Since the cornea is the main responsible for the refraction of the eye, as its refractive power is greater than 70% of the total refraction of the eye, so modification of its refractive properties are used to change the optical system of the eye. Hence, laser-assisted in situ keratomileusis has become the most commonly procedure used to correct the refractive errors of the eye. The most important step in laser-assisted in situ keratomileusis is the creation of the corneal flap, which its thickness may judge the whole outcome of the surgery . So trying to minimize the variation in the thickness of the resultant flap in comparison to what planned flap thickness preoperatively become our target.

As laser-assisted in situ keratomileusis procedure started to use automated microkeratomes in creating corneal flaps since 1989, and science go on until United states Food and Drug Administration approved the IntraLase laser for flap creation in January 2000 femtosecond lasers work by emitting light pulses of short duration (10-15 s) at 1053 nm wavelength that cause photodisruption of the tissue with minimum collateral damage . This enables no blade incisions to be performed within the tissue at various patterns and depth with high precision.

Aim of the work To evaluate and compare the variation in corneal flap thickness created from use of a femtosecond laser and a MORIA microkeratome when making a 110-µm- and 90- µm thick corneal flap and to identify the potential factors that affect corneal flap thickness.

Inclusion Criteria:

• Age 18-40 year
• Preoperative spherical refraction of -2.00 to -10.00D.
• Refractive cylinder of less than -3.00D.
• A stable refractive state for 2 years.
• An intraocular pressure (IOP) of <22 mm Hg.

Exclusion Criteria:

• A history of any systemic autoimmune disease.
• A history of diabetes.
• Other ophthalmic disorders.
• A history of ocular trauma and surgical history.

population attending specialized eye centers