Acanthamoeba keratitis (AK) is a rare disease in which amoebae of the genus Acanthamoeba invade the clear portion of the front (cornea) of the eye. It affects roughly 100 people in the United States each year. Acanthamoeba are protozoa found nearly ubiquitously in soil and water and can cause infections of the skin, eyes, and central nervous system.Infection of the cornea by Acanthamoeba is difficult to treat with conventional medications, and AK may cause permanent visual impairment or blindness, due to damage to the cornea or through damage to other structures important to vision. Recently, AK has been recognized as an orphan disease and a funded project, orphan diseases Acanthamoeba keratitis (ODAK), has tested the effects of a diverse range drugs and biocides on AK. Pathogenesis
In the United States, Acanthamoeba keratitis is nearly always associated with soft contact lens use. Acanthamoeba spp. is most commonly introduced to the eye by contact lenses that have been exposed to the organism through the use of contaminated lens solution, using homemade saline-based solution or tap water, or from wearing contact lenses while bathing or swimming. However, it may also be introduced to the eye by exposure to soil or vegetation, or by trauma. In fact, the first case of Acanthamoeba keratitis described was due to ocular trauma. Once on the contact lens, Acanthamoeba is able to survive in the space between the contact lens and the surface of the eye.
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain. [1]. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy. The main symptom is loss of vision, with colors appearing subtly washed out in the affected eye. A pale disc is characteristic of long-standing optic neuropathy. In many cases, only one eye is affected and patients may not be aware of the loss of color vision until the doctor asks them to cover the healthy eye. Optic neuropathy is often called optic atrophy, to describe the loss of some or most of the fibers of the optic nerve. Ischemic optic neuropathy
In ischemic optic neuropathies, there is insufficient blood flow (ischemia) to the optic nerve. The anterior optic nerve is supplied by the short posterior ciliary artery and choroidal circulation, while the retrobulbar optic nerve is supplied intraorbitally by a pial plexus, which arises from the ophthalmic artery, internal carotid artery, anterior cerebral artery, and anterior communicating arteries. Ischemic optic neuropathies are classified based on the location of the damage and the cause of reduced blood flow, if known. Anterior ischemic optic neuropathy (AION) includes diseases that affect the optic nerve head and cause swelling of the optic disc. These diseases often cause sudden rapid visual loss in one eye.