1. THE USE OF SODIUM HYALURONATE GEL 0.3% IN THE MANAGEMENT OF POST-KERATOPLASTY PATIENTS, AND PATIENTS WITH CHRONIC REFRACTORY DRY EYE AND OTHER OCULAR SURFACE PROBLEMS. Prof. Clive Peckar. Dept. Ophthalmology. Warrington. UK. Purpose: Topical Sodium Hyaluronate (SH) 0.18% has been used in the management of Dry Eye Syndrome (DES) and corneal surface problems. Associated with symptoms of ocular discomfort, dryness, scratchiness, burning, soreness and grittiness, the underlying mechanism of DES is still unclear. Therefore, treatment is based on symptom relief rather than cure. Because of its ability to stabilise the tear film and promote epithelial healing via its preservative- free, specific muco-adhesive, water retentive, and viscoelastic properties, 0.18% SH has proved effective in reducing subjective symptoms intensity on VAS and objective corneal staining with fluorescein. Moderate to severe dry eye cases often require hourly or half hourly treatment with ocular lubricants, but despite this regime many patients remain symptomatic. As rapid and recurrent blinking – a characteristic symptom of more pronounced DES - correlates with a rapid tear film break up time (TFBUT), the manufacturers of Vismed carried out research to find if different concentrations of topical SH might prove more effective in retaining tear film integrity. The non-Newtonian behaviour of tear film reduces viscosity as shear rate increases, this viscoelasticity is emulated by Vismed (fig. 1).The in vitro study by Nakamura et al (1993) investigated the potential for hyaluronan (0.1%, 0.5% and 1.0%) to retain water. A significant (p<0.05) difference was found between vehicle and all of the SH concentrations assessed, and a dose- dependent increase in water retention was observed. Based in part on these findings, a highly viscous 0.3% preservative-free Sodium Hyaluronate Gel was introduced in 2004 for the effective management of persistent and severe symptomology associated with DES. This paper describes 20 patients who attended with severe dry eyes and were treated with 0.3% Sodium Hyaluronate in order to achieve a more stable pre-corneal tear-film, and thus a relief of symptoms. Patients and Methods: Location: Warrington Hospital and Spire Cheshire Hospital, Warrington UK.Patients attending between May 2004 and January 2008 20 Patients with severe kerato-conjunctivitis sicca, who remained symptomatic following puncto-canalicular occlusion with intra-canalicular implants (SmartPlugs™) and regular instillation Sodium Hyaluronate 0.18% drops (Vismed™), were changed to Sodium Hyaluronate 0.3% (Vismed Gel™). Conclusion: Sodium Hyaluronate 0.3% (Vismed Gel™) is effective, safe, and well tolerated in treating symptoms associated with severe “dry eye syndrome”, and represents a valuable addition to the Ophthalmic Specialist’s armamentarium for the management of patients with severe dry eyes. Results Fig.1

2. The tears produced by the glands in the secretory system combine in the eye to form a thin tear film that covers the corneal epithelium A stable precorneal tear film is vital for the health of the cornea as well as the optical quality of the cornea During blinking, the rate of shear can be very high which, if transmitted to the epithelial surfaces, can cause cell damage The viscoelastic properties of the tear film lubricate and cushion the eye during all types of eye movement The non-Newtonian behaviour of tear film reduces viscosity as shear rate increases Its elastic component can help absorb energy during rapid eye movements In a healthy eye, the precorneal tear film begins to evaporate after 15 to 30 seconds between blinks. If the tear film isn’t regenerated, dry spots can form on the cornea, leading to problems such as dry eye Role of the mucus layer The mucus layer plays a vital role in tear film stability and allows the aqueous layer to adhere to the epithelial cells of the cornea. By lowering the surface tension between these two layers, it acts as a wetting agent as well as a stabilising agent for the thin precorneal tear film between blinks. The mucus strands trap desquamated epithelial cells, excessive lipid contamination and debris (especially microorganisms). These are then removed from the eye in the aqueous layer during the blinking process. Mucus displays non-Newtonian and elastic behaviour (viscoelasticity). This viscoelasticity is emulated by the main component in Viscoseal – Hyaluronic Acid. Mucus is relatively thick and clings to the surface of the eye when the eye is at rest; however, when the eye blinks the mucus layer becomes much thinner and spreads easily over the surface, providing lubrication. The elastic properties of the mucus help this layer to absorb energy during the blinking process.Rate of shear = the relative velocity of the lid and eyeball, divided by the thickness of the fluid layer. During blinking, the rate of shear can be very high. If shearing forces are transmitted to the epithelial surfaces, cell damage and painful dragging sensations may occur. The non-Newtonian behaviour of tear film can help by reducing viscosity as the shear rate increases. The elastic component of the tear film helps it to absorb energy during blinking. In combination, the viscoelastic properties of the mucus strands (in the aqueous layer) and the mucus gels (close to the epithelial surface) cushion and lubricate the eye during all types of eye movement. Hydrophilic side Hydrophobic side A vesicle-like foamy secretion is evident along the lower lid margin. The tear film break-up time was reduced to less than 2 seconds. The patient had a pronounced dry eye syndrome with disturbance of the composition of the tear film Due to its amphiphilic structure, HA can trap and retain large volumes of water.