sɪsBased on the Random House Dictionary, © Random House, Inc. 2013.
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ptosis (ˈtəʊsɪs) ![[Click for IPA pronunciation guide]](http://static.sfdict.com/dictstatic/g/d/dictionary_questionbutton_default.gif) | |
| —n , pl ptoses | |
| prolapse or drooping of a part, esp the eyelid | |
| [C18: from Greek: a falling] | |
| ptotic | |
| —adj | |
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| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
ptosis pto·sis (tō'sĭs)
n. pl. pto·ses (-sēz)
Abnormal lowering or drooping of an organ or a part, especially a drooping of the upper eyelid caused by muscle weakness or paralysis.
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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ptosis
drooping of the upper eyelid. The condition may be congenital or acquired and can cause significant obscuration of vision. In congenital ptosis the muscle that elevates the lid, called the levator palpebrae superioris, is usually absent or imperfectly developed. If severe and not corrected in a timely manner, congenital ptosis can lead to amblyopia and permanent vision loss. Congenital palsy of the third (oculomotor) cranial nerve (which normally stimulates elevation of the upper lid) is a more rare cause of congenital ptosis.
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