Eye Care Glossary of Terms
To help you understand and discuss your ocular health and our services, we have provided this eye care glossary of terms.
To help you understand and discuss your ocular health and our services, we have provided this eye care glossary of terms.
Accommodation- Increase in optical power by the eye in order to maintain a clear image (focus) as objects are moved closer. Occurs through a process of ciliary muscle contraction and zonular relaxation that causes the elastic-like lens to "round up" and increase its optical power. Natural loss of accommodation with increasing age is called presbyopia.
Acuity- Sharpness, acuteness, or keenness of vision.
Amaurosis Fugax- loss of vision in one eye due to a temporary lack of blood flow to the retina. It may be a sign of an impending stroke.
Amblyopia- Dullness or obscurity of sight for no apparent organic reason, therefore not correctable with glasses or surgery. Sometimes called a lazy eye, wherein one eye becomes dependent on the other eye to focus, usually developed in early childhood.
Age Related Macular Degeneration (AMD) (ARMD)- 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 (neovascularization), further disturbing macular function. Most common cause of decreased vision after age 60.
Amsler Grid- Hand held chart featuring horizontal and vertical lines, usually white on black background, used to test for central visual field defects.
Anterior Chamber- Space between the cornea and the crystalline lens , which contains aqueous humor .
Angle- Drainage area of the eye formed between the cornea and the iris , named for its angular shape, which is why you see the word "angle" in the different glaucoma names.
Aphakia- Absence of the lens of the eye.
Argon Laser - device used to treat glaucoma (usually open angle) and diabetic retinopathy using a thermal beam.
A-Scan- Type of ultrasound, radar-like device that emits very high frequency waves that are reflected by the ocular structures and converted into electrical impulses. Used for differentiating normal and abnormal eye tissue or for measuring length of eyeball.
Astigmatism- Structural defects of the eye in which the light rays from a viewed object do not meet in a single focal point, resulting in blurred images being sent to the brain. An astigmatic cornea is not perfectly rounded like a basketball but has an irregular shape more like the side of a football. Astigmatism is most often combined with myopia or hyperopia .
Axis - Optical - a straight line through the centers of both surfaces of a lens. Visual - a straight line from the object of vision to the fovea of the eye.
Aqueous Humor - Transparent fluid occupying the anterior chamber and maintains eye pressure.
Bacterial Conjunctivitis- inflammation of the conjunctiva(the outermost layer of the eyeand the inner surface of the eyelids) due to common pyogenic (pus-producing) bacteria. Marked symptoms include grittiness/irritation and a stringy, opaque, grayish or yellowish mucopurulent discharge that may cause the lids to stick together, especially after sleep. Another symptom that could be caused by bacterial conjunctivitis is severe crusting of the infected eye and the surrounding skin.
Basal malignant neoplasm- cancerous eye tumor caused by Basal-cell carcinoma (most common type of skin cancer.) This tumor can grow around the eye but rarely spreads to other parts of the body.
Bell's palsy or idiopathic facial paralysis- is a dysfunction of cranial nerve VII (the facial nerve) that results in inability to control facial muscles on the affected side. Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea may be permanently damaged resulting in impaired vision.
Benign Neoplasm of Eyelid- noncancerous tumor located on the eyelid.
Best corrected visual acuity (BCVA)- Best possible vision a person can achieve with corrective lenses, measured in terms of Snellen lines on an eye chart .
Beta-carotene- Member of the carotinoid family of vitamins, a precursor to vitamin A, thought to be beneficial to the eyes, helpful in treating diseases such as glaucoma.
Bifocals -Eyeglasses that incorporate two different powers in each lens, usually for near and distance corrections.
Binocular vision -Blending of the separate images seen by each eye into one composite image.
Blepharitis -Inflammation of the eyelids, usually with redness, swelling, and itching.
Blepharoconjunctivitis - the dual combination of conjunctivitis with blepharitis
Blepharospasm- It normally refers to benign essential blepharospasm, a focal dystonia—a neurological movement disorder involving involuntary and sustained contractions of the muscles around the eyes. In most cases the twitching is chronic and persistent, causing lifelong challenges. The symptoms are often severe enough to result in functional blindness. The person's eyelids feel like they are clamping shut and will not open without great effort. Patients have normal eyes, but for periods of time are effectively blind due to their inability to open their eyelids.
Blindness- total blindness is the complete lack of form and visual light perception and is clinically recorded as NLP, an abbreviation for "no light perception”. In North America and most of Europe, legal blindness is defined as visual acuity (vision) of 20/200 or less in the better eye with best correction possible.
Blind spot- The area of the optic disk where the optic nerve fibers exit the eye and where there are no light-sensitive cells. This small area can be measured and in glaucoma, as the nerve fibers die, the blind spot tends to enlarge and elongate. This is one of the diagnostic hallmarks of glaucoma.
Bowman's membrane- Extremely thin second layer of the cornea, situated between the epithelium and stroma, thought to be responsible for epithelium adhesion.
B-scan- Type of ultrasound; provides a cross-section view of tissues that cannot be seen directly. High frequency waves are reflected by eye tissues and orbital structures and converted into electrical pulses, which are displayed on a printout.
Bullous keratopathy- is a pathological condition in which small vesicles, or bullae, are formed in the cornea due to endothelial (single layer of cells on the inner surface of the cornea) dysfunction.
Capsular Haze- A thin film of scar tissue that occasionally forms on the posterior capsule behind the intraocular lens implant following cataract surgery and removed with a Yag laser.
