Predictability of the corneal flap creation with the femtosecond laser in LASIK

Objective To observe the predictability of corneal flap creation with the FEMTO LDV femtosecond laser and analyze preliminarily the factors correlating to the thickness and diameter of the flap.Methods It was a study of serial cases.260 eyes of 130 consecutive patients were treated with the FEMTO LDV.The eyes were assigned to two groups according to intended flap thickness,110 μm (208eyes) and 90μm (52 eyes).Intended flap diameter varied from 8.5 to 9.5 mm.Difference analysis of flap diameter and intended diameter as well as flap thickness and intended thickness were made.The data was analyzed with SPSS to sum up a multiple stepwise regression formula that could express their quantitative relationship.Results The 90 μm flap group had a average flap thickness of (95.12 ±7.65)μm,while for the 110 μm group the average flap thickness was (104.81 ±t 3.09 )μm.The difference between right and left eyes was not statistically significant ( t110 μm =- 1.223,t90 μm =- 1.343,P ＞ 0.05 ).Corneal flap thickness was inversely correlated with flap diameter ( r110 μm =- 0.143,r90μm =- 0.315,P ＜ 0.05 ),but was not related to preoperative patient age,corneal thickness,keratometric value K or intraocular pressure (r110μm =-0.160,0.054,-0.011,-0.363; r90:=0.024,0.074,-0.212,-0.434,all P＞0.05).Corneal flap diameter was positively correlated with preoperative corneal keratometric value K and thickness ( P ＜0.001,P ＜0.05).Multiple stepwise regression analysis showed flap diameter was an influencing factor for flap thickness.Preoperative corneal keratometric value K and thickness were influencing factors for flap diameter. Conclusions The LASIK flap creation with the FEMTO LDV laser has relatively good predictability.Flap diameter is an influencing factor for flap thickness. Key words: Lasers;  Surgical flaps;  Keratomileusis,laser in situ