Clinical observation on removing or reserving the epithelial flap in high myopia correction by LASEK / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To compare the clinical effects of removing or reserving the epithelial flap in high myopia correction by laser subepithelial keratomileusis(LASEK). <p>METHODS: Retrospective analysis of 58 patients(115 eyes)with high myopia received LASEK were selected and divided into reserving the epithelial flap group(30 patients, 59 eyes)and removing epithelial flap group(28 patients, 56 eyes)according to the order of the alternating vists. The changes of corneal irritation, epithelial healing time,uncorrected visual acuity and the occurrence of haze after surgery were observed.<p>RESULTS:Postoperative 1d, 2d, 3d, respectively, the pain score of the two groups were 1.64±0.64, 1.57±0.57; 0.83±0.49, 0.84±0.56; 0.36±0.48, 0.34±0.47, respectively, the differences were not significant(<i>P</i>>0.05). Postoperative 1wk, 1mo, 3mo, respectively, the uncorrected visual acuity of two group was 0.15±0.06, 0.12±0.05; 0.032±0.004, 0.041±0.003; 0.018±0.004, 0.022±0.005, and the differences were not significant(<i>P</i>>0.05). After 1mo, 3mo of surgery, the differences of the haze less than grade one of the two group, respectively, and were not significant(<i>P</i>>0.05), the differences of the haze of grade two of the two groups, respectively, and the differences were significant(<i>P</i><0.05). The epithelial healing time of the two groups were 4.22±0.30d, 3.89±0.32d(<i>P</i><0.05). The number of epithelial delayed healing of two groups was 0 eye and 10 eyes(<i>P</i><0.05).<p>CONCLUSION:It was similar both the changes of corneal irritation and uncorrected visual acuity of two groups,the rate of level two haze was higher in removing epithelial flap group. The time of healing of epithelium was quick than reserving the epithelial flap group,but the rate of delayed healing and poor healing of epithelium was higher than reserving the epithelial flap group. Therefore, for high myopia, it is worthy of clinical application of reserving the epithelial flap by LASEK.

Meta-analysis of clinical effectiveness of on-flap and off-flap epi-LASIK for myopia / 中华实验眼科杂志

Background Recently,whether the epithelial flaps should be removed or preserved during the Epi-LASIK and its affection on clinical results are concerned.Objecfive This system analysis was to evaluate and compare the clinical effectiveness between on-flap Epi-LASIK and off-flap epi-LASIK for myopia. Methods A systematic literature retfieval was conducted in the MEDLINE,EMBase,Coehrane Library,CBM disc,CNKI from 2003 through 2009.The possible differences in reepithelization time,pain sensation,and haze after surgery were compared between on-flap and off-flap Epi-LASIK for myopia.The statistical analysis was performed using a RevMan 4.2 software.The data was extracted,and the methodological quality was evaluated by two reviewers independently with weighted mean difierence(WMD)for the effectiveness analysis and odds ratio(OR)for counting variable.The quality of included literature was scored according to the Jadad Scale. Results A total of 8 studies involving 251 patients(502 eyes)were included in the meta-analysis.Of these eight studies.five studies were randomized clinical trials and the other three studies were retrospective cohort studies.Compared with on-flap Epi-LASIK group,off-flap Epi-LASIK group had a better postoperative outcome in the mean reepithelization time(WMD=1.32,95％CI-1.82to-0.82,P<0.01)and pain scores at 3,5 day(WMD=-O.99,95％CI-1.71 to-0.28,P(0.01)(WMD=-0.94.95％CI-1.35 to-0.54,P<0.01)after surgery.No significant difierenees were found in the eye numbers of haze at 1 month(OR=0.62,95％C1 0.34 to 1.12,P=0.11),3 months(OR=0.70,95％C1 0.31 to 1.55,P=0.38)and 6 months(OR=1.14,95％C1 0.58 to 2.26,P=0.71)between these two types of operation.The pain scores at the first day after surgery was not significantly different between these two groups(WMD=-0.17,95％CI -0.55 to 0.20,P=0.37). Conclusion The effectiveness of off-flap Epi-LASIK is superior to on-flap Epi-LASIK for myopia.Some high-quality randomlizd and control studies are needed for the further clinical evaluation.

Factors Associated with Incomplete Cleavage of the Corneal Epithelium in Alcohol-Assisted LASEK

PURPOSE: To evaluate the factors associated with unsuccessful cleavage of corneal epithelium in alcohol-assisted LASEK. METHODS: A total of 274 eyes in 137 patients who had received alcohol-assisted LASEK were enrolled in the present study. Associations of central corneal thickness, refractive error, pre-operative corneal curvature, ablation depth, anterior chamber volume and depth, and history of wearing contact lenses with epithelial cleavage were investigated. RESULTS: Complete epithelial cleavage was achieved in 198 eyes (72.3%) and incomplete epithelial cleavage in 76 eyes (27.7%). A history of wearing contact lenses (p = 0.018), continuous use of contact lenses (p = 0.034), longer use of contact lenses (p = 0.000), anterior chamber volume (p = 0.012) and depth (p = 0.012) were significantly associated with incomplete epithelial cleavage. CONCLUSIONS: Alcohol-assisted LASEK may cause problems in patients who experience continuous use of contact lenses and longer use of contact lenses. Patients with incomplete epithelial cleavage have small anterior chamber volume and shallow anterior chamber depth.

