N
“N” selections in the Glossary of Terms for
Anatomy, Physiology & Pathology of the Human Eye
To see another alphabetized section, click on a letter below:
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
- nanometer (nm)
- millimicron; one billionth of a meter
- nearpoint stress
- stress placed on the ciliary muscles of the eyes from weeks or months of prolonged near work without sufficient rest; can cause eyelid twitching, eyestrain, headaches, and even myopia or increased myopia
- nearsightedness
- see myopia
- nerve, optic
- see optic nerve
- neuritis, optic
- see optic neuritis
- neuropathy, Leber’s hereditary optic (LHON)
- see Leber’s hereditary optic neuropathy (LHON)
- neuropathy, optic
- see optic neuropathy
- nevus
- a raised freckle, usually present at birth, on the skin, choroid, or iris; contains melanocytes; sometimes can develop into a malignant melanoma
- nucleus
- the central, most dense portion of the crystalline lens; a specialized organelle of eukaryotic cells that is essential to cellular functions (as reproduction, metabolism, and protein synthesis), is composed of nuclear fluid and a nucleoprotein-rich network from which the genetic material (chromosomes and nucleoli) arise, and is enclosed in a definite membrane; a mass of gray matter or group of nerve cells in the central nervous system
- nystagmus
- involuntary, rhythmical, repeated oscillations of one or both eyes, in any or all fields of gaze; may be pendular (with undulating movements of equal speed, amplitude, and duration, in each direction) or jerky (with slower movements in one direction, followed by a faster return to the original position); reduced acuity caused by the inability to maintain steady fixation; exact cause unknown
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