Conference: Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO) Location: Vancouver, CANADA Date: APR 28-MAY 02, 2019

Laser and light diagnostic and theraphy has become a standard of care for multiple eye diseases or disorders. It is impossible to imaging ophthalmology without lasers today, due to the appearance of an ever increasing number of laser and light sources, improved understanding of light-tissue interactions and the expanding range of clinical research and experience in opthalmology.

Purpose:To evaluate and compare the safety and efficacy of accelerated (AXL) and standard corneal cross-linking (CXL) protocols in patients with progressive keratoconus.Methods:Progressive keratoconus patients (14-40 years) received either standard-intensity CXL or high-intensity CXL (AXL). Corneas were exposed to ultraviolet-A 365 nm light for 30 minutes at an irradiance of 3.0 mW/cm(2) in the standard CXL group and to ultraviolet-A 365 nm light for 10 minutes at 9.0 mW/cm(2) in the AXL group. Changes in uncorrected visual acuity, best spectacle-corrected visual acuity, refractive astigmatism, K-max, and K-mean were used to determine treatment efficacy. Safety was determined by the incidence of adverse events and occurrence of loss of 2 or more lines of best spectacle-corrected visual acuity. Outcomes for CXL versus AXL were compared to determine differences in safety and efficacy between treatment groups.Results:Thirty-six eyes of 34 patients (mean age, 27.9 7.6 years) underwent AXL; 66 eyes of 53 patients (mean age, 30.0 +/- 8.0 years) underwent standard-intensity CXL. There was no significant difference in any outcome measures between the groups. For AXL, there seemed to be more corneal flattening, with a statistically significant reduction in K-mean at 6 and 12 months postoperatively, when compared preoperatively (P < 0.01). There were no adverse events or complications in any patients.Conclusions:There was more corneal flattening in AXL patients 6 to 12 months postoperatively, suggesting that AXL may be a promising alternative to CXL in stabilizing corneal ectasia.

To evaluate and compare the safety and efficacy of accelerated (AXL) and standard corneal cross-linking (CXL) protocols in patients with progressive keratoconus.Progressive keratoconus patients (14-40 years) received either standard-intensity CXL or high-intensity CXL (AXL). Corneas were exposed to ultraviolet-A 365 nm light for 30 minutes at an irradiance of 3.0 mW/cm in the standard CXL group and to ultraviolet-A 365 nm light for 10 minutes at 9.0 mW/cm in the AXL group. Changes in uncorrected visual acuity, best spectacle-corrected visual acuity, refractive astigmatism, Kmax, and Kmean were used to determine treatment efficacy. Safety was determined by the incidence of adverse events and occurrence of loss of 2 or more lines of best spectacle-corrected visual acuity. Outcomes for CXL versus AXL were compared to determine differences in safety and efficacy between treatment groups.Thirty-six eyes of 34 patients (mean age, 27.9 ± 7.6 years) underwent AXL; 66 eyes of 53 patients (mean age, 30.0 ± 8.0 years) underwent standard-intensity CXL. There was no significant difference in any outcome measures between the groups. For AXL, there seemed to be more corneal flattening, with a statistically significant reduction in Kmean at 6 and 12 months postoperatively, when compared preoperatively (P < 0.01). There were no adverse events or complications in any patients.There was more corneal flattening in AXL patients 6 to 12 months postoperatively, suggesting that AXL may be a promising alternative to CXL in stabilizing corneal ectasia.

PURPOSE: To determine the diffusion of riboflavin from intrastromal channels through the effective diffusion coefficients compared with traditional axial diffusion with epithelium on or off.SETTING: Advanced Optical Imaging Laboratory, University College Dublin, and Wellington Eye Clinic, Sandyford, Dublin, Ireland.DESIGN: Experimental study.METHODS: The rate of diffusion in whole-mounted porcine eyes was monitored for a 30 minutes using an optical setup with a charge-coupled device camera and a bandpass filter (central wavelength 550 nm and 40 nm bandpass) to image the fluorescence under ultraviolet illumination (365 nm wavelength). For comparison, an isotropic corneal stroma with an annular channel was modeled numerically for different diffusion constants and boundary conditions.RESULTS: Numerical and experimental results were compared, allowing determination of the effective diffusion coefficient for each case. Experimental results for 6 different riboflavin solutions were in all cases found to be higher than for the common crosslinking (CXL) riboflavin protocol, where the diffusion constant is D-0 = 6.5 x 10(-5) mm(2)/sec. For the intrastromal channel, 2 isotonic solutions containing riboflavin 0.1% correlated with a diffusion constant of 5D(0) = 32.5 x 10(-5) mm(2)/sec. Hypotonic solutions and transepithelium had a higher diffusion coefficient approaching 10D(0) = 65.0 x 10(-5) mm(2)/sec, which is an order-of-magnitude increase compared with the typical diffusion coefficient found in standard CXL.CONCLUSIONS: In this study, riboflavin had a faster stromal diffusion when injected into a corneal channel than when applied as drops to the anterior corneal surface. Further numerical modeling might allow optimization of the channel structure for any specific choice of riboflavin. (c) 2016 ASCRS and ESCRS

To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results. The model takes account of the initial riboflavin concentration and bleaching, light intensity and time of illumination.