Study Title: Evaluation of different lenticule diameters in myopic astigmatic correction with SMILE procedures Primary Investigator: Dr. Ahmed Sedky (Eye Subspecialty Center, Cairo, Egypt, 18 Elkhalifa Elmamoun Street, Heliopolis, Cairo, Egypt) Co-Investigators: Sherine S Wahba, Maged M Roshdy, Nermeen A Refaat Study Objectives Primary Objective: To study the effect of changing the lenticule diameter on the safety and effectiveness of myopic astigmatism correction with the SMILE procedure.
Secondary Objective: To compare other outcomes such as visual outcomes including immediate visual acuity, contrast sensitivity, and epithelial remodeling.
Participants and Methods:
Study Setting: Eye Subspecialty Center, Cairo, Egypt, 18 Elkhalifa Elmamoun Street, Heliopolis, Cairo, Egypt and Al Watany Eye Hospital, Althawra Street, Cairo, Egypt Study design: Hospital-based, comparative, prospective, interventional contralateral eye study Sample size and randomization: 50 participants fulfilling the inclusion criteria will be enrolled in the study. Their right eyes undergo SMILE procedure using the standard 6.5 mm lenticule diameter and their left eyes undergo SMILE procedure but using a larger lenticule diameter of 7.0 mm.
Ethical issues:
Institutional ethics committee approval will be obtained. Participants' informed consent will be taken and the procedure explained to them in their own language. Any intra-operative or post-operative complications occurring in either group will be documented and duly informed to the ethics committee
Preoperative evaluation:
1. Anterior and posterior segment clinical examination
2. Uncorrected distance visual acuity (UDVA) in decimal and logMAR units
3. Corrected distance visual acuity (CDVA) in decimal and logMAR units
4. Corneal tomography using the Pentacam high resolution (HR) (Oculus Optikgeräte, Wetzlar, Germany) including the flattest and steepest meridians (in keratometric diopters (D), the axes (in degrees)
5. Contrast sensitivity (CSV1000E test (Good-Lite, Elgin, Illinois, USA)) in 4 different special frequencies
6. Anterior segment Optical Coherence Tomography (Cirrus, Carl Zeiss Meditec, Jena, Germany) measurement of total corneal and epithelial thickness in µm Study duration: 3 months for recruitment of the patients.
Surgical technique:
All surgeries will be performed under topical anesthesia using the VisuMax femtosecond laser with the following parameters:
Cap thickness of 120 μm Cap diameter is either 7.5 mm for lenticule diameter 6.5 mm or 8.0 mm for lenticule diameter 7.0 mm.
Cap side cut angle 70° 3 mm incision positioned at 100° and angled at 45° A transition zone of 0.1 mm and clearance of 0.5 mm Lenticule side cut angle of 90° and edge lenticule thickness of 15 μm Directly preoperative, the limbus will be marked in the 0° to 180° axis with a marker pen in the upright head position on the slit lamp. Then, the patient will be positioned under the VisuMax femtosecond laser and instructed to look into the green flashing fixation light. Once proper centration is achieved, the eye will be docked to the patient interface and suction will be applied.
Manual compensation will be done by gently rotating the contact glass to align the horizontal marks on the eye to the 0° to 180° axis. Once both are aligned, the laser process will be done to create the refractive lenticule followed by its dissection and washing of the interface by a balanced salt solution.
Medication: will be the standard treatment; topical steroids and antibiotics 4 times per day for 10 days and tear substitutes 4 times daily for one to two months.
Postoperative evaluation:
Follow-up of the subjects will be done in 1 day, 1 week, 3 months, and 6 months.
Data will be collected for analysis starting from 1 week, including:
1. Uncorrected distance visual acuity (UDVA) in decimal and logMAR units
2. Corrected distance visual acuity (CDVA) in decimal and logMAR units
3. Corneal tomography using the Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) including the flattest and steepest meridians (in diopters (D), the axes (in degree)
4. Contrast sensitivity (CSV1000E test (Good-Lite, Elgin, IL, USA)) in 4 different special frequencies
5. Anterior segment Optical Coherence Tomography (Cirrus HD-OCT, Carl Zeiss Meditec, Jena, Germany) measurement of total corneal and epithelial thickness in µm.
