Prevention And Management Of Corneal Ectasia After Lasik- Case Report

To display the fundamentals in preoperative examination of patients undergoing refractive corneal procedures and to assess the results of crosslinking after post-LASIK-ectasia. Although some patients may develop ectatic disorders without any corneal procedures, prevention is the best treatment and a thorough preoperative assessment is imperative. Corneal ectasia is a rare complication after corneal refractive surgery- 0.04% up to 0.6% of procedures- LASIK, PRK and SMILE. Post-LASIK ectasia includes increasing myopic astigmatism, loss of UVA and BCVA, with corneal steepening, posterior corneal elevation, with or without central/paracentral corneal thinning, and topographic evidence of asymmetric inferior corneal steepening.

96% of cases of ectasia appear to be as a result of LASIK- the creation of a stromal flap leads to a loss of biomechanical integrity, subsequent thinning and steepening of the tissue. Cases of ectasia after SMILE have also been reported. Ectasia Risk Score System (Randleman and colleagues) and Percent Tissue Altered (PTA) formula are complimentary in preoperative assessment. PTA over 40% was the most significant variable associated with post-LASIK-ectasia in eyes with normal looking corneas. 

A case report of patient who developed post-LASIK- ectasia in his left eye. After a full eye examination and corneal tomography (Pentacam), the patient was treated with crosslinking using the Dresden protocol with consequent follow-up of 5 years. Preoperative assessment includes full eye examination with cycloplegic refraction, corneal tomography, OCT, optical biometry, ocular and corneal aberrometry, corneal epithelium mapping. Crosslinking may be used postoperatively to halten the progression of ectasia and to stabilize irregular corneas. Its importance is unmeasurable because otherwise the last solution for a postoperative ectasia is only corneal transplant.

A 41-year old male underwent LASIK in 2016 for -3.0 dpt myopia (another clinic). He complained of decreased VA in his LE two years after LASIK. BCVA was 0.9-1.0 with +1.00DS/-1.0DCx30* in the RE and in the LE was 0.5 with +1.25DS/-1.25DCx125*. Corneal tomography revealed corneal ectasia in his left eye with inferior steepening, Inferior-Superior assimmetry of over 11D, back elevation +49 and maximal keratometry reading (Kmax) of 48.2D. RE showed assymetry in posterior elevation only. LE was treated with crosslinking, using standard Dresden protocol (30 min riboflavin with methylcellulose soak followed by 3mW/cm² irradiation/30 min). 5 years later, a comparative exam revealed  2.0 dpt decrease in Kmax and stabilization of the cornea.

Front elevation/axial map is not enough for accurate distinction of mild keratoconus or forma frusta. The Ectasia Risk Score System (Randleman and colleagues) may help to identify high-risk patients preoperatively. Diagnostic methods of screening for preoperative ectasia have changed dramatically over the past 10 years, and now include possibly more sensitive techniques of corneal 'tomography' (Pentacam, Orbscan, Gallei) which can measure posterior corneal curvature rather than placido-disc based 'topography' which only measure anterior corneal curvatures (AAO). Adding the Percent Tissue Altered Formula (PTA) to the preoperative protocol will increase the chance of identifying patients with normal tomography who have high risk of ectasia.