The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome

Figures & data

Table 1 Pre- and postoperative data

	ASA	L-90	L-130	p-value
				L-90 vs ASA	L-130 vs ASA	L-90 vs L-130	ANOVA
Sample size	n=19 eyes (10 patients)	n=16 eyes (11 patients)	n=16 eyes (11 patients)
Mean age at time of surgery	29.3±5.8 years	30.3±9.4 years	29.3±5.8 years	0.732	0.901	0.720	0.931
Mean MRSE	−3.86±2.05 D	−4.35±1.43 D	−3.68±1.35 D	0.408	0.774	0.184	0.485
Mean preoperative spherical error	−3.37±1.94 D	−3.64±1.23 D	−3.34±1.27 D	0.408	0.964	0.507	0.767
Mean preoperative cylindrical error	−0.97±0.72 D	−1.44±1.16 D	−0.58±0.44 D	0.408	0.054	0.012	0.017
Mean preoperative corneal thickness	548±45 µm	539±37 µm	560±33 µm	0.483	0.411	0.105	0.329
Mean central ablation depth	61±24 µm	72±20 µm	59±19 µm	0.12	0.870	0.070	0.163
Mean preoperative CH	10.47±0.88 mmHg	10.52±1.36 mmHg	11.28±1.49 mmHg	0.728	0.071	0.231	0.043
Mean reduction of CH after surgery	1.75±1.02 mmHg	1.66±1.0 mmHg	2.62±1.03 mmHg	0.805	0.017	0.012	0.017
Mean reduction of CH per micron of ablation depth	0.031 mmHg/µm	0.023 mmHg/µm	0.049 mmHg/µm	0.285	0.049	0.002	0.0052
Mean preoperative CRF	10.11±1.28 mmHg	10.34±1.87 mmHg	10.62±1.76 mmHg	0.676	0.345	0.671	0.660
Mean reduction of CRF after surgery	2.33±1.35 mmHg	2.77±1.03 mmHg	2.93±1.1 mmHg	0.285	0.162	0.681	0.308
Mean reduction of CRF per micron of ablation depth	0.039 mmHg/µm	0.040 mmHg/µm	0.05 mmHg/µm	0.891	0.076	0.081	0.112

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; ANOVA, analysis of variance; MRSE, manifest refractive spherical equivalent; CH, corneal hysteresis; CRF, corneal resistance factor.

Figure 1 Mean preoperative corneal hysteresis and corneal resistance factor.

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; LASIK, laser in situ keratomileusis; SD, standard deviation.

Figure 2 Mean reduction of corneal hysteresis 3 months after surgery showing a greater reduction in corneal hysteresis in the thick-flap LASIK group compared to the thin-flap LASIK and ASA groups.

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; LASIK, laser in situ keratomileusis.

Figure 3 Mean reduction of corneal resistance factor 3 months after surgery showing a greater reduction in corneal resistance factor in the thick-flap LASIK group compared to the thin-flap LASIK and ASA groups.

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; LASIK, laser in situ keratomileusis.

Figure 4 Mean reduction of corneal hysteresis per micron of ablation depth 3 months after surgery showing a greater reduction in corneal hysteresis in the thick-flap LASIK group compared to the thin-flap LASIK and ASA groups.

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; LASIK, laser in situ keratomileusis; SD, standard deviation.

Figure 5 Mean reduction of corneal resistance factor per micron of ablation depth 3 months after surgery showing a greater reduction in corneal resistance factor in the thick-flap LASIK group compared to the thin-flap LASIK and ASA groups.

Abbreviations: ASA, advanced surface ablation; L-90, LASIK 90 µm group; L-130, LASIK 130 µm group; LASIK, laser in situ keratomileusis; SD, standard deviation.