Al Zubi 2019.

Study characteristics
Methods	Study design: parallel‐group, randomized controlled trial Number randomized (total and per group): 80 in total; 40 into each group Unit of randomization (individual or eye): individual (1 eye per participant) Number analyzed (total and per group): not explicitly reported Unit of analysis (individual or eye): individual (1 eye per participant) Exclusions and losses to follow‐up (total and per group): not explicitly reported How were missing data handled?: not reported Length of follow‐up: 12 months Reported power calculation (Y/N), if yes, sample size and power: not reported
Participants	Country: Jordan Setting: tertiary care Baseline characteristics Transepithelial CXL, n = 40 Age (mean ± SD, range): 23.55 ± 4.01 years (age range: 18 to 27 years) Gender: 31 males (77.5%) and 9 females (11.25%) Maximum K: 54.04 ± 3.99 D CDVA (logMAR): 0.332 ± 0.09 Epithelium‐off CXL, n = 40 Age (mean ± SD, range): 22.89 ± 3.99 years (age range: 18 to 29 years) Gender: 29 males (72.5%) and 11 females (27.5%) Maximum K: 54.88 ± 4.06 D CDVA (logMAR): 0.35 ± 0.09 Overall, n = 80 Age (mean ± SD, range): 23.2 ± 4.0 years (age range: 18 to 29 years) Gender: 60 men and 20 women Maximum K: 54.5 ± 4.05 D CDVA (logMAR): 0.34 ± 0.09 Inclusion criteria: "participants with keratoconus aged 18 years or above with documented progression of keratoconus (greater than 0.5D rise in six months or greater than 1 D rise in steep K/12months), keratometry (between 46 D and 56 D along with the corneal thickness being ≥400 μm) from the thinnest point, and no corneal scarring on presentation were included in this study" Exclusion criteria: none listed Baseline equivalence: it was unclear if participants were comparable at baseline. The authors reported: "While, mean Sim K astigmatism was 6.73 ± 1.98D in group 2 (range 4.3 D to 11.1 D). There was a significant difference between the two groups (P = 0.02)"; however, equivalent data in Table 2 showed a P value of 0.3.
Interventions	1. Transepithelial CXL 0.5% of proparacaine anesthetic drops administered 3 times with an interval of 5 minutes before introducing 0.1% isotonic riboflavin solution in 20% dextran. Post‐cleaning and covering of the eye: riboflavin drops administered every 3 to 5 minutes for about half an hour, in addition to recurrent eye drops of proparacaine Biomicroscopy end result was established through monitoring anterior chamber fluorescence on the slit‐lamp at the end of half hour. UVA radiation provided with the help of 2 ultraviolet diodes (intensity of desired radiation 3 mW/cm2, along with a UVA meter placed at a centimeter distance). Radiation of 370 nm wavelengths provided to participants for about half an hour. During this period, proparacaine and riboflavin eye drops administered every 3 to 5 minutes. 0.1% fluorometholone administered 4 times a day since 1st day (lessen slowly and stopped after a month). 2. Epithelium‐off CXL Proparacaine eye drops administered every 5 minutes. Disposable corneal trephine used to label or mark the corneal epithelium center. This marked corneal epithelium of 7 mm scraped off using a Merocel sponge. Irradiation treatment analogous to the transepithelial protocol for CXL was followed. A soft dressing contact lens was recommended, which was then removed after 3 to 5 days to ensure that the epithelium had healed completely. Moxifloxacin 0.3% topical drops recommended to be instilled 4 times a day. 0.1% fluorometholone administered 4 times a day after healing of epithelium (lessen slowly and stopped after a month) in addition to artificial eye drops used at least 4 times daily.
Outcomes	Primary outcomes: CDVA, UDVA, central corneal thickness Secondary outcomes: keratometric astigmatism, flattest keratometry, steepest keratometry Adverse outcomes: Transepithelial CXL: no complications Epithelium‐off CXL: stromal haze in the posterior stroma of 4 eyes in the initial postoperative period that persevered until 3 to 4 months Measurement time points: 3, 6, and 12 months Other issues with outcome assessment (e.g. quality control for outcomes, if any): none
Notes	Study period: not reported Publication language: English Trial registration: not found Conflicts of interest: "The authors declare no conflict of interest, financial or otherwise" Funding source: "The authors declare no conflict of interest, financial or otherwise"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	It was unclear what "odd‐even number allocation method, known as a randomized controlled trial" means: "the keratoconus patients were allocated to one of the two groups in a random fashion in accordance with the odd‐even number allocation method, known as a randomized control trial."
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was unclear: "the keratoconus patients were allocated to one of the two groups in a random fashion in accordance with the odd‐even number allocation method, known as a randomized control trial."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Masking of participants and personnel was not reported.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Masking of outcome assessors was not reported.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Numbers excluded or lost to follow‐up were not explicitly reported.
Selective reporting (reporting bias)	High risk	UDVA, which was proposed in the methods, was not reported in the results.
Other bias	Unclear risk	It was unclear if participants were comparable at baseline. The authors reported: "While, mean Sim K astigmatism was 6.73 ± 1.98D in group 2 (range 4.3 D to 11.1 D). There was a significant difference between the two groups (P = 0.02)"; however, equivalent data in Table 2 showed a P value of 0.3. Lack of use of standard outcome measures (authors cite seminal papers that use standard measures)