Caruncle- Small, red portion of the corner of the eye that contains modified sebaceous and sweat glands.
Cataract- Gradual clouding of the crystalline lens resulting in reduced vision or eventual blindness, correctable by cataract surgery.
Cataract (Senile) -Occurring in the elderly, is characterized by an initial opacity in the lens, subsequent swelling of the lens and final shrinkage with complete loss of transparency
Cataract (Nuclear Sclerotic)-This is the most common type of age-related cataract, caused primarily by the hardening and yellowing of the lens over time. "Nuclear" refers to the gradual clouding of the central portion of the lens, called the nucleus; "sclerotic" refers to the hardening, or sclerosis, of the lens nucleus. A nuclear sclerotic cataract progresses slowly and may require many years of gradual development before it begins to affect vision.
Cataract (Cortical) – “Cortical" refers to white opacities, or cloudy areas, that develop in the lens cortex, which is the peripheral (outside) edge of the lens. Changes in the water content of the lens fibers create clefts, or fissures, that look like the spokes of a wheel pointing from the outside edge of the lens in toward the center. These fissures can cause the light that enters the eye to scatter, creating problems with blurred vision, glare, contrast, and depth perception.
Cataract (Posterior Subcapsular)-This type of cataract begins as a small opaque or cloudy area on the "posterior," or back surfaceof the lens. It is called "subcapsular" because it forms beneath thelens capsule, which is a small "sac," or membrane, that encloses the lens and holds it in place. Subcapsular cataracts can interfere with reading and create "halo" effects and glare around lights. People who use steroids, or have diabetes, extreme nearsightedness, and/or retinitis pigmentosa may develop this type of cataract. Subcapsular cataracts can develop rapidly and symptoms can become noticeable within months.
Cataract (Secondary) -Can sometimes develop after undergoing eye surgery, such as surgery for glaucoma or retinal surgery.
Cataract Surgery- Removal of a cataract , replacing it with an intraocular lens implant .
Central Retinal Artery- First branch of the ophthalmic artery; supplies nutrition to the inner two-thirds of the retina.
Central Island- Central islands are a small mound of central tissue, which can interfere with vision and occur when the laser beam does not uniformly remove tissue in the center of the treatment.
Central Retinal Vein -Blood vessel that collects retinal venous blood drainage; exits the eye through the optic nerve.
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- Inflamed lump in a meibomian gland (in the eyelid). Inflammation usually subsides, but may need surgical removal.
Choiriorentinitis- is an inflammation of the choroid (thin pigmented vascular coat of the eye) and retina of the eye. It is also known as choroid retinitis.
Choroid Membrane- Dark, vascular, thin skin-like tissue, situated between the sclera and the retina, forming the middle coat of the eye. The choroid membrane nourishes the outer portions of the retina and absorbs excess light.
Chronic- Of long duration, going on for some time.
Ciliary Body- Part of the eye that connects the choroid membrane to the iris . Produces aqueous humor that fills the front part of the eye and maintains eye pressure.
Ciliary Muscle- Muscle attached to the crystalline lens responsible for focus (the same as ciliary body , but used in a different context).
Colorblindness- Inaccurate term for a lack of perceptual sensitivity to certain colors. Absolute color blindness is almost unknown.
Comprehensive Eye Exam- Evaluation of the complete visual system.
Cones- One of the two types of light-sensitive cells, concentrated in the center of the retina There are about 6.5 million cones in each eye - 150,000 cones in every square millimeter - responsible for detailed visual acuity and the ability to see in color.
Conjunctiva- Mucous membrane lining the inner surface of the eyelids and covering the front part of the sclera (white part of eye), responsible for keeping the eye moist.
Depth perception- Ability of the vision system to perceive the relative positions of objects in the visual field.
Dermatochalasis- an excess of skin in the upper or lower eyelid. It may be either an acquired or a congenital condition. It is generally treated with blepharoplasty.
Detached retina- A retinal detachment occurs when the retina is pulled away from its normal position in the back of the eye.
Diabetes mellitus- Chronic metabolic disorder characterized by a lack of insulin secretion and/or increased cellular resistance to insulin, resulting in elevated blood levels of simple sugars (glucose) and including complications involving damage to the eyes, kidneys, nervous system and vascular system
Diabetes type I (IDDM)- Insulin dependent, resulting from destruction of the insulin producing pancreatic islet cells
Diabetes type II (NIDDM)- Non-insulin dependent, resulting from tissue resistance to insulin
Diabetic retinopathy- Deterioration of retina blood vessels in diabetic patients, possibly leading to vision loss.
Dilated, dilation- Enlarged pupil, resulting from contraction of the dilator muscle or relaxation of the iris sphincter. Occurs normally in dim illumination, or may be produced by certain drugs (mydriatics, cycloplegics) or result from blunt trauma.
Diopter- Unit of measure of the refractive power of an optical lens (equal to the power of a lens with a focal distance of one meter). A negative diopter value (such as -3D) signifies an eye with myopia and positive diopter value (such as +3D) signifies an eye with hyperopia .
Diplopia- Condition in which a single object is perceived as two; also called double vision.
Divergence: Turning of the eyes outwards so that they are both "aimed" towards the object being viewed. Normally works in harmony with convergence.
Drusen- Tiny, white hyaline deposits on Bruch's membrane (of the retinal pigment epithelium). Common after age 60; sometimes an early sign of macular degeneration.
Dry eye- Corneal and conjunctival dryness due to deficient tear production, predominantly in menopausal and post-menopausal women. Can cause foreign body sensation, burning eyes, filamentary keratitis, and erosion of conjunctival and corneal epithelium.
