Loss of vision is a very serious issue as eyesight is the sense bringing us about 90% of information from the surroundings. This is the reason why vision loss is a greatly feared condition.
Visual sensations are transmitted through ocular apparatus to retina. Retina contains many specialized cells that are capable of converting the visual input into neuroelectric signals that are transmitted into brain by nerve fibers forming optical nerve. An error occurring anywhere in this complex system may result in vision loss.
In the present day, cataract is in developed countries probably the most common cause of visual impairment including blindness. It is a disease of eye lens that loses its quality and is no longer able to transmit visual perception to the retina. Fortunately, this is a very well treatable condition; surgical treatment of cataracts is nowadays performed routinely.
Glaucoma is related to increased pressure of the intraocular fluid. The pressure damages the retina and if long-time untreated, it can cause blindness. The therapy is either conservative (medication reducing intraocular pressure) or invasive (eye surgery aimed at ensuring better outflow of ocular fluid).
Macula is a location in retina with the highest concentration of sensory cells. Macular area is the best in perceiving colors and ensures the best image quality. Disease is typical for the elderly and its gradual occurrence involves influence of age, oxidative stress and atherosclerosis of retinal arterioles. It is reported the proportion of zinc deficiency.
This is a dangerous complication of untreated diabetes. Blood vessels of the retina are permanently damaged by diabetes, clog and this process is associated with formation of new blood vessels. These new are however poor, insufficient can crack and bleed can irreversibly damage the retina. That is the reason why patients with diabetes must regularly attend an eye examination to timely treatment to avoid blindness.
This used to be the most common cause of blindness worldwide and it is still widespread in developing countries. Trachoma incidence however sharply decreases with generally improvement of quality and accessibility of medical care. Trachoma is an infectious disease caused by intracellular organism known as chlamydia.
There are a number of birth defects causing blindness either alone or combined with deafness and other symptoms. Especially albinos (people with congenital deficiency of pigment) tend to be relatively more affected by blindness. Congenital blindness occurs in children whose mothers underwent rubella.
This compound is chemically similar to alcohol. It comes into existence, for example, by poor distillation of alcoholic products. In our body it is metabolized by the same enzymes as alcohol, but methanol is converted to highly toxic products including formic acid. These aggressive substances may damage a number of organs including the optic nerve.
Any physical damage of eye may be associated with the loss of its function. Eye damage caused by corrosive acids and bases is especially dangerous.
Vitamin A is essential for production of visual pigment rhodopsin that is essential for vision in shadow. Therefore, vitamin A deficiency leads to visual impairment that is evident especially in dim lighting (so-called night blindness). More serious consequence is disruption of mucosal tear ducts leading to drying up of the conjunctiva and cornea. If this condition is not solved, it can eventually lead to irreversible eye damage and permanent loss of vision.
Form of shingles that affects eye and surrounding skin can cause vision loss. Therefore, patients with ocular form of shingles are usually hospitalized and receive intravenously higher doses of antiviral drugs.
It is not so common but disruption of vision may be related to affection of nerve pathway or visual center in brain cortex. It happens usually in a brain tumor of pituitary gland. Pituitary gland is located near crossing of both optic nerves. Tumors may oppress nerve fibers and cause visual field defects. If not treated the patient may gradually become completely blind.
Short-term monocular blindness may be caused by blood clot affecting artery that nourishes the eye with blood. Such blood clotting may be a warning sign of an impending stroke. This short-term monocular blindness is technically referred to as amaurosis fugax and it is a good reason to immediately visit a doctor.