Accommodation  Increase in optical power by the eye in order to maintain a clear image (focus) as objects are moved closer.
After-cataract, secondary cataract  Remnants of an opaque lens remaining in the eye, or opacities forming, after extra-capsular removal.
Age-related macular degeneration (AMD,ARM) Group of conditions that include deterioration of the macula, resulting in loss of sharp central vision. Two general types: “dry”, which is more common, and “wet”, in which abnormal new blood vessels grow under the retina and leak fluid and blood, further disturbing macular function. Most common cause of decreased vision after age 60.
Amblyopia “lazy eye” Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways.Usually uncorrectable by eyeglasses or contact lenses.
Amsler grid Test card; grid (black lines on white background or white lines on black background) used for detecting central visual field distortions or defects, such as in macular degeneration.
Angle, anterior chamber angle Junction of the front surface of the iris and back surface of the cornea, where aqueous fluid filters out of the eye.
Anterior chamber Fluid-filled space inside the eye between the iris and the innermost portion of the corneal.
Aphakia Absence of the eye’s natural  crystalline lens.
Aqueous, aqueous humor Clear, watery fluid that  fills the space in the anterior chamber. Produced by the ciliary processes.Factor in intraocular pressure for all patients especially glaucoma patients.
Asthenopia Vague eye discomfort arising from use of the eyes; may consist of eyestrain, headache, and/or brow ache. May be related to uncorrected refractive error or poor ability of the eyes to fuse an image.
Astigmatism Refractive power concern in which light enters the eye and is focused in various places (meridians) within the eye. This prevents formation of a sharp image focus on the retina.Uncorrected astigmatism may result in significant blurred vision and headache.
Bifocals Eyeglasses that incorporate two different correcting powers in each lens; usually for near and distance corrections.
Binocular vision Seemless blending of each eyes separate images meshed into one multi-dimensional image/scene.
Blepharitis Typically a chronic inflammatory condition of the eyelids which may involve crusting, burning, itching, and other symptoms.
Blind spot Normal area within a person’s field of vision that is devoid of any vision.Anatomically due to an absence of light sensitive photoreceptors where the optic nerve enters the eye.
B-scan Type of ultrasound; provides a cross-section view of tissues that cannot be seen directly.
Cataract Opacity or cloudiness of the natural  crystalline lens. There are many types of cataracts, each over time impact quality of vision.  Surgical removal of the lens may be necessary  and is generally replaced with an intraocular lens, contact lens, or aphakic spectacles. Most common etiologies are: advanced age, health issues, medications, trauma, and congenital.
Central vision An eye’s best vision; used for reading and discriminating fine detail and color.Results from stimulation of the fovea and the macular area.
Chalazion Infection of a meibomian gland (in the eyelid). May be treated with oral and or topical medications. On occasion, may need minor surgical intervention.
Color blindness Reduced or the absence to discriminate between certain colors like red, green, and rarely blue.
Cone Light-sensitive retinal receptor cell provides sharp visual acuity and color discrimination.
Conjunctiva Transparent membrane covering the outer surface of the eyeball and also lines the inner eyelid surface.
Conjunctivitis, “pink eye” Inflammation of the conjunctiva.Characterized by discharge, redness and swelling.May be viral, bacterial or allergic. If viral, it can be contagious.
Convergence The movement of both eyes inward.
Cornea Transparent front part of the eye that covers the iris, pupil, and where a contact lens sits upon.
Cross-eyes (see esotropia) is a form of strabismus (involuntary eye turn) wherein one or both eyes turns inward.
Crystalline lens The eye’s natural lens and main structure to help us focus. Clear when young and begins to cloud as we mature.
Cycloplegic refraction Assessment of a dilated eye’s refractive error (prescription) as the eye’s focusing system is now at rest.
Diabetic retinopathy Retinal changes accompanying  uncontrolled diabetes. Various stages present from background retinopathy to proliferative retinopathy. Uncontrolled diabetes can lead to retinal detachment and ultimately blindness.
