To evaluate the safety and efficacy of ReLEx SMILE Xtra in patients with thin corneas and/or borderline topography

Session Details

Session Title: Cross-linking I

Session Date/Time: Monday 15/09/2014 | 14:30-16:30

Paper Time: 15:54

Venue: Capital Hall A

First Author: : S.Brar INDIA

Co Author(s): :    S. Ganesh   R. Gupta           

Abstract Details

Purpose:

To describe a new technique, SMILE Xtra, which may safely allow laser refractive correction in patients with higher refractive errors (Sph Eq upto -10D) and / or thinner corneas(<480µ) , borderline topography without increasing risk of ectasia in future

Setting:

Nethradhama Superspeciality Eye hospital, Bangalore, India

Methods:

SMILE Xtra was performed in 40 eyes of 20 patients of which 12 were females and 8 were males. Mean age at presentation was 26.4 years(23-30) years. Preoperatively, detailed assessment including the recording of UCVA and BCVA, slit lamp examination, corneal topography, dry eye assessment, specular microscopy and contrast sensitivity was done. Patients first underwent ReLEx SMILE procedure using the Visumax femtosecond laser , for correction of myopia and myopic astigmatism. Following removal of the lenticule through 2mm incision,0.1-0.2ml riboflavin(0.25%) was applied to the interface and allowed to diffuse for 60seconds. Interface was washed and then exposed to UV-A radiation with energy of 45mW/ cm² to facilitate cross-linkage for 75 seconds( high fluence UV radiation). Total energy delivered was 3.4 J/cm². Mean pre op spherical equivalent was -5.026 ± 2.06 D, mean pachymetry 501.3 ±10.06 µ , average Keratometry ( K mean) 45.46 ± 1.40 D and average endothelial cell density (ECD) 2872 cells/mm². There were no intraoperative complications. Patients were followed up at day 1, 15 and 3 months postoperatively.

Results:

At postoperative day 1 and 15 , all patients had clear corneas and there was no haze or interface issues. Patients were comfortable and did not report any significant complaints. 3months post op, mean residual SEQ was -0.32 ± 0.22 D, mean pachymetry 414.8 ±15.36 µ , K mean 41.28 ± 2.20 and mean ECD 2764.3 cells/mm² . There were no post operative complications/ adverse effects following the procedure at the end of mean follow up of 3 months ± 10 days.

Conclusions:

SMILE Xtra may to be a safe and promising modality to prevent corneal ectasia in thinner corneas / borderline topography and higher refractive errors. The anticipated benefits of this technique over the conventional LASIK Xtra technique , other than the ones that SMILE has over LASIK , are- ( 1) SMILE Xtra offers more efficient cross linkage compared to LASIK Xtra due to two reasons. The injection of the dye into the pocket in SMILE , ensures better diffusion and hence cross linkage compared to diffusion of the dye under an open flap in LASIK , as chances of spill over are higher with LASIK. In SMILE Xtra, the dye gets diffused in both the overlying cap and the underlying stroma, resulting in better diffusion and efficient cross linkage compared to LASIK Xtra , where the dye is diffused only in the part of stroma underlying the flap. Since the dye does not diffuse in the flap , the thickness of the cornea corresponding to the flap neither contribute to the strength of the cornea nor participates in cross linkage. (2) Even after cross linkage with LASIK, the procedure does not offer security against flap dislocation in future . (3) Compared to conventional cross linkage there is no de- epithelisation, minimal chances of infection, no haze or delayed post op recovery. Results of our study show that SMILE Xtra may be a safe and effective technique compared to LASIK Xtra for future applications to prevent ectasia in susceptible individuals and does not affect the refractive outcomes.However, longer follow up and biomechanical studies on larger cohorts are warranted to establish the long term efficacy and effects on corneal stabilization.

Financial Interest:

NONE