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It occurs when exposure to a substance – specifically, a neurotoxin or neurotoxicant– alters the normal activity of the nervous system in such a way as to cause permanent or reversible damage to nervous tissue. [1] This can eventually disrupt or even kill neurons, which are cells that transmit and process signals in the brain and other ...
Bilateral cataracts in an infant due to congenital rubella syndrome. Signs and symptoms vary depending on the type of cataract, though considerable overlap occurs. People with nuclear sclerotic or brunescent cataracts often notice a reduction of vision. Nuclear cataracts typically cause greater impairment of distance vision than of near vision.
Visual impairment can also be caused by problems in the brain due to stroke, premature birth, or trauma, among others. [12] These cases are known as cortical visual impairment. [12] Screening for vision problems in children may improve future vision and educational achievement. [13] Screening adults without symptoms is of uncertain benefit. [14]
At some point—usually as you enter middle age—most people develop this eye condition, which is a clouding of the eye’s lens that can get progressively worse and impair your vision.
Long-term contact lens use can lead to alterations in corneal thickness, stromal thickness, curvature, corneal sensitivity, cell density, and epithelial oxygen uptake. . Other structural changes may include the formation of epithelial vacuoles and microcysts (containing cellular debris), corneal neovascularization, as well as the emergence of polymegethism in the corneal endoth
The optic nerve can be at very high risk for damage from insufficient blood supply due to swelling (from lack of oxygen) in a confined bony space resulting in a compartment syndrome. Restricted blood flow can lead to permanent damage to the optic nerve and result in blindness (often in both eyes).
Trauma can cause cataracts in childhood. [2] [4] There are different types of traumatic injury that cause cataracts in different parts of the world. Child abuse may cause traumatic injury to the eye and cataracts. [2] Open globe injuries are more often associated with cataracts than closed globe injuries. [4]
Global brain ischemia occurs when blood flow to the brain is halted or drastically reduced. This is commonly caused by cardiac arrest. If sufficient circulation is restored within a short period of time, symptoms may be transient. However, if a significant amount of time passes before restoration, brain damage may be permanent.