Noor Shazana Md Rejab
Muhammad Emy Iekmal Bin Yusof
Mohd Radzi Hilmi
Khairidzan Mohd Kamal

Abstract Background: Flap creation during laser refractive surgery restructures the anterior cornea, particularly the stroma, reducing the keratocyte cell density (KCD). This reduced density makes it challenging to completely regenerate to the presurgical phase. The aim of the present study was to investigate the effects of two types of artificial tear (AT) interventions on KCD up to ۳ months after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery. Methods: This prospective, double-blind, comparative, interventional, contralateral eye study recruited patients with myopia scheduled for FS-LASIK. Inclusion criteria were healthy individuals aged ۱۹ – ۲۵ years with moderate or high myopia, a maximum cylindrical error of - ۱.۲۵ diopters, and a maximum pupil size of ۶.۵ mm who had undergone FS-LASIK and completed ۳ months of follow-up. Complete optometric and ophthalmologic examinations were performed. Bilateral simultaneous FS-LASIK surgery was performed using the same femtosecond laser platform as in the standard procedure. The Research Randomizer was used to determine the eye to be treated with Systane® Hydration (Alcon Laboratories, Inc., Fort Worth, TX, USA) or Systane® ULTRA (Alcon Laboratories, Inc., Fort Worth, TX, USA) AT. KCD was examined using real-time images obtained from in vivo confocal microscopy (Heidelberg Retina Tomograph ۳ with the Rostock Cornea Module, HRT III RCM); Heidelberg Engineering GmbH, Heidelberg, Germany) at baseline and ۱- and ۳-month postoperative visits. Results: We included ۶۰ eyes of ۳۰ participants with a mean (standard deviation) age of ۲۱.۳۴ (۱.۸۵) years and a male-to-female ratio of ۱:۱ who completed ۳-month post-FS-LASIK surgery follow-up. KCD did not differ significantly between the two groups at any visit (all P > ۰.۰۵); nevertheless, mean KCD was initially reduced up to ۱ month postoperatively and then revealed a slight increase up to ۳ months postoperatively in Systane® Hydration-treated eyes and continued to reduce in Systane® ULTRA-treated eyes. Intragroup comparisons revealed that the eyes treated with ATs experienced a significant reduction in KCD between the preoperative and ۱-month postoperative visits and between the preoperative and ۳-month postoperative visits (all P < ۰.۰۵). Treatment-related complications were not observed. Conclusions: Overall, KCD reduced up to ۳ months post-FS-LASIK surgery. Both AT types exerted a comparable effect on postoperative KCD up to ۳ months. Future studies with a more frequent administration of ATs, longer follow-up periods, and a control group are required before preliminary outcomes of the present study can be generalized. Keywords: artificial tear laser assisted stromal in situ keratomileusis LASIK corneal keratocyte cell density sodium hyaluronate