Reaction-diffusion model as framework for understanding the role of riboflavin in “eye defence” formulations

Modified Sodium hyaluronate conjugated to riboflavin (Har® 0.1 %) as lubricant eyedrops in the treatment of dry eye: A prospective randomised study

Background

This study evaluates the therapeutic efficacy of HAr® (a novel ophthalmic solution containing modified hyaluronic acid covalently linked to riboflavin) compared to hyaluronic acid eye drops in patients with dry eye disease (DED).

Methods

Sixteen consecutive patients with bilateral medium to severe DED were divided into two groups. Group 1 received HAr® 0.1 % (Ribohyal®), while Group 2 received HA 0.1 % eye drops. Parameters such as Ocular Surface Disease Index (OSDI) score, osmolarity, break-up time (BUT), non-invasive BUT (NIBUT), tear meniscus measurement, Schirmer test, and Oxford Staining were evaluated. This study has been successfully registered on ClinicalTrials.gov public (Identifier NCT06122428).

Results

The Ribohyal group showed faster improvement in OSDI scores, with a statistically significant difference at 2 h (mean classification difference: -51.75; p = 0.0003). Photophobia significantly reduced at 2 h, 4 weeks, and 8 weeks in the Ribohyal group compared to baseline (p < 0.0001). Osmolarity improved significantly after 8 weeks in both groups (p < 0.0001).

Conclusions

HAr® 0.1 % (Ribohyal®) effectively reduced DED symptoms and improved photophobia within 2 h of instillation, lasting up to 8 weeks.

Corneal collagen cross-linking in patients with keratoconus from the Dresden protocol to customized solutions: theoretical basis

Keratoconus is an ectatic condition characterized by gradual corneal thinning, corneal protrusion, progressive irregular astigmatism, corneal fibrosis, and visual impairment. The therapeutic options regarding improvement of visual function include glasses or soft contact lenses correction for initial stages, gas-permeable rigid contact lenses, scleral lenses, implantation of intrastromal corneal ring or corneal transplants for most advanced stages. In keratoconus cases showing disease progression corneal collagen crosslinking (CXL) has been proven to be an effective, minimally invasive and safe procedure. CXL consists of a photochemical reaction of corneal collagen by riboflavin stimulation with ultraviolet A radiation, resulting in stromal crosslinks formation. The aim of this review is to carry out an examination of CXL methods based on theoretical basis and mathematical models, from the original Dresden protocol to the most recent developments in the technique, reporting the changes proposed in the last 15y and examining the advantages and disadvantages of the various treatment protocols. Finally, the limits of non-standardized methods and the perspectives offered by a customization of the treatment are highlighted.

Antioxidant Nutraceutical Strategies in the Prevention of Oxidative Stress Related Eye Diseases

This review aims to discuss the delicate balance between the physiological production of reactive oxygen species and the role of antioxidant nutraceutical molecules in managing radicals in the complex anatomical structure of the eye. Many molecules and enzymes with reducing and antioxidant potential are present in different parts of the eye. Some of these, such as glutathione, N-acetylcysteine, α-lipoic acid, coenzyme Q10, and enzymatic antioxidants, are endogenously produced by the body. Others, such as plant-derived polyphenols and carotenoids, vitamins B2, C, and E, zinc and selenium, and omega-3 polyunsaturated fatty acids, must be obtained through the diet and are considered essential nutrients. When the equilibrium between the production of reactive oxygen species and their scavenging is disrupted, radical generation overwhelms the endogenous antioxidant arsenal, leading to oxidative stress-related eye disorders and aging. Therefore, the roles of antioxidants contained in dietary supplements in preventing oxidative stress-based ocular dysfunctions are also discussed. However, the results of studies investigating the efficacy of antioxidant supplementation have been mixed or inconclusive, indicating a need for future research to highlight the potential of antioxidant molecules and to develop new preventive nutritional strategies.

Compaction of very thin corneas from ultraviolet A riboflavin-vitamin E transepithelial cross-linking

The purpose of the study was to determine the decrease in pachymetry of very thin corneas with advanced keratoconus due to corneal compaction from the ultraviolet-A (UV-A) irradiation phase of transepithelial (epi-on) cross-linking. Twenty removed corneal buttons were obtained from patients who underwent penetrating keratoplasty for advanced keratoconus. Removed corneal buttons selected from among the post-surgical specimens for this study had intact epithelium, no scarring or surgical cautery, endothelial cell density >2500 cells/mm², and average pachymetry over the measured points of below 400 μm. Corneas were mounted in a Franz chamber. Each epithelial surface was soaked in isotonic riboflavin and D-alpha-tocopheryl polyethylene glycol 1000 succinate (Ribocross® IROMED Group, Italy) for 15 min. Pachymetry was measured at three points over both the shielded and unshielded corneal halves for each corneal button. Surfaces were then washed in saline to remove the Ribocross®. Shields from UV-A irradiation over half of each cornea were then fixed to stand 5 mm above the test corneas. UV-A irradiation using the custom fast cross-linking (CF-CXL) protocol was then performed for the typical 10 ± 1.5 min, for a total energy of 1.08 ± 0.6 J/cm² after which pachymetry was re-measured. The average percent change in pachymetry was -0.43% ± 0.38% (maximum -1.06%) in the shielded half. Pachymetry change was -6.2% ± 2.2% (maximum 12%) in the cross-linked halves. In conclusion, we estimate that the change in corneal thickness from corneal compaction due to the cross-linking reaction itself was -5.8% ± 2.2%. Scanning electron microscopy of cross-linked corneal segments showed stromal fiber contraction.