Dilated pupil Enlarged pupil. Occurs normally in dim illumination, or may be induced by certain legal or illegal drugs (mydriatics, cycloplegics).May also result as a consequence from ocular trauma or potentially serious neurological issues.
Diopter Unit of measurement  to designate a patient’s numerical prescription value.
Diplopia, double vision Perceptually seeing more than one of the same image; may be noted horizontal, vertical or diagonal.
Drusen Tiny deposits on the retinal tissue.Common after age 60; if found in the macular area, may be an early sign of macular degeneration.
Dry eye syndrome May be due to tear production and or quality deficiency.Occurs more often in women than men.Symptoms may cause foreign body sensation, burning eyes,  watering, grittiness, light sensitivity, and contact lens intolerance.
Ectropion Outward turning of the upper or lower eyelid so that the lid margin does not rest against the eyeball.May lead to serious corneal exposure issues.Primarily etiology is aging.
Emmetropia The state in which no refractive error is found.ie: No eyeglass prescription needed.
Entropion Inward turning of upper or lower eyelid so that the lid margin and lashes  rests against and rubs the eyeball.
Esotropia , cross-eyes Eye misalignment in which one or both eyes deviates inward.
Excimer laser Class of lasers that removes corneal tissue accurately without heating it.Used for photorefractive keratectomy (PRK) and LASIK (laser in situ keratomileusis) proceedures.
Exotropia Eye misalignment in which one or both eyes deviate outward (away from nose).
Extraocular muscles Six muscles that move the eyeball (lateral rectus, medial rectus, superior oblique, inferior oblique, superior rectus, inferior rectus) through all cardinal positions.
Eyelids Structures covering the front of the eye, which significantly help to protect it from debris or injury. Helps to distribute the tear film over the corneal surface.
Farsightedness A farsighted eye must use the focusing system to keep maintain clear distance vision and must expend even greater focusing effort to maintain clear close up vision
Floaters Vitreal gel changes located in the back of the that are described as spots, cobwebs, spider web, etc. Can present normally with aging or may be associated with a pending retinal tears or detachment, or internal inflammation.
Fovea Central area of the macula that produces the sharpest vision possible.
Fundus Most  posterior portion of the eyeball that contains the retina, optic nerve, macula,  and blood vessels.
Glaucoma Group of diseases characterized by increased intraocular pressure resulting in damage to the optic nerve and retinal nerve fibers.An insidious quiet eye disease that can  destroy your vision without symptoms until it is too late. May be treated well (NOT CURED) by prescription eye drops, minor laser procedures, or via filtration surgery.
Gonioscopy Process of evaluating the anterior chamber angle through a gonio lens.
Hyperopia See Farsightedness.
Hyphema Blood in the anterior chamber.May occur after blunt trauma, surgery, or infection.
Intraocular pressure The normal occurring pressure that is measured  through a technique called tonometry.
IOL (intraocular lens) Special polymer material that is surgically implanted in an eye replacing the eye’s natural lens that has become cloudy (cataract).
Iris Pigmented tissue that color to the eye (e.g., blue eyes). Controls light entering the eye by varying the size of the pupil.
Keratoconus Degenerative corneal disease that can over time severly affect vision. Characterized by generalized thinning and a cone-shaped protrusion of the central cornea.Generally occurs in both eyes. Primary treatment custom rigid gas permeable contacts.
Lacrimal gland Gland responsible for producing the aqueous portion of a tear.
LASIK Acronym: LAser in SItu Keratomileusis.Type of refractive surgery wherein the cornea is reshaped to change its optical power. Used for correcting myopia, hyperopia, and astigmatism.
Legal blindness Best-corrected visual acuity of 20/200 or less, or reduction in visual field to 20o or less, in the better seeing eye.
Lens; Crystalline lens The eye’s natural lens. Transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the retina.
Low vision Term usually used to indicate vision of less than 20/200.
Macula Small central area of the retina surrounding the fovea.Anatomical structure responsible for sharp crisp vision.
Myopia, nearsightedness Focusing defect in which the eye is overpowered. Specifically vision is naturally clear up close and blurry far away.
Nearsightedness See myopia.