Ectropion - Outward turning of the upper or lower eyelid so that the lid margin does not rest against the eyeball, but falls or is pulled away. Can create corneal exposure with excessive drying, tearing, and irritation. Usually from aging.
Emmetropia - Refractive state of having no refractive error when accommodation is at rest. Images of distant objects are focused sharply on the retina without the need for either accommodation or corrective lenses.
Endophthalmitis - Inflammation of the internal coats of the eye. It is a dreaded complication of all intraocular surgeries, particularly cataract surgery, with possible loss of vision and the eye itself.
Endothelium- Cellular tissue that covers the inner surface of the eye within the closed cavity, typically referring to the cornea.
Enhancement- An additional LASIK procedure, used in the refinement of Personal Best Vision.
Entropion- Inward turning of upper or lower eyelid so that the lid margin rests against and rubs the eyeball.
Epidemic Keratoconjunctivitis (EKC) - Inflammation of the cornea and conjunctiva caused by an adenovirus. It is named epidemic for the epidemic way the infection spreads. Symptoms include: sudden onset of irritated, red eye, watery discharge, and foreign body sensation.
Epithelium- Cellular tissue that covers the outer surface of the eye. Consists of one or several layers of cells with only little intercellular material.
Episcleritis- Inflammation of the episclera (outer most layer on the white of the eyes), a less serious condition that seldom develops into scleritis (inflammation that effects the sclera).
Epiphora- Overflow of tears onto the face. A clinical sign or condition that constitutes insufficient tear film drainage from the eyes in that tears will drain down the face rather than through the nasolacrimal system
Esophoria- Position of the eyes in an over-converged position compensated by the external eye muscles so that the eyes do not appear turned inward.
Esotropia- Position of the eyes in an over-converged position so that non-fixating eye is turned inward. One eye looks straight; one looks inward.
Excimer laser- Laser used in LASIK surgery that operates in the ultraviolet wavelength, producing a cool beam.
Exophoria- Position of the eyes in an over-diverged position compensated by the external eye muscles so that the eyes do not appear turned outward.
Exophthalmos- Bulging of the eye anteriorly out of the orbit
Exotropia- Position of the eyes in an over-diverged position so that non-fixating eye is turned outward. One eye looks straight ahead and one turns outward.
Extraocular muscles- Six muscles that control eye movement. Five originate from the back of the orbit; the other one originates from the lower rim of the orbit. Four move the eye up, down, left and right, the other two control the twisting motion of the eye when the head tilts. All six muscles work in unison; when they do not function properly, the condition is called strabismus .
Eye chart- Technically called a Snellen chart, a printed visual acuity chart consisting of Snellen optotypes, which are specifically formed letters of the alphabet arranged in rows of decreasing letter size.
Eyelid- Either of two movable, protective, folds of flesh that cover and uncover the front of the eyeball.
Farsighted- Common term for hyperopia. Hyperopia is the inability to see near objects as clearly as distant objects, and the need for accommodation to see distant objects clearly.
Femtosecond laser- Used in the IntraLASIK procedure to make a safer and more precise flap than the older mechanical microkeratome technology, it uses a longer wavelength, smaller spot, and shorter duration per pulse than the excimer laser used to reshape the cornea .
Field of vision- Entire area which can be seen without shifting the gaze.
Flap- Part of the cornea consisting of epithelium , Bowman's membrane and some stroma , cut with a remaining hinge and lifted up as part of the LASIK procedure.
Flashes & Floaters- Light spots or streaks and dark moving specks due to the vitreous traction on the retinal (light flashes) and solid vitreous material or blood (floaters). Occurs normally with aging or with vitreous detachment, retinal tears, or inflammation.
Floppy Eyelid Syndrome- is a relatively uncommon ocular condition characterized by flaccid, easily everted upper lids. It is usually seen in overweight, middle-aged males, although it may occasionally be encountered in women and non-obese individuals. A fair percentage of these patients also suffer from obstructive sleep apnea. Symptoms generally consist of ocular injection, irritation, itching and stringy mucous discharge, particularly upon awakening.
Fluorescein Angiography- Diagnostic test by which the veins deep inside the eye are examined. Used for visualizing and recording location and size of blood vessels and any eye problems affecting them. Dye is injected into a vein in the arm and circulated by the blood to the back of the eye, allowing for visual examination.
Foreign Body- Airborne particles can lodge in the eyes of people at any age. These foreign bodies often result in allergies which are either temporary or even turn into a chronic allergy. This is especially evident in the case of dust particles. It is also possible for larger objects to lodge in the eye.
Fourth nerve palsy- is a condition caused by weakness or paralysis of the superior oblique muscle. This condition often causes double vision, as the weakened muscle prevents the eyes from moving in the same direction.
Fovea- Small depression in the retina, the point where vision is most acute.
Fundus-Furthest point at the back of the eye, consisting of the retina, choroid membrane, sclera optic disc and blood vessels, seen by means of the ophthalmoscope.
Ghost image- Faint second image of the object you are viewing.
Giant papillary conjunctivitis- Type of conjunctivitis wherein bumps or ridges form on the inside of eyelids, which make wearing contact lenses uncomfortable; in fact, this condition is often caused by overwearing of certain contact lenses
Glare- Scatter from bright light that decreases vision.
Glaucoma- Group of diseases characterized by increased intraocular pressure resulting in damage to the optic nerve and retinal nerve fibers. A common cause of preventable vision loss. There are two main types of glaucoma: open-angle glaucoma and closed-angle glaucoma. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination). May be treated by prescription drugs or surgery.
