Background Keratoconus is a progressive ectatic corneal condition that results in corneal thinning leading to irregular astigmatism, corneal ectasia, and significant visual impairment. Conventional corneal collagen cross-linking (CXL) techniques aim to reinforce the corneal structure and slow disease progression. However, patients with thin corneas less than 400 μm are often excluded due to the potential risk of endothelial damage from excessive ultraviolet (UV) exposure. This study examines the Sub400 protocol, an adapted CXL technique that adjusts UV irradiation based on individual pachymetry measurements. Patients and methods An interventional analytical study was performed on 50 eyes from 50 patients aged 16 to 30 years who underwent the Sub400 protocol. The procedure involved epithelial debridement, riboflavin instillation, intraoperative pachymetry, and UV-A irradiation at 3 mW/cm² with adjusted exposure durations. Postoperatively, a bandage contact lens was placed, and antibiotic and corticosteroid drops was administered. Patients were re-examined at the slit lamp on postoperative day 1, and daily until the epithelium is healed, as well as for 1 year after the procedure. Pre and postprocedural assessments were conducted using Pentacam and specular microscopy. Results Pentacam analysis showed a statistically significant reduction in K-max (from 58.48 ± 4.68 preoperatively to 56.38 ± 4.96 postoperatively P < 0.05) and corneal thickness (from 345.3 ± 33.15 μm preoperative to 330.5 ± 34.64 μm postoperative P < 0.05). Specular microscopy indicated no significant changes in endothelial cell density (from 2661.5 ± 102.9 preoperative to 2643.5 ± 102.8 postoperative P0.153), polymegethism (from 29.21 ± 3.21 preoperatively to 29.40 ± 3.16 postoperative P0.584), or pleomorphism (from 54.16 ± 3.69 preoperative to 54.32 ± 3.63 postperative P0.159). Visual acuity showed a slight, nonsignificant improvement (P = 0.083), best-corrected visual acuity from 0.39 ± 0.13 to 0.40 ± 0.14 Decimal. Conclusion The Sub400 protocol presents a safe and effective treatment for managing keratoconus in patients with thin corneas. This method has the potential to broaden eligibility for CXL, benefiting those with thin corneas who are ineligible for standard CXL procedures.
Sawan et al. (Tue,) studied this question.