Glossary of Ophthalmic Terms

Accommodation - adjustment by the eye for seeing at different distances, accomplished by changing the shape of the crystalline lens through action of the ciliary muscle.

Amblyopia - decreased visual acuity without any apparent disease of the eye; also referred to as "lazy eye."

Aqueous - nutrient rich fluid that fills the front portion of the eye.

Astigmatism - the optical distortion caused by an irregularly shaped cornea.

Bifocal - a lens with two optical zones, one for near vision and one for distance vision.

Binocular Vision - the ability to use both eyes simultaneously to focus on the same object; also known as "depth perception."

Blindness - having central visual acuity of less than 20/200 or peripheral vision of less than 20 degrees.

Cataract - a clouding of the crystalline lens of the eye leading to blurring of vision.

Central Vision - the ability to see objects in front of us.

Chalazion - infection of the oil glands in the eyelid.

Color Deficiency - diminished ability to perceive differences in color most often for red or green.

Conjunctiva - clear membrane that covers the white of the eye and inner eyelids.

Contact Lenses - lenses which fit on the surface of the cornea to replace glasses for correction of refractive errors.

Cornea - the transparent, dome-shaped tissue covering the pupil and colored part of the eye.

Corneal Transplant - replacement of scarred or diseased cornea with clear corneal tissue from a donor.

Cycloplegic - a drug that temporarily puts the ciliary"s muscle at rest and dilates the pupil; often used to as part of an eye exam.

Depth Perception - the ability to perceive the relative position of objects in space; in other words, how far away an object is from you.

Diabetic Retinopathy - retinal changes caused by long-standing diabetes mellitus that can lead to blindness.

Diopter - a unit of measurement of strength or refractive power of lenses; used to prescribe glasses and contacts.

Drusen - tiny, white deposits on the retina. Common after 60 and sometimes an early sign of macular degeneration.

Dyslexia - a learning disorder with difficulty processing printed material, causing difficulty reading in spite of good intelligence.

Esophoria - a tendency of the eyes to turn too far inward under certain conditions.

Esotropia - a condition in which one or both eyes turn too far inward, sometimes called crossed eyes.

Exophoria - a tendency of the eye to turn too far outward under certain conditions.

Exotropia - a condition in which one or both eyes turn too far outward, sometimes called divergent strabismus.

Eyelids - structures covering the front of the eye.

Eyestrain - symptom of discomfort while using eyes for visual tasks such as computer work.

Farsightedness - close up vision is blurred and distance vision is clear.

Field of Vision (peripheral or side-vision) - the entire area which can be seen without moving the eyes.

Floaters - spots in the field of vision due to opacities or changes in the vitreous of the eye.

Focus - the point to which rays are converged after passing through a lens.

Fundus - the back of the eye which can be seen during an eye exam.

Gas Permeable Lenses - a rigid contact lenses that allow oxygen to pass through them.

Glaucoma - a disease that damages the optic nerve leading to a loss of vision usually due to an increase in the intraocular pressure.

Gonioscope - a magnifying device which is placed on the cornea and, in conjunction with strong illumination, is used to examine for certain types of glaucoma.

Giant Papillary Conjunctivitis - an allergic reaction, resulting in bumps called papillae developing on the underside of the upper eyelid, usually accompanied by mucous discharge and itching.

Hyperopia - a refractive condition of the eye that can cause blurred vision at near. In higher amounts, vision is blurred at all distances.

Hyperphoria - a tendency of one eye to drift upward under certain conditions.

Intraocular Pressure - fluid pressure inside the eye, usually measured to diagnose glaucoma.

Iris - the colored part of the eye located behind the cornea. The iris regulates the amount of light entering the eye by changing the size of the pupil.

Iritis - Inflammation of the iris; the condition is marked by pain, inflammation, and discomfort from light.

Jaeger Test - a test for near vision.

Keratitis - an inflammation of the cornea.

Keratoconus - a deformity in which the corneal curvature gets progressively steeper making the cornea somewhat cone-shaped.

Keratometry - the measurement of the anterior curvatures of the cornea.

Lacrimal System - special organs around the eye that produce tears along with the structures that drain them.

Light Adaption - the power of the eye to adjust itself to variations in the amount of light.

Low Vision Aids - high-powered lenses and telescopes with high magnification; designed to help patients who have poor vision.

Macula - the small area of the central retina that provides the distinct vision in the retina used for reading.

Miotic - a drug that causes the pupil to contract.

Monovision - a type of contact lens fitting in which one eye is corrected for distance vision and the other is corrected for near vision.

Mydriatic - a drug that dilates the pupil.

Myopia - often called nearsightedness; a refractive error caused by the eyeball being too long in relation to its focusing power; vision is thus blurred for distance.

Nearsightedness - not being able to see objects clearly in the distance.

Near Vision - the ability to distinctly perceive objects at normal reading distance.

Night Blindness - a condition in which vision diminishes greatly in faint light.

Ophthalmology - the branch of medicine dealing with medical and surgical treatment for disease of the eye.

Ophthalmoscope - used to examine the inside of the eye.

Optic Nerve - the nerve that serves as the connection of images from the eye to the brain.

Optic Neuritis - inflammation of the optic nerve.

Peripheral Vision - the ability to perceive the presence, motion or color of objects outside of the direct line of vision.

Phacoemulsification - use of ultrasonic vibration to break up a cataract and gently vacuum it from the eye.

Photophobia - sensitivity to and discomfort from light.

Posterior Chamber - the space behind the iris and in front of the retina.

Presbyopia - a condition common after age forty in which a gradual lessening of the eye's power of accommodation causes difficulty in seeing near objects.

Pterygium - a triangular fold of tissue that grows from the white of the eye across the cornea.

Ptosis - a drooping of the upper eyelid.

Pupil - the circular black area in the center of the iris which regulates the amount of light that enters the eye.

Refraction - A test to determine the refractive error of an eye so that contacts or glasses can be prescribed.

Refractive Error - a defect in the eye that prevents light rays from being brought to a single focus exactly on the retina.

Retina - a thin membrane lining the back of the eye where optical images are received. The retina converts these images into electronic impulses thus making a "picture" that is then transmitted to the brain.

Retinal Detachment - separation of the retina from the underlying back portion of the eye.

Safety Glasses - impact-resistant spectacles, which are available with or without a prescription for protection of the eyes in hazardous situations.

Sclera - the white part of the eye " a tough covering which forms the external, protective shell of the eye.

Scleritis - inflammation of the sclera.

Slit Lamp - a microscope used to examine the eye.

Soft Lens - a contact lens made of soft plastic which contains water and allows for oxygen transmission. Soft lenses are characterized by comfort and ease of adaptation.

Strabismus - failure of the two eyes to direct their gaze at the same object simultaneously because of muscle imbalance; also known as "crossed eyes."

Stye - infection involving the oil glands on the edge of the eyelid.

Tonometer - An instrument used to measure intraocular pressure.

Toric - a contact lens used to correct astigmatism.

Visual Acuity - ability of the eye to perceive the shape of objects in the direct line of vision, usually measured in terms of a Snellen fraction, e.g., 20/20.

Visual Field - extent of space visible to an eye as it fixates straight ahead.

Vitreous - the gelatinous, transparent, colorless substance filling the space between the crystalline lens and the retina.