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Influence of flap thickness on visual acuity and refractive outcome after laser in situ keratomileusis (LASIK) with a mechanical microkeratome
Session Title: Refractive
Session Date/Time: Sunday 16/02/2014 | 08:30-11:00
Paper Time: 09:10
Venue: Kosovel Hall (Level -2)
First Author: : Maria LuisaColaco PORTUGAL
Co Author(s): : Cristina Pereira Mónica Franco Sofia Rodrigues Hugo Nogueira Ana Maria Carvalho José Maia Seco
The aim of our work was to study the effect of flap thickness on visual acuity and refractive outcome following standard LASIK for myopia or myopic astigmatism with a mechanical microkeratome, using two different cutting blades (130 μm and 90 μm).
There is still controversy about optimal flap thickness in LASIK. Thick flaps were associated with corneal biomechanical weakening and increased risk of ectasia. Thin flaps reduce this risk, allow correction of larger refractive errors, better contrast sensitivity and faster visual recovery. Nevertheless they may have higher risk of intraoperative complications.
Retrospective study of 48 patients from the Refractive Surgery department of Dr. Gama Pinto Institute of Ophthalmology in Lisbon, who underwent LASIK between January 2012 and July 2013. The mechanical microkeratome MORIA One Use-Plus SBK was used to create the flap with a cutting blade of 130 microns (group A) or 90 microns (group B). We evaluated at the third postoperative month uncorrected visual acuity for distance (UCVA), best corrected visual acuity for distance (BCVA), manifest refraction spherical equivalent (SE) and the percentage of hipocorrections requiring reintervention in both groups. Afterwards we studied if there were any significant differences between both groups.
We evaluated 52 eyes of 26 patients in group A and 43 eyes of 22 patients in group B. The average age was 33.5 years +/- 5.7 in group A and 34.5 +/- 6.0 in group B. Mean preoperative SE was -3.5 +/- 1.6 diopters and -3.4 +/- 1.4 diopters in groups A and B respectively, with no statistically significant differences between them (p=0.87). The postoperative uncorrected visual acuity was 0.85 +/- 0.19 in group A and 0.91 +/- 0.12 in group B. No statistically significant differences were found between SE and UCVA in the 2 groups at the third postoperative month (p=0.08 and p=0.07 respectively). The overall percentage of hipocorrections requiring a new intervention was 13.5% in group A and 4.7% in group B.
In our study, no significant differences were found between SE and UCVA postoperatively in the 2 groups with different flap thicknesses. The flap thickness didn’t affect visual acuity or refractive outcome with either of two types of cutting blade. However there appears to be a tendency towards better results in the group with the thinner flap which is in accordance with other previously published studies. FINANCIAL INTEREST: NONE