| A | B |
|---|
| Accommodation | The eye’s ability to automatically change focus from seeing at one distance to seeing at another |
| Amblyopia | Undeveloped central vision in one eye that leads to the use of the other eye as the dominant eye |
| Anisocoria | Unequal pupil size |
| Anisometropia | Condition where the eyes have a significantly different refractive power from each other |
| Asthenopia | Fatigue or tiring of the eyes |
| Bifocal | Lens with one segment for near vision and one segment for far vision |
| Binocular vision | The ability of both eyes to work together to achieve proper focus, depth perception and range of vision |
| Cataract | Clouding of the natural lens of the eye |
| Contralateral | Pertaining to, situated on, or coordinated with the opposite side |
| Convergence | Ability of the eyes to turn inward |
| Diplopia | Double vision |
| Divergence | Ability of the eyes to turn outward in relation to each other |
| Fixation | The eye’s ability to maintain gaze upon an object |
| Glaucoma | A disease characterized by elevated intraocular pressure, which causes optic nerve damage and subsequent peripheral vision loss |
| Heterochromia | A condition where one eye is a different color from the other or one eye is more than one color |
| Ipsilateral | Pertaining to, situated on, or affecting the same side of the body |
| Isocoria | Equality in the size of the two pupils |
| Metamorphopsia | A vision problem in which objects appear distorted |
| Miosis | Constriction of the pupil |
| Monovision | A vision correction method in which one eye is corrected for near and the other for far |
| Multifocal | Lens that includes more than one area through which the eye focuses, such as a bifocal or trifocal |
| Mydriasis | Dilation of the pupil |
| Progressive | Multifocal lens that eliminates the lines of a bifocal or trifocal lens by having a corridor of increasing gradient power starting at the top of the lens and ending at the bottom of the lens; also known as a no-line bifocal |
| Ptosis | Drooping of the eyelid |
| Strabismus | Misalignment of the eyes |
| Trifocal | Lens with one segment for near vision, one segment for intermediate vision and one segment for far vision |
| Ametropia | Faulty refraction of light rays by the eye, resulting in refractive error |
| Anti-reflective coating | A thin layer applied to a lens to reduce the amount of reflected light and glare that reaches the eye |
| Astigmatism | Refractive error that occurs when the cornea is curved unevenly and light does not focus on the retina evenly |
| Diopter | Unit of measure for the refractive power of a lens used in eyeglass and contact lens prescriptions |
| Emmetropia | The state of vision where an object at infinity is in sharp focus with the lens in a neutral or relaxed state |
| Esotropia | Occurs when one or both eyes point inward, so that the eyes are crossed |
| Exotropia | Occurs when one or both eyes point outward, also known as eyes are wall-eyed |
| Hi-index | Having a higher density, allowing light to travel faster through the medium |
| Hyperopia | Farsightedness; occurs when the eyeball is too short or the cornea has too little curvature and light focuses behind the retina |
| Myopia | Nearsightedness; occurs when the eyeball is too long or the cornea has too much curvature, resulting in light that focuses in front of the retina |
| Ophthalmologists | Physicians who specialize in the comprehensive care of the eyes and visual system in the prevention of eye disease and injury and perform major surgical procedures concerning the eyes |
| Opticians | Professionals in the field of designing, finishing, fitting and dispensing of eyeglasses and contact lenses |
| Optometric assistants | Professionals that are primarily involved in front –office procedures, optical dispensing and contact lens patient education |
| Optometric technicians | Professionals that are prepared for widely diversified job duties through academic and clinical experience and assist in areas of patient examination and treatment, including contact lenses, low vision, vision therapy, optical dispensing and office management |
| Optometrists | Independent healthcare providers who examine, diagnose, treat and manage diseases and disorders of the visual system, the eye and associated structures, as well as diagnose related systemic conditions, prescribe glasses and contact lenses, low vision rehabilitation, vision therapy, medications and perform minor surgical procedures |
| Phoropter | The instrument that patients sit behind while the eye care professional changes lenses and asks the patient for subjective feedback to find the best corrective lenses to prescribe |
| Photochromic | Having the ability to change color or darkness or density depending on the degree of exposure to light |
| Photophobia | Discomfort from the sun or other light |
| Polarized | Having the ability to block light reflected from horizontal surfaces, such as water, to reduce glare |
| Polycarbonate | Plastic material that is very impact resistant and is often used in spectacles for children under the age of 18 |
| Presbyopia | An age-related condition in which the ability to focus up close becomes more difficult and the patient loses his ability to accommodate |
| Prism | A transparent optical element with flat polished surfaces that refracts light prescribed to compensate for eye alignment problems. |
| Prism diopter | Unit of measurement of the deviation of light, equal to the deflection of light 1 cm at a distance of 1 m |
| Refraction | The clinical test that eye care professionals use to determine the refractive error and other measurements important in diagnosing a patient’s visual state |
| Refractive error | An error in the focusing of light by the eye and is a frequent reason for reduced visual acuity; is often expressed as the patient’s prescription |
| Visual acuity | The measure of the spatial resolution of the visual processing system |
| Add | The magnifying power applied to the bottom part of multi-focal lenses to correct presbyopia |
| Anterior chamber | The space between the cornea and iris that is filled with a special transparent fluid that nourishes the eye |
| Aqueous humor | The clear, watery fluid that fills the front part of the eye between the cornea, lens and iris |
| Axis | Lens meridian that contains the cylinder power to correct astigmatism |
| Choroid | The middle layer of the eyeball, which contains veins and arteries that nourish the eye, especially the retina |
| Ciliary muscle | The muscle that helps to change the shape of the lens and assists in accommodation |
| Conjunctiva | The mucous membrane that lines the eyelids and covers the front part of the eyeball |
| Cornea | The transparent dome in front of the eye that transmits and focuses light into the eye |
| CYL | Amount of astigmatism |
| Eyelid | The layer of skin that protects the eye and helps keep the eye clean and moist by opening and closing several times a minute |
| Fovea | The tiny area located in the macula that is the area of the clearest vision on the retina |
| Iris | The colored part of the eye that helps to regulate the amount of light that enters the eye |
| Lens | The transparent structure behind the iris that helps to focus light rays onto the retina |
| Macula | The small area in the retina with special light sensitive cells that helps to see fine details clearly |
| Optic nerve | The nerve that connects the eye to the brain, which carries impulses formed by the retina to the brain |
| PD | Distance between the centers of the pupils in each eye |
| Pupil | The dark center in the middle of the eye, which changes size in response to the amount of illumination in order to control the amount of light that enters the eye |
| Retina | The nerve layer that lines the back of the eye, senses light and creates nerve impulses that are sent through the optic nerve to the brain |
| Rods and cones | The photoreceptors that process light |
| Sclera | The white part of the eyeball that is made of tough material and covers most of the eyeball |
| Segment height | The distance in millimeters, from the bottom of the lens to the top of the reading area of the lens |
| SPH | Sphere power |
| OD | Right eye |
| OS | Left eye |
| OU | Both eyes |
| Vitreous | The clear, jelly-like substance that fills the space between the lens and retina |
