Late-onset corneal edema after customized crosslinking for progressive keratoconus

Purpose: We describe a patient after customized crosslinking (CXL) for progressive keratoconus who developed corneal edema with spontaneous resolution. Observations: A 24-year-old male with progressive keratoconus of the left eye underwent a customized CXL procedure with a total energy of 10 J/cm2 for 16.4 minutes. Preoperative corrected distance visual acuity (CDVA) was 20/30 with a maximum keratometry (K)-value of 58.6 diopter (D) and the thinnest point measured 414 µm. The preoperative endothelial cell density (ECD) was 2414 cells/mm2. During treatment, corneal thickness was 325 µm after epithelial debridement and 375 µm after the application of 0.1 % riboflavin containing HPMC. After the treatment, antibiotic and steroid drops were prescribed for 5 days and 3 weeks, respectively. At the 1-month post-CXL visit the patient had no complaints, visual acuity and clinical examination showed no irregularities. At the 4-months post-CXL visit the patient complained of blurry vision. The CDVA was 20/100 and slit-lamp examination showed microcystic corneal edema. The corneal thickness at the thinnest point measured 440 µm. One month later the edema had resolved spontaneously and CDVA had restored to 20/25. Corneal thickness at the thinnest point measured 415 µm, the ECD was 1514 cells/mm2 and confocal microscopy showed normal structural changes in the anterior stroma after CXL, with the demarcation line located at a depth of 414 µm, just above the corneal endothelium. Conclusions and importance: We report a case of corneal edema following customized CXL with endothelial cell loss that resolved spontaneously. We recommend either adhering to a minimal stromal thickness of 400 µm before administering UV-A irradiation, using a contact lens or adjusting the irradiation to prevent this complication.