Tear meniscus evaluation after microkeratome laser in situ keratomileusis, femtosecond laser and femtosmile laser techniques using anterior segment optical coherence tomography

Figures & data

Figure 1 Marginal tear strip as seen by AS-SD-OCT.

Abbreviation: AS-SD-OCT, anterior segment spectral domain optical coherence tomography.

Figure 2 Tear meniscus parameters as measured by AS-SD-OCT.

Abbreviations: AS-SD-OCT, anterior segment spectral domain optical coherence tomography; TMH, tear meniscus height; TMD, tear meniscus depth; TMA, tear meniscus area.

Table 1 Mean, SD and range of TMH in the different LASIK techniques at different times of follow-up

TMH	Microkeratome LASIK		FS-LASIK		FS-SMILE
	Mean ± SD (μm)	Range (μm)	Mean ± SD (μm)	Range (μm)	Mean ± SD (μm)	Range (μm)
Preoperative	0.254 ± 0.020	0.220–0.288	0.255 ± 0.032	0.200–0.293	0.255 ± 0.022	0.228–0.295
1 week postoperative	0.167 ± 0.027	0.133–0.213	0.189 ± 0.033	0.130–0.230	0.224 ± 0.019	0.198–0.263
1 month postoperative	0.177 ± 0.026	0.135–0.220	0.198 ± 0.034	0.133–0.243	0.235 ± 0.018	0.212–0.268
3 months postoperative	0.193 ± 0.029	0.140–0.245	0.225 ± 0.040	0.150–0.273	0.244 ± 0.019	0.220–0.280
6 months postoperative	0.217 ± 0.029	0.165–0.270	0.245 ± 0.036	0.175–0.290	0.251 ± 0.021	0.225–0.288

Notes: Greenhouse–Geisser F = 324.9, P < 0.001, for the time factor; Greenhouse–Geisser F = 28.8, P < 0.001, for the time–technique interaction and Greenhouse–Geisser F = 0.258, P = 0.614, for the eye. F-test between techniques = 8.620 and P = 0.001 with significant all pairwise comparison.

Abbreviations: TMH, tear meniscus height; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction; SD, standard deviation.

Table 2 Mean, SD and range of TMD in the different LASIK techniques at different times of follow-up

TMD	Microkeratome LASIK		FS-LASIK		FS-SMILE
	Mean ± SD (μm)	Range (μm)	Mean ± SD (μm)	Range (μm)	Mean ± SD (μm)	Range (μm)
Preoperative	0.164 ± 0.020	0.128–0.190	0.183 ± 0.017	0.150–0.210	0.166 ± 0.018	0.135–0.195
1 week postoperative	0.136 ± 0.021	0.105–0.178	0.156 ± 0.017	0.130–0.200	0.145 ± 0.018	0.105–0.168
1 month postoperative	0.137 ± 0.021	0.108–0.178	0.162 ± 0.017	0.135–0.198	0.151 ± 0.015	0.120–0.170
3 months postoperative	0.146 ± 0.020	0.120–0.180	0.172 ± 0.026	0.143–0.248	0.157 ± 0.014	0.135–0.180
6 months postoperative	0.155 ± 0.022	0.123–0.183	0.177 ± 0.017	0.145–0.200	0.161 ± 0.015	0.135–0.185

Notes: Greenhouse–Geisser F = 345.054, P < 0.001, for the time factor; Greenhouse–Geisser F = 2.168, P = 0.056, for the time–technique interaction and Greenhouse–Geisser F = 0.0.491, P = 0.487, for the eye. F-test between techniques = 6.02 and P = 0.005.

Abbreviations: SD, standard deviation; TMD, tear meniscus depth; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction.

Table 3 Mean, SD and range of TMA in the different LASIK techniques at different times of follow-up

TMA	Microkeratome LASIK		FS-LASIK		FS-SMILE
	Mean ± SD (mm)	Range (mm)	Mean ± SD (mm)	Range (mm)	Mean ± SD (mm)	Range (mm)
Preoperative	20.96 ± 3.72	15.25–26.00	23.39 ± 4.29	15.55–28.60	21.16 ± 3.26	16.50–26.80
1 week postoperative	11.43 ± 3.23	7.25–18.90	15.05 ± 3.27	9.40–21.50	16.29 ± 2.45	11.30–21.30
1 month postoperative	12.28 ± 3.20	7.50–18.65	16.08 ± 3.61	9.90–21.90	17.70 ± 2.22	13.45–21.30
3 months postoperative	14.22 ± 3.67	8.35–20.20	19.00 ± 4.39	12.15–25.00	19.03 ± 1.97	16.10–22.40
6 months postoperative	16.97 ± 4.29	11.30–24.60	21.61 ± 4.35	14.3–28.25	20.21 ± 2.69	16.50–25.50