Gonioscopy- Viewing procedure utilizing a mirror/lens device placed directly upon the cornea that is used to view the drainage area called "the angle" through which aqueous fluid exits the eyeball.
Halos- Rings around lights due to optical imperfections in, or in front of, the eye.
Haptics- The arms of an intraocular lens , which holds it in place once inserted inside the eye.
Haze: Corneal clouding that causes the sensation of looking through smoke or fog.
Heterophoria- Constant tendency of one eye to deviate in one or another direction due to imperfect balance of ocular muscles.
Herpes Simplex (Keratitis) - Viral infection of the cornea is often caused by the herpes simplex virus which frequently leaves what is called a 'dendritic ulcer'.
Herpes Zoster Iridocyclitis - a type of anterior uveitis, is a condition in which the uvea of the eye is inflamed caused by Herpes Zoster (ocular viral infection).
Herpes Zoster Opthalmicus (Shingles) - a specific type of herpes zoster (viral disease characterized by a painful skin rash with blisters) affecting the ophthalmic division of the fifth cranial nerve.
Holmium laser- A laser which operates in the infrared wavelength, producing a hot beam. It is used in Laser Thermokeratoplasty surgery and more commonly in surgical procedures involving the disintegration of stones and fibrous tissue ablation .
Hyperopia- Also called farsightednesss, hyperopia is the inability to see near objects as clearly as distant objects, and the need for accommodation to see distant objects clearly.
Hypertensive Retinopathy- is damage to the retina due to high blood pressure
Hyphema- Blood in the anterior chamber, such as following blunt trauma to the eyeball.
Hypoxia-Deficiency of oxygen supply to a tissue.
iDESIGN WaveScan System: WaveScan-driven laser vision correction with the potential to produce better vision than is possible with glasses or contact lenses, and enable surgeons to measure and correct unique imperfections in each individual's vision.
Image- Light reflected into the eye, off objects in front of the eye. This light contains all the information about the objects (such as color, shadow. motion and detail) that are translated to the brain and allow you to "see" (know about the objects).
Inflammation- Body's reaction to trauma, infection, or a foreign substance, often associated with pain, heat, redness, swelling, and/or loss of function.
In Situ- Term meaning "in place".
Intracapsular cataract surgery- Cataract surgery in which both the lens and capsule are completely removed, a rarely used procedure.
Intraocular lens implant (IOL)- Permanent, artificial lens surgically inserted inside the eye to replace the crystalline lens following cataract surgery or clear lens extraction .
Intraocular pressure (IOP)- Fluid pressure within the eye created by the continual production and drainage of aqueous fluid in the anterior chamber .
Iridotomy- Treatment for closed-angle glaucoma, one of the many types of glaucoma, usually done with a laser .
Iris- Colored part of the eye. Elastic, pigmented, muscular tissue in front of the crystalline lens that regulates the amount of light that enters the eye by adjusting the size of the pupil in the center.
Ischemia- Restriction or blockage of blood flow through a blood vessel. Ischemia is a causative agent of certain heart attacks and strokes and is involved in various types of visual field losses.
Intacs- Surgically implanted plastic half rings that change the shape of the cornea
Just had my LASIK done last week. Wore contacts for the last ten years and my vision was terrible, couldn't see 20 feet in front of me. And now I have 20/20 vision and couldn't be happier.
Keratectomy- Surgical removal of cornea tissue.
Keratitis- Inflammation of the cornea
Keratotomy- Surgical incision (cut) of the cornea
Keratoconous- Rare, serious, degenerative cornea disease, in which the cornea thins and assumes the shape of a cone.
Keratoconjunctivitis - is inflammation of the cornea and conjunctiva
Keratomileusis- Carving of the cornea to reshape it.
Keratoplasty- Surgical reshaping of the cornea
Keratometry- Obtaining corneal curvature measurements with a keratometer
Macula- Yellow spot on the retina , where the photoreceptors are most dense and responsible for the central vision. Has the greatest concentration of cones, responsible for visual acuity and the ability to see in color.
Macular Edema- Occurs when fluid and protein deposits collect on or under the macula of the eye, a yellow central area of the retina, causing it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball. Cystoid macular edema (CME) is any type of macular edema that involves cyst formation. Diabetic macular edema is swelling in the macular due to diabetic retinopathy.
Macular Degeneration (AMD)- A medical condition which usually affects older adults that results in a loss of vision in the center of the visual field (the macula) because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of visual impairment in older adults (>50 years). Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life.
Macular Drusen- Are tiny yellow or white accumulations of extracellular material that build up in Bruch's membrane of the eye. The presence of larger and more numerous drusen in the macula is a common early sign of age-related macular degeneration (AMD).
Macular Hole- A small break in the macula, located in the center of the eye's light-sensitive tissue called the retina.
Macular Pucker (Epiretinal Membrane) - A disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in posterior vitreous detachment (PVD). PVD can create minor damage to the retina, stimulating exudate, inflammation, and leucocyte response. These cells can form a transparent layer gradually and, like all scar tissue, tighten to create tension on the retina which may bulge and pucker.
Macular Scar – Scar located on the macular
Malignant Neoplasm of the Eyelid – Noncancerous eye lid tumor.
