Evaluation of corneal endothelium cell density pre and post Lasik with accelerated cross-linking

Background: Myopia is a common refractive error all over the world. Many methods can 
be used for correction of myopia. LASIK has become one of the most popular procedures 
for the reduction or elimination of myopic refractive errors and has emerged as the 
refractive corneal surgical procedure of choice for the correction of myopia, in correcting 
moderate to high myopia (equal or more than -6.00 D in the least-minus meridian). 
Significant long-term regression and Post LASIK ectasia was the motivation behind 
attempting to apply prophylactic in situ corneal collagen cross-linking (CXL) on the 
stromal bed, concurrently with the LASIK procedure, particularly in high-myopic eyes with 
thin residual stroma and in younger patients who may not yet have exhibited ectasia risk 
factors. Corneal endothelium is a mono layer of the cornea that maintains corneal 
deturgescence and transparency through regulating fluid and solute transport between the 
aqueous and corneal stroma. Endothelial cell analysis is one of the methods that is used to 
assess the health of the cornea, especially after surgical intervention and is also one of the 
major criteria that are used to assess the long-term outcomes of any corneal surgery. The 
aim of the study is to assess the safety of CXL on the corneal endothelium density by 
endothelial specular microscopy before and after the procedure. Patients and methods:
This prospective study was included 30 myopic patients (7 male and 23 female, 60 eyes) 
with range of age from 18 to 35 years. Patients were divided into two groups, Group A 
Included 30 eyes of 15 patients, treated by LASIK, Group B Included 30 eyes of 15 
patients, treated by LASIK associated with accelerated CXL. Results: Qualitative and 
quantitative analysis of the corneal endothelial cells comparing the two groups showed a 
statistically significant changes in ECD (P=0.040) 3 months follow up after the procedure 
which improved to reach a value close to preoperative values with no significant changes 
between the two groups at 6 months follow up (P=0.081), there were no significant changes 
in evaluating CV (polymegathism) and percentage of hexagonal cells (pleomorphism) in 
each group and in comparing between the two groups 3 and 6 months after follow up.
Conclusion: Specular microscopy is a non-invasive fast technique for evaluation of corneal 
endothelium Lasik with accelerated CXL is a new, innovative procedure, aimed at reducing 
some of the challenges associated with LASIK (weaker corneas, and regression of the 
refraction over time). This study revealed that LASIK with accelerated CXL (30 mW/cm2
for 90 seconds) is safe and has no toxic effect on corneal endothelium.