Purpose The aim of this study was to evaluate and to compare the thickness and morphology of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and mechanical microkeratome flaps using anterior segment optical coherence tomography (AS-OCT). Patients and methods This prospective, interventional, comparative clinical study was performed on 60 eyes of 30 patients. Flaps were created in 30 eyes using the WaveLight FS200 FS laser and in 30 eyes using the Moria M2 microkeratome. AS-OCT was used at 1 month postoperatively to evaluate the thickness of each flap at four points, which were 1 and 2 mm from the corneal vertex on the horizontal meridian. Results At the sixth month postoperatively, the uncorrected visual acuity was 0.98±0.10 in the FS-LASIK group and 0.98±0.11 in the microkeratome group, which denotes the efficacy of both procedures. No vision-threatening complications occurred in either group. The average flap thickness at 1 mm was 114.93±3.04 µm in the FS-LASIK group compared with 128.57±3.98 µm in the microkeratome group, with a statistically significant difference (P=0.000). The difference between the achieved and intended flap thickness at 1 mm (accuracy) was 4.93±3.04 µm in the FS-LASIK group compared with 18.57±3.98 µm in the microkeratome group, with a statistically significant difference (P=0.000). At 2 mm, the average flap thickness was 115.22±3.34 µm in the FS-LASIK group compared with 139.00±4.75 µm in the microkeratome group (P=0.000). The flap accuracy at 2 mm was 5.22±3.34 µm and 29.00±4.75 µm in the FS-LASIK group and the microkeratome group, respectively (P=0.000). Flap morphology showed a planar shape (uniform) in the FS-LASIK group and a meniscus shape in the microkeratome group. Conclusion Both FS-LASIK and microkeratome techniques were safe and efficient in correcting myopia and myopic astigmatism, achieving good visual outcome. AS-OCT showed that flaps created by the FS laser were more accurate and uniform than those created by the Moria M2 microkeratome.

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Article informationBackground: Proper calculation of ablation depth associated with LASIK and FEMTOLASIK surgeries is mandatory to estimate the post-refractive surgery remaining stroma to avoid the possibility of post-operative ectasia and to correct the maximum error to meet the patient's needs and safety. Purpose: The current work aimed to assess the actual depths of ablation after the LASIK versus the FEMTO-LASIK surgeries. Patients and Methods: Forty eyes of 20 patients were included in this prospective nonrandomized interventional study. They had myopia or myopic astigmatism, and scheduled for LASIK or FEMTOLASIK surgery. Pentacam was used to check the thickness of the thinnest corneal location and to exclude the possibility of keratoconus. They were divided into two groups according to the technique used to correct the error. Group I for LASIK and Group II for FEMTOLASIK surgery. Ablation was performed in all cases using the Allegretto excimer laser machine.After surgery, all patients received a combination of topical tobramycin 0.3% and dexamethasone 0.1% eye drops four times daily for 10 days, and topical Sodium Hyaluronate eye drops [2 mg/ml] four times daily for one month. All patients were examined at one day and one week postoperatively for evidence of flap malposition, striae, epithelial defects, or diffuse lamellar keratitis. Pentacam was used for follow up at 3 months after surgery to re-evaluate the thinnest central location. Results: In group I, the mean actual tissue ablation per one diopter was 13.3 microns for 6.5 mm treatment zone, and 11.9 microns for 6.0 mm treatment zone, while in group II, it was 13.4 microns for 6.5 treatment zone, and 11.8 microns for 6.0 treatment zone. There was insignificant difference between actual tissue ablation following the LASIK versus the FEMTOLASIK surgeries. Conclusion:The actual ablation depth should be considered to calculate the remaining stromal depth after LASIK or FEMTOLASIK surgeries for treatment of myopia or myopic astigmatism to avoid the possibility of post-LASIK or FEMTOLASIK ectasia and to correct the maximum error that meets the patient's needs.