Info

Polyquaternium-1

«6000

Yes

Yes

Abbreviations: RGP, rigid gas permeable; PMMA, polymethyl methacrylate.

Abbreviations: RGP, rigid gas permeable; PMMA, polymethyl methacrylate.

short lens-soaking period; (ii'i) it should not bind to the lens surface; and (iv) it should be compatible with the lens and not cause lens discoloration or alter the tint of colored contact lenses. Polyquad and dymed have most of these characteristics. They have been introduced recently into the marketplace and are performing to expectations (398,399).

Contact lens wearers may experience increasing awareness of their lenses during the day owing to ocular dryness (400). With some lens materials, this increase in awareness may arise from a decrease in the wettability of the lens surface. Dehydration of the lens or accumulation of debris on the lens surface can cause similar symptoms (401). The lens wearer may achieve relief from these symptoms with periodic administration of lubrication of rewetting drops (402). These solutions contain polymers or surfactants that enhance the wettability of the surface, facilitate the spreading of tears, and improve the stability of the tear film. They may also provide cushioning and lubrication actions, thereby reducing the frictional force between the eyelids and the lens. Some products are specifically designed to rehydrate the lens. These products are unpreserved and packaged in a unit-dose container. However, a preservative is required for a multidose product.

The emphasis that patients place on convenience has led to the development of single-bottle care products referred to as "multipurpose solutions". Such products do not require a separate cleaner and in some instances can be used as a rewetting drop. However, they require rubbing and rinsing of lenses to achieve adequate cleaning. Recent advances in technology along with careful selection of formulation components have resulted in products that do not require a rubbing step (403). These products have met all the microbiological and cleaning efficacy requirements, including those proposed in the ISO Guidelines. However, some newer products, although meeting the regulatory requirements during development, were found to cause microbial infection (404). FDA/ CDRH issued advice to patients wearing soft contact lenses, alerting them regarding an increase in incidence of reports of fungal infection in the United States. This fungal keratitis caused by Fusarium fungus can result in permanent loss of vision. Several patients with this infection required corneal transplants to save their vision.

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