**Author details**

*A Practical Guide to Clinical Application of OCT in Ophthalmology*

extending through the anterior 200 μm of the cornea [27].

of in vivo riboflavin penetration in to the corneal stroma.

**cross-linking**

stroma during CXL.

concentration.

epithelial removal [26].

method [28].

**7. Conclusions**

**Conflict of interest**

to the article.

**6. Other applications of intraoperative OCT for corneal collagen** 

OCT has been used for in vivo evaluation of the riboflavin penetration to the

Mahotra et al. evaluated the depth of hyper-reflective band (representing penetration of riboflavin) in the anterior corneal stroma after riboflavin saturation of the stroma in 20 patients undergoing CXL with either complete epithelial removal or grid-like epithelial removal (leaving behind intact islands of epithelium) using hand-held spectral domain OCT. In the complete removal group, the hyper-reflective band was homogenous, extending to a mean depth of 54.2 ± 5.2 μm in the stroma. However, the hyper-reflective band was uneven in the grid pattern

Vinciguerra et al. measured the depth of hyper-reflective band after riboflavin saturation of the stroma using two different methods (epithelium-off and iontophoresis method) in six patients. In the conventional epi-off group, after 30 minutes of riboflavin instillation, a homogeneous hyper-reflective band without fading was measured at a mean depth of 80 μm. In the iontophoresis group, a less homogeneous but deeper hyper-reflective band with a fading effect was observed

Pahuja et al. used a microscope-integrated real-time spectral domain optical coherence tomography (ZEISS OPMI LUMERA 700 and ZEISS RESCAN 700) to compare the penetration of riboflavin between epithelium-on and epitheliumoff methods in keratoconus patients undergoing accelerated CXL. The mean depth of the hyper-reflective stromal band was 149.39 and 191.04 microns in the epithelium-on and epithelium-off groups, respectively. These results are compatible with enhanced riboflavin corneal penetration with the epithelium-off

Intraoperative OCT can be used safely and effectively to monitor corneal pachymetry during CXL. Among the advantages of this technology is its ability to provide a more detailed profile of the corneal thickness in a noncontact manner, which is especially advantageous for monitoring corneal pachymetry in the setting of CXL in KCN patients compared to the conventional ultrasound method. OCT has also been used for evaluation of other aspects of the CXL procedure like evaluation

The authors declare no conflict of interest regarding any material related

Riboflavin penetration of the cornea is associated with a hyper-reflective signal change in the corneal stroma. Although the correlation between the band's intensity and riboflavin stromal concentration has not been directly investigated, it is speculated that a higher OCT reflectivity should be positively correlated with riboflavin

**44**

Reza Ghaffari1 \*, Hassan Hashemi2 and Soheila Asghari3

1 Farabi Eye Hospital, Tehran, Iran

2 Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran

3 Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran

\*Address all correspondence to: ghaffaryreza@yahoo.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
