[Transepithelial iontophoresis corneal collagen cross-linking for progressive keratoconus: one year results]

To evaluate the early clinical results of keratoconic eyes treated with transepithelial iontophoresis corneal collagen cross-linking (i-CXL) within 1 year.

Propective nonrandomized study. Twenty-three eyes of 23 patients with progressive keratoconus with minimum corneal thickness from 380 µm to 420 µm (including the epithelium) were included in this prospective, nonrandomized clinical study and treated with i-CXL. Scoring of pain and foreign body sensation, slit lamp examination, uncorrected visual acuity (UCVA) and best corrected distance visual acuity (BCVA), corneal topography, anterior segment optical coherence tomography (AS-OCT), in vivo corneal confocal microscopy and endothelial cell count were assessed before surgery and at 1, 3, 6 and 12 months (m) postoperatively. Paired t test was applied for statistical analysis.

Moderate pain and foreign body sensation were reported by most patients on postoperative Day (D) 1, but rapidly decreased and eventually disappeared on D3. Mild epithelial damage was observed on D1, and the epithelium fully recovered on D3. Improvement of UCVA and BCVA were recorded at 3 months and 12 months postoperatively. Orbscan II corneal topography revealed the significant reductions of Kmax and Kmin from 3m to 12m (Kmax, t = 2.912, P < 0.01, Kmin, t = 2.508, P < 0.05) postoperatively while the other parameters remained stable. The Kmax and Kmin at 12m was (52.94 ± 4.87) and (46.78 ± 3.71) respectively, while the preoperative values was (54.37 ± 5.56) and (48.53 ± 3.57) respectively. Within 1m postoperatively, AS-OCT exhibited an increase of reflectance with a white line (demarcation line) in the anterior stroma, in vivo confocal microscopy also showed the significant thickening and increased connections of collagen fibers with maximal depth of about 133 µm. The corneal endothelial cell density remained stable (t = 0.915, P > 0.05). None of the patients showed postoperative complications such as corneal infection, scarring, ulcer, persistent epithelial defect, etc.

Priliminary clinical results within 1 year postoperatively demonstrated the efficacy and safety of i-CXL for the management of progressive keratoconus. This technique was applicable for keratoconic eyes with minimum corneal thickness around 400 µm. i-CXL showed the advantage of short time consuming in surgery, rapid recovery and few complication, and has the potential to become a valid alternative for the treatment of keratoconus.