eTable 1.

Detail description of different corneal collagen cross-linking protocol used in the systematic review and meta-analysis

CXL protocol	Salient features of the protocol
Conventional epi-off protocol (C-CXL)	First corneal epithelium is removed (7-9 mm), then isotonic riboflavin solution is applied over the area for 30 min, then cornea eradiated with UV-A (370 nm) wavelength, power 3 mW/cm2 or 5.4 J/cm2 surface radiation for 30 min (riboflavin drop applies throughout the eradiation period every 5 min)[1]
TE-CXL (TE-CXL)	In this procedure, corneal epithelium is not removed instead various modalities have been used to enhance riboflavin penetration through intact epithelium, e.g., TE-CXL using chemical enhancer (banzalkonium chloride, ethylenediamine tetraacetic acid, etc.), TE-CXL using T-Ionto/small electrical current through the tight junction of corneal epithelium (T-Ionto-CXL),TE-CXL using epithelium disruption (performing mechanical disruption of corneal epithelium e.g., Daya epithelial disruptor)[1]
A-CXL (A-CXL)	Utilizing “Bunsen-Roscoe Law of photochemical reciprocity” which states “Same photochemical effect can be achieved by reducing the irradiation interval but keeping the total energy level constant by a corresponding increase in the irradiation intensity,” i.e., high energy UV-A dose (up to 30 mW/cm2, total energy limit is kept constant at 5.4 J/cm2) applied for short duration[1]
CRXL	After application of riboflavin, a semi-scleral rigid contact lens is sutured over cornea which followed UV-A irradiation. During the UV-A eradiation, riboflavin drop is applied under contact lens every 5 min using a blunt cannula[2]
PiXL	Customized topography-guided photorefractive intrastromal cross-linking with asymmetrical treatment zones and variable treatment energies used in this technique. 9 mm of central epithelium is removed, 0.1% dextran-free riboflavin is applied every 2 min when and 1s on/1s off-pulsed 370 nm UV-A irradiation of 30 mW/cm2 applied (total duration 10 min)[3]
CXL along with ICRS	ICRS implanted in the mid-peripheral deep stroma to reduce central corneal curvature/regularizing and decreasing pathologic corneal steepening (e.g., Intacs , Ferrara Ring) which is combined with CXL procedure to stop the disease progression.[4] The optimal timing for ICRS implantation remains varies from author to author, e.g., simultaneous ICRS with CXL, CXL followed by ICRS, or ICRS followed by CXL, etc.[4]
Athens protocol	This protocol involves topography-guided transepithelial partial PRK followed by CXL.[5-10]
Cretan protocol	This protocol uses epithelium removal with t-PTK[11]

CRXL=Corneal reshaping and crosslinking, PiXL=Photorefractive intrastromal cross-linking, ICRS=Intracorneal ring segment, CXL=Corneal collagen cross-linking, TE-CXL=Transepithelial-CXL, C-CXL=Conventional-CXL, A-CXL=Accelerated-CXL, T-Ionto=Iontophoresis, PRK=Photorefractive keratectomy, t-PTK=Transepithelial phototherapeutic keratectomy, UV-A=Ultra violet A