IntraLASIK and LASIK in Correction of High hyperopia and Hyperopic Astigmatism (Comparative Analysis)

Purpose
Comparison evaluation of the volume of stromal bed, diameter and profile of the thickness of the corneal cap, refractive and aberrometric parameters after IntraLASIK and LASIK in correction of high hyperopia and complex hyperopic astigmatism.

Material and methods
The study included 11 eyes after IntraLASIK and 10 eyes after LASIK, age of patients varied from 15 to 56 years (average — 33,2±7,4 years). The follow-up was six months. IntraLASIK was performed in two stages: The first one — resection of the corneal cap by femtosecond laser «IntraLase 60 kHz» (IntraLase FS, USA); the second one – excimer laser ablation with 6,5 mm optic zone and 9,2 mm total zone using «Microscan 200 Hz» device (Troitsk, Russia). LASIK was performed using «Microscan 200 Hz» with microkeratome «Moria M2» (Antony, France) with disposable 90 um head, 6,3 mm optic zone and 8,75 mm total zone of ablation. Predicted diameter of the corneal cap diameter in all cases was 9,5 mm.

Results
Femtosecond laser «IntraLase 60 kHz» forms the corneal cap with average deviation of 8 um in thickness and 0,11 mm in diameter; microkeratome «Moria M2» with disposable 90 um head — with average deviation of 23 um in thickness and 0,30 mm in diameter. Effective zone of the stromal bed after resection of the corneal cap by femtosecond laser significantly exceeds the field created by the keratome «M2». Preoperatively, sphere equivalent (SE) in IntraLASIK group averaged at +7,18±1,55 D, after 6 months — +0,23±0,45 D; in LASIK group, preoperatively — +7,44±1,70 D, after 6 months — +1,25±0,77 D. IntraLASIK induces increase in high aberrations by 1.78 times while LASIK — by 3,65 times as compared to initial data.

Conclusions
By functional results in correction of hyperopia, IntraLASIK has an advantage as compared to LASIK as the femtosecond laser cuts the corneal cap with high accuracy and creates greater stromal bed that is important for performance of complex profile of hyperopic ablation.