Transepithelial Iontophoresis Cross-Linking: A Breakthrough in Keratoconus Treatment for Young Patients

Introduction

Keratoconus (KC) is a progressive corneal disorder. It causes the cornea to thin and bulge, leading to irregular astigmatism and visual impairment. KC is typically diagnosed in adolescence and may progress over 3 to 4 decades. It often affects one eye more severely than the other. Studies show that the severity and progression can vary significantly between the eyes. This asymmetry increases as keratoconus worsens in the affected eye. Advanced diagnostic methods can enhance the detection of keratoconus by analyzing specific corneal parameters.

Monitoring keratoconus is essential, as patients with initially unilateral keratoconus often develop the condition in the fellow eye over time. The detected prevalence of unilateral KC has decreased due to improved detection techniques. Research indicates that true unilateral keratoconus does not exist.

Several treatments have been developed to slow the progression of keratoconus. Corneal collagen cross-linking (CXL) is considered the gold standard. Standard cross-linking (S-CXL) has shown effectiveness in halting disease progression and improving visual acuity. However, the traditional method has drawbacks, such as postoperative pain and delayed healing.

To alleviate these issues, iontophoresis cross-linking (I-CXL) has been introduced. This method enhances riboflavin penetration without removing the corneal epithelium. It may reduce discomfort and infection risk, leading to faster recovery.

Our study aims to evaluate the outcomes of I-CXL in patients under 25 with high corrected distance visual acuity (CDVA) keratoconus, where the fellow eye had undergone S-CXL.

Materials and Methods

This study included patients with bilateral, asymmetric keratoconus under 25 who received CXL at Humanitas San Pio X in Milan, Italy, from 2015 to 2020. According to the European General Data Protection Regulation, data processing for research can occur without explicit consent if safeguards, like data anonymization, are in place. The study followed ethical standards set by the Declaration of Helsinki.

Inclusion criteria required that the eye with more severe disease underwent S-CXL. The fellow eye, regardless of disease stage, needed a CDVA worse than 0.2 logMAR.

The I-CXL procedure involved a 0.1% riboflavin solution. An electrode connected to a current generator delivered 5 minutes of treatment at 1 mA. The cornea was then exposed to ultraviolet (UV) light for 9 minutes.

Re-progression after CXL was defined as meeting at least two of three specific criteria.

Results

At the 24-month follow-up, none of the patients showed re-progression of keratoconus based on our criteria.

Discussion

No standard method exists for assessing re-progression after CXL. Some studies found progression rates significantly different between S-CXL and I-CXL groups. For example, one study reported a 55% re-progression rate in I-CXL patients over three years. Another found a progression rate of 26% in eyes treated with I-CXL after seven years.

Conclusion

Our findings suggest that I-CXL may be a suitable alternative for managing less advanced keratoconus in patients with high visual acuity. However, further research is necessary to confirm these results and establish guidelines for I-CXL in clinical settings.