Notes: Greenhouse–Geisser F = 345.05, P < 0.001, for the time factor; Greenhouse–Geisser F = 16.396, P < 0.001, for the time–technique interaction and Greenhouse–Geisser F = 0.677, P = 0.415, for the eye. F-test between techniques = 6.536 and P = 0.003.

Abbreviations: SD, standard deviation; TMA, tear meniscus area; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction.

Table 4 P-value in pairwise comparison of the TMH between the three LASIK techniques at different times of follow-up

TMH	Microkeratome LASIK vs FS-LASIK	Microkeratome LASIK vs FS-SMILE	FS-LASIK vs FS-SMILE
Preoperative	0.998	0.994	0.998
1 week postoperative	0.075	<0.001*	0.003*
1 month postoperative	0.093	<0.001*	0.002*
3 months postoperative	0.019*	<0.001*	0.191
6 months postoperative	0.032*	0.007*	0.824

Note:

* Statistically significant difference between any two techniques at specific time of follow-up.

Abbreviations: TMH, tear meniscus height; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction.

Figure 3 In all techniques, TMH dropped after 1 week to the lowest level.

Notes: The FS-SMILE technique showed the least drop and returned to 95% of its preoperative level after 1 month. FS-LASIK reached to its preoperative level at 6 months, while microkeratome LASIK did not.
Abbreviations: TMH, tear meniscus height; FS-SMILE, femtosecond small incision lenticule extraction; FS-LASIK, femtosecond laser in situ keratomileusis; LASIK, laser in situ keratomileusis; CI, confidence interval.

Table 5 P-value in pairwise comparison of the TMD between the three LASIK techniques at different times of follow-up

TMD	Microkeratome LASIK vs FS-LASIK	Microkeratome LASIK vs FS-SMILE	FS-LASIK vs FS-SMILE
Preoperative	0.017*	0.983	0.026*
1 week postoperative	0.017*	0.378	0.288
1 month postoperative	0.001*	0.110	0.216
3 months postoperative	0.004*	0.344	0.128
6 months postoperative	0.006*	0.066	0.586

Note:

* Statistically significant difference between any two techniques at specific time of follow-up.

Abbreviations: TMD, tear meniscus depth; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction.

Figure 4 In all techniques, TMD dropped after 1 week to the lowest level.

Notes: With FS-SMILE, TMD started to increase from the first month, while with FS-LASIK, the increase started after 3 months. However, with microkeratome, TMD remained low till 6 months.
Abbreviations: TMD, tear meniscus depth; LASIK, laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction; FS-LASIK, femtosecond laser in situ keratomileusis; CI, confidence interval.

Table 6 P-value in pairwise comparison of TMA between the three LASIK techniques at different times of follow-up

TMA	Microkeratome LASIK vs FS-LASIK	Microkeratome LASIK vs FS-SMILE	FS-LASIK vs FS-SMILE
Preoperative	0.194	0.989	0.248
1 week postoperative	0.005*	<0.001*	0.503
1 month postoperative	0.004*	<0.001*	0.323
3 months postoperative	0.002*	<0.001*	1.000
6 months postoperative	0.006*	0.066	0.586

Note:

* Statistically significant difference between any two techniques at specific time of follow-up.

Abbreviations: TMA, tear meniscus area; LASIK, laser in situ keratomileusis; FS-LASIK, femtosecond laser in situ keratomileusis; FS-SMILE, femtosecond small incision lenticule extraction.

Figure 5 In all techniques, TMA dropped after 1 week to the lowest level.

Note: FS-SMILE and FS-LASIK reached the preoperative level at 6 months, while microkeratome LASIK did not.
Abbreviations: TMA, tear meniscus area; FS-SMILE, femtosecond small incision lenticule extraction; FS-LASIK, femtosecond laser in situ keratomileusis; LASIK, laser in situ keratomileusis; CI, confidence interval.