COT key terms

A measurement of how well a person sees letters at a standard test distance, written as a fraction where the top number is the testing distance and the bottom is the distance at which a normal eye could read that line.

A quick check in which the patient looks through a tiny hole; if vision improves, the cause is likely a refractive error rather than disease of the eye itself.

The sharpest vision a patient can achieve while wearing the proper prescription, used as a baseline before and after treatment.

A bedside screening in which the examiner moves a target or hand into view from the side to compare the patient's peripheral awareness with their own.

A grid of straight lines the patient views one eye at a time to report wavy, missing, or distorted areas, mainly used to monitor macular problems.

Distortion of vision in which straight lines appear bent or wavy, often a sign of retinal swelling or scarring at the macula.

The fluid pressure inside the eye, measured in millimeters of mercury; it is a major risk factor for glaucoma but is not the same thing as having the disease.

A method of measuring eye pressure by flattening a small, fixed area of the cornea with a calibrated probe while the patient sits at a slit lamp.

An orange dye that glows green under blue light; used to stain the tear film for pressure measurement and to reveal corneal scratches or defects.

Examination of the front and back of the eye using a narrow beam of light and a microscope, allowing the clinician to see tissue layers at high magnification.

A view of the retina, optic nerve, and blood vessels after eye drops widen the pupil, needed to inspect the far periphery of the retina.

A drug that enlarges the pupil; such drops are used for examination but can blur near vision and raise pressure in some patients with narrow drainage angles.

Use of a special contact lens and slit lamp beam to inspect the drainage angle where the iris meets the cornea, which cannot be seen directly.

A non-contact imaging test that uses light to build cross-sectional pictures of the retina or optic nerve, showing layer thickness and fluid.

The process of finding the lens power that places a clear image on the retina, done by retinoscopy, autorefraction, or manual lens changes.

A technique in which the examiner shines a light into the eye and observes the movement of the reflected glow to estimate the patient's prescription objectively.

Measurement of refractive error after drops relax the focusing muscle, revealing the full amount of hyperopia hidden by accommodation.

Any mismatch between the eye's focusing power and its length that blurs vision without glasses, including myopia, hyperopia, and astigmatism.

A condition in which distant objects are blurred because light focuses in front of the retina, usually from a long eye or strong corneal curvature.

A condition in which the eye is optically too weak or too short, so clear focus requires effort; young patients may see well until the focusing muscle tires.

Blur caused by unequal curvature across the cornea or lens, so light rays in different meridians focus at different points instead of one.

The eye's automatic increase in focusing power when looking at near objects, produced by contraction of the ciliary muscle and rounding of the lens.

The age-related loss of near focusing ability as the lens stiffens, typically noticed in the forties when reading material must be held farther away.

Measurement of the curvature of the central cornea, used to fit contact lenses and to detect irregular astigmatism.

A progressive thinning and bulging of the cornea that produces irregular astigmatism and often requires rigid contact lenses for good vision.

A firm contact lens made of material that lets oxygen pass through; it holds its shape on the eye and can correct irregular corneal astigmatism.

Problems from wearing lenses too long, including corneal swelling, redness, and reduced oxygen to the eye surface.

A scratch or loss of surface cells on the clear front window of the eye, causing pain, tearing, and sensitivity to light.

Clouding of the eye's natural lens that gradually reduces vision and can make lights appear glaring or colors look dull.

Cataract surgery in which a fine probe breaks up the clouded lens with ultrasound and removes it through a small incision.

A permanent artificial lens implanted inside the eye, usually at cataract surgery, with power chosen to match the patient's measurements.

A group of optic nerve diseases that slowly destroy peripheral vision, often but not always associated with raised eye pressure.

Enlargement of the pale central hollow of the optic nerve head, a structural sign of nerve fiber loss in glaucoma.

A sudden or chronic form of glaucoma in which the iris blocks the eye's drainage angle, causing pressure to rise quickly or gradually.

Degeneration of the central retina in older adults that damages sharp vision while leaving side vision largely intact.

The small central area of the retina packed with cone cells, responsible for detailed vision, color, and reading.

Damage to retinal blood vessels from long-standing high blood sugar, which can leak fluid or grow fragile new vessels that bleed.

Separation of the light-sensitive retina from the wall behind it, causing flashes, floaters, and a curtain-like loss of vision that needs urgent repair.

A blind or reduced area in the patient's side or central vision, mapped by perimetry and used to track nerve or brain damage.