Structural Changes in Thin Keratoconic Corneas Following Crosslinking with Hypotonic Riboflavin: Findings on In Vivo Confocal Microscopy

Aalia Rasool Sufi; M Soundaram; Nilam Gohil; Jeremy D Keenan; N Venkatesh Prajna

doi:10.18502/jovr.v16i3.9429

Structural Changes in Thin Keratoconic Corneas Following Crosslinking with Hypotonic Riboflavin: Findings on In Vivo Confocal Microscopy

J Ophthalmic Vis Res. 2021 Jul 29;16(3):325-337. doi: 10.18502/jovr.v16i3.9429. eCollection 2021 Jul-Sep.

Authors

Aalia Rasool Sufi¹, M Soundaram¹, Nilam Gohil¹, Jeremy D Keenan^{2

3}, N Venkatesh Prajna¹

Affiliations

¹ Department of Cornea and Refractive Surgery, Aravind Eye Hospital, Madurai, India.
² Francis I. Proctor Foundation, University of California, San Francisco.
³ Department of Ophthalmology, University of California, San Francisco, California, USA.

Abstract

Purpose: To report structural changes observable in in vivo confocal microscopy (IVCM) in keratoconic corneas $<$ 400 μm treated with hypotonic riboflavin and collagen crosslinking (CXL).

Methods: Ten eyes of ten patients with progressive keratoconus and corneal thickness between 350 and 399 μm underwent CXL with hypotonic riboflavin. IVCM was performed preoperatively and at one month, three months, and six months after the procedure.

Results: IVCM analysis one month postoperatively showed complete absence of the subepithelial nerve plexus with gradual regeneration over six months in 8 of the 10 eyes, and poor regeneration in the remaining 2 eyes. The anterior stroma showed extracellular lacunae and hyper-reflective cytoplasm in a honeycomb appearance signifying edema at one month which gradually decreased over six months post CXL. Stromal keratocyte apoptosis was evident in the anterior stroma in all cases and extended to the posterior stroma in four eyes with gradual regeneration evident at three and six months. The specular endothelial count decreased by 8% (P = 0.005) post-CXL, but no corneas developed clinical signs of endothelial trauma.

Conclusion: IVCM analysis of thin corneas after hypotonic CXL showed posterior corneal structural changes. Posterior stromal changes were accompanied by a decrease in the endothelial cell count. This case series was a preliminary feasibility study that might necessitate conducting a well-designed controlled study.

Keywords: Hypotonic Riboflavin; In Vivo Confocal Microscopy; Keratoconus; Collagen Crosslinking.