Some injury or surgery might leave people with corneal scarring. Normally cornea is transparent and clear and it protects soft eyes from damages from UV radiations, wind and dusts. It is transparent to let light travel through and focus on the retina. Once cornea scar formed, the cornea becomes opaque and cloudy that light can't travel through, leading to vision loss. Once corneal scar finally formed, lasik surgery can't fix the problem, but corneal transplant needed. Lasik surgery is a refractive surgery to correct vision problem such as myopia, hyperopia and astigmatism. Corneal transplant surgery will remove the scarring part of corneal with a healthy one from a donor. If you are diagnosed as corneal scarring, you should visit your oculist at the earliest to lessen the damages.
If you have the corneal scar, you need to ask the doctor whether you could accept the lasik surgery by asking whether the position will affect the surgery. Usually there are a lot of exams before you do the lasik surgery. You just need to follow the doctor's requirements. You should protect the eyes carefully which are the important parts of the whole body.