Anisometropia refers to a condition when two eyes have unequal refractive power. Generally, a difference in power of one diopter (1D) or more is the accepted threshold to label the condition anisometropia. Patients can tolerate 3 D of anisometropia before it becomes clinically symptomatic with headaches, asthenopia, double vision and photophobia.In certain types of anisometropia, the visual cortex of the brain will not process images from both eyes together (binocular summation), and will instead suppress the central vision of one of the eyes. If this occurs often enough during the first 10 years of life while the visual cortex is developing, it can result in amblyopia, a condition where even when correcting the refractive error properly, the persons vision in the affected eye is still not correctable to 20/20. The name is from four Greek components: an- "not," iso- "same," metr- "measure," ops "eye." Antimetropia is a rare sub-type of anisometropia, in which one eye is myopic (nearsighted) and the other eye is hyperopic (farsighted). Around 0.1% of the population may be antimetropic. Causes
Anisometropia is caused by common refractive errors, such as astigmatism, far-sightedness, and myopia, in one eye.Anisometropia is likely the result of both genetic and environmental influences.Some studies suggest, in older adults, developing asymmetric cataracts may cause worsen anisometropia. However, anisometropia is associated with age regardless of cataract development: a rapid decrease in anisometropia during the first years of life, an increase during the transition to adulthood, relatively unchanging levels during adulthood but significant increases in older age.
Young athletes can reduce their risk of traumatic bone cyst by wearing protective mouth wear or protective headgear. History
Aneurysmal bone cysts are benign neoformations which can affect any bone. More than half occur in the metaphysis of long bones (especially femur and tibia) and between 12 and 30% in the spine. They were described in 1893 by Van Arsdale, who called these lesions "homerus ossifying haematoma". In 1940 Ewing used the term "aneurismal" to describe these lesions. Jaffé and Lichtenstein first coined the term "aneurismal cyst" in 1942 In 1950 they modified this term to "aneurismal bone cyst". They may be associated with bone tumors. The simple bone cyst is a common, benign, fluid-containing lesion, most commonly found in the metaphysis of long bones, typically the proximal humerus or femur. Pathologic fractures are common, often with minor trauma. These cysts typically resolve after skeletal maturity and are not typically associated with bone tumors. The cause  is unknown. These were first recognised as a distinct entity in 1910. Jaffe and Lichtenstein provided a detailed discussion of simple bone cysts in 1942.The traumatic bone cyst, also referred to as a simple bone cyst or hemorrhagic cyst, is a pseudocyst that most commonly affects the mandible of young individuals. It is a benign empty or fluid-containing cavity within the mandible body that does not have evidence of a true epithelial lining. This type of bone cyst is a condition found in the long bones and jaws.