Postoperative Pain and Epithelial Wound Healing in Epi-LASIK With and Without an Epithelial Sheet Preservation

PURPOSE: To investigate the influence of preservation of an epithelial sheet in Epi-LASIK on postoperative pain and epithelial wound healing time. METHODS: This prospective study included 34 eyes of 17 patients with myopia who received Epi-LASIK. An epithelial flap was created using the epikeratome (Centurion SES, Norwood Abbey EyeCare, Australia). After the stroma was ablated using the MEL 80 (Carl Zeiss Meditec. Germany) excimer laser, the epithelial sheet was replaced on the stromal bed in one randomly selected eye of each patient, and removed in the contralateral eye. The pain scores at postoperative day 0, 1, 2, 5 and the numbers of days for the complete epithelial wound healing were compared between the sheet-preserved and the sheet-removed eyes. At 1 month postoperative, uncorrected visual acuity (UCVA), refractive error and corneal haze were also compared. RESULTS: Pain scores on the day of operation were lower in sheet-preserved group and statistically significant (p=0.01). On postoperative day 1, 2, and 5, pain scores did not reach statistical significance (p=0.24, 0.08, 0.56, respectively). The mean epithelial healing time was 4.88+/-0.93 days for the flap-preserved eyes and 4.29+/-0.77 days for the flap-removed eyes, which showed statistical significance (p=0.01). No significant difference was noted between the 2 groups for mean UCVA, corneal haze and refractive error at 1 month postoperative. CONCLUSIONS: A preserved epithelial sheet reduced early postoperative pain but did not accelerate epithelial wound-healing rate.

Comparison of Corneal Haze according to the Success of Corneal Epithelial Flap after Laser Subepithelial Keratomileusis

PURPOSE: This present study aims at comparing the degree of corneal opacity after LASEK according to the status of corneal epithelial flap in myopia of low, moderate and high myopic patients. METHODS: In this study, 75 eyes of 39 patients treated with LASEK were examined during three months. We subdivided into three groups which were high myopia(>or=-6 diopter), moderate myopia(>or=-3 diopter, <-6 diopter), and low myopia(<-3 diopter) group. The corneal epithelial flap was classified into good, moderate, and poor flap according to the state after repositioning epithelium, also the corneal opacity was described by Fantes classification and measured at post-LASEK one, three day, one week, one month, and three months. RESULTS: The 10 eyes of 12 eyes with poor corneal flap had corneal opacity of grade 1 and over at 1 month. The corneal opacity of four eyes among them improved less than trace at 3 months. The degree of corneal opacity by corneal epithelial flap had a significant difference in low and moderate myopic groups at first month after the surgery. The more the myopic degree was, the more the degree of corneal opacity was. CONCLUSIONS: The degree of corneal opacity was affected by the status of corneal epithelial flap. Therefore, careful managements of epithelial flap were needed during LASEK.

Studies of Laser Subepithelial Keratomileusis (LASEK) using Leghorn Chick Eye

PURPOSE: Using the effect of 20% ethanol on Leghorn chick cornea, a suitable animal model for LASEK(Laser subepithelial keratomileusis) and effect on LASEK were evaluated. METHODS: Twenty Chick corneas were divided into 4 groups (n=5/group) to be exposed to 20% ethanol for 30 sec, 45 sec, 1 minute and 2 minutes respectively and changes were observed. Another 4 groups of Chick cornea, total of 20 (n=5/group) were prepared to perform nothing, PRK after mechanical or 20% ethanol-assisted debridement, or LASEK respectively and corneal changes were observed. RESULTS: Exposure of the corneal epithelium to 20% ethanol for more than 30 seconds allowed reproducible separation of epithelial flaps in Leghorn chick eyes. TUNEL staining of corneas obtained 4 hours after surgery revealed TUNEL-positive cells in the central superficial stroma and more abundantly in the peripheral superficial stroma around the epithelial flap margin and in the epithelial flap itself, particularly in the basal epithelial layer. Transmission electron microscopy showed similar evidence of apoptosis in the epithelium and anterior stroma. CONCLUSIONS: The Leghorn chick eye appears to be a reasonable model for LASEK surgery. Treatment with 20% ethanol for 30 seconds results in reproducible epithelial flap creation in the chick cornea and in relatively low levels of stromal and epithelial cell death after surgery.

Effect of Corneal Epithelial Flap on the corneal wound healing of canine eyes

PURPOSE: LASEK is a newly developed refractive surgery technique that can make up for the complications from PRK and LASIK. The most unique procedures in LASEK is covering of the cornea with epithelial flap after keratectomy. We examined the effect of corneal epithelial flap on the wound healing of canine cornea. METHODS: Operation was performed in eyes from 12 dogs, and the 12 eyes were recovered with epithelial flap and the remaining 12 eyes were recovered without epithelial flap. Wound healing process was compared using fluorescein staining, light and transmission electron microscopic examination. RESULTS: Fluorescein stained area of the cornea was reduced with time in both groups, and from 9 hours after the operation, it was significantly reduced in the group with epithelial flap compared with those of the group without epithelial flap (p< 0.05). On light microscopic examination of the group with epithelial flap, and normal epithelial structure was found at 24 and 48 hours, respectively. However, in the group without epithelial flap, no complete reepithelialization had occurred on center at 48 hours after the operation. On transmission electron microscopic examination, eyes of the group with epithelial flap showed hemidesmosomes in the area where epithelial flap was closely contacted with the stroma at 24 hours, and they were completely developed at 48 hours. On the other hand, in the group without epithelial flap, hemidesmosomes developed only in the proximal portion but not at the leading edge even at 48 hours. CONCLUSIONS: These results suggest that corneal epithelial flap accelerate the wound healing process of the cornea and the wound healing process depend on the vitality of the epithelial flap.