Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2001-09-25
2003-03-04
Delcotto, Gregory (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S421000, C510S434000, C510S488000, C510S510000, C134S042000, C514S912000
Reexamination Certificate
active
06528465
ABSTRACT:
The present invention relates to a viscosity enhanced ophthalmic solution, having a detergent action on contact lenses. In particular, the invention relates to a preparation in the form of a collyrium to prevent the build up of hydrophobic deposits on contact lenses after having worn them, while maintaining the wettability and transparency, and at the same time to improve the tolerability and reduce the irritating capability thereof.
Any kind of contact lens constitutes a foreign body placed on the ocular surface, the tolerability there of being directly related t o the presence and quality of the preocular lacrimal film. The latter is a complex structure that covers the conjunctiva and the exposed surface of the eyeball, resulting from the co-operation of a solid layer constituted of the complex of the epithelium cornea and glycocalyx (the glycoproteic coating of the epithelial cells, consisting of their secretions), with a liquid layer that consists of the lacrimal film itself. The solid layer has the function of allowing the adherence of the fluid part of the lacrimal film to the ocular surface, while the liquid layer is constituted by three superposed layers, each having a different constitution: a mucous layer, an aqueous layer and a lipid layer.
The internal mucous layer of the fluid lacrimal film is constituted of a mixture of viscoealstic, hydrated glycoproteins (mucin), which represent three quarters of the film and that adhere to the above mentioned solid layer, thus constituting a hydrophilic surface. The aqueous layer is the intermediate portion of the lacrimal film, that is distributed on said hydrophilic surface and that is essentially constituted of water, inorganic and organic salts, sugars, proteins, enzymes and other complex structure biopolymers (such a s the mucins themselves). The substances dissolved in this layer perform structural, osmotic, buffering, nutritional, and defence functions for the lacrimal film with respect to the tissues of the ocular surface. The external lipid layer is constituted of waxes, fatty acids, and cholesterol esters and performs the function of stabilizing the lacrimal film, controlling the water loss caused by evaporation.
The above described three-layer structure constitutes a complex biological system, the main functions of which a re that of protecting the surface of the eye, of maintaining its hydration, lubrication and the cleaning of the cornea surface and as a whole to ensure correct vision. The perfect balance and the continuous renewal of the lacrimal film are necessary conditions so that it may perform these functions. In particular, a constant but not excessive evaporation of water from the ocular surface must be obtained, in order to maintain the osmolarity around the physiological value of about 300 mOsm/l, and the lacrimal film must be continuously re-distributed over the cornea surface as a consequence of blinking. This is more important for wearers of contact lenses, because in this case only a lacrimal film that is stable, sufficiently thick, regularly renewed, with an adequate chemical composition and correct osmolarity, can set-up the correct environment for rendering the contact lens biologically compatible with the ocular surface.
In normal physiological conditions, the production rate of the aqueous portion of tears is, under minimum stimulation conditions, of about 1 &mgr;l/min, while the tear turnover time in rest conditions is of about 16-20 minutes. Such turnover is on the contrary faster under conditions of eye irritation, and very slow in the case of lacrimal hyposecretion. The presence of the contact lens over the ocular surface tends to increase the lacrimal secretion rate as well as the blinking rate.
However, persons having tolerance problems with contact lens tend to increase the secretion rate more slowly or to blink in an incomplete way. With prolonged use, the lens may produce a weakening of the lacrimal film structure (also because of greater evaporation) and, consequently a reduced supply of oxygenated tears to the cornea and a reduction of the tolerability of the lens by the ocular surface.
As a consequence, the reduction of the lacrimal volume available for the ocular surface and/or the presence of an unstable lacrimal film increase the rate of formation of deposits on the ocular surface and on the inner surface of the lens, and these may cause an appreciable reduction of the wettability of the lens itself, thus accelerating the formation of new deposits.
It may be noted that any material that contacts a biological fluid containing proteins is almost immediately covered by a thin protein film; if such film deposited on the lens surface has the time to dry-up between two subsequent blinks, it may be contaminated by lipids constituting the surface layer of the lacrimal film. A hydrophobic area is then set up on the lens surface that is poorly wettable by the lacrimal fluid and which reduces the transparency of the lens over time.
A part of the hydrophobic deposits formed on the lens may be detached and carried away by the rubbing action of the eyelids during the blinking. However the part that adheres to the lens undergoes a protein denaturation following drying and may cause the creation of stable bonds between the deposits and the polymer of which the lens is formed. A undesired feedback is therefore generated, in which the reduced wettability of the lens leads to an increase of the deposits thereon and on the eye, and vice-versa.
As a consequence, the contact lens becomes less transparent and loses its initial optical characteristics. This may not only cause bad vision, but may also be the source of irritation and inflammatory processes of the ocular surface, of progressive intolerance to lenses, of modifications to the conjunctival epithelial structure with a loss of mucous-secreting cells and of allergic phenomena such as giganto-papillar conjunctivitis (GPC).
In order to improve the tolerability of contact lenses and to reduce the feeling of irritation and corneal dryness, usually the same drop-instilled ophthalmic solutions are used, known commonly as artificial tears. The latter are used to treat dry-eye syndrome or dry keratoconjuctivitis, a pathology generally caused by lacrimal senile hyposecretion, or by the use of some systemic drugs. In the simplest case, these preparations have only a moistening action, and are constituted by physiological solutions which are neutral and isotonic with respect to the lacrimal fluid, based only on sodium chloride or on a balanced mixture of several electrolytes. Such formulations achieve the objects of increasing the lacrimal volume, humidifying the ocular surface, diluting the mucus deposits and to a small extent, carrying away debris and foreign bodies. They however have an extremely reduced duration of activity (of the order of few minutes) because the solution is rapidly drained by the conjunctival sac.
In order to overcome the above disadvantages, various formulations of artificial tears have been introduced which are made viscous by means of the addition of high molecular weight agents, usually hydrosoluble polymers of synthetic, semi-synthetic or natural origin. In this respect, it has been experimentally shown that an artificial tear, in order to have a high precorneal permanence time and in order to be at the same time tolerated by the patient, must have properties as close as possible to those of the mucin dispersions, i.e. it must behave as much as possible as a mucomimetic substance. This requires, first of all, a particular non-Newtonian rheologic behaviour, in which the viscosity is not constant, but changes as a function of the shear stress to which the fluid is subjected.
Glycoproteins of the lacrimal fluid in an aqueous solution have a high viscosity in rest conditions, i.e. between two consecutive blinkings and a very low viscosity during a blinking, i.e. when they are subjected to a shear stress. This rheological behaviour typical of non-Newtonian fluids, and in particular of the pseudoplastic ones, lead, on one hand to hig
Browning Clifford W.
Delcotto Gregory
Laboratoire Medidom S.A.
Woodard, Emhardt, Naughton Moriarty & McNett LLP
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