Patel_group 2010.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: within person Number randomly assigned: 42 eyes, 21 participants Exclusions after randomization: 0 Number analyzed: 42 eyes Unit of analysis: eye Losses to follow‐up: 1 participant, 2 eyes Handling of missing data: eyes with missing data excluded from analysis Power calculation: "The trial was powered a priori to detect a difference of 0. 15 logMAR in UCVA or BCVA at 3 years after LASIK by assuming that the standard deviation of the difference in visual acuity would be 0.15 logMAR. This required a minimum sample size of 16 subjects ( 0.05/6, 0.20, paired test)." Study dates: 2004 to 2005
Participants	Country: USA Overall mean age: 41.5 years (SD 10) Age range: 29 to 55 years Gender: not reported Setting: refractive surgery service at Mayo Clinic Equivalence of baseline characteristics: yes Inclusion criteria: people with myopia or myopic astigmatism (D not reported) Exclusion criteria: any corneal abnormalities; a history of ocular disease, trauma, or surgery; or diabetes mellitus or other systemic disease known to affect the eye; or if they used ocular medications. Systemic medications were permitted unless they were known to affect the cornea or anterior segment.
Interventions	Laser for ablation: VISX Star S4 excimer laser Intervention 1 Intervention: LASIK with a Hansatome microkeratome Flap dimensions: 160 μm thickness, 9.0 mm diameter, superior hinge Number of people randomized: 21 eyes, 21 participants Length of follow‐up: Planned: not reported Actual: 36 months Intervention 2 Intervention: LASIK with an IntraLase femtosecond laser Flap dimensions: 120 μm thickness, diameter not reported, and superior hinge, degrees not reported Number of people randomized: 21 eyes, 21 participants Length of follow‐up: Planned: not reported Actual: 36 months
Outcomes	Mean UCVA after surgery Intervals at which outcome assessed: 1, 3, 6, 12 and 36 months Planned follow‐up: not reported Actual follow‐up: 36 months Scale: logMAR Instrument for measurement: Electronic Early Treatment of Diabetic Retinopathy trial testing protocol BCVA after surgery Intervals at which outcome assessed: 1, 3, 6, 12 and 36 months Planned follow‐up: not reported Actual follow‐up: 36 months Scale: logMAR Instrument for measurement: Electronic Early Treatment of Diabetic Retinopathy trial testing protocol Proportion of eyes within ± 0.5 D of target refraction after surgery Intervals at which outcome assessed: 1, 3, and 6 months Planned follow‐up: not reported Actual follow‐up: 6 months Scale: D Instrument for measurement: not reported Mean spherical equivalent of the refractive error after surgery Intervals at which outcome assessed: 1, 3, 6, 12 and 36 months Planned follow‐up: not reported Actual follow‐up: 36 months Scale: D Instrument for measurement: not reported Sub‐basal nerve density Intervals at which outcome assessed: 1, 3, 6, 12 and 36 months Planned follow‐up: not reported Actual follow‐up: 36 months Scale: ɥm/mm2 Instrument for measurement: ConfoScan 3 & 4 confocal microscope (Nidek Technologies, Greensboro, North Carolina) Corneal sensitivity Intervals at which outcome assessed: 1, 3, 6, 12 and 36 months Planned follow‐up: not reported Actual follow‐up: 36 months Scale: mL/min Instrument for measurement: gas esthesiometer Adverse events reported: no
Identification	Sponsorship source: National Institutes of Health, Bethesda, Maryland (Grant EY 02037; W.M.B.); Research to Prevent Blindness, Inc, New York, NY (S.V.P. as Olga Keith Wiess Special Scholar, and an unrestricted departmental grant); and Mayo Foundation, Rochester, MN Country: USA Setting: Institute of Ophthalmology Comments: none Author's name: Sanjay V Patel Institution: Department of Ophthalmology, Mayo Clinic Email: patel.sanjay @mayo.edu Address: 200 First St SW, Rochester, MN 55905
Notes	Trial registration number: NCT00350246
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "patients were stratified by ocular dominance and then 1 eye of each patient was randomized to LASIK with the flap created by a femtosecond laser, and the other eye to LASIK with the flap created by a mechanical microkeratome." Comment: random component in the sequence generation process not described
Allocation concealment (selection bias)	Unclear risk	Comment: concealment not described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "It was not possible to mask patients as to which treatment was received in each eye."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The videokeratography maps of each cornea were examined by 1 masked observer, and the map with the most complete image and the smallest nondigitized areas was selected for assessment of wavefront errors from the anterior corneal surface."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "All subjects were included for analysis through 12 months of follow‐up after LASIK. After 1 year, 4 eyes of 2 patients required enhancement procedures for mild undercorrections, which were similar in the fellow eyes; data for these eyes were retained in the analysis at 36 months. Visual acuity and whole‐eye aberrometry data were excluded in both eyes of 1 patient at 36 months because of the presence of visually significant nuclear sclerotic cataracts; corneal topography data for this patient were included. One eye of 1 patient experienced trauma‐induced recurrent erosions between 13 and 22 months after surgery; no erosions occurred after that time and data for this eye were included at 36 months."
Selective reporting (reporting bias)	Unclear risk	Comment: some outcomes reported in the different reports of the trial were not prespecified in trial registration (www.clinicaltrials.gov/ct2/show/trial/NCT00350246)
Other bias	Low risk	Comment: trial appeared free of other sources of bias