Prevalence of central islands after small incision lenticule extraction (SMILE) and influence in the postoperative refraction

Session Details

Session Title: Moderated Poster Session: Refractive Surgery: Can Results Improve Even Further?

Venue: Poster Village: Pod 2

First Author: : J.Fernández SPAIN

Co Author(s): :    M. Rodriguez-Vallejo   J. Garcia-Montesinos   J. Martinez   D. Pinero Llorens              

Abstract Details

Purpose:

To evaluate the prevalence of central islands and their influence in the postoperative refraction or visual acuity at six months follow-up

Setting:

Qvision, Vithas Virgen del Mar Hospital, Almería, Spain

Methods:

Data of 152 eyes from 76 subjects were retrieved from our database. Best spectacle refraction, corrected and uncorrected distance visual acuities, and corneal tomography measured with Pentacam were evaluated for the preoperative and 6 month follow-up visits. Central islands were assessed by means of the induced total corneal spherical aberration Z(4,0), vertical Z(3,-1) and horizontal Z(3,1) coma at 4 mm. Two groups were created, Group-A included eyes with postoperative Z(4,0) > -0.05 microns and Group B with Z(4,0) ≤ -0.05 microns. Both eyes of each subject were included in the analysis because of the low inter-eye correlation for Z(4,0).

Results:

Postoperative Z(4,0) was significantly correlated with Z(3,-1) (rho=-0.29, p<0.0005) and with the postoperative spherical refraction (rho=-0.19, p=0.021) but not with the astigmatism (rho=0.07, p=0.39). 110 eyes (72%) were included in the Group-A and 42 eyes in the Group-B (28%). Median [Interquartile range] postoperative refraction was 0 [0.25] D for Group-A and -0.25 [0.50] for Group-B (p=0.001). The UDVA was better in the Group-A (-0.1 [0.1] logMAR) than in the Group-B (0 [0.2] logMAR) (p = 0.007) but no significant differences were found for CDVA with both groups achieving (-0.1 [0.1] logMAR) (p = 0.12).

Conclusions:

Central islands have been previously described for PRK and LASIK with different definitions, generally through the size and dioptric power of the island in the topography. This kind of pattern results in an increase of negative spherical aberration in central part of the cornea. Therefore, total corneal aberrations can be used for assessing this adverse event. Central islands can also appear after SMILE resulting in an increase of spherical aberration and coma. Considering a cut-off value of Z(4,0)=-0.05 microns, the prevalence of islands after SMILE was of 28% and were related with a slight myopic shift in spherical refraction.

Financial Disclosure:

None