The Biconvex Lenticule - Change In Objective Refraction, Keratometry, Asphericity And Aberrations After A New Keratorefractive Lenticule Extraction Procedure

To evaluate visual outcomes including post-operative refractive error, corneal higher order aberrations, anterior and posterior corneal curvature changes after Small Incision Lenticule extraction (SILK) in low, moderate and high myopia

Tertiary Eye Care Centre in North India

This prospective interventional study included 110 eyes of 55 patients, divided in three groups: low myopia (myopia 3 D [diopters] spherical equivalent [SE]), moderate myopia (myopia 3 D and 5 D SE), and high myopia (myopia >5 D SE). The ELITA femtosecond LASER (Johnson & Johnson) was used to perform SILK for the correction of myopia and myopic astigmatism. The Pentacam HR (Oculus Optikgeräte, Germany) and itrace (Tracey Technologies Corp., Houston,USA) were used to measure the corneal asphercity, keratometry and aberrations. The Casia 2 Anterior segment OCT (Tomey, Nagoya, Japan) was used to assess changes in anterior and posterior corneal curvature at 1 and 3 months postoperatively. Refractive visual outcomes were studied postoperatively.

The total higher order aberrations including spherical aberration did not show significant change after the procedure (P=0.65). 95 % eyes attained a UDVA of 20/25 or better on day one. 90 percent eyes were within 1 D of targeted spherical and cylindrical correction. There was no significant change in mean keratometric power in the 3, 5 and 7 mm zones of the posterior corneal surface compared with its pre-SILK value after 3 months in the mild (pre-operative [pre-op] - 6.10 + 0.23, post-operative [post-op]  -6.06  +  0.22, P= 0.8) ,moderate (pre-op -6.06  +  0.16, post-op -6.05  +.18, P= 0.58), and high myopia group (pre-op -5.93  +  0.17, post-op -5.92. +  0.15, P=0.53). 

Lenticule Extraction with the ELITA Platform was found to be accurate, safe and effective. SILK does not induce significant changes in posterior corneal keratometric power in low, moderate and high myopia. The asphericity of the posterior cornea did show a significant change however there was no change in higher order aberrations after the procedure.