Contact lens and opthalmic solutions

Drug – bio-affecting and body treating compositions – Plant material or plant extract of undetermined constitution...

Reexamination Certificate

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C424S732000, C424S737000, C514S839000, C514S840000, C510S112000

Reexamination Certificate

active

06793941

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to contact lens and ophthalmic solutions and in particular relates to methods to disinfect and clean soft and rigid gas permeable (RGP) contact lenses, effectively and safely while maintaining convenience and comfort for the contact lens wearer.
By “effectively” we mean that the levels of specified pathogenic micro-organisms as well as other contaminants such as proteins, lipids, etc., are removed or reduced by a prescribed amount within the period of time contact lenses are kept in their storage case and storage solution. This is commonly taken to be “overnight” which is estimated as 6 hours. By “safely” we mean that the prescribed reduction in pathogen and other contaminant levels is accomplished without concomitant damage to the tissues of the human eye and without deleterious alteration of the contact lens itself. By “convenience” we mean that the contact lens care solution will be such that a minimum number of steps will be required to render the contact lenses clean and disinfected and the complete compliance of the wearer to the prescribed contact lens care procedures will be more likely. By “comfort” we mean that the eyes of the wearer will be able to tolerate the direct instillation of the solution.
2. Description of Related Art
Currently available contact lenses are made of hydrogels causing them to be soft so that they can be comfortably worm. Previously, contact lenses were either hard plastic (PMMA) or RGP and required the contact lens wearing patient to adjust to the uncomfortable sensation of a foreign body in the eye. The advent of soft contact lenses has resulted in an increased adoption of contact lenses by the general population.
Contact lenses are commonly worn on a daily basis and kept in a storage case/solution during the night hours or whenever they are not being worn. During the wear and normal handling of contact lenses, microorganisms as well as biomolecules such as lipids, proteins, etc. can become adhered to the contact lenses and thus transferred to the storage case/solution. Furthermore, a tear film that contains proteins, lipids, and even microorganisms, which represent the natural flora of the ocular surface, covers the surface of the eye. Any of these components found in the tear film or on the external surface of the eye or the surrounding skin can be carried into the storage case/solution on the contact lens.
Some of the microorganisms that may be transferred from the eye or fingers to the storage case/solution may multiply therein and may later be pathogenic to the human cornea or other ocular structures. When the contact lens is returned to the eye following its overnight soaking period, it is possible for these pathogens to be applied to the surface of the eye. Although human tears contain natural anti-microbial agents, a pathogen-bearing lens in contact with the cornea of the eye can serve as a reservoir of infection that might overcome the eye's natural defenses. This is especially the case for soft contact lens as the material tends to uptake the microorganisms. The result of microbial growth—bacterial, protozoan or even fungal—can cause damage to the eye resulting in impaired vision and even blindness. Therefore, contact lenses should be daily disinfected to eliminate pathogenic organisms, usually overnight, i.e., six to eight hours, to protect the wearer's eyes from infection.
As has been stated earlier, it is also possible that other materials of biological origin can be transferred to the contact lens during wear and upon handling and transfer between the eye and the storage case/solution. These materials include cellular debris, proteins, lipids, and inorganic ions such as those of calcium and magnesium. Such materials can adsorb to the surface or become embed in the sub-surface matrix of the soft contact lens often creating persistent deposits that can cause irritation by abrasion against ocular tissues, e.g., cornea and inner surfaces of the eye lids. Furthermore, these deposits can become sufficiently severe to significantly reduce the transparency of the contact lens perhaps leading to impairment of the optical performance of the contact lens. It is therefore of interest to prevent the deposition of or to break up any aggregations of these contaminating molecules during the period of overnight immersion of the contact lenses in the storage case/solution.
Various solutions have been developed over the years to ensure that contact lenses are essentially pathogen and deposit free and can be safely and comfortably worn following overnight storage. These contact lens solutions typically include anti-microbial substances as well as cleaning (active against both lipids and proteins), wetting and other agents for the disinfection and cleaning of contact lenses during storage after wear. These solutions generally have sufficient microbicidal activity that the numbers of potentially pathogenic microorganisms are reduced to a prescribed level during the overnight soaking period.
Disinfection agents typically used for other applications such as hard surface disinfection, instrument disinfection, topical skin disinfection, etc. are not necessarily applicable to contact lens and ophthalmic solutions. The high concentration used and aggressive nature of many of these agents are unsuitable for use with contact lenses due to interaction or damage to the lens or irritation to ocular tissue. “Strong” disinfecting agents are compounds such as thimerasol, chlorhexidine, hydrogen peroxide, and benzalkonium chloride. For example, three (3%) percent hydrogen peroxide instilled directly in the eye or a lens soaked in hydrogen peroxide and applied to the eye will result in pain and severe irritation.
In the case of hydrogen peroxide, prior art answers to the problem of irritation are disclosed in U.S. Pat. No. 3,912,451, 4,585,488, 5,145,644 and 5,7666,931. These references show various methods and chemistries wherein the disinfecting period is followed by a neutralizing step using catalase, an enzyme that catalyzes the breakdown of hydrogen peroxide to water. This approach has found some level of acceptance among contact lens wearers. However, acceptance has remained limited, because of the multiple steps of disinfection, neutralization, and rinsing are not convenient to the wearer. More importantly, the potential exists for the neutralization and rinsing steps to be completed incorrectly (non-compliance) leading to the potential for some residual hydrogen peroxide to come in contact with the surface of the eye with the onset of severe stinging and irritation.
More recently, so-called multipurpose solutions (MPS) with chemical disinfection agents, as disclosed in U.S. Pat. No. 4,407,791, 4,525,346, 4,758,595, 4,820,352, 4,836,956, 5,422,073, 5,560,186, 5,593,637, and 5,756,045, have largely supplanted hydrogen peroxide systems in the marketplace because they are far more convenient than the hydrogen peroxide systems. In this case the wearer need only purchase and use a single solution leading to advantages in cost and convenience. The challenge of disinfection and cleaning without harm to the eye or the lens is particularly acute with the MPS products, however, since all of the various activities, e.g., wetting, contaminant dispersion, and disinfection, are required to co-exist in a single solution without antagonistic effects of one component on the activity of another. Furthermore, because the MPS can be instilled directly into the eye, the active anti-microbial component of these solutions must provide the required degree of pathogen reduction while being free of irritating or damaging sequelae to the surface and the anterior segment of the eye or to the contact lens itself. There is no opportunity with an MPS to neutralize or rinse away the anti-microbial agent prior to applying the contact lens to the eye.
Generally therefore the art has found it difficult to formulate these MPS solutions to satisfy the following performance criteria. The successful solu

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