Higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus

Figures & data

Table 1 Baseline characteristics of the epithelium-off and transepithelial groups

Baseline parameters	Epithelium-off corneal CXL	Transepithelial corneal CXL	P-valuea
Number	26	35
Right eyes/left eyes	13/13	19/16
Males/females	19/7	28/7
Age (years)	25.9 (7.6)	26.9 (8.0)	0.60
Spherical equivalent (D)	−3.0±3.0	−1.5±2.5	0.04
UDVA (logMAR)	1.1±0.6	0.8±0.5	0.03
CDVA (logMAR)	0.3±0.3	0.3±0.3	0.58
Pachymetry thinnest point (mm)	467±29	457±27	0.17
Maximal keratometry (D)	57.8±7.2	56.4±5.0	0.38
Endothelial cell count (cells/mm^2)	2,764±252	2,627±363	0.14
LOAs (RMS)
Total LOAs	11.8±5.6	11.8±4.4	0.56
Defocus $(Z_2^0)$	3.01±2.95	2.95±2.92	0.93
Vertical astigmatism $(Z_2^{-2})$	1.47±1.20	1.55±1.33	0.81
Horizontal astigmatism $(Z_2^2)$	2.10±2.08	1.90±1.44	0.66
HOAs (RMS)
Total HOAs	3.29±1.42	3.09±1.18	0.97
Vertical trefoil $(Z_3^{-3})$	0.22±0.16	0.28±0.21	0.22
Vertical coma $(Z_3^{-1})$	2.69±1.45	2.56±1.23	0.71
Horizontal coma $(Z_3^1)$	0.94±0.71	0.86±0.67	0.67
Horizontal trefoil $(Z_3^3)$	0.25±0.18	0.19±0.20	0.26
Spherical aberration $(Z_4^0)$	0.66±0.63	0.56±0.52	0.53

Notes: Except when indicated otherwise, values are presented as a mean ± standard deviation.

a P-values were calculated using the independent samples t-test. Significant P-values (<0.05) are shown in bold.

Abbreviations: CXL, crosslinking; D, diopter; UDVA, uncorrected distance visual acuity; logMAR, log of the minimal angle of resolution; CDVA, corrected distance visual acuity; LOAs, lower order aberrations; RMS, root mean square; HOAs, higher order aberrations.

Table 2 Epithelium-off vs transepithelial corneal CXL for keratoconus: outcomes 1, 3, 6, and 12 months after CXL relative to baseline

Parameter	Group	1 month	3 months	6 months	12 months	P-valuea
ΔMaximal keratometry (D)	Epi-off	0.3±1.1	−1.2±2.0	−1.4±2.0	−1.5±2.0	0.02
	Trans	−0.1±1.1	0.0±1.0	−0.1±1.2	0.3±1.8
ΔCDVA (logMAR)	Epi-off	0.09±0.18	−0.04±0.18	−0.09±0.23	−0.07±0.21	0.02
	Trans	−0.05±0.24	−0.10±0.21	−0.12±0.22	−0.14±0.21
ΔUDVA (logMAR)	Epi-off	−0.10±0.36	−0.18±0.31	−0.16±0.35	−0.15±0.43	0.59
	Trans	−0.06±0.25	−0.08±0.29	−0.02±0.31	−0.06±0.37
ΔSpherical equivalent (D)	Epi-off	0.6±1.4	0.5±1.6	0.9±1.8	0.4±3.0	0.44
	Trans	0.4±1.1	0.3±1.1	0.3±1.6	0.3±1.6
ΔCorneal thickness (μm)	Epi-off	−18±10	−14±15	−9±11	−4±8	<0.001
	Trans	0±7	2±9	−3±8	0±12

Notes: Except when indicated otherwise, values are presented as a mean ± standard deviation.

a P-values were calculated using trend analysis with generalized estimating equations while correcting for baseline values. Significant P-values (<0.05) are shown in bold.