Neovascularization Abnormal formation of blood vessels within the eye. Can develop in patients with diabetes, wet macular degeneration, post-trauma, etc.
Non- contact tonometry (NCT) Measures the amount of pressure inside one’s eye via an air puff.
Nystagmus Involuntary and rhythmic oscillating eye movements faster in one direction than the other.
Ophthalmologist (MD) specializing in surgery and problems related to eye from systemic and ocular diseases and disorders.
Optic disc, optic nerve head The main nerve that enters the back of the eye.Brain tumors, glaucoma, and neurological disorders may be observed from changes to the optic nerve.
Optician A non-doctor eye care professional who makes and adjusts eyeglass lenses from prescriptions supplied by an optometrist. Can become certified by The American Board of Opticianry reflecting special skills and knowledge.
Optometrist Is a licensed Doctor of Optometry (OD) who specializes in diagnosing refractive errors and binocular vision problems and prescribe glasses and contact lenses. They also routinely diagnose, treat and manage eye disease, infection, and injuries.
Orthoptics Discipline dealing with the diagnosis and treatment of defective eye coordination, binocular vision, and functional amblyopia by non-medical and non-surgical methods, e.g., glasses, prisms, exercises.
Perimetry Refers to testing the peripheral vision of an eye. Information obtained of a patient’s visual field can indicate glaucoma, neurological issues, pituitary tumors, brain injuries, etc.
Peripheral vision The area of noticeable side vision in all meridians per eye.
Punctal plug A small medical device made of silicone and or collagen that is painlessly inserted into the tear duct (puncta) of an eye to block the duct. Used in dry eye patients and sometimes as a proactive tool in LASIK patients.
Pupil The black circular opening in the center of the iris that regulates the amount of light that enters the eye.
Radial keratotomy (RK) Series of spoke-like (radial) cuts made from the corneal periphery to correct nearsightedness and astigmatism.Common refractive procedure in the 1980’s-2000.
Refraction Test to determine an eye’s refractive error resulting in the best corrective lenses needed to sharpen vision.
Refractive error An optical defect causing a blurred retinal image.Typically corrected by eyeglasses, contact lenses, or refractive surgery (LASIK, PRK).
Retina The layer of highly sensitive visual tissue in the back of the eye. Equivalent to the film in a camera.
Retinal detachment Separation of one or more layers of the retina tissue. Markedly disturbs vision if the detachment is located centrally. Most are asymptomatic and found during routine dilated retinal exam or viewing an Optomap® image. Generally  requires immediate surgical repair.
Sclera Opaque, fibrous, protective outer layer of the eye (“white of the eye”).
Secondary cataract See after-cataract.
Slit lamp  Specialized microscope used for examining the eye’s anatomy.
Snellen chart Test chart used for assessing visual acuity. Contains rows of letters, numbers, or symbols in standardized graded sizes.
Strabismus Eye misalignment caused by extraocular muscle imbalance.
Sty, stye An acute pustular-like infection of the natural glands located in an eyelash follicle along the eyelid margin.
Tonometry Measurement device used to ascertain the eye’s intraocular pressure.(see also non-contact tonometry).
Trifocal Eyeglass lens that incorporates three specific visual areas of  clarity. The top portion is for distance vision(>20 ft.), the middle section is for the computer/dashboard distance, and the lower segment is designed for reading vision (~16 in.).
20/20 What is deemed as a normal visual acuity.
Visual acuity Assessment of the eye’s ability to clearly distinguish details and shape of an object
Visual field The cumulative side (peripheral) vision seen per eye. The loss of any portion of the peripheral vision, which is almost always unnoticed by the person, is a serious sign and can signify glaucoma, pituitary tumor, stroke, and or eurological diseases.
Vitreous, vitreous humor Transparent, colorless gelatinous mass that fills the rear two-thirds of the eyeball, between the lens and the retina.
Vitreous detachment Separation of vitreous gel from retinal surface. Usually innocuous, but may cause retinal tears, which could lead to retinal detachment. Frequently occurs with aging as the vitreous liquifies yet can be found in some disease states, e.g.diabetes and high myopia.