Post-LASIK ectasia is a condition similar to keratoconus where the cornea starts to bulge forwards at a variable time after LASIK, PRK, or SMILE corneal laser eye surgery.[1] However, the physiological processes of post-LASIK ectasia seem to be different from keratoconus. The visible changes in the basal epithelial cell and anterior and posterior keratocytes linked with keratoconus were not observed in post-LASIK ectasia.[2]

Risk factors

Before corneal refractive surgery such as LASIK, SMILE, and PRK, people must be examined for possible risk factors such as keratoconus.[3]

Abnormal corneal topography compromises of keratoconus, pellucid marginal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more[4] 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.[5][6]

Treatments

Treatment options include contact lenses,[7][8] intrastromal corneal ring segments, custom topography-guided transepithelial PRK combined with corneal collagen cross-linking,[9] 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.[10] 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.[10][11][12]

In 2016, the FDA approved the KXL system and two photoenhancers for the treatment of corneal ectasia following refractive surgery.[13]

References

  1. ^ "Ectasia After LASIK". American Academy of Ophthalmology.
  2. ^ "What Is Keratoconus? Everything You Need to Know". Clearview Vision Institute. 15 December 2020. Retrieved 15 December 2020.
  3. ^ Finn, Peter (20 December 2012). "Medical Mystery: Preparation for surgery revealed cause of deteriorating eyesight". The Washington Post.
  4. ^ Rabinowitz, YS; McDonnell, PJ (1989). "Computer-assisted corneal topography in keratoconus". Refractive & Corneal Surgery. 5 (6): 400–8. doi:10.3928/1081-597X-19891101-10. PMID 2488838.
  5. ^ Kohlhaas, M; Spoerl, E; Schilde, T; Unger, G; Wittig, C; Pillunat, LE (February 2006). "Biomechanical evidence of the distribution of cross-links in corneas treated with riboflavin and ultraviolet A light". Journal of Cataract and Refractive Surgery. 32 (2): 279–83. doi:10.1016/j.jcrs.2005.12.092. PMID 16565005. S2CID 30983601.
  6. ^ Randleman, JB; Banning, CS; Stulting, RD (January 2007). "Corneal ectasia after hyperopic LASIK". Journal of Refractive Surgery. 23 (1): 98–102. doi:10.3928/1081-597X-20070101-17. PMID 17269252.
  7. ^ Marsack, Jason D.; Parker, Katrina E.; Applegate, Raymond A. (December 2008). "Performance of Wavefront-Guided Soft Lenses in Three Keratoconus Subjects". Optometry and Vision Science. 85 (12): E1172–E1178. doi:10.1097/OPX.0b013e31818e8eaa. PMC 2614306. PMID 19050464.
  8. ^ Marsack, JD; Parker, KE; Niu, Y; Pesudovs, K; Applegate, RA (November 2007). "On-eye performance of custom wavefront-guided soft contact lenses in a habitual soft lens-wearing keratoconic patient". Journal of Refractive Surgery. 23 (9): 960–4. doi:10.3928/1081-597X-20071101-18. PMID 18041254.
  9. ^ Lam, Kay; Rootman, Dan B.; Lichtinger, Alejandro; Rootman, David S. (6 January 2013). "Post-LASIK ectasia treated with intrastromal corneal ring segments and corneal crosslinking". Digital Journal of Ophthalmology. 19 (1): 1–8. doi:10.5693/djo.02.2012.10.001. ISSN 1542-8958. PMC 3689440. PMID 23794955.
  10. ^ a b Stephenson, Michelle (2014). "LASIK Xtra: Is It for Everyone?". Review of Ophthalmology. Jobson Medical Information LLC.
  11. ^ Kanellopoulos, AnastasiosJohn; Pamel, GregoryJ (2013). "Review of current indications for combined very high fluence collagen cross-linking and laser in situ keratomileusis surgery". Indian Journal of Ophthalmology. 61 (8): 430–2. doi:10.4103/0301-4738.116074. PMC 3775081. PMID 23925331.
  12. ^ LASIK Treatment
  13. ^ "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.
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