Sight is a very precious sense. Most information about our surroundings is gathered by the eye, which is literally a 'window' for the brain. With an aging population, the prevalence of sight-threatening ocular diseases continues to increase. Thus, for instance, more than 70 million people suffer from glaucoma worldwide.1-3 Visual impairment caused by diabetes affects up to 90% of diabetics over 10 years of age. Likewise, pathological dry eye and ocular allergic conditions afflict > 100 million patients worldwide, and age-related macular degeneration (AMD) is the leading cause of blindness among the elderly, affecting up to 28% of patients after the seventh decade of life.2 Consequently, the discovery and development of therapeutic products for the treatment of these various ocular diseases is of paramount importance, and is being actively pursued within the pharmaceutical industry.1-3
The eye is a somewhat immune-privileged organ, composed of the cornea and conjunctiva on the ocular surface (Figure 1). The anterior chamber of the eye, between the lens and cornea, contains the aqueous humor (AH), a fluid that is continuously produced by the nonpigmented ciliary epithelial cells of the ciliary body process. The AH drains from the eye via the trabecular meshwork into the canal of Schlemm and then into the venous circulation. Under normal circumstances the rate of influx and efflux of AH is constant, maintaining a certain intraocular pressure (IOP), that keeps the eye rigid and thus permits light to be transmitted from the cornea through the lens to the retina at the back of the eye. The AH also provides vital nutrients to the avascular corneal and lens tissues. The iris lies in front of the lens and forms the pupil, which controls the amount of light transmitted through the lens to the retina. The retina relays the images to the brain via the optic nerve at the posterior end of the eye. Behind the lens is a jelly-like material (vitreous humor) that keeps the posterior chamber of the eye filled and rigid, and thereby provides a cushion and support for the retina lining the posterior wall of the eye. The retina is nourished by a vascular bed of capillaries of the choroid plexus that also remove the waste products from the retinal tissues. Nerve impulses from the retina are transmitted to the brain via the optic nerve. The various diseases of the eye, their etiologies, and treatments are discussed herein, with priority given to the most prevalent and sight-threatening diseases.
Was this article helpful?