Вот например http://medportal.ru/enc/ophthalmology/reading/12/http://ru.wikipedia.org/wiki/%D0%92%D0%B8%D1%82%D0%B0%D0%BC%D0%B8%D0%BD%D0%BD%D0%BE-%D0%BC%D0%B8%D0%BD%D0%B5%D1%80%D0%B0%D0%BB%D1%8C%D0%BD%D1%8B%D0%B5_%D0%BA%D0%BE%D0%BC%D0%BF%D0%BB%D0%B5%D0%BA%D1%81%D1%8B_%D0%B4%D0%BB%D1%8F_%D0%B7%D1%80%D0%B5%D0%BD%D0%B8%D1%8F