Meibomian Glands (Tarsal Glands)- Are a special kind of sebaceous glands at the rim of the eyelids inside the tarsal plate, responsible for the supply of meibum, an oily substance that prevents evaporation of the eye's tear film, prevents tear spillage onto the cheek, makes the closed lids airtight and acts as a blockade for tear fluid, trapping tears between the oiled edge and eyeball.
Meibomitis- Inflammation of the meibomian glands causes the glands to be obstructed by thick waxy secretions and often cause dry eyes/belpharitis.
Meridian- Orientation of a particular curve, often used in relation to the cornea .
Microkeratome- Mechanical surgical device that is affixed to the eye by use of a vacuum ring. When secured, a very sharp blade cuts a layer of the cornea at a predetermined depth.
Miosis- Pupillary constriction.
Migraine (Ocular) - A retinal disease often accompanied by migraine headache and typically affects only one eye. It is caused by an infarct or vascular spasm in or behind the affected eye. Retinal migraine is associated light sensitivity and with transient monocular visual loss (scotoma) in one eye lasting less than one hour.
Monovision- Purposeful adjustment of one eye for near vision and the other eye for distance vision.
Multiple Sclerosis (MS)- is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms. Common cause of optic neuritis. Inflammation of the optic nerve causes loss of vision usually because of the swelling and destruction of the myelin sheath covering the optic nerve.
Mydriasis- Pupillary dilation.
Myokymia - Involuntary eyelid muscle contraction.
Myopia-Also called nearsightedness or shortsightedness, the inability to see distant objects as clearly as near objects.
Nasolacrimal duct (sometimes called tear duct) - carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus. This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops.
Nasolacrimal duct probe/irrigation- procedure preformed to unclog tear ducts which causes excess tearing. A thin, blunt metal wire is gently passed through the tear duct to open any obstruction. Sterile saline is then irrigated through the duct into the nose to make sure that there is now an open path.
Near point of accommodation- Closest point in front of the eyes that an object may be clearly focused.
Near point of convergence- Maximum extent the two eyes can be turned inwards.
Nearsighted- Common term for myopia .
Neodymium YAG Laser- Laser used to treat Posterior Capsular Opacification (PCO) as well as open angle glaucoma Selective Laser Trabeculoplasty
Neoplasm- is an abnormal mass of tissue usually resulting in a lump or tumor.
Neovascularization- Abnormal formation of new blood vessels, usually in or under the retina or on the iris surface. May develop in diabetic retinopathy, blockage of the central retinal vein, or macular degeneration.
Nerve fibers/axons- Extensions of photoreceptors that form the nerve bundle that is called the optic nerve.
Neuro-ophthalmology- Subspecialty that treats the nervous and vascular systems that involve the eye.
Nevus- medical term for birthmark or mole
Normal Vision- Occurs when light is focused directly on the retina rather than in front or behind it.
Ocular herpes: A recurrent viral infection caused by the herpes simplex virus. Ocular herpes represents the most common infectious cause of corneal blindness in the United States.
Ocular hypertension: Elevated fluid pressure. The normal pressure is about 10 to 21mmHg, with the majority of people falling between 13 and 19. Over 21 is considered suspicious. Over 24 cautiously concerned - warranting immediate investigation. Over 30 is considered urgent and a potential emergency situation.
Occlusion, Branch Retinal (BRVO) – is a blockage of the small veins that carry blood away from the retina.
Occlusion, Central Retinal (CRVO)- is a blockage of the central retinal vein. Since the central retinal artery and vein are the sole source of blood supply and drainage for the retina, such blockage can lead to severe damage to the retina and blindness, due to ischemia (restriction in blood supply) and edema (swelling).
OD: Abbreviation standing for "oculus dextrum" meaning: right eye.
Open angle glaucoma: Glaucoma conditions of long duration (chronic).
Ophthalmologist: An ophthalmologist is either a medical doctor (MD) or an osteopathic physician (D.O.) who is qualified and especially trained to diagnose and treat all eye and visual system problems, both medically and surgically, as well as diagnose general diseases of the body.
Ophthalmoscope: Instrument used to examine the interior of the eye: it consists of a perforated mirror arranged to reflect light from a small bulb into the eye.
Ophthalmoscopy: Examination of the internal structures of the eye using an illumination and magnification system.
Optic disc: The head of the optic nerve that is formed by the meeting of all retina l nerve fibers.
Optic nerve:Bundle of nerve fibers that connect the retina with the brain. The optic nerve carries signals of light to the area of the brain called the visual cortex, which assembles the signals into images called vision.
Optic Neuritis- is inflammation of the optic nerve. It may cause sudden, reduced vision in the affected eye.
Optic Neuropathy-also known asAnterior ischemic optic neuropathy (AION)is damage to the optic nerve. The optic nerve carries images of what we see from the eye to the brain. Symptoms: Optic nerve atrophy causes vision to dim and reduces the field of vision.
Optician: Expert who designs, verifies and dispenses lenses, frames and other fabricated optical devices upon the prescription of an ophthalmologist or an optometrist.
Optometrist: Eye care professional, graduate of optometry school, provides non-surgical visual care. Specifically educated and trained to examine the eyes, and determine visual acuity as well as other vision problems and ocular abnormalities. An optometrist prescribes glasses and contact lenses to improve visual acuity.
Orbit: Boney socket containing the eyeball, fat, extraocular muscles, nerves and blood vessels.
Orbital blowout fracture - a fracture of the walls or floor of the orbit. Intraorbital material may be pushed out into one of the paranasal sinuses. This is most commonly caused by blunt trauma of the head, generally personal altercations.
Orthokeratology (OK): Non-surgical procedure using contact lenses to alter the shape of the cornea to effect a change in the refractive error .
