Glossary of Terms
Accommodation, Accommodation is the process by which the eye increases optical power to maintain a clear image (focus) on an object as it draws near the eye.
Achromatopsia, Achromatopsia (ACHM) is the inability to see color. Although the term may refer to acquired disorders such as color agnosia and cerebral achromatopsia, it typically refers to an autosomal recessive congenital color vision disorder, also called rod monochromacy and total congenital color blindness.
Age-Related Macular Degeneration, Age-related macular degeneration begins with characteristic yellow deposits in the macula (central area of the retina which provides detailed central vision, called fovea) called drusen between the retinal pigment epithelium and the underlying choroid.
Amblyopia, A disorder of the visual system that is characterized by poor or indistinct vision in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities. It has been estimated to affect 1–5% of the population.
Anterior Chamber of the eyeball, The front section of the eye’s interior where aqueous humor flows in and out providing nourishment to the eye and surrounding tissues.
Aphakia, The absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly
Aqueous Humor, The aqueous humor is a thick watery substance that fills the space between the lens and the cornea.
Asthenopia, Asthenopia or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, red eyes, eye strain, pain in or around the eyes, blurred vision, headache and occasional double vision. Symptoms often occur after reading, computer work, or other activities that involve tedious visual tasks.
Astigmatism, Astigmatism is when an optical system has different foci for rays that propagate in two perpendicular planes.
Bandage Contact Lens, A contact lens applied to an injured cornea, providing protection and allowing it to heal, while alleviating the constant rubbing of the eyelids.
Basal Cell Carcinoma, Is the most common form of skin cancer. It can be destructive and disfiguring. The risk of developing BCC is increased for individuals with a family history of the disease and with a high cumulative exposure to UV light via sunlight.
Bell’s Palsy, Paralysis of the facial nerve resulting in an inability to control facial muscles on the affected side.
Beta-blocker, Beta blockers block the action of endogenous catecholamines (epinephrine (adrenaline) and norepinephrine (noradrenaline) in particular), on β-adrenergic receptors, part of the sympathetic nervous system which mediates the”fight or flight” response.
Bifocals, Bifocals are eyeglasses whose corrective lenses each contain regions with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hypermetropia, and/or astigmatism.
Blepharitis, Inflammation of the eyelids. It is characterized by inflammation of the eyelid margins. Blepharitis usually causes redness of the eyes and itching and irritation of the eyelids in both eyes. Its appearance is often confused with conjunctivitis and due to its recurring nature, it is the most common cause of”recurrent conjunctivitis” in older people.
Blepharospasm, Any abnormal tic or twitch of the eyelid.
Blind Spot, A blind spot, also known as a scotoma, is an obscuration of the visual field. A particular blind spot is known as the blind spot, or physiological blind spot, or punctum caecum in medical literature is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through it.
Blindness, Blindness is the condition of lacking visual perception due to physiological or neurological factors.
Carbonic Anhydrase Inhibitor, Carbonic anhydrase inhibitors are used to treat glaucoma.
Cataract, A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Early on in the development of age-related cataract, the power of the crystalline lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colors.
Chalazion, A cyst in the eyelid that is caused by inflammation of a blocked meibomian gland, usually on the upper eyelid. Chalazions differ from styes (hordeolums) in that they are usually painless apart from the tenderness caused when they swell up, and in size (chalazia tend to be larger than styes). A chalazion may eventually disappear on its own after a few months, though more often than not, some treatment is necessary.
Choroid, The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye lying between the retina and the sclera, with a thickness about 0.5 mm. The choroid provides oxygen and nourishment to the outer layers of the retina.
Choroiditis, Uveitis in the back part of the eye (choroiditis)
Color Blindness, Or color vision deficiency, in humans is the inability to perceive differences between some of the colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals.
Conjuctivia, Thin layer membrane that covers the eyelids and eyeball to form a seal
Conjuctivitis, Commonly called”Pink Eye” is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), most commonly due to an allergic reaction or an infection (usually bacterial, or viral).
Contact Dermatitis of Eyelid, Term for a skin reaction resulting from exposure to allergens (allergic contact dermatitis) or irritants (irritant contact dermatitis), in this case occurring on the eyelid.
Contact Lenses, A corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. Modern contact lenses were invented by the Czech chemist Otto Wichterle, who also invented the first gel used for their production.Contact lenses usually serve the same corrective purpose as conventional glasses, but are lightweight and virtually invisible—many commercial lenses are tinted a faint blue to make them more visible when immersed in cleaning and storage solutions. Some cosmetic lenses are deliberately colored to alter the appearance of the eye.
