AIM: To compare the effect of iris location guided sub-bowman keratomileusis(SBK)and iris location guided thin-flap laser in situ keratomileusis(LASIK)for extremely high myopia treatment.

METHODS:Iris location guided SBK was performed in 64 eyes of 32 patients with extremely high myopia and 42 eyes of 84 patients were received iris location guided thin-flap LASIK. All the patients' spherical refraction was -9.00D～-11.00D and the age was 22～35 years. Uncorrected visual acuity(UCVA), refraction, split-lamp examination, topography examination, central corneal stroma thickness, thickness of central corneal flap, thickness of peripheral corneal flap and complication was examined in these patients and follow-up was 6mo.

RESULTS: At 6mo after surgery, 93.8% of the patients received iris location guided SBK and 92.9% received iris location guided thin-flap LASIK achieved a UCVA better than 20/20. There was no significant difference between two groups. Refraction between ±0.5D was 89.1% of SBK group and 84.5% of LASIK group. There was no significant difference. Corneal rear surface height of SBK was 0.046±0.012μm and LASIK was 0.056±0.015μm. Thickness of corneal stroma after surgery was 328.6±14.7μm in SBK group, while it was 301.2±21.6μm in LASIK group and there was significant difference(t=3.127, P=0.001). BUT was 11.38±4.02s and 17.81±4.89s in SBK and LASIK group respectively, with no statistical difference. There was no serious complication in two groups.

CONCLUTION: Both iris location guided SBK and thin-flap LASIK are effective for extremely high myopia, but SBK is safer and more predictive than thin-flap LASIK.