[Clinical study of femtosecond laser corneal small incision lenticule extraction for correction of myopia and myopic astigmatism].

OBJECTIVE: To evaluate the safety, efficacy, predictability, stability and complications of femtosecond laser corneal small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism. METHODS: In this prospective study, 50 patients (88 eyes) with myopia and myopic astigmatism were chosen to be performed SMILE procedure randomly. These patients were followed up at 1 day, 1 week, 1 month and 3 months postoperatively and were examined for uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction, intraocular pressure (IOP) and corneal topography. The results were analyzed with paired-t test, independent-samples t test and regression analysis. RESULTS: SMILE procedure was performed well in all patients, only 3 cases (3 eyes, 3.4%) suffered from the suction loss, 14 cases (26 eyes, 29.5%) developed opaque bubble layer. All patients gained perfect UCVA (20/20), no eye had decrease of BCVA. The residual spherical equivalent was (-0.11 ± 0.29) D, the astigmatism was (0.01 ± 0.33) D 3 months postoperatively. The incidence of diffuse lamellar keratitis and haze was low, and no other complications were observed. The IOP was decreased slightly after 1 month(t = 6.238, P < 0.05), but no changes after 3 months (t = 0.053, P < 0.05). CONCLUSION: The SMILE procedure is good at the safety, efficacy, predictability and stability for the correction of myopia and myopic astigmatism.

[Early outcomes of corneal sensitivity changes after small incision lenticule extraction and femtosecond lenticule extraction].

OBJECTIVE: To evaluate and compare the recovery of central and peripheral corneal sensitivity in the early period after small incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx). METHODS: In this study, 47 cases (87 eyes) which underwent SMILE and FLEx were included. Central, superior, inferior, nasal and temporal corneal sensitivity was measured using a Cochet-Bonnet esthesiometer (Luneau Ophthalmologic) before and 1 week, 1 month, and 3 months after SMILE and FLEx. The results were analyzed with Mann-Whitney test by SPSS13.0 software. RESULTS: There were statistical differences between SMILE and FLEx group in the central, inferior, nasal and temporal corneal sensitivity at 1 week, 1 month and 3 months postoperatively (Z = -5.219, -7.120, -6.735, -7.139, -5.945, -6.644, -7.006, -7.121, -5.262, -3.086, -4.140, -3.523. P < 0.01). However, the superior corneal sensitivity in the SMILE group did not show significant difference (Z = -1.807, P = 0.071) as compared to FLEx group (with exception of 1 week postoperatively). At 1 month and 3 months postoperatively, corneal sensitivity in the superior quadrant were (5.23 ± 0.62) and (5.57 ± 0.57) cm in the SMILE group, and were (4.43 ± 1.20) and (4.85 ± 1.11) cm in the FLEx group. There were statistical differences between these two groups (Z = -2.935, -2.678. P = 0.003, 0.007). In the SMILE group, corneal sensitivity in the central, superior, inferior, nasal and temporal quadrants at 3 months postoperatively was (5.74 ± 0.51), (5.57 ± 0.57), (5.70 ± 0.55), (5.83 ± 0.37), (5.84 ± 0.30) cm respectively, there were no significant differences as compared with preoperative data (Z = -1.255, -0.893, -0.570, -0.630, -0.935. P = 0.209, 0.440, 0.569, 0.529, 0.350). In the FLEx group, corneal sensitivity in the superior at 3 months postoperatively was 4.85 ± 1.11, there was not significant difference compared with preoperative data (Z = -1.095, P = 0.272). There were no correlations between the changes of central corneal sensitivity and central corneal ablation depth, central corneal thickness and preoperative spherical equivalent (SMILE group: r = 0.159, -0.202, 0.106, 0.060. P > 0.05. FLEx group: r = -0.156, -0.059, 0.058, -0.005. P > 0.05) after SMILE and FLEx surgery. CONCLUSIONS: Corneal sensitivity decreases after SMILE and FLEx, and then returns to its original state over time. The decrease of corneal sensitivity after the SMILE was fewer and the recovery was faster as compared with FLEx.

[Research on the visual performance and effects of higher order aberration after Epi-LASIK for myopia].