Cornea, The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eye’s optical power. Together with the lens, the cornea refracts light, and as a result helps the eye to focus, accounting for approximately 80% of its production to 20% of the lens focusing power
Corneal Abrasion, scraping away or denuding of the corneal surface resulting from external forces physically applied to the corneal surface
Corneal Erosion, recurrent, Disorder of the eyes characterized by the failure of the cornea’s outermost layer of epithelial cells to attach to the underlying basement membrane. The condition is frequently painful because the loss of these cells results in the exposure of sensitive corneal nerves.
Corneal Foreign Body, Foreign material found in or on the cornea
Corneal Pachymetry, Measurement of the thickness of the cornea.
Corneal Scar, Scarring of the cornea
Corneal Ulcer, marginal, An inflammatory or more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma.
Cryotherapy, The most general definition is the local or general use of low temperatures in medical therapy or the removal of heat from a body part to decrease cellular metabolism, increase cellular survival, decrease inflammation, decrease pain and spasm, promote vasoconstriction, and when using extreme temperatures, to destroy cells by crystallizing the cytosol. It can also be called crymotherapy.
Cyclitis, Inflammation of the ciliary body.
Dacryocystitis, acute, Inflammation of the nasolacrimal (tear) sac. Symptoms include discharge, a sticky eye, eye pain or discomfort, a red or pink eye, swelling around the eye and tearing.
Dermatochalasis, A medical condition defined as an excess of skin in the upper or lower eyelid. It is generally treated with blepharoplasty.
Diabetes, A syndrome characterized by disordered metabolism and abnormally high blood sugar (hyperglycemia) resulting from low levels of the hormone insulin with or without abnormal resistance to insulin’s effects.
Diabetic Retinopathy, Retinopathy (damage to the retina) caused by complications of diabetes mellitus, which could eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all diabetics who have had diabetes for 10 years or more.
Dilation, Is a physiological response that varies the size of the pupil of the eye via the iris dilator muscle. It can have a variety of causes. It may be an involuntary reflex reaction to exposure to light.
Diopter, A dioptre, or diopter, is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres (that is, 1/metres).
Diplopia, Commonly known as double vision, is the simultaneous perception of two images of a single object. These images may be displaced horizontally, vertically, or diagonally (i.e. both vertically and horizontally) in relation to each other.
Drusen, Tiny yellow or white accumulations of extracellular material that build up in Bruch’s membrane of the eye.
Dry Eye Syndrome, An eye disease caused by decreased tear production or increased tear film evaporation.
Ectropion, A medical condition in which the lower eyelid turns outwards.
Endophtalmitis, acute, An inflammation of the internal coats of the eye.
Entropion, A medical condition in which the eyelids fold inward. It is very uncomfortable, as the eyelashes rub against the cornea constantly. Entropion is usually caused by genetic factors and may be congenital. Trachoma infection may cause scarring of the inner eyelid, which may cause entropion.
Enucleation, Removal of the eye, leaving the eye muscles and remaining orbital contents intact.
Epiphora, Excessive tear production, usually a result of an irritation of the eye. 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.
Epiretinal Membrane, A disease of the eye in response to changes in the vitreous humor or more rarely, diabetes.
Episcleritis/Scleritis, A serious inflammatory disease that affects the white outer coating of the eye, known as the sclera.
Excimer Laser, A form of ultraviolet laser which is commonly used in eye surgery and semiconductor manufacturing. The UV light from an excimer laser is well absorbed by biological matter and organic compounds. Rather than burning or cutting material, the excimer laser adds enough energy to disrupt the molecular bonds of the surface tissue, which effectively disintegrates into the air in a tightly controlled manner through ablation rather than burning. Thus excimer lasers have the useful property that they can remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact. These properties make excimer lasers well suited to precision micromachining organic material (including certain polymers and plastics), or delicate surgeries such as eye surgery (LASIK).
Excise Chalazion, Removal of a chalazion
Extended Ophthalmoscopy, A method of examination of the posterior of the eye.
Eye Injuries, Physical or chemical injuries to the eye can be a serious threat to vision if not treated appropriately and in a timely fashion. The most obvious presentation of ocular (eye) injuries is redness and pain in the affected eyes.
Eye Pain, Eye pain is a common reason for people to seek care from their ophthalmologist (a medical doctor who specializes in eye care and surgery). Eye pain may be described as burning, sharp, dull, gritty,” something in my eye,” aching, throbbing, or stabbing.
