 0.28*	0.57 ± 0.23*

Note: *P-value < 0.05 (compared to Day 0).

Abbreviations: CDVA, corrected distance visual acuity; D, diopter; HOA, higher-order aberration; MRSE, manifest refraction spherical equivalent; rms, root mean square; UCVA, uncorrected visual acuity.

Table 3 Topographic Indices In Each Visit (Mean ± Standard Deviation)

	Day 0	Month 1	Month 3	Month 6
ISV	21.63 ± 5.27	39.41 ± 22.09*	43.07 ± 24.36*	49.56 ± 28.20*
IVA	0.14 ± 0.05	0.36 ± 0.26*	0.40 ± 0.33*	0.46 ± 0.41*
KI	1.04 ± 0.02	1.00 ± 0.05*	1.00 ± 0.04*	0.99 ± 0.05*
CKI	1.01 ± 0.02	1.00 ± 0.02*	0.99 ± 0.02*	0.99 ± 0.02*
IHA	7.65 ± 3.90	9.45 ± 8.95	13.38 ± 10.11*	16.68 ± 15.85*
IHD	0.01 ± 0.01	0.03 ± 0.02*	0.03 ± 0.03*	0.04 ± 0.04*
Rmin	7.25 ± 0.29	7.46 ± 0.26*	7.46 ± 0.28*	7.47 ± 0.24*

Note: *P-value < 0.05 (compared to Day 0).

Abbreviations: CKI, central keratoconus index; IHA, index of height asymmetry; IHD, index of height decentration; ISV, index of surface variance; IVA, index of vertical asymmetry; KI, keratoconus index; Rmin, minimum radius of curvature.

Table 4 Corneal Densitometry (Gray Scale Unit; GSU) In Each Visit (Mean ± Standard Deviation)

	Day 0	Month 1	Month 3	Month 6
Anterior
0–2 mm	24.27 ± 1.52	26.17 ± 2.58*	25.86 ± 2.79*	24.53 ± 1.60
2–6 mm	21.92 ± 1.78	23.56 ± 2.25*	23.27 ± 2.57*	22.64 ± 1.97
6–10 mm	25.30 ± 6.10	24.53 ± 5.99*	23.65 ± 5.51*	24.89 ± 7.04*
Center
0–2 mm	14.35 ± 0.92	15.71 ± 1.45*	15.49 ± 1.22*	14.70 ± 0.59
2–6 mm	13.06 ± 1.21	14.04 ± 1.51*	14.00 ± 1.14*	13.77 ± 1.15
6–10 mm	16.65 ± 5.04	16.85 ± 4.84	16.73 ± 4.21*	17.51 ± 5.70*
Posterior
0–2 mm	13.02 ± 1.16	13.50 ± 1.50	13.10 ± 0.72	13.18 ± 0.94
2–6 mm	11.94 ± 1.24	12.39 ± 1.05*	12.37 ± 1.18	12.76 ± 1.05
6–10 mm	15.11 ± 4.01	15.80 ± 3.88	16.07 ± 4.18	16.72 ± 5.06

Notes: *P-value < 0.05 (compared to Day 0), p-value < 0.05 (compared to adjacent previous visit).