Hwabyeong or Hwapyŏng (hangul: 화병, hanja: 火病) is a Korean somatization disorder, a mental illness which arises when people are unable to confront their anger as a result of conditions which they perceive to be unfair. Hwabyeong is known as a Korean culture-bound syndrome. Hwabyeong is a colloquial name, and it refers to the etiology of the disorder rather than its symptoms or apparent characteristics. In one survey, 4.1% of the general population in a rural area in Korea were reported as having hwabyeong. Hwabyeong is similar to Amuk. The word hwabyeong is composed of hwa (the Sino-Korean word 火 for "fire" which can also contextually mean "anger") and byeong (the Sino-Korean word 病 for "syndrome" or "illness"). It may also be called ulhwabyeong (鬱火病), literally "depression anger illness". Symptoms
Physical symptoms include:

palpitations
anorexia
dry mouth
insomnia
thoracic/chest pressure
respiratory difficulties
epigastric mass
headache
a whole-body sensation of heat (distinct from heat intolerance, a symptom of hyperthyroidism)Psychological symptoms include:

being easily startled
externalization of anger, also known in Korean as "bun" (憤, "eruption of anger"), a Korean culture-related sentiment related to social unfairness
generally sad mood
frequent sighing
a feeling of "eok-ul" (抑鬱, [feeling of] unfairness)
being easily agitated
feelings of guilt
feelings of impending doomDiagnosed patients may also have a medical history of prior major depressive disorder, dysthymic disorder, anxiety disorders, somatoform disorders, or adjustment disorder according to the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) criteria.Diagnosed patients are most likely to be middle-aged, post-menopausal women with low socio-economic status.
A Brazilian study published in 2005 found that 34% of the students in one city were astigmatic. Regarding the prevalence in adults, a recent study in Bangladesh found that nearly 1 in 3 (32.4%) of those over the age of 30 had astigmatism.A Polish study published in 2005 revealed "with-the-rule astigmatism" may lead to the onset of myopia.A number of studies have found the prevalence of astigmatism increases with age. History
As a student, Thomas Young discovered that he had problems with one eye in 1793. In the following years he did research on his vision problems. He presented his findings in a Bakerian Lecture in 1801.Independent from Young, George Biddell Airy discovered the phenomenon of astigmatism on his own eye. Airy presented his observations on his own eye in February 1825 at the Cambridge Philosophical Society. Airy produced lenses to correct his vision problems by 1825, while other sources put this into 1827 when Airy obtained cylindrical lenses from an optician from Ipswich. The name for the condition was given by William Whewell.By the 1860s astigmatism was a well established concept in ophthalmology, and chapters in books described the discovery of astigmatism.In 1849, Irish English physicist and mathematician George Stokes invented Stokes lens to detect astigmatism. In 1887 American ophthalmologist Edward Jackson revised the Stokes lens concept and made a cross cylinder lens to refine power and axis of astigmatism. In 1907 Jackson described determination of the axis of a correcting cylinder in astigmatism using a cross cylinder.