Wallerstein A, Gauvin M, Rocha G, Sison S,  Korban S, Cohen M. J Refract Surg. 2022. Accepted. The article link will be posted shortly.

Purpose: This study investigates the 36-month safety and clinical outcomes of under-flap stromal bed CXL (ufCXL) and reports on its ability to stabilize post LASIK ectasia.

Methods: Case series of 20 eyes with diagnosed early PLE treated with ufCXL. Inclusion criteria were early, mild PLE defined as new onset postoperative manifest refraction cylinder ≤ 1.50 D, with new topographic inferior steepening consistent with ectasia, UDVA of 20/40 or better, and CDVA of 20/25 or better. The existing LASIK flap was lifted, 0.25% isotonic riboflavin was applied directly to the stromal bed, flap was repositioned, and 18 mW/cm 2 UV light was applied for 5 minutes to the corneal flap surface. Post-ufCXL ophthalmic data were compared to pre-ufCXL baseline measurements.

Results: Visual outcomes were maintained from pre-ufCXL to 36 months post-ufCXL, with preserved safety index (P = 0.6545), efficacy index (P = 0.4980), spherical equivalent accuracy (P = 0.1536), defocus equivalent accuracy (P = 0.1032), central corneal thickness (P = 0.5196) and corneal irregularity indices at 3 mm (P = 0.8548) and 5 mm (P = 0.3399). Refractive astigmatism significantly decreased from 0.83 D pre-ufCXL to 0.55 D post-ufCXL (P = 0.0439). Maximal keratometry decreased from 42.4 D pre-ufCXL to 42.0 D post-ufCXL (P = 0.0238). CXL demarcation line depth was 336 ± 21 μm post-ufCXL, with normal endothelial cell density (2574 ± 203 cells/mm2)

Conclusions: Under-flap CXL is safe, stabilizing early post-LASIK ectasia. Visual function, refractive astigmatism, and maximal keratometry were maintained, with no evidence of progression at 36 months post-ufCXL.