| Background and ObjectiveLaser in situ keratomileusis is currently mainstream refractive surgery procedure.The first step of this surgery was made a corneal flap with microkeratome then excimer laser ablation the corneal stromal bed in correcting myopia and hyperopia and astigmatism.The advantage of this surgery was remained corneal epithelium and bowman's membrane integrity. After operation visual acuity recover fast and less pain. The disadvantage of this surgery was used microkeratome. Many of the serious complications of laser assisted in situ keratomileusis are related to the use of the microkeratome. So creation of corneal flap is one of the most key procedure in LASIK which is also the most difficult part of the operation.The femtosecond laser is human currently in laboratory condition can obtain the shortest pulse. The femtosecond laser duration is very short, only a few femtosecond.Because cut corneal tissue safety and precised femtosecond laser widely use ophthemology field. Especially femtosecond laser made corneal flap in refractive surgery.This study was explore visual quality in LASIK using a femtosecond laser and microkeratome creat corneal flap.MethodsTwo hundred eyes of 100 cases were treated with laser in situ keratomileusis. The patients were devided into two groups.50patients with 100eyes created corneal flap by Ziemer femtosecond laser as the femtosecond group, another 50patients with 100eyes created corneal flap with a mechanical microkeratome as the microkeratome group. All eyes received wavefront-guided LASIK treatments performed with Technolas 217z100 excimer laser. Anterior segment optical coherence tomography was used to assess the thickness of corneal flap after 1month. The aberration and contrast sensitivity and visual acuity were analyzed 1week,1month,3month postoperatively respectively.Statistical analysis software SPSS16.0 was used to analyze the experimental data and clinical data.α=0.05 was used as a standard test.Results1 Corneal flap:Mean flap thickness in group femtosecond laser was 103.54±5.60(range88to131)μm. Mean flap thickness in group femtosecond laser was 102.17±4.80μm in right eyes and 104.42±4.97μm in left eyes. Mean flap thickness in group microkeratome was 130.30±14.03μm (range90to158)μm. Mean flap thickness in group microkeratome was 127.17±16.6μm in right eyes and 109.42±16.8μm in left eye.2 Aberration:The total high order aberrations and vertical comatic aberrations were significantly increased at postoperative in the microkeratome group, but not in the femtosecond group, there were statistical differences in each time point between two groups.(P<0.05). The postoperative spherical aberrations and horizontal comatic aberrations in two groups were higher than that before operation, and the increases of the microkeratome group were higher than that of the femtosecond group. 3 Contrast sensitivity:There were no statistically significant differeence for all spatial frequencies in photopic and photopic with glare condition postoperatively. In mesopic condition the contrast sensitivity improved at the spatial frequency(12.0,18.0cycles/degree) only in the femtosecond laser groups after 1 week.In mesopic with glare condition the contrast sensitivity all spatial frequencies have an improvement in femtosecond laser groups. However the contrast sensitivity in microkeratome group was decrease for all spatial frequencies 1 week postoperatively and restore to preoperative level 3 month.Conclusion1 Corneal flaps created with the femtosecond laser is extremely accurate and repeatability.2 Femtosecond laser shows induction of higher order aberrations to the microkeratome.3 The corneal flaps created with the femtosecond laser resulted in a faster recovery than mechanical microkeratome. |
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