Effect of laser in situ keratomileusis on Q value of anterior and posterior corneal surface and its relation with myopia

Objective To study the effect of laser in situ keratomileusis（LASIK） on Q values of anterior and posterior corneal surface and its relation with myopia. Methods Ninety-six patients（192 eyes） undergone LASIK in June-September 2009 were divided into low myopia group and high myopia group according to their diopter.Pentacam was performed to detect the Q₂₀,Q₂₅,Q₃₀ and Q₃₅ values of the anterior and posterior corneal surface before and 1 week after LASIK. Results No difference was observed in Q₂₀,Q₂₅,Q₃₀ and Q₃₅ values of the anterior and posterior corneal surface between low and high myopia groups before operation.The Q₂₀,Q₂₅,Q₃₀ and Q₃₅ values of the anterior and posterior corneal surface were significantly changed after operation.The diopter was related with ΔQ₂₀（r=0.29,P=0.004）,ΔQ₂₅（r=0.30,P=0.003）,ΔQ₃₀（r=0.31,P=0.002） and ΔQ₃₅（r=0.23,P=0.021） of anterior corneal surface but not with ΔQ of the posterior corneal surface（r=-0.115,-0.12,-0.135,-0.152,P＞0.05） in low and high myopia groups. Conclusion The Q₂₀,Q₂₅,Q₃₀ and Q₃₅ values of the anterior and posterior corneal surface will change after LASIK.The Q values of anterior corneal surface are related with equivalent diopter.