Experimental study of cornea reparation after epipolis laser in situ keratomileusis

Background The cornea healing process after epipolis laser in situ keratomileusis (Epi-LASIK) was unknown.There is no convincing support in histopathology after Epi-LASIK.Objective This study was to observe the cornea healing process after Epi-LASIK.Methods Myopia Epi-LASIK animal models were established in lateral eyes of 57 rabbit eyes,and photorefractive keratectomy (PRK) was performed in fellow eyes.Other 6 eyes of 3 normal rabbits were used as normal control group.The epithelial flap specimens were obtained during the surgery and stained with trypan blue and alizarin red to evaluate corneal epithelial cell viability under the light microscopy.Corneal epithelial thickness was measured and the anterior keratocytes were calculated by hemotoxylin and eosin staining.Haze was observed with slit-lamp examination and graded on the Hanna criteria.Results The healing time of corneal epithelium was (4.67±0.41) days after Epi-LASIK and (2.75±0.27) days after PRK,showing a significant difference (t=9.550,P=0.000).The epithelial cell viability ratio immediately after surgery was (85.83±2.07)% and that in 3 days and 5 days was (48.67±3.41)% and (91.33±3.10)% respectively,showing a significant increase (F=215.060,P=0.000).The score of corneal haze after PRK was higher than that of Epi-LASIK (Z=2.27,P=0.02).The corneal epithelial thickness value was highest in 1 month after Epi-LASIK and gradually declined in 3 months and then closed to normal value till 6 months postoperatively.After PRK,the epithelial thickness increased from 1 month through 6 months postoperatively.Statistically significant differences were found in corneal epithelial thickness between these two operative fashions from 1 month through 6 months (q=6.14,q=5.74,q=14.052,q=6.08,P0.05).The anterior keratocyte density was highest after Epi-LASIK in 1 month and declined in 3 months and returned to normal till 6 months postoperatively,showing considerably differences in comparison with PRK (q=56.00,q=83.50,q=58.67,P0.05).Conclusion The epithelial cell viability decline gradually after Epi-LASIK with a slow repair process.Damage of corneal epithelium is mild and repairing process of keratocytes is faster after Epi-LASIK than PRK.