Abstract
Purpose: :
To determine if differences in epithelial flap vitality after Epi–LASIK (EL) and LASEK (LA) would differentially influence post operative stromal cellular proliferation
Methods: :
Flap vitality after EL or LA (20% alcohol) without stromal ablation was determined using fresh pig eyes and propidium iodide vitality staining. Control flaps were exposed to 100% alcohol. Secondly, human corneas in organ culture had EL (n=7) or LA (n=7) with a –6.0D 6mm stromal correction. Uninjured corneas and the 100% alcohol flap plus ablation were used as controls. Corneas were kept alive for 1 week and then stained for stromal cellular proliferation with Ki67. Images were captured by confocal microscopy and analysed by a blinded observer.
Results: :
Percentage dead cells after EL,LA and 100% alcohol were 1.3, 12.3 and 100% of the flap population (p<0.0001). Mean anterior stromal percentage keratocyte proliferation was 42%(sd 22.5)EL, 15% (sd 16.7)AL, 10% (sd 7) 100% alcohol and 5% (sd 9.1) uninjured (p<0.0001 one way anova).
Conclusions: :
In–vitro, epithelial flap vitality is greatest following EL. However there is significantly greater anterior stromal cell proliferation following EL compared with LA versus controls. This may represent increased epithelio–stromal stimulus from the more vital flap following EL. A less vital or dead flap may be favourable clinically in terms of haze. Clinical results following EL are eagerly anticipated and may corroborate these in–vitro observations.
Keywords: cornea: stroma and keratocytes • cornea: basic science • refractive surgery