The most common diseases of the eye are conjunctivitis and myopia. Conjunctivitis is common in children and young adults, who may suffer from bacterial conjunctivitis due to improper eye hygiene, mainly due to yellow, pus-like stools. Young people may suffer from viral conjunctivitis, mainly due to redness, tearing, and foreign body sensation, if they have been drinking alcohol or have a decreased systemic resistance. Allergic conjunctivitis is also common in spring and fall, mainly due to red, itchy eyes and often combined with allergic rhinitis. In addition, middle-aged people may often suffer from iridocyclitis, which is mainly characterized by redness and swelling of the eyes. Cataracts or glaucoma are most common in the elderly, mainly due to clouding of the lens or increased intraocular pressure. Myopia is common in children, mainly because they do not see distant objects clearly and have myopic refraction after dilated pupils, so myopia is very common in children who use more eyes.