It is important to keep all the surfaces as hydrated and lubricated as possible. The boundary between two different substances creates an interface.
Muco-mimetic tear substitutes act by lubricating and hydrating the interfaces, simulating, normalising and increasing the volume of the natural tear film
In order to increase the permanence of tear substitutes on the interfaces, it is necessary to increase the mucoadhesive properties of the substitute
The tear film has several functions: keeping the ocular surface healthy, protecting it from harmful foreign bodies, repairing damage and creating an anterior refraction surface.
The ideal tear substitute in a contact lens should compensate for the inadequate lubrication of the ocular surface.
Fonte: Current Medical Research and Opinion (2006)
HA: Hyaluronic Acid
TSP: Tamarind Seed Polysaccharyde
HPMC: Hydroxypropyl methylcellulose
CMC: Carboxymethyl cellulose
PVA: Polyvinyl alcohol
The characteristics of the two natural polymers, TSP and HA, provide the opportunity to create a synergy that enhances their already notable properties: hydration, wetting, protection of the ocular surface and favouring the regrowth of the epithelial microvilli. The microvilli act as support for the glycocalyx, a glycoproteic structure that increases the wettability of the ocular surface (normally hydrophobic) reducing the surface tension of the tear film and stabilising it for a longer period of time
First and only completely natural molecule used in contact lenses. It is an excellent natural lubricant. It prevents cell damage resulting from physical stress. Its purpose in nature is to attract and retain water maintaining high levels of hydration in cell tissues.
It is a substance with excellent mucomimetic properties, with rheological behaviour, similar to the tear film, characterised by high solubility in water with a three dimensional network structure (gel effect) It has pseudo plastic behaviour, when rubbed it loses viscosity becoming more fluid. It has non Newtonian behaviour or rather it acquires its original form once released from compression. It is thermo reversible and thermo resistant, fundamental characteristics for the production process. It is highly efficient even at low concentrations (1gr per litre of solution) and it is a gel with important bio-adhesive characteristics, fundamental in order for it to stay on the interfaces
• Increases the time of corneal permanence
• Increases tear volume
• Stabilises tears
• Improves tolerability
• Improves re-epithelialization
• Reduces friction
HA is one of the most absorbent molecules that exist in nature. The exceptional hydro-absorbent properties of this biopolymer improve the hydration of the interfaces and stabilise the tear film.
It is a polymer with an average molecular weight of 52,350 and is made up of three sugars; glucose, galactose and xylose in the molar ratio of 3:1:2. TSP has a branched chain made up of a cellulose polysaccharide protruding from the main chain that transports xylose
and galactose, similar to the MUC1 mucin, naturally present in tears. It is insoluble in organic solvents and it disperses in hot water forming a highly viscose gel, with maximum tolerability and adhesiveproperties.
This non-toxic and non-irritating polymer is a galactoxyloglucan, belonging to the xyloglucan family. It has non-Newtonian characteristics, rheological behaviour similar to that of the tear film. It also has mucomimetic, mucoadhesive and pseudo plastic properties.
TSP is a natural polymer, extracted from the Tamarind seeds. Its mucin-like molecular structure guarantees its muco-adhesive properties without increasing the viscosity.
TSP has a mucin-like ramified structure, similar to MUC1. The tear mimic carachteristics of this polymer enhances itsmuco-adhesive properties.
fusion technology uses the synergic interaction between HA and TSP to create a totally natural biocopolymer which is inserted into the contact lens material, thanks to Safilens' patented thermo-reversible hydration technique.
The release of the fusion copolymer onto the interfaces is caused by a series of interrelated factors: eyelid pressure, blinking and body temperature
• Sponge effect: due to eyelid pressure that squeezes and deforms the lens favours the release of the copolymer.
• Blinking: thanks to eyelid friction, reduces the viscosity of the copolymer, helping it to be released.
• The increased temperature of the cl when it comes into contact with the ocular surface exploits the thermo-reversible properties of the copolymer guaranteeing optimal dynamic viscosity
This patented technology, which incorporates the fusion copolymer into the contact lens and its subsequent release during wear, changes the interaction between the contact lens and the tear film, improving stability between the interfaces of the contact lens, tear film and epithelium
Soft contact lenses with FUSION technology have proven to have an important stabilising effect on the interfaces between contact lens - tear film - epithelium, which allows an effective and long lasting normalising effect on the tear film. This action provides effective protection to the ocular surface, thanks to the unique and excellent muco-adhesive and bio-adhesive properties of the natural TSP and HA copolymer
To achieve a brilliant beauty of the eye, it is important that the tear film surface is smooth and stable with adequate tear volume and that the tear lipid layer is present in adequate thickness.
QUOTE FROM The brilliant beauty of the eye: Light reflex from the cornea and tear film CORNEA 2006