Multi modal imaging in corneal edema after corneal collagen cross-linking (CXL); a case-based literature review

BACKGROUND: Keratoconus (KCN) is a common ectatic disorder of the cornea. Corneal collagen cross-linking (CXL) is used as an effective option to slowdown the disease progression. Although CXL is considered a safe procedure, corneal endothelial damage, especially in corneal thickness of less than 400 μm, has been reported. CASE PRESENTATION: A 25-year-old man known case of KCN was referred with complaints about blurred vision and discomfort of the right eye 3 days after performing CXL. The preoperative thinnest point was 461 μm. His presenting BCVA was CF at 1 m. Examination showed central corneal edema and stromal haziness. ASOCT demonstrated increased central corneal thickness and very deep CXL line. In the confocal scan, anterior stroma showed hyper-reflective lines without recognizable cells and nerves, the middle stroma showed rare active and edematous keratocytes and a hyper-reflective reticular pattern with elongated keratocytes and needle-like structures involving the posterior stroma indicated increased depth of CXL. To manage the patient, debridement of loosened epithelium was done. Non-preservative steroid 1% eye drop was prescribed frequently. The corneal edema was completely resolved during 2 months with no need for surgical procedure and BCVA of 20/30 in his right eye. CONCLUSION: The corneal thickness of more than 400 μm cannot guarantee the absence of corneal edema after corneal collagen cross-linking, which can pertain to several factors such as inadvertently using of higher energy as well as the incorrect observance of all guidelines, instructions, and other precautions, even by a trained surgeon.