| Objective: This paper sought to study the treatment effects of excimer laser therapeutic keratectomy (PTK) on rabbit corneal shallow scar and the effects of different depth of ablation on rabbit corneal transparency, thickness and shapes of cornea. Methods: Depending on the depth of models created by controllable keratotome, 60 eyes of 30 rabbits were divided into three groups. 40 model eyes of corneal shallow scar in 2-3 mm diameters were prepared with mechanical method combined with acid burning method, and be detected by slit lamp microscopy ,corneal fluorescein vital staining (FLS) test, Intraocular pressure (IOP) measurement, corneal thickness (CT) measurement and corneal topography, etc. To compare and analyze the changes in FLS, IOP, CT, CIM and SF between the control group and experimental groups with PTK operation .Results:1. PTK: After PTK operation, 1 eye (5%) in the group with 100-um scar delayed in healing of corneal epithelium and 19 eyes were healed in 5 days. 23±9.8 days after PTK, 3 eyes (6%) appeared corneal nebula. 5 eyes (25%) in the group with 200-um scar delayed in healing of corneal epithelium, with an average of 8±6.4 days. 2 eyes (10%) after operation occurred with corneal nebula and 18 eyes (90%) corneal macula. 2 Intraocular pressure: After models creation, IOP in the group with 100-um scar and the group with 200-μm scar increased compared with the control group and the difference was of statistical significance (P <0.05). After operation, IOP in the group with 100-μm scar and the group with 200-μm scar were lower than that of pre operation and the difference had no statistical significance (P>0.05). In the group with 200-μm scar, there was statistically significant difference compared with that of pre operation (P<0.05). 3 Central corneal thicknesses: Pre and post models establishment, the differences in the group with 100-μm scar and the group with 200-μm scar were statistically significant (P<0.05). After PTK operation, corneal thickness in the group with 100-μm scar and the group with 200-μm scar decreased compared with that of pre operation. The corneal thickness in the group with 200-μm scar was thinner than that of the group with 100-μm scar, and the difference was statistically significant (P<0.05). However, there were no statistically significant differences between 4 weeks group and 8 weeks group after PTK operation (P>0.05). 4 Corneal curvatures: Corneal curvatures in the group with 100-μm scar and the group with 200-μm scar after model establishment increased compared with pre model establishment, and the difference was of statistical significance (P<0.05). Corneal curvatures in both groups post PTK operation decreased compared with that of pre operation and the differences were statistically significant (P<0.05). The corneal curvature in the group with 100-μm scar after operation trended to reduce, 4 weeks group and 8weeks group after PTK operation compared with the group with 200-μm scar, and the difference had no statistical significance (P > 0.05). 5 Corneal astigmatism: the corneal astigmatism in the group with 100-μm scar and the group with 200-μm scar post model creation, increased compared with that of pre model creation, and the differences were statistically significant (P<0.05). The corneal astigmatism after PTK operation in both groups decreased compared with that of pre operation, and the corneal astigmatism after operation in the group with 100-μm scar was smaller than that of the group with 200-μm scar, the difference in both groups statistically significant (P<0.05). The group with 100-um scar trended to reduce, 4 weeks group and 8 weeks group after PTK operation compared with the group with 200-μm scar, while the difference had no statistical significance (P>0.05). 6 Corneal irregular measurements: After models established, CIM in the group with 100-μm scar and the group with 200-μm scar was increased compared with that of pre model creation and the difference was statistically significant (P<0.05). CIM after PTK operation in both groups decreased compared pre operation and the difference was statistically significant (P<0.05). CIM in the group with 100-μm scar was smaller compared with the group with 200-μm scar and the difference was statistically significant (P<0.05). The difference in both groups,4 weeks group and 8 weeks group after operation, were statistically significant (P<0.05). 7 Corneal shape factors: SF value after model established in the group with 100-um scar and the group with 200-μm scar increased compared with that of pre model creation. SF after PTK operation in both groups was negative in value, and the difference was statistically significant compared with that of pre operation (P<0.05). The deviation after PTK operation of both 4 weeks group and 8 weeks group decreased, and tend to be normal and the difference was statistically significant (P<0.05). Conclusion: The creation of rabbit corneal scar model with mechanical method of controllable keratotome controlling the depth combined with 20% acid burning method is simple, feasible and stable. In PTK treatment, ablation depth should be controlled within the first 1/3 of corneal thickness, which has small impact on cornea and is safe and effective.
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