Orthoptics: Exercises designed to help the eye muscles work together to improve visual perception.
OS: Abbreviation standing for "oculus sinistrum" meaning: left eye
Overcorrection: Occurence in refract ive surgery where the achieved amount of correction is more than desired; in LASIK , typically due to a patent's over-response to the laser ablation.
OU:Abbreviations standing for “oculus utro” meaning: both eyes
Pachymeter: Instrument that measures the distance between the top of the corneaepitheliumand the bottom of the cornea endothelium used as diagnostic testing device measuring for corneathickness.
Pachymetry: Exam for measuring corneathickness.
Papilledema: Non-inflammatory swelling/elevation of the optic nerve often due to increased intracranial pressure or space-occupying tumor.
Pannus (Corneal): refers to the growth of blood vessels into the peripheral cornea
Papilledema: is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks.
Papilloma: benign epithelial tumor, growing exophytically (outwardly projecting)
PD: Used on prescriptions to indicate the distance between the pupils of both eyes.
Pellucid marginal degeneration: A bilateral, noninflammatory, peripheral corneal thinning disorder, which is characterized by a peripheral band of thinning of the inferior cornea.
Peripheral vision: Ability to perceive the presence, motion, or color of objects outside the direct line of vision.
Personal Best Vision: Best possible vision for each individual as corrected.
Phacoemulsification cataract surgery: Cataractremoval procedure which involves making a tiny incision, about 1/8" long. A pen-like instrument, inserted through the opening, is used to emulsify and aspirate the clouded lens material, using gentle sound waves. Then an intraocular lensis inserted into place.
Phakic Intraocular Lenses (IOLs): Placed inside the eye without removing the natural lens, and performs much like an internal contact lens.
Phoropter: A common device found in most eye doctor's offices, with mulitple lenses, used to measure refractive errors. A phoropter calculates the prescription required for corrective lenses.
Photocoagulation: Focusing of powerful light rays onto tiny spots on the back of the eye, producing heat, which seals retinatears and cauterizes small blood vessels.
Photophobia: Sensitivity to light.
Photoreceptors: Microscopic light-sensitive cells that are located in the retinacalled rodsand cones. There are approximately 7 million cones and 125 million rods
Photo Refractive Keratectomy (PRK): Surgery in which a small area on the corneaepithelium(surface cells) is gently polished away. The laserthen reshapes the cornea surface in exactly the same way as for LASIKsurgery.
Pingecula: Irritation caused degeneration of the conjunctiva resulting in a thickening and yellowing of the normally thin transparent tissue.
Pink eye: Type of conjunctivitis, commonly seen in children.
Plaquenil: medication used to reduce inflammation in the treatment of rheumatoid arthritis and lupus. One of the most serious side effects is a toxicity in the eye (generally with chronic use), and requires regular screening even when symptom-free.
Posterior capsule: The thin membrane in the eye that holds the crystalline lens in place.
Posterior chamber: The back section of the eye's interior.
Posterior optical segment: Part of the eye posterior (behind) to the crystalline lens, including the vitreous, choroid retina and optic nerve.
Posterior Vitreous Detachment (PVD): Separation of the vitreous body from its attachment from the retina surface due to shrinkage from degenerative or inflammatory conditions or trauma. An age-related condition.
Prelex: Surgical procedure that attempts to correct presbyopia.
Presbyopia: Inability to maintain a clear image (focus) as objects are moved closer. Presbyopia is due to reduced elasticity of the lens with increasing age.
Prescription: Amount of vision correction necessary, written in a form that can be utilized during the manufacture of corrective lenses or to configure a laser machine
Progressive lenses: Bifocal or trifocal lenses which appear to be single vision with no distinct lines between the various focal lengths.
Punctal occlusion: Treatment for dry eye in which plugs are inserted into the punctum in order to retain lubricating tears naturally produced by the eye.
Punctum: The hole in the upper and lower eyelids through which tears exit the eye. In patients with dry eyes, temporary or permanent plugs may be inserted to help keep tears in the eye. Tears flow through the punctum to the nose, which is why people often experience a runny nose when crying.
Pupil: Black circular opening in the center of iris through which light passes into the crystalline lens . It changes size in response to how much light is being received by the eye, larger in dim lighting conditions and smaller in brighter lighting conditions.
Radial Keratotomy (RK): Outdated procedure once used to correct mild to moderate myopia , whereby making a series of spoke-like incisions around its periphery flattens the cornea .
Refract: To bend aside, as in "the crystalline lens refract s the light as it passes through", or to measure the degree the eyes or lenses bend light, as in "the doctor refract s a patient's eyes".
Refraction: Test to determine the refractive power of the eye; also, the bending of light as it passes from one medium into another.
Refractive errors: The degree of visual distortion or limitation caused by inadequate bending of light rays, includes hyperopia , myopia , and astigmatism .
Refractive power: Ability of an object, such as the eye, to bend light as light passes through it.
Refractive surgery: Type of surgery (such as LASIK ) that affects the refract ion of vision.
Retina: Layer of fine sensory tissue that lines the inside wall of the eye, composed of light sensitive cells known as rods and cones . Acts like the film in a camera to capture images, transforms the images into electrical signals, and sends the signals to the brain by way of the optic nerve.
