Evaluation of a Modified Scleral Contact Lens as a Riboflavin Delivery Device for Corneal Collagen Crosslinking

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Introduction: Keratoconus is a complex corneal disease that reduces visual acuity by progressively modifying the corneal shape and thickness, usually producing myopia and irregular astigmatism. Corneal collagen crosslinking with riboflavin + ultraviolet-A radiation (CXL) has become a widely accepted treatment for progressive keratoconus. During CXL, riboflavin administration is performed by repeated manual instillation of solution drops on the cornea for 30 minutes, a procedure that is often uncomfortable for many patients and that consumes surgical facilities and staff resources. In this study, especially modified scleral contact lenses (MSCL) were employed for delivering riboflavin to the cornea during CXL. Objective: The study aimed at evaluating the safety and efficacy of MSCL as a drug delivery system, verifying if anterior chamber flare confirms riboflavin penetration and describes the impact on patient comfort and optimization of surgical staff and facility resources. Material and Method: This study included 8 eyes of 6 patients aged 16 - 25 years old with history of progressive keratoconus. After mechanical removal of corneal epithelium, the concave surface of the modified scleral contact lens was filled with riboflavin solution and the lens was placed on the patient’s eye during 30 minutes. The lens design allows the formation of a riboflavin layer between the lens and the exposed corneal stroma to facilitate riboflavin penetration. Patients with lens were allowed to stand up and wait for the second UVA phase outside the surgical room. Riboflavin diffusion was confirmed by biomicroscopic examination of the corneal stroma and anterior chamber with the lens in place. Patients returned and the lens was removed before UV-A irradiation at 3 mW/cm2 for 30 minutes. Statistical analysis was performed by comparing the following parameters of each patient pre- and post-CXL: Spherical equivalent (Sph.Eq.), Mean simulated keratometry (SimK-m) and corrected distance visual acuity (CDVA) using the Wilcoxon method for non-parametric data (p < 0. 05). Results: The MSCL allowed patients to be transferred from the surgical room to wait for corneal impregnation with riboflavin. The MSCL was effective in delivering riboflavin to the cornea as confirmed by biomicroscopic examination of the cornea and anterior chamber. No intraoperative or postoperative complications were observed. MSCL use improved the patient comfort and reduced the burden on surgical staff and facilities. All analyzed parameters showed statistically significant differences pre- and post-CXL: Sph.Eq. p = 0. 018 (Median: -2.50; Average: -2.52); SimK-m p = 0. 006 (Median: 47.92; Average: 45.56). CDVA p = 0. 012 (Median: -0.45; Average: 0.42). Conclusion: The MSCL is a safe and efficacious device for riboflavin delivery during CXL. The present study permits slit lamp observation of anterior chamber flare to confirm riboflavin penetration, and provides added safety and comfort for the patient and convenience to healthcare providers by optimizing the use surgical facilities and staff. Keratometric, visual and refractive results were similar to those reported in the literature for CXL with manual riboflavin instillation. Additional studies with larger numbers of patients are needed to confirm the study findings.