[Rapid eye fatigue--causes and therapy].

Tired eyes even after a short period of strain are well known as asthenopia. This term derives from a Greek expression meaning 'weak eye'. The following reasons are to be taken into account: uncorrected refractional errors such as hyperopia and astigmatism, accommodative and fusional defects and heterophoria, or combinations there of. With many cases of asthenopia the clinical symptomatology may resemble an organic eye disease or an affection of the brain [dry eye, Graves' disease, myasthenia, special form of essential blepharospasm, neurogenic latent eye muscle palsies, narcolepsy]. It is the aim of a precise patient's history to differentiate between functional and organic causes. By means of case reports and diagnostic tools, the development of symptomatology and the therapy are discussed.