In vivo imaging of riboflavin penetration during collagen cross-linking with hand-held spectral domain optical coherence tomography.
OBJECTIVE
To compare the effect of complete versus grid-like epithelial removal on riboflavin penetration during collagen cross-linking (CXL) in vivo using hand-held spectral domain optical coherence tomography (OCT, Bioptigen Inc).


METHODS
In this prospective, observational, comparative case series, patients with progressive keratoconus undergoing CXL with riboflavin and ultraviolet A (UVA) light were enrolled. Twenty eyes (20 patients) undergoing CXL using 0.1% riboflavin and UVA light (365 nm) were imaged intraoperatively at 30 and 60 minutes after starting the procedure, using hand-held spectral domain OCT. In 10 eyes, the epithelium was removed completely in the central 7-mm zone (complete removal group) whereas in the remaining 10 eyes, the epithelium was removed in a grid pattern, leaving behind intact islands of epithelium (grid-like removal group). The depth of hyperreflective band (representing penetration of riboflavin) in the anterior corneal stroma was measured.


RESULTS
In the complete removal group, the hyper-reflective band was homogenous, extending to a mean depth of 54.2±5.2 μm and 72.4±7.1 μm at 30 and 60 minutes, respectively (P<.001). In the grid-like removal group, the mean depth of the hyperreflective band was uneven, being significantly more in the "epithelium off" areas (56.90±4.66 μm and 74.2±6.7 μm at 30 and 60 minutes, respectively) (P<.001) compared to the "epithelium on" areas (18.9±2.3 μm and 24.7±2.3 μm at 30 and 60 minutes, respectively) (P<.001).


CONCLUSIONS
Epithelial removal appears to be an essential step prior to performing CXL, as an intact epithelium appears to block penetration of riboflavin in the anterior corneal stroma.
Narayana Nethralaya Eye Hospital, Bangalore, India.
Chintan
C
Malhotra
Rohit
R
Shetty
Rajesh S
RS
Kumar
Himabindu
H
Veluri
Harsha
H
Nagaraj
K Bhujang
KB
Shetty
D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism*; D003646:Debridement; D019573:Epithelium, Corneal / Q000378:metabolism; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy / Q000378:metabolism*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000493:pharmacokinetics*; D011446:Prospective Studies; D012256:Riboflavin / Q000493:pharmacokinetics*; D041623:Tomography, Optical Coherence / Q000295:instrumentation; D014466:Ultraviolet Rays; D055815:Young Adult
D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin