Part Clinical And Experimental Study For Moderate And High Myopia Therapy By LASIK And LASEK

Purpose: To observe and analyze the effect of LASIK and LASEK for the correction ofmoderate to high myopia. To investigate the clinical effect of amniotic membrane overlay for theepithelial-flap abnormality of LASEK and evaluate the safety and the histopathologicalcharacteristics of creating the cornea epithelial-flap with different chemistry tries.Methods: 1. 332 eyes of 176 myopia patients were performed by LASIK and LASEK on theophthalmology center in our hospital from 2005.03-2006.03 and were followed up for 12 months.Collect the datas before,in and after operation, establish the database and analyze themstastically. 2. Select 40 eyes of 20 myopia patients with the epithelial-flap abnormality ofLASEK from 2005.03-2006.03 and randomly divide them into two groups. The therapy wasgiven amniotic membrane(AM)+soft contact lens and the control was given soft contact lenspostoperatively. They were followed up for 12 months with one-blind method. Collect the datasand analyze them stasticaUy. 3. The corneas of healthy roosters were exposed by differentchemistry tries and different time and the epithelium flaps of corneas were created. The completecorneas with the epithelial flaps were cut off for histopathological eximination. Themorphological changes of cornea epithelial cells and the integrity between basement membraneand Bowman's membrane were observed under light microscopy.Results: 1. On the aspect of moderate and high myopia therapy:①there were 3 incompletecornea flaps during the operation of LASIK and were performed again by LASIK after 3 months;there were 15 incomplete cornea epithelial-flaps during the operation of LASEK and they weredirectly changeovered PRK.②The reepitheliation time was shorter in LASIK(24.13±2.41)hthan in LASEK(72.70±6.94)h(P＜0.05). LASIK is stastically superior to LASEK in BCVA andresidual diopter(P＜0.05).③there were stastical differences postoperatively between LASIKand LASEK on corneal stimulating symptom in 2 days, haze in 6 months and corneal topographyin 12 months(P＜0.05).④there were no stastical differences in two groups betweenpreoperation and postoperation of 12 months on intraocular pressure and central corneathickness(P＞0.05).2. On the aspect of LASEK with the epithelial-flap abnormality therapy:①The reepitheliationtime was shorter in AM(2.31±0.71)d than in the control(3.17±0.84)h(P＜0.05). AM is stasticallysuperior to the control in BCVA,haze and residual diopter(P＜0.05).②AM is stastically superior to the control in corneal stimulating symptom in 3 days(P＜0.05) while it is on thecontrary in the fourth day(P＜0.05).③there were no stastical differences in two groups betweenpreoperation and postoperation of 12 months on corneal topography,intraocular pressure andcentral cornea thickness(P＞0.05).3. On the aspect of histopathology:①when exposed to the centrations of 15% ethanol for 20sand 25s, there was an incomplete separation between basement membrane and Bowman'smembrane.②when exposed to the concentrations of 20% ethanol for 20s and 25s, there was acomplete separation between basement membrane and Bowman's membrane and slight edema inthe superficial epithelium and basal cells.③when exposed to the concentrations of 25% ethanolfor 20s and 25s, there was a complete separation between basement membrane and Bowman'smembrane and the superficial epithelium layer partly broke with obvious edema, the basal cellswith obvious edema lined up intidily.④when exposed to the concentrations of 0.5% Alcaine and0.4% Oxybuprocain for 30s and 40s, there was a complete separation between basementmembrane and Bowman's membrane, when 30s, the superficial epithelium remain intact and thevolume of basal cells was enlarged slightly, when 40s, the basal cells with obvious edema linedup intidily and the connections became loose.Conclusions: 1. LASIK is superior to LASEK in reepitheliation time,corneal stimulatingsymptom,BCVA,haze and residual diopter postoperatively in short time and there was noobvious difference after 6 months. The corneal topography is more regular in LASEK than inLASIK and in high myopia mitomycin C with LASEK can degrade the incidence rate of hazeand relieve the degree of haze. when the incomplete flaps occurred during the operation, LASEKwas directly performed by PRK inⅠstage while LASIK must be performed inⅡstage.2. AM is superior to the control in reepitheliation time,corneal stimulating symptom,BCVA,haze and residual diopter postoperatively in short time and there was no obvious difference after3 months. AM is removed necessarily from the eye in the 3rd day.3. when exposed to the concentrations of 0.5% Alcaine and 0.4% Oxybuprocain for 30s, theepithelium flaps have complete organize structure and better cellular morphous relatively. 0.5%Alcaine or 0.4% Oxybuprocain are a selective and better chemistry try for creating theepithelium flaps in LASEK.