Glossary

Abrasion: An abrasion or "excoriation" is a wearing away of the upper layer of skin as a result of applied friction force. In dentistry an "abrasion" is the wearing away of the tooth substance.

Acanthamoeba keratitis: is a rare disease where amoebae invade the cornea of the eye causing possible blindness. Often associated with improper contact lens use.

Accommodate: In the occulat sense this is the eye's ability to focus.

Accommodative dysfunction: focusing trouble, for a variety of reasons (muscle spasm, too much near work etc) the eye has trouble focusing swiftly, effortlessly and subconsciously.

Acute: Of abrupt onset, in reference to a disease. Acute often also connotes an illness that is of short duration, rapidly progressive, and in need of urgent care.

Acute angle-closure glaucoma: Increased pressure in the front chamber (anterior chamber) of the eye due to sudden (acute) blockage of the normal circulation of fluid within the eye. The block takes place at the angle of the anterior chamber formed by its junction of the cornea with the iris. This angle can be seen by simply looking at someone's eye from the side. Angle-closure glaucoma tends to affect people born with a narrow angle. People of Asian and Innuit ancestry are at higher risk of developing it. Age and family history are risk factors. It occurs in older women more often than others.

Aging: The process of becoming older, a process that is genetically determined and environmentally modulated.

Allergy: A misguided reaction to foreign substances by the immune system, the body system of defence against foreign invaders, particularly pathogens (the agents of infection). The allergic reaction is misguided in that these foreign substances are usually harmless. The substances that trigger allergy are called allergen. Examples include pollens, dust mite, moulds, danders, and certain foods. People prone to allergies are said to be allergic or atopic.

Ametropia: An eye abnormality, such as nearsightedness, farsightedness, or astigmatism, resulting from faulty refractive ability of the eye.

Anatomy: The study of form. Gross anatomy involves structures that can be seen with the naked eye. It is as opposed to microscopic anatomy (or histology) which involves structures seen under the microscope. The most celebrated textbook of anatomy in the English-speaking world is Gray's Anatomy, still a useful reference book. The word "anatomy" comes from the Greek ana- meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up. The abbreviation for anatomy is anat.

Angle-closure glaucoma: This condition can be acute or chronic. It consists of increased pressure in the front chamber (anterior chamber) of the eye due to sudden (acute) or slowly progressive (chronic) blockage of the normal circulation of fluid within the eye. The block takes place at the angle of the anterior chamber formed by its junction of the cornea with the iris. This angle can be seen by simply looking at someone's eye from the side. Angle-closure glaucoma tends to affect people born with a narrow angle. People of Asian and Eskimo ancestry are at higher risk of developing it. Age and family history are risk factors. It occurs in older women more often than others. When the pupil of the eye is wide open (dilated), the iris is retracted and thickened and it block the canal of Schlemm, a key component of the drainage pathway for fluid within the eye. Blocking the drainage canal of Schlemm sends the pressure within the eye up. With acute angle-closure glaucoma, there is an abrupt increase in intraocular pressure (IOP) due to the build-up of aqueous (fluid) in the eye. The high pressure can damage the optic nerve (the nerve to the eye) and lead to blindness. The elevated pressure is best detected before the appearance of symptoms. That is why when the eyes are dilated in a doctor's office for a refraction, eye pressures are checked. When symptoms of acute angle glaucoma do develop, they include severe eye and facial pain, nausea and vomiting, decreased vision, blurred vision and seeing haloes around light. The eye in a far advanced case of angle closure glaucoma appears red with a steamy (clouded) cornea and a fixed (nonreactive) dilated pupil. Acute angle-closure glaucoma is an emergency because optic nerve damage and vision loss can occur within hours of the onset of the problem. Administering medications to lower the pressure within the eye is done first. In the past, a piece of the iris was then surgically removed in a procedure called an iridectomy to make a hole in the iris and create a channel (other than the canal of Sclemm) to permit the free flow of fluid. Today, a comparable procedure can be done by laser to burn a small hole in the iris to keep the intraocular pressure within normal limits. This condition can be chronic (progressing slowly or occurring persistently) or acute (occurring suddenly). Chronic angle-closure glaucoma, like the more common type of glaucoma (open-angle glaucoma), may cause vision damage without symptoms.

Anterior: The front, as opposed to the posterior. The anterior surface of the heart is toward the breast bone (the sternum).

Anterior chamber: The space in the eye that is behind the cornea and in front of the iris.

Antidepressants: Anything, and especially a drug, used to prevent or treat depression.

Antihistamines: Drugs that combat the histamine released during an allergic reaction by blocking the action of the histamine on the tissue. Antihistamines do not stop the formation of histamine nor do they stop the conflict between the IgE and antigen. Therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects. Antihistamines frequently cause mouth dryness and sleepiness. Newer "non sedating" antihistamines are generally thought to be somewhat less effective. Antihistamine side effects that very occasionally occur include urine retention in males and fast heart rate.

Aqueous Humour: The aqueous humour is a thick watery substance filