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.
A Zenkers diverticulum, also pharyngeal pouch, is a diverticulum of the mucosa of the human pharynx, just above the cricopharyngeal muscle (i.e. above the upper sphincter of the esophagus). It is a pseudo diverticulum (not involving all layers of the esophageal wall). It was named in 1877 after German pathologist Friedrich Albert von Zenker. Signs and symptoms
In simple words, when there is excessive pressure within the lower pharynx, the weakest portion of the pharyngeal wall balloons out, forming a diverticulum which may reach several centimetres in diameter. More precisely, while traction and pulsion mechanisms have long been deemed the main factors promoting development of a Zenkers diverticulum, current consensus considers occlusive mechanisms to be most important: uncoordinated swallowing, impaired relaxation and spasm of the cricopharyngeus muscle lead to an increase in pressure within the distal pharynx, so that its wall herniates through the point of least resistance (known as Killians triangle, located superior to the cricopharyngeus muscle and inferior to the thyropharyngeus muscle. Thyropharyngeus and cricopharyngeus are the superior and inferior parts of inferior constrictor muscle of pharynx respectively). The result is an outpouching of the posterior pharyngeal wall, just above the esophagus.While it may be asymptomatic, Zenker diverticulum can present with the following symptoms:

Dysphagia (difficulty swallowing), and sense of a lump in the throat
Food might get trapped in the outpouching, leading to:
Regurgitation, reappearance of ingested food in the mouth
Cough, due to food regurgitated into the airway
Halitosis, smelly breath, as stagnant food is digested by microorganisms
InfectionIt rarely, if ever, causes any pain.