Abstract
Glaucoma is an optical neuropathy associated to a progressive degeneration of retinal ganglion cells with visual field loss and is the main cause of irreversible blindness in the world. The treatment has the aim to reduce intraocular pressure. The first therapy option is to instill drugs on the ocular surface. The main limitation of this is the reduced time of the drug staying on the cornea. This means that high doses are required to ensure its therapeutic effect. A drug-loaded contact lens can diffuse into the post lens tear film in a constant and prolonged flow, resulting in an increased retention of the drug on the surface of the cornea for up to 30 min and thus providing a higher drug bioavailability, increasing the therapeutic efficacy, reducing the amount of administered drug, and thereby provoking fewer adverse events. Several different systems of drug delivery have been studied in recent decades; ranging from more simple methods of impregnating the lenses, such as soaking, to more complex ones, such as molecular imprinting have been proposed. Moreover, different drugs, from those already commercially available to new substances such as melatonin have been studied to improve the glaucoma treatment efficacy. This review describes the role of contact lenses as an innovative drug delivery system to treat glaucoma.
Highlights
Glaucoma covers a group of multifactorial optical neuropathies associated to a progressive degeneration of retinal ganglion cells that leads to a characteristic visual field loss pattern [1].These cells are central nervous system neurons with their cell bodies in the inner retina and the axons in the optic nerve, whose degeneration results in the cupping distinctive appearance of the optic disc and visual loss [2]
The main concern with this type of glaucoma is that 50% of the patients who suffer from it have intraocular pressure (IOP) values between 10 and 21 mm Hg at diagnosis, which is considered a normal range [6] and only after 30% of retinal ganglion cells have been lost do visual field defects not appear on perimetric testing [21,22]
Contact lenses are divided into two main groups according to their material: soft contact lenses, which are composed of hydrogel or silicone-hydrogel polymers, or rigid gas permeable (RGP) contact lenses
Summary
Glaucoma covers a group of multifactorial optical neuropathies associated to a progressive degeneration of retinal ganglion cells that leads to a characteristic visual field loss pattern [1]. There are several types of glaucoma, but the most common forms are primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG), the first being about seven times more frequent than the second in the United States and Europe [9] If this glaucoma is not treated, the course of the pathology is chronic, progressive and results in an irreversible loss of visual field that progresses in the form of tunnel vision and central vision is lost. The prevalence and risk of blindness from glaucoma are higher in developing countries [9]
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