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Short-term visual and biomechanical outcomes and efficacy of refractive surgery using sub-bowman keratomileusis (SBK) versus femtosecond laser flaps using 5th generation iFS femtosecond lasers

Poster Details

First Author: A.Gupta INDIA

Co Author(s):    S. Gupta   J. Ram           

Abstract Details


Comparison of refractive outcomes as well as corneal biomechanical changes in eyes undergoing LASIK surgery using 5th generation 150 KHz iFS Femtosecond (Abbot Medical Optics IntraLase FS; IntraLase corp, Irvine, California, USA) laser versus mechanical Sub-bowman Keratomileusis (SBK) using Moria SBK microkeratome (Moria, Antony, France).


Advanced Eye Centre, Post Graduate Institute Of Medical Education And Research, Chandigarh, India


This non-randomized prospective clinical study included 100 eyes of 50 patients having myopia and myopic astigmatism. These eyes were divided into two groups. Group I (SBK) included 50 eyes of 25 patients undergoing LASIK surgery with mechanical Moria SBK microkeratome (Moria, Antony, France). Group II (iFS) included 50 eyes of 25 patients undergoing LASIK surgery with 150 KHz iFS femtosecond laser. All eyes were subjected to detailed preoperative ophthalmological assessment including evaluation of uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), mean refractive spherical equivalent (MRSE), corneal topography using the Occulus Pentacam, corneal biomechanics using the ORA (Ocular Response Analyzer, Reichert Ophthalmic Instruments, Inc., Buffalo, NY, USA) and corneal aberrations using the WASCA (Carl Zeiss, Jena, Germany). Statistical differences were examined for preoperative to postoperative changes in UCVA (logMar), BCVA (logMar), MRSE (Mean Refractive Spherical Equivalent), corneal biomechanical values including corneal hysteresis (CH), corneal resistance factor (CRF), corneal topography and corneal aberrations at each follow up visit scheduled at 1 week, 1 month and 3 months, postoperatively.


UCVA (logMar) improved from +1.4 ± 0.34 to +0.1 ± 0.23 in group I and from +1.3 ± 0.44 to +0.1 ± 0.11 in group II, respectively at the last follow up. The mean refractive spherical equivalent (MRSE) was reduced from -2.95 ± 0.65 D to 0.188 ± 0.45 D in SBK group and from -4.04 ± 0.64 to 0.167 ± 0.57 D in iFSgroup at 3 months follow-up. Mean changes in UCVA as well as MRSE values were comparable in both the groups at all the visits. CH decreased from preoperative value of 10.31 ± 1.56 to 8.3 ± 1.53 and CRF decreased from 10.61 ± 2.59 to 7.6 ± 2.33 at the last follow up of 3 months in SBK group. In iFS group, CH decreased from 9.24 ± 3.24 to 7.5 ± 1.2 at 3 months follow up and CRF decreased from 9.35 ± 1.66 to 6.69 ± 1.02 at 3 months follow up. However, mean change in the values of CH and CRF at each follow up visits were comparable in both the groups. Similarly, no significant change in other parameters like higher order aberrations was observed postoperatively in the two groups.


This is the first prospective clinical study comparing 5th generation iFS femtosecond laser with mechanical microkeratome in LASIK surgery. It has been earlier postulated that better, stronger and thinner flaps created with iFS cause less significant changes in corneal biomechanical properties and superior visual outcome. Thus, femtosecond lasers give more predictable postoperative outcome as far as corneal biomechanics are concerned. However, in our study both the groups were comparable in terms of both the refractive outcomes and changes in corneal biomechanical properties. The two clinical groups were comparable in all clinical outcomes including uncorrected visual acuity, best corrected visual acuity, manifest refraction, wavefront aberrometry. Thus, although 5th generation 150 KHz iFS femtosecond laser has been advocated as a method of creating superior quality flaps, we found that Sub-bowman Keratomileusis is equally efficacious as the 5th generation femtosecond laser. FINANCIAL DISCLOSURE?: No

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