RESUMEN
Background Tight junctions are thought to play a significant role in the maintenance of the corneal epithelial defense for the eye,and the restoration of the tight junctions is critical during epithelial wound healing after refractive surgery.However,there are few reports about this study. Objective The aim of this study was to investigate and compare the expression of occludin in corneal epithelium following flap-free epipolis laser insitu keratomileusis (Epi-LASIK) and laser-assisted subepithelial keratectomy ( LASEK ). Methods Forty-eight clean New Zealand white rabbits were randomized into 2 groups,and 24 rabbits for each group.Flap-free Epi-LASIK and LASEK were performed in the right eyes of the rabbits in two groups,and other 2 age matched normal rabbits were as normal controls.The animals were sacrificed and the corneal samples were obtained at 1,2,3,5 days after surgery.Immunofluorescence staining was used to detect the expression of occludin in the corneal epithelium,and RT-PCR was used to identify the level of occludin mRNA in the central cornea. Results Occludin protein was expressed innormal corneal epithelium and showed the green fluorescence with the regular arrangement.The fluorescence intensity was lower in 1 -2 days in LASEK group with the irregular arrangement;while the fluorescence signal in corneal epithelium was stronger in flap-free Epi-LASIK group.3-5 days after surgery,the fluorescence intensities were bothenhanced in two groups.RT-PCR showed that the relative expression of occludin mRNA in corneal epithelium was 0.11 ±0.02,0.25 ± 0.03,0.43 ± 0.04 in LASEK group 1,2,3 days after surgery,respectively,and was lower than those of flap-free Epi-LASIK group ( 0.20± 0.04,0.44 ± 0.04,0.76 ± 0.04 ),showing significant differences between these two groups ( t =6.476,12.898,17.315,P＜ 0.05 ).No significant difference was seen in the expression of occludin mRNA in 5 days after surgery between two groups( t=-0.733,P＞0.05).The relative values of occludin mRNA expression in corneal epithelium were gradually increased with time prolongation,presenting a significant difference among various time points ( Ftime =768.903,P =0.000). Conclusions The reformation of occludin in flap-free Epi-LASIK group is faster than that in LASEK group.Therefore,flap-free Epi-LASIK is prominant in reducing the stimulated symptoms and complication after the surgery.
RESUMEN
Background Compare with the lamellar laser refractive surgery,the laser slip on the surface operation is a better method in the correct of refractive error without the flap-related complications.However,whether to remain corneal epithelial flap and its influence for epithelial healing and visual restoration are still under investigation.Objective The aim of this study was to compare the short-term clinical efficacy of epipolis laser insitu keratomileusis (Epi-LASIK) and flap-free Epi-LASIK for correction of refractive error in high myopia.Methods The paired control design was adopted.Sixty eyes of consecutive 30 patients with high myopia were collected in this study.The written consent form was obtained from each patients prior to operation.Regular EpiLASIK was performed in the right eyes and the flap-free Epi-LASIK was carried out in the left eyes.Patients were followed-up for one month.The postoperative ocular irritation symptoms were scored,and the healing period of corneal epithelium and uncorrected visual acuity were examined at 1,3 and 5 days after operation.The naked visual acuity,diopter,best corrected visual acuity and the grading of haze were recorded and compared between the two groups at one month after operation.Results After surgery,the scores of corneal irritation were 3.13 ±0.43 and 3.30±0.47on the first day,showing insignificant differences between these two groups (t =- 1.54,P＞0.05 ).However,there existed statistically significant difference in the scores of corneal irritation on the third day after operation between the two groups (t =- 17.95,P＜0.01 ).The average time of corneal epithelial healing were (2.58 ±0.49 ) days in the flapfree Epi-LASIK group and ( 3.98 ±0.74) days in Epi-LASIK group with the significant difference between them (t=-11.36,P＜0.01 ).There was no statistical difference in uncorrected visual acuity in the first day (0.59±0.12 vs 0.58±0.11,t=0.39,P＞0.05),the fifth day (0.69±0.08 vs 0.67±0.09,t=0.84,P＞0.05) and 1 month (t =-1.90,P＞0.05 ).No significant difference was seen in the diopter between the two groups in 1 month after surgery (-1.03±0.45 vs -1.07 ±0.38,t =-0.31,P＞0.05 ).The eye numbers of corneal haze for 0 grade were 27 ( 90.00％ ) and over the 0.5 grade were 3 ( 10.00％ ) in flap-free Epi-LASIK group respectively,and those of corneal haze for 0 grade were 26(86.66％ ) and above the 0.5 grade were 4 (13.33％) in Epi-LASIK group respectively,showing a considerably difference between the two groups (x2 =0.0031,P＞0.05).Conclusions Both the flapfree or reserved epithelial Epi-LASIK allow the safe and effective correction of refractive error in high myopia,showing good predictability and stability in short term.Flap-free Epi-LASIK can relieve the corneal irritation symptom and accelerate the healing of corneal epithelium and recovery of visual acuity.