Retinal Degeneration: is the deterioration of the retina caused by the progressive and eventual death of the cells of the retina. There are several reasons for retinal degeneration, including artery or vein occlusion, diabetic retinopathy, R.L.F./R.O.P. (retrolental fibroplasia/ retinopathy of prematurity), or disease (usually hereditary). These may present in many different ways such as impaired vision, night blindness, retinal detachment, light sensitivity, tunnel vision, and loss of peripheral vision to total loss of vision. Of the retinal degenerative diseases retinitis pigmentosa (RP) is a very important example.
Retinal Detachment: Condition wherein retina breaks away from the choroid membrane , causing it to lose nourishment and resulting in loss of vision unless successfully surgically repaired.RK: Abbreviation for " radial keratotomy ", an outdated procedure once used to correct mild to moderate myopia , whereby making a series of spoke-like incisions around its periphery flattens the cornea .
Retinal Scar: scarring of the retina may be as a result of trauma or a retinal detachment.
Retinal Edema: fluid accumulation within the retina
Retinal Hemorrhage: is the abnormal bleeding of the blood vessels in the retina, the membrane in the back of the eye.
Retinal Neovascularization: Formation of new blood vessels originating from the retinal veins and extending along the inner (vitreal) surface of the retina.
Rods: One of the two types of light-sensitive cells, located primarily in the side areas of the retina (also see cones). There are about 125 million rods , which are responsible for visual sensitivity to movement, shapes, light and dark (black and white) and the ability to see in dim light.
Routine eye exam: To test the overall condition of the eye and prescribe corrective measures such as glasses, contact lenses or LASIK .
Schirmer test: Test for dry eyes, which uses a thin strip of filter paper placed at the edge of the eye.
Sclera: White part of the eye. Tough covering that (with the cornea ) forms the external, protective coat of the eye.
Scleritis: is an inflammation of the sclera (the white outer wall of the eye). Symptoms: Blurred vision; Eye pain and tenderness - severe; Red patches
Scotoma: Area of partial or complete loss of vision surrounded by an area of normal vision, as what can occur in advanced ARMD or glaucoma.
Single vision: Lenses with only one focal length.
Sixth nerve palsy: is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve), which is responsible for contracting the lateral rectus muscle to abduct (i.e., turn out) the eye. The inability of an eye to turn outward results in a convergent strabismus or esotropia of which the primary symptom is double vision or diplopia in which the two images appear side-by-side. The condition is commonly unilateral but can also occur bilaterally.
Slit-Lamp: Ophthalmic instrument producing a slender beam of light used to illuminate and examine the external and internal parts of the eye.
Sloan eye chart: A common chart used to test visual acuity with black letters of various sizes against a white background.
Snellen eye chart: Most common chart used to test visual acuity with black letters of various sizes against a white background.
Snellen lines: Snellen optotypes arranged in horizontal rows called "lines".
Snellen optotypes: Specifically formed letters of the alphabet arranged in rows of decreasing letter size on the Snellen chart.
Sphere: Focusing power of the corrective lens.
Stereoscopic vision: Ability to see in three-dimension.
Stereopsis: Ability to perceive three-dimensional depth.
Strabismus: Condition occurs when the muscles of the eye do not aligned properly and binocular vision is not present. Patients with a history of strabismus may develop double vision after refractive eye surgery.
Stroma: Middle, thickest layer of tissue in the cornea .
Suppression: Inability to perceive all of part of objects in the field of vision of one eye.
Suspensory ligament of lens: Series of fibers that connect the ciliary body of the eye with the lens, holding it in place; ; also known as zonules.
Sympathetic ophthalmia: Inflammation of one eye following inflammation in the other eye.
Tear Film: Tears are formed by tiny glands that surround the eye. The tear film is comprised of three layers: oil, water, and mucous. The tear film serves several purpose. It keeps the eye moist, creates a smooth surface for light to pass through the eye, nourishes the front of the eye, and provides protection from injury and infection.
Tear Film Insufficiency (dry eyes): is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. Aging is one of the most common causes for dry eyes, due to tear production decreasing with age.
Tonometry: Procedure for the measurement of intraocular pressure. A test for glaucoma.
Topography: A tool used to see the refractive problems that might be present in the cornea. Corneal topography is used not only for screening all patients before refractive surgery like LASIK but also for fitting contacts.
Toric: Lens (eyeglasses, intraocular lens , or contact lens) that is the warped (astigmatic) opposite to that of the eye, thereby canceling out the error.
Trabecular meshwork: Drainage channels located inside the eye.
Trabeculoplasty: A procedure for the treatment of glaucoma, using a laser ( Argon or Nd:YAG ). Trabeculoplasty remodels the trabecular meshwork in order to increase drainage of aqueous and lower the intraocular pressure .
Trifocals: Lenses containing three focal lengths, usually arranged with the focus for distance above, intermediate distance in the middle, and near vision below.
Trichiasis: is a medical term for abnormally positioned eyelashes that grow back toward the eye, touching the cornea or conjunctiva. This can be caused by infection, inflammation, autoimmune conditions, congenital defects, eyelid agenesis and trauma such as burns or eyelid injury.
Twenty-twenty, 20/20 vision: Normal visual acuity. Upper number is the standard distance (20 feet) between an eye being tested and the eye chart; lower number indicates that a tested eye can see the same small standard-sized letters or symbols as a normal eye at 20 feet.
Ultrasound waves: Sound waves above 20,000 vibrations per second, above the range audible to the human ear, used in medical diagnosis and surgery.
Ultrasonography: Recordings of the echoes of ultrasound waves sent into the eye and reflected from the structures inside the eye or orbit. Ultrasonography is used to make measurements and to detect and localize tumors and retina l detachments.