Abbreviations: CDVA, corrected distance visual acuity; CXL, crosslinking; D, diopter; Epi-off, epithelium-off; logMAR, log of the minimal angle of resolution; trans, transepithelial; UDVA, uncorrected distance visual acuity.

Table 3 Trend analysis on LOAs and HOAs 1, 3, 6, and 12 months after CXL relative to baseline

Parameter	Group	Baseline	1 month	3 months	6 months	12 months	P-valuea
LOAs (RMS)
ΔTotal LOAs	Epi-off	11.8±5.6	0.31±1.83	−0.66±1.79	−1.10±2.35	−1.12±1.86	0.42
	Trans	11.8±4.4	0.04±1.20	−0.06±1.33	−0.34±1.86	−0.13±2.21
ΔDefocus $\left(Z\frac{0}{2}\right)$	Epi-off	3.01±2.95	0.71±1.70	−0.47±1.61	−0.46±1.39	−0.36±1.48	0.90
	Trans	2.95±2.92	0.12±0.82	0.14±1.17	−0.05±1.11	0.06±1.43
ΔVertical astigmatism $\left(Z\frac{-2}{2}\right)$	Epi-off	1.47±1.20	0.07±0.69	0.14±0.75	0.00±0.63	−0.10±0.74	0.59
	Trans	1.55±1.33	0.03±0.51	0.01±0.42	0.00±0.46	0.23±0.63
ΔHorizontal astigmatism $\left(Z\frac{2}{2}\right)$	Epi-off	2.10±2.08	0.21±0.55	0.11±0.40	−0.10±0.50	0.08±0.78	0.18
	Trans	1.90±1.44	−0.08±0.48	−0.03±0.55	−0.02±0.53	−0.06±0.70
HOAs (RMS)
ΔTotal HOAs	Epi-off	3.29±1.42	0.16±0.44	−0.06±0.37	−0.16±0.43	−0.18±0.36	0.98
	Trans	3.09±1.18	0.02±0.27	0.01±0.33	−0.03±0.37	0.03±0.54
ΔVertical trefoil $\left(Z\frac{-3}{3}\right)$	Epi-off	0.22±0.16	−0.02±0.20	0.07±0.24	0.05±0.17	0.01±0.28	0.29
	Trans	0.28±0.21	0.02±0.29	−0.01±0.31	−0.01±0.26	0.02±0.33
ΔVertical coma	Epi-off	2.69±1.45	0.05±0.43	−0.07±0.29	−0.19±0.38	−0.17±0.40	0.44
	Trans	2.56±1.23	−0.01±0.27	0.02±0.29	−0.02±0.35	−0.05±0.58
ΔHorizontal coma $\left(Z\frac{1}{3}\right)$	Epi-off	0.94±0.71	0.20±0.30	0.08±0.28	0.09±0.22	0.06±0.26	0.45
	Trans	0.86±0.67	0.10±0.19	0.00±0.23	0.02±0.18	0.03±0.23
ΔHorizontal trefoil $\left(Z\frac{3}{3}\right)$	Epi-off	0.25±0.18	−0.08±0.17	−0.07±0.22	−0.05±0.22	0.05±0.19	0.04
	Trans	0.19±0.20	0.09±0.28	0.04±0.22	0.02±0.18	0.11±0.31
ΔSpherical aberration $\left(Z\frac{0}{4}\right)$	Epi-off	0.66±0.63	0.16±0.23	−0.09±0.29	−0.07±0.28	−0.05±0.25	0.42
	Trans	0.56±0.52	0.03±0.12	0.01±0.19	0.01±0.21	0.05±0.23

Notes: Except when indicated otherwise, values are presented as a mean ± standard deviation.

a P-values were calculated using trend analysis with generalized estimating equations while correcting for baseline values. Significant P-values (<0.05) are shown in bold.

Abbreviations: Epi-off, epithelium-off; LOAs, lower order aberrations; HOAs, higher order aberrations; CXL, crosslinking; RMS, root mean square; trans, transepithelial.