Blindness is the inability to see. The leading causes of chronic blindness include cataract, glaucoma, age-related macular degeneration, corneal opacities, diabetic retinopathy, trachoma, and eye conditions in children (e.g. caused by vitamin A deficiency).

Age-related blindness is increasing throughout the world, as is blindness due to uncontrolled diabetes. On the other hand, blindness caused by infection is decreasing, as a result of public health action. Three-quarters of all blindness can be prevented or treated.

Mángzhèng jiùshì wú-shìjué. Mànxìng mángzhèng de shǒuyào yuányīn bāokuò báinèizhàng, qīngguāngyǎn, niánlíng-xiāngguānxìng huángbān tuìhuà, jiǎomó hùnzhuó, tángniàobìng shìwǎngmó-bìngbiàn, shāyǎn hé értóngqī yǎnjí (lìrú, yóu wéishēngsù A quēfázhèng zàochéng de yǎnjí).

Yǔ niánlíng yǒuguān de mángzhèng tóng bùjiā kòngzhì de tángniàobìng yǐnqǐ de mángzhèng yīyàng, zài shìjiè gèdì bùduàn zēngduō. Lìngyī fāngmiàn, gǎnrǎn yǐnqǐ de mángzhèng zhújiàn jiǎnshǎo, zhè shì yóuyú cǎiqǔle gōnggòng wèishēng xíngdòng. Sì fēnzhī sān de mángzhèng shì kěyǐ yùfáng huò zhìliáo de.