Before corneal refractive surgery such as LASIK, SMILE, and PRK, people must be examined for possible risk factors such as keratoconus.
Abnormal corneal topography compromises of keratoconus, pellucid marginal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more is the most significant risk factor. Low age, low residual stromal bed (RSB) thickness, low preoperative corneal thickness, and high myopia are other important risk factors.
Treatment options include contact lenses, intrastromal corneal ring segments, custom topography-guided transepithelial PRK combined with corneal collagen cross-linking, or corneal transplant.
When cross-linking is performed only after the cornea becomes distorted, vision remains blurry even though the disease is stabilised. As a result, combining corneal collagen cross-linking with LASIK ('LASIK Xtra') aims to strengthen the cornea at the point of surgery and may be useful in cases where a very thin cornea is expected after the LASIK procedure. This would include cases of high spectacle power and people with thin corneas before surgery. Definitive evidence that the procedure can reduce the risk of corneal ectasia will only become available a number of years later as corneal ectasia, if it happens, usually occurs in the late post-operative period. Some study show that combining LASIK with cross-linking adds refractive stability to hyperopic treatments and may also do the same for very high myopic treatments.
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- Stephenson, Michelle (2014). "LASIK Xtra: Is It for Everyone?". Review of Ophthalmology. Jobson Medical Information LLC.
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- "Highlights of Prescribing Information: PHOTREXA VISCOUS (riboflavin 5'-phosphate in 20% dextran ophthalmic solution) 0.146% for topical ophthalmic use PHOTREXA (riboflavin 5'-phosphate ophthalmic solution) 0.146% for topical ophthalmic use For use with the KXL® System" (PDF). U.S. Food and Drug Administration. pp. 5–14.