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- macula
- Small centralized area of the retina responsible for acute central vision. Damage to this
portion of the retina severely limits a patient’s ability to read, recognize faces and perform
any other task that requires straight-ahead vision.
See Free Eye Tests.
- macula lutea
- The cone-rich area of the human eye that contains the fovea. Also called yellow spot.
- macular degeneration
- Degeneration of the photoreceptors in the macula or central region of the retina. This area
of the retina is responsible for central vision, used for reading, seeing faces, and so on.
Often associated with aging.
See Age-related Macular Degeneration in Eye Care Encyclopedia.
- malignant melanoma
- Cancer of the melanocytes, the cells that produce pigment in the skin. Most common in people with fair skin, but can occur in all races. Appears as a dark, mole-like spot that spreads and, unlike a mole, has an irregular border. Tendency toward melanoma may be inherited, and risk increases with overexposure to the sun and sunburn. Fair-skinned people and people with a family history of melanoma should always use a high-SPF sunscreen when outdoors. Detected early, melanoma is almost always treatable, but undetected melanoma can spread and become fatal.
- medial
- Medical term used to indicate “nasal or towards the nose.”
- meibomian gland
- Little glands in the eyelids that make a fatty lubricant which they discharge through tiny openings in the edges of the lids. The meibomian glands can become inflamed, a condition termed meibomianitis or meibomitis. Chronic inflammation of the meibomian glands leads to a cyst, also called chalazion, which is a pimple in the margin of the eyelid. The meibomian glands are also known as the palpebral glands, tarsal glands, or tarsoconjunctival glands.
- melanin
- Black pigment in the pigment epithelium cells that absorbs light not captured by the retina, thereby preventing the light from being reflected off the back of the eye.
- mesopic
- Intensities of light under which both cones and rods operate.
- microkeratome
- Sophisticated surgical device used to shave a very thin amount of the cornea at a
predetermined depth. Used in LASIK refractive vision correction procedure to
create the corneal “flap” which is lifted. Then the Excimer laser sculpts the
underlying corneal tissue.
See Laser In-situ Keratomileusis in Eye Care Encyclopedia.
- microspectrophotometry
- A procedure that involves passing a narrow measuring beam through the outer segments of individual photoreceptors to measure absorbancy in excised retinas.
- miosis
- Condition in which the pupil is constricted. Occurs as a normal response to a
bright light stimulus, to focusing on a near object (known as accommodation), or
to administer certain drugs.
See Free Eye Tests.
- monochromat
- An individual who is completely color-blind.
- mucoprotein
- mucoid
- Any of a group of various complex conjugated proteins that occur in body fluids and tissues.
- multi-focal
- Eyeglasses or contact lenses that allow the wearer to focus through different
prescriptions for different distances on the same lens. Bifocals have two points of
focus, one for distance and the other for near, while trifocals have three points of
focus — distance, intermediate and near. Progressive “no-line” eyeglass lenses
offer a continuous range of focus from top to bottom.
See Free Eye Tests.
- multiple sclerosis
- Chronic central nervous system disorder in which there is loss of the protective myelin
sheath surrounding nerve tissue. Effects on the eye include optic nerve inflammation with
reduced vision, double vision and involuntary eye oscillations.
See Free Eye Tests.
- mydriasis
- Increase in pupil size (dilation) occurring normally in the dark. May occur artificially
through the use of drugs.
See Free Eye Tests.
- mydriatic
- A drop that dilates the pupil.
- myope
- Medical term for nearsighted person. A person with good reading vision, but who has
difficulty seeing distant objects.
- myopia
- Also called nearsightedness. The front curvature of the cornea is too steep in a
nearsighted person, causing good reading vision but poor distance vision.
See Free Eye Tests.
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