Comparative Analysis of the Visual Performance After TICL Implantation in Patients With Stable Keratoconus

Inclusion Criteria: * age (25-38). * Stable refraction was distinctive by 6 subjective refractions within ± 0.50 diopters(D) of spherical equivalent during 6 months after CXL. * best spectacle-corrected visual acuity (BCVA) of +0.4 LogMAR (20/40) or better, -clear central cornea. * normal anterior chamber depth at least 3 mm to endothelium . * intraocular pressure (IOP)\<20 mm Hg and preoperative endothelial cell count related to age and the anterior chamber depth with regard to Food and Drug Administration recommendations. * Width of Angle greater than 30°, a pupil diameter of less than 6.25 mm. Exclusion Criteria: * Patients with central corneal thickness of less than 450 μm. * endothelial cell count of less than 2,000 cells/mm2 . * anterior chamber depth of \<3 mm from endothelium to anterior capsule . * Corneal opacification or scars, cataract, retinal detachment, glaucoma, retinopathy, macular degeneration, neuro ophthalmic diseases or ocular inflammation, history of keratitis (any form), peripheral marginal degeneration, previous corneal and/or intraocular surgeries, and autoimmune and/or connective tissue disease. The central corneal thickness limit of 450 μm would account for around 400 μm of remaining stromal thickness after removal of the epithelium, which is considered as the safety thickness for the residual stroma to avoid endothelial cell damage during the CXL procedure.