Influence Of Cap Thickness On Corneal Densitometry After SMILE

Purpose: To investigate the impact of cap thickness on corneal densitometry for small incision lenticule extraction(SMILE).Methods: This prospective,randomized controlled study was conducted with 35 patients(70 eyes)who underwent binocular SMILE surgery between November 2019 and June 2021.Corneal cap thickness was randomly designed to be 110 μm in one eye and 140 μm in the other.Pentacam HR(Oculus Optikger(?)te,Wetzlar,Germany)was used for corneal densitometry(CD)analysis preoperatively and at 1 day,1 week,1month,and 3 months postoperatively.CD was evaluated in four corneal layers i.e.,the anterior layer,central layer(CL),posterior layer,and total layer for four different annuli(0–2 mm,2–6 mm,6–10 mm,and total 0–12mm).The CD values were recorded in standardized grayscale units.Results: At 1 week post-operation,the CD values in the four different annuli of the CL were significantly higher in the 140 μm group than in the110 μm group(P < 0.001,< 0.001,0.006,< 0.001,respectively).In the 110μm group,the changes in CD values for 0-2 mm and 2-6 mm in the CL were significantly less than those in the 140 μm group at 1 day(P =0.009,0.005)and 1 week(P = 0.002,0.006)post-operation.Conclusions: In the early postoperative period after SMILE,the CD value of the thicker corneal cap was higher and changed more in the CL.