Eyeglasses, Frames bearing lenses worn in front of the eyes, normally for vision correction, eye protection, or for protection from UV rays.
Eyelid Inflammation, Inflammation of the eyelid
Farsightedness, See Hyperopia
Fluorescein Angiography, Fluorescein angiography (fluorescein – the type of dye that is used; angiogram – a study of the blood vessels) is an extremely valuable test that provides information about the circulatory system and the condition of the back of the eye.
Fovea, Also known as the fovea centralis, is a part of the eye, located in the center of the macula region of the retina. The fovea is responsible for sharp central vision, which is necessary for humans for reading, watching television or movies, driving, and any activity where visual detail is of primary importance.
Glaucoma, Group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy
Gonioscopy, An eye examination to look at the front part of your eye (anterior chamber) between the cornea and the iris
Headaches, A condition of pain in the head; sometimes neck or upper back pain may also be interpreted as a headache. It ranks amongst the most common local pain complaints.
High-Risk Medication (Plaquenil), Used to reduce inflammation.
Hyperopia, Also known as hypermetropia or colloquially as farsightedness or longsightedness, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance.
Intraocular, Located or occurring within or administered through the eyeball.
Iris, The contractile, circular diaphragm forming the colored portion of the eye and containing a circular opening, the pupil, in its center.
Iritis, A form of anterior uveitis and refers to the inflammation of the iris of the eye.
Keratitis, unspecified, A condition in which the eye’s cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.
Keratoconus, Degenerative non-inflammatory disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking, and sensitivity to light all often reported by the patient.
Lagopthalmos, The inability to close the eyelids completely.
Laser – Iridotomy, Known as a surgical iridectomy or corectomy, is the surgical removal of part of the iris
LASIK Surgery, Laser-Assisted in situ Keratomileusis (LASIK) is a type of refractive laser eye surgery performed by ophthalmologists for correcting myopia, hyperopia, and astigmatism.
Legal Blindness, Central visual acuity of 20/200 or less in the better eye with corrective glasses or central visual acuity of more than 20/200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye.
Lipoma, A common, benign tumor composed of fatty tissue. Lipomas are soft to the touch, usually movable, and are generally painless.
Macula, An oval yellow spot near the center of the retina of the human eye.
Macula Degeneration, A medical condition which the center of the inner lining of the eye, known as the macula area of the retina, suffers thinning, atrophy, and in some cases, bleeding. This can result in loss of central vision, which entails an inability to see fine details or to read.
Macular Degeneration, A medical condition predominantly found in young children in which the center of the inner lining of the eye, known as the macula area of the retina, suffers thickening, atrophy, and in some cases, watering. This can result in loss of side vision, which entails an inability to see coarse details, to read, or to recognize faces.
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.
Macular Hole, A macular hole is a small break in the macula, located in the center of the eye’s light-sensitive tissue called the retina.
Macular Pucker, 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.
Myopia, See Nearsightedness
Nasolacrimal Duct Obstruction, A fairly common condition in which there is failure of the nasolacrimal (tear drainage) duct to open into the nose. This results in failure of tears, mucous, and bacteria to be properly cleared from the eye, and a consequent”goopy” eye, as most parents would call it.
Nearsightedness, A refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed. Nearby objects clearly but distant objects appear blurred.
Night blindness (Nyctalopia), A condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, a lack of vitamin A).
Ocular, Pertaining to the eye
Ocular Hypertension, Is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.
Ophthalmologist, A medically trained specialist who deals with the diseases and surgery of the visual pathways
Ophthalmoscope, The ophthalmoscope is an instrument used to examine the eye
Optic Neuritis, Sometimes called retrobulbar neuritis, is the inflammation of the optic nerve that may cause a complete or partial loss of vision.
Optometrist, A health care profession concerned with eyes and related structures, vision, visual system and vision information processing in humans
Papilledema, unspecified, 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.
Pars Plana Vitrectomy, General term for a group of operations accomplished in the deeper part of the eye, all of which involve removing some or all of the vitreous – the eye’s clear internal jelly.
Peripheral Iridectomy, A procedure in which a small section of peripheral iris is excised through a limbal incision.
Peripheral Vision, Is a part of vision that occurs outside the very center of gaze.
Photocoagulation, The coagulation (clotting) of tissue using a laser which produces light in the visible green wavelength that is selectively absorbed by hemoglobin, the pigment in red blood cells, in order to seal off bleeding blood vessels.
