<qa>  What is the safety thickness for the residual stroma?- 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 andor intraocular surgeries, and autoimmune andor 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. 