Ultraviolet radiation: Radiant energy with a wavelength just below that of the visible light. UV-c is the shortest wavelength at 200-280 nm and is absorbed by the atmosphere before reaching the surface. UV-b, at 280-315 nm is the burning rays of the sun and damages most living tissue. UV-a, at 315-400 nm is the tanning rays of the sun and is somewhat damaging to certain tissues. UV radiation has been described as a contributing factor to some eye disease processes, which result in ARMD and cataract s and causes exposure keratitis.
Uncorrected visual acuity (UCVA): Best possible vision a person can achieve without corrective lenses measured in terms of Snellen lines on an eye chart .
Undercorrection: Occurence in refract ive surgery where the achieved amount of correction is less than desired; in LASIK , typically due to a patient under-responding to the laser treatment.
Uveal tract: Pigmented, middle layers of the eye, which include the choroid , ciliary body and iris .
Uveitis: Inflammation of any portion of the uveal tract.
(Anterior) uveitis, or iridocyclitis: is the inflammation of the iris and anterior chamber. Anywhere from two-thirds to 90% of uveitis cases are anterior in location. This condition can occur as a single episode and subside with proper treatment or may take on a recurrent or chronic nature. Symptoms include red eye, injected conjunctiva, pain and decreased vision. Signs include dilated ciliary vessels, presence of cells and flare in the anterior chamber, and keratic precipitates ("KP") on the posterior surface of the cornea.
(Intermediate) uveitis, or pars planitis: consists of vitritis - inflammatory cells in the vitreous cavity, sometimes with snowbanking, or deposition of inflammatory material on the pars plana.
(Posterior) uveitis, or chorioretinitis: is the inflammation of the retina and choroid.
(Pan) uveitis: is the inflammation of all the layers of the uvea.
Vascular Attenuation: Blood vessel attenuation describes changes in the appearance of the retinal blood vessels that line the back part of the eyes. Narrowing of the blood vessels can occur when blood pressure has been high for an extended period of time. Other conditions, such as diabetes, may also cause changes in the appearance of the retinal vessels.
Vision: The ability of the brain to see and interpret what is in front of the eyes.
Vision therapy: Orthoptics, vision training, eye exercises. Treatment process for the improvement of visual perception and/or coordination of the two eyes, for more efficient and comfortable binocular vision.
Visual acuity: Clearness of vision; the ability to distinguish details and shapes, which depends upon the sharpness of the retina l image.
Visual cortex: That part of the brain responsible for vision.
Visual field: Area or extent of space visible to an eye in a given position of gaze. There is a central visual field - the area directly in front of us, and a peripheral visual field - our "side vision". The fields of each eye partly overlap. We do not perceive the blind spots from each eye because the area that is missing in one eye is present in the other.
Visual field (test): Preformed to measure a patient’s field of vision or “side vision”. The patient sits in front of a concave dome with a target in the center. The eye that is not being tested is covered. A button is given to the patient to be used during the exam. The patient is set in front of the dome and asked to focus on the target at the center. A computer then shines lights on the inside dome and the patient clicks the button whenever a light is seen. The computer then automatically maps and calculates the patient's visual fields.
VISX STAR S4 Excimer laser System: Highly advanced laser technology platform, the VISX STAR S4 combines Variable Spot Scanning (VSS) and ActiveTrak 3-D Active Eye Tracking along with the WavePrint.
Vitreous detachment (PVD, post vitreous detachment): Separation of vitreous gel from retinal surface. Usually innocuous, but can cause retinal tears, which may lead to retinal detachment. Frequently occurs with aging as the vitreous liquefies, or in some disease states, e.g. diabetes and high myopi
Vitreous Floaters: Particles that float in the vitreous and cast shadows on the retina; seen as spots, cobwebs, spiders, etc. Occurs normally with aging or with vitreous detachment, retinal tears, or inflammation.
Vitreous Hemorrhage: A vitreous hemorrhage is a result of a blood vessel in the retina leaking or torn. Vitreous hemorrhage can result from a retinal tear, contusion to the eye, vascular diseases such as diabetes, sickle cell disease and central retinal vein occlusion.
Vitreous humor, fluid, or body: Jelly-like, colorless, transparent substance occupying the greater part of the cavity of the eye, and all the space between the crystalline lens and the retina .
Vitrectomy: Surgical removal of vitreous humor that is diseased or has lost its transparency.
Wavefront: Wavefront technology produces a detailed map of the eye. The information is transferred to the laser via computer software.
Xanthelasma (or xanthelasma palpebrarum): a sharply demarcated yellowish collection of cholesterol underneath the skin, usually on or around the eyelids. Though not harmful or painful, these minor growths may be disfiguring and can be removed.
Xerophthalmia: a medical condition in which the eye fails to produce tears. It may be caused by a deficiency in vitamin A and is sometimes used to describe that lack, although there may be other causes. The conjunctiva becomes dry, thick and wrinkled. If untreated, it can lead to corneal ulceration and ultimately to blindness as a result of corneal damage.
YAG laser surgery: Properly called: Yag laser capsulotomy, a procedure using :YAG (neodymium-yttrium-aluminum-garnet) laser, used primarily to treat secondary cataracts (capsular haze) that occur subsequent to the primary cataract procedure, or to relieve increased pressure within the eye from acute angle-closure glaucoma via a peripheral iridotomy. It can also be used to treat open angle glaucoma in a procedure called selective laser trabeculoplasty.
Zonules: Radially arranged fibers that suspend the lens from the ciliary body and hold it in position.