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Eye Health Glossary

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macula

A small dark area of the retina that contains the photoreceptors responsible for sharp, high resolution central vision. The macula is the area of the retina that is involved in macular degeneration.

maculopathy

Any condition in which a disease is affecting the macula.

macular degeneration

Progressive eye disease affecting the macula which eventually leads to loss of central vision. Age-related macular degeneration is the most common cause of blindness in people aged 65 and over. Learn more about macular degeneration.

madarosis

Loss of eyelashes (or eyebrows).

medial rectus

The extraocular muscle (EOM) responsible for turning the eye toward the nose.

meibomian gland

Oil glands that are located within the eyelids. Meibomian glands secrete oils through pores along the lining of the eyelids that contribute to a stable tear film. Blockage of the meibomian gland can lead to the formation of a stye.

meningitis

Inflammation of the meninges, which is the membrane that covers the brain and the spinal cord.

metamorphopsia

Defect in vision that produces distorted images. Metamorphopsia is a potential symptom of progressive macular degeneration that can be detected using an Amsler grid.

microcornea

Cornea that is abnormally small.

microkeratome

A surgical device that is used to create the flap in LASIK eye surgery. A microkeratome works in essentially the same way that a deli meat slicer works, ensuring a clean cut that is of a pre-determined depth.

microphthalmia

Eyeball that is abnormally small.

miosis

Constriction of the pupil. Occurs reflexively to an increase in light levels, to a switch in fixation from a distant object to a near object, or in response to certain miotic drugs.

monocular

Refers to use of only one eye.

monovision

A refractive correction of presbyopia, in which one eye is corrected for distance vision and the other eye is corrected for near vision, either by contact lenses, glasses, or laser eye surgery. While monovision eliminates the need for bifocals or reading glasses, depth perception is essentially disabled because the eyes are no longer working together (instead one eye is used for distance and the other eye is used for near vision).

mucormycosis

Rare fungal infection that is frequently fatal.

multifocal

Any lens that has more than one focal length (ie. more than one power). Bifocals, trifocals, and progressive addition lenses (PALs) are all examples of multifocal lenses.

myasthenia gravis

Neuromuscular disorder that commonly affects the muscles of the eye. Muscle weakness, fatigue, and disability leads to various complications, including ptosis and double vision.

Mydriacil

Commercial name for a drug known as tropicamide that is used as an anesthetic, cycloplegic and mydriatic, to pharmaceutically dilate the pupil.

mydriasis

Dilation of the pupil. Occurs reflexively to a decrease in light levels or in response to certain mydriatic drugs (such as Mydriacil (tropicamide) or atropine).

myokymia

Involuntary eye twitch. For most people, an eye twitch is vaguely bothersome and subsides within a few hours (or even minutes). Learn more about Myokymia.

myopia

Common refractive vision problem in which the focusing power of the eye is too strong such that an image comes to focus before the retina. Myopia (nearsightedness) is corrected with concave (minus) lenses. Learn more about Myopia.

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