A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision.
The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a point.
Uveitis is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. The uvea consists of the middle layer of pigmented vascular structures of the eye and includes the iris, ciliary body, and choroid. Uveitis is described anatomically, by the part of the eye affected, as anterior, intermediate or posterior, or panuveitic if all parts are involved. Anterior uveitis (iridocyclytis) is the most common, with the incidence of uveitis overall affecting approximately 1:4500, most commonly those between the ages of 20-60. Symptoms include eye pain, eye redness, floaters and blurred vision, and ophthalmic examination may show dilated ciliary blood vessels and the presence of cells in the anterior chamber. Uveitis may arise spontaneously, have a genetic component, or be associated with an autoimmune disease or infection. While the eye is a relatively protected environment, its immune mechanisms may be overcome resulting in inflammation and tissue destruction associated with T-cell activation.
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each 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].
Presumed ocular histoplasmosis syndrome (POHS) is a syndrome affecting the eye, which is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc and maculopathy.
Ocular ischemic syndrome is the constellation of ocular signs and symptoms secondary to severe, chronic arterial hypoperfusion to the eye. Amaurosis fugax is a form of acute vision loss caused by reduced blood flow to the eye; it may be a warning sign of an impending stroke, as both stroke and retinal artery occlusion can be caused by thromboembolism due to atherosclerosis elsewhere in the body. Consequently, those with transient blurring of vision are advised to urgently seek medical attention for a thorough evaluation of the carotid artery. Anterior segment ischemic syndrome is a similar ischemic condition of anterior segment usually seen in post-surgical cases. Retinal artery occlusion leads to rapid death of retinal cells, thereby resulting in severe loss of vision.
Susac's syndrome is a very rare form of microangiopathy characterized by encephalopathy, branch retinal artery occlusions and hearing loss. The cause is unknown but it is theorized that antibodies are produced against endothelial cells in tiny arteries which leads to damage and the symptoms related to the illness. Despite this being an extremely rare disease, there are 4 registries collecting data on the illness; two are the United States, one in Germany, and one in Portugal.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is an acquired inflammatory uveitis that belongs to the heterogenous group of white dot syndromes in which light-coloured (yellowish-white) lesions begin to form in the macular area of the retina. Early in the course of the disease, the lesions cause acute and marked vision loss that ranges from mild to severe but is usually transient in nature. APMPPE is classified as an inflammatory disorder that is usually bilateral and acute in onset but self-limiting. The lesions leave behind some pigmentation, but visual acuity eventually improves even without any treatment.
Macular telangiectasia is a condition of the retina, the light-sensing tissue at the back of the eye that causes gradual deterioration of central vision, interfering with tasks such as reading and driving.
White dot syndromes are inflammatory diseases characterized by the presence of white dots on the fundus, the interior surface of the eye. The majority of individuals affected with white dot syndromes are younger than fifty years of age. Some symptoms include blurred vision and visual field loss. There are many theories for the etiology of white dot syndromes including infectious, viral, genetics and autoimmune.
Bonnet–Dechaume–Blanc syndrome, also known as Wyburn-Mason syndrome, is a rare congenital disorder characterized by arteriovenous malformations of the brain, retina or facial nevi. The syndrome has a number of possible symptoms and can, more rarely, affect the skin, bones, kidneys, muscles, and gastrointestinal tract. When the syndrome affects the brain, people can experience severe headaches, seizures, acute stroke, meningism, and progressive neurological deficits due to acute or chronic ischaemia caused by arteriovenous shunting.
Behçet's disease (BD) is a type of inflammatory disorder which affects multiple parts of the body. The most common symptoms include painful sores on the mucous membranes of the mouth and other parts of the body, inflammation of parts of the eye, and arthritis. The sores can last from a few days, up to a week or more. Less commonly there may be inflammation of the brain or spinal cord, blood clots, aneurysms, or blindness. Often, the symptoms come and go.
Punctate inner choroiditis (PIC) is an inflammatory choroiditis which occurs mainly in young women. Symptoms include blurred vision and scotomata. Yellow lesions are mainly present in the posterior pole and are between 100 and 300 micrometres in size. PIC is one of the so-called White Dot Syndromes. PIC has only been recognised as a distinct condition as recently as 1984 when Watzke identified 10 patients who appeared to make up a distinct group within the White Dot Syndromes.
Vogt–Koyanagi–Harada disease (VKH) is a multisystem disease of presumed autoimmune cause that affects melanin-pigmented tissues. The most significant manifestation is bilateral, diffuse uveitis, which affects the eyes. VKH may variably also involve the inner ear, with effects on hearing, the skin, and the meninges of the central nervous system.
Photic retinopathy is damage to the eye's retina, particularly the macula, from prolonged exposure to solar radiation or other bright light, e.g., lasers or arc welders. The term includes solar, laser, and welder's retinopathy and is synonymous with retinal phototoxicity. It usually occurs due to staring at the Sun, watching a solar eclipse, or viewing an ultraviolet, Illuminant D65, or other bright light.[1]
The visual pathway consists of structures that carry visual information from the retina to the brain. Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
Retina→Optic nerve→Optic chiasma →Optic tract→Lateral geniculate body→Optic radiation→Primary visual cortex
Indocyanine green angiography (ICGA) is a diagnostic procedure used to examine choroidal blood flow and associated pathology. Indocyanine green (ICG) is a water soluble cyanine dye which shows fluorescence in near-infrared range, with peak spectral absorption of 800-810 nm in blood. The near infrared light used in ICGA penetrates ocular pigments such as melanin and xanthophyll, as well as exudates and thin layers of sub-retinal vessels. Age-related macular degeneration is the third main cause of blindness worldwide, and it is the leading cause of blindness in industrialized countries. Indocyanine green angiography is widely used to study choroidal neovascularization in patients with exudative age-related macular degeneration. In nonexudative AMD, ICGA is used in classification of drusen and associated subretinal deposits.
Sickle cell retinopathy can be defined as retinal changes due to blood vessel damage in the eye of a person with a background of sickle cell disease. It can likely progress to loss of vision in late stages due to vitreous hemorrhage or retinal detachment. Sickle cell disease is a structural red blood cell disorder leading to consequences in multiple systems. It is characterized by chronic red blood cell destruction, vascular injury, and tissue ischemia causing damage to the brain, eyes, heart, lungs, kidneys, spleen, and musculoskeletal system.