Pingueculae, A pinguecula is one or more soft yellowish patches of tissue growing on the white (sclera) of the eye just beyond the colored part of the eye. Typically, pinguecula is located toward the corners of the eye at the 3 or 9 o’clock position. They are usually harmless but can be precursors of ptergia.
Presbyopia, The condition where the eye exhibits a progressively diminished ability to focus on near objects with age.
Prosthesis, one eye, A prosthesis is an artificial extension that replaces a missing body part.
Pseudophakia, The substitution of the natural crystalline lens with a synthetic lens. Pseudophakic IOLs are used in cataract surgery.
Pterygium, Usually refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is associated with and thought to be caused by ultraviolet-light exposure (e.g. sunlight), low humidity, and dust.
Ptosis, An abnormally low position (drooping) of the upper eyelid. The drooping may be worse after being awake longer when the individual’s muscles are tired.
Pupil, The variable-sized, black circular or slit-shaped opening in the center of the iris that regulates the amount of light that enters the eye. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye.
Radial Keratotomy, A refractive surgical procedure to correct myopia.
Refraction, A clinical test in which a phoropter may be used by an optometrist to determine the eye’s refractive error and the best corrective lenses to be prescribed. A series of test lenses in graded optical powers or focal lengths are presented to determine which provide the sharpest, clearest vision.
Retina, A thin layer of neural cells that lines the back of the eyeball of vertebrates and some cephalopods. It is comparable to the film in a camera
Retinal Detachment, A disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.
Retinal Detachment w/SB, A disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.
Retinal Detachment, tractional, A disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.
Retinal Detachment, w/defect, A disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.
Retinitis Pigmentosa, A group of inherited disorders in which abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina lead to a progressive visual loss.
Retinoblastoma, Cancer of the retina
Retinopathy, General term that refers to some form of non-inflammatory damage to the retina of the eye. Most commonly it is a problem with the blood supply that is the cause of this condition.
Routine Eye Exam, All people should have periodic and thorough eye examinations as part of routine primary care, especially since many eye diseases are silent or asymptomatic.
Sclera, The white or white of the eye
Secondary Lens Implant, A small, plastic lens that an eye surgeon can put in your eye to replace a lens that has been removed because of a cataract.
Stenosis, An abnormal narrowing of a blood vessel or other tubular organ or structure. It is also sometimes called a”stricture”.
Strabismus, A condition in which the eyes are not properly aligned with each other.
Strabismus (cross eyes), Condition in which the eyes are improperly aligned
Sty, An infection of the sebaceous glands at the base of the eyelashes. While they produce no lasting damage, styes can be quite painful.
Subconjunctival Hemorrhage, A subconjunctival hemorrhage is bleeding underneath the conjunctiva. The conjunctiva contains many small, fragile blood vessels that are easily ruptured or broken. When this happens, blood leaks into the space between the conjunctiva and sclera.
Trabeculectomy, primary, Surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye’s trabecular meshwork and adjacent structures.
Trabeculectomy, w/scarring, a Surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye’s trabecular meshwork and adjacent structures.
Trauma, Physical Injury
Trichiasis, Trichiasis is a medical term for ingrown eyelashes. This can be caused by infection, inflammation, autoimmune conditions, and trauma such as burns or eyelid injury.
Uveitis, Uveitis specifically refers to inflammation of the middle layer of the eye, termed the”uvea” but in common usage may refer to any inflammatory process involving the interior of the eye.
Visual Acuity, Acuteness or clearness of vision, especially form vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain.
Visual Field, The visual field is the spatial array of visual sensations available to observation
Visual Field Deficit, unspecified, A visual field defect is a loss of part of the usual field of vision, so it does not include blindness of either one eye or both.
Vitrectomy, Vitrectomy is a surgery to remove some or all of the vitreous humor from the eye
Vitrectomy, Anterior, Surgery to remove some or all of the vitreous humor from the eye.
Vitreous Body, The clear gel that fills the space between the lens and the retina of the eyeball.
Vitreous Degeneration, The degeneration or deterioration of the vitreous
Vitreous Floaters, Floaters are deposits of various size, shape, consistency, refractive index, and motility within the eye’s vitreous humour, which is normally transparent
Vitreous Hemorrhage, Vitreous hemorrhage is a condition of intraocular (inside the eye) bleeding that usually presents with sudden vision loss, frequently with complaints of floaters or”spots” in the vision. The condition is not due to bleeding of the vitreous humor, but rather bleeding from the retinal vessels or underlying choroid (layer of capillaries beneath the retina) in most cases.
Vitreous Humour, The clear gel that fills the space between the lens and the retina of the eyeball.