OBJECTIVE: To investigate changes of visual performance and effects of higher order aberration on visual performance after Epi-LASIK for myopia. METHOD: In this prospective study, 102 patients were included. The trial group had 52 patients with Epi-LASIK, and 50 cases with LASIK as the control group. Ocular higher order aberrations were measured with the Hartman-shack wavefront analyzer, and high (100%), moderate (25%), low contrast (10%) and very low contrast (5%) visual acuity with and without glare were measured with Multi-Function Visual Acuity Tester under mesopic condition preoperatively and 4 - 6 months after surgery. 35 subjects in Epi-LASIK and 33 cases in LASIK were followed up 4 - 6 months later. Paired t test were used to analyze different contrast visual acuity before and after Epi-LASIK. Multiple linear regression analysis was performed to find the explanatory aberrations which contributed to the visual acuity. The Pearson correlation was used to explore the correlation between high- and low-contrast visual acuity and the explanatory higher order aberrations. The independent t test was used to analyze the difference of refraction power and visual acuity between Epi-LASIK and LASIK. RESULTS: There were significantly statistical differences at 5% and 10% contrast level compared to preoperation with glare and with no glare. With no glare, the mean logMAR visual acuity at 5% and 10% contrast level were 0.32 + or - 0.14 and 0.21 + or - 0.12 preoperatively, and 0.47 + or - 0.15 and 0.33 + or - 0.16 postoperatively (t = -4.863, 3.950; P = 0.000, 0.000). With glare, the mean logMAR visual acuity were 0.37 + or - 0.20 and 0.22 + or - 0.13 preoperatively, and 0.46 + or - 0.18 and 0.30 + or - 0.17 postoperatively (t = -1.949, -2.283; P = 0.047, 0.029). Using stepwise multiple linear regressions to evaluate which higher order aberration was significantly associated with each contrast VA. For each order RMS, S(4) was positive correlated with 5% contrast visual acuity (r(2) = 0.282;P = 0.025); S(4) was positive and S(5) was negative correlated with 10% contrast visual acuity (r(2) = 0.192;P = 0.033). None of the higher order RMS can significantly affect the 25% and 100% contrast visual acuity. For each Zernike coefficients, C(4)(0) and C(6)(4) were positive correlated with 5% contrast visual acuity (r(2) = 0.233; P = 0.024); C(4)(-4) was negative, C(4)(0) and C(5)(-5) were positive correlated with 10% contrast visual acuity (r(2) = 0.289; P = 0.013); None of Zernike coefficients had a significant correlation with 25% and 100% contrast visual acuity. The Pearson correlated coefficients between S(4), C(4)(0) and each contrast visual acuity increased as the contrast level decreased. S(4) and C(4)(0) were associated significantly with 5% contrast visual acuity, the correlation coefficients were 0.378 and 0.390 (P = 0.025 and 0.021). The visual acuity under 100% contrast with no glare was a little poorer than in LASIK. CONCLUSIONS: At the early stage after Epi-LASIK, the visual acuity for lower contrast level was worse compared to preoperative with glare and with no glare. Spherical aberration and the spherical-like aberration may contribute to this.

[The expression of TGF-beta1 and bFGF after LASEK and the effects of 20% ethanol exposure on corneal wound healing].

OBJECTIVE: To assess the effects of 20% ethanol used in LASEK on corneal wound healing. METHODS: Forty-eight eyes from 24 rabbits were deepithelialized by two techniques. The epithelium were detached with either 20% ethanol (applied for 30 seconds) or mechanical scraping, then ablated was performed. The number of superficial stromal keratocytes was counted and the morphologic changes were observed. Expression of TGF-beta1 and bFGF mRNAs was detected and analyzed by reverse transcription-polymerase chain reaction and immunocytochemical methods at 1, 7, 30 and 90 days after the surgery. RESULTS: One day after the surgery, the expression of TGF-beta1 and bFGF in the keratocytes in both treated groups was lower than that of the normal controls. Seven days after the surgery, the expression of TGF-beta1 and bFGF in both treated groups was greater than that of the normal controls (P < 0.01). The expression in the alcohol-treated group was greater than that of the surgical-treated group (P < 0.01). The expression of TGF-beta1 and bFGF reached the peak 30 days after the surgery, no significant difference was detected between the alcohol-treated and surgical-treated groups. There was no significant difference in expression level between the alcohol-treated and surgical-treated groups 3 months after the surgery; as well as between treated groups and normal group. The amount of TGF-beta1 and bFGF mRNA was positively correlated with the number of keratocytes. The correlation coefficient between TGF-beta1 and bFGF mRNA and the number of the keratocytes was 0.744 (P < 0.01) and 0.738 (P < 0.01) in the alcohol-treated group; and was 0.664 (P < 0.01) and 0.785 (P < 0.01) in the surgical-treated group, respectively. CONCLUSIONS: The expression of TGF-beta1 and bFGF mRNA undergo a dynamic process of "decrease-increase-normal". Although ethanol has a slight toxic effect on rabbit epithelial cells, but the effects do not persist over time, therefore, it is relatively safe to use the alcohol treatment in the LASEK.