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Digitized evaluation of femtosecond laser-assisted, myopic LASIK flap parameter accuracy (x and y diameter, OCT determined topographic thickness variation) and OBL occurrence and extent

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Session Details

Session Title: Presented Poster Session 21: Keratorefractive Surgery Outcomes - Myopia 3

Session Date/Time: Tuesday 16/09/2014 | 09:30-11:00

Paper Time: 10:00

Venue: Pod 3 (Poster Village)

First Author: : G.Asimellis GREECE

Co Author(s): :    A. Kanellopoulos   V. Moustou           

Abstract Details


To determine flap parameter (diameter and thickness) precision and accuracy (in comparison to programmed settings) as well as opaque bubble layer extent in femtosecond laser-assisted myopic LASIK.

Setting: Eye Institute, Athens, Greece


Seventy eyes of 35 consecutive myopic LASIK patients were evaluated. The flaps created with the FS200 femtosecond laser (Alcon, Ft. Worth, TX) were imaged intra-operatively with the build-in digital camera. Meridional anterior segment OCT corneal scans were also recorded during one-day, one month and 3 month follow-up visit intervals to measure central and mid-peripheral flap thickness and variation. Digital image processing by specially developed software was employed to investigate flap diameter, opaque bubble layer (OBL) occurrence and its extent as a percentage of the flap surface area. Additionally, thickness precision (by comparing similar flaps) and accuracy (by comparing achieved vs intended diameter and thickness) with the proprietary designed software. Correlation between the achieved and intended flap diameter was assessed using paired two-tailed t-tests, coefficient of determination (r2), trend line linearity, bias, and plots of differences against means.


The intended flap diameters were either 8.00 or 8.50 mm. The achieved flap diameters were on average: 7.85 mm (± 0.04) for the 8.00 mm intended flap diameter, and 8.38 mm (± 0.03) for the 8.50 mm intended flap diameter. Central flap thickness was 113.29 (± 1.19 μm) for 110 μm planned, intra-flap thickness variation was under 5 μm (1-4) in all cases. OBL was noted in 5 eyes (7.1%), always adjacent to the flap hinge, while graded as very mild, since its extent did not exceed in average 7% (5-13%) of the total flap surface area.


This study confirms that femtosecond laser-created LASIK flaps have high precision, impressive accuracy and reproducibility. Modern devices and revised treatment parameters may offer significant reduction of clinical OBL occurrence.

Financial Interest:

One or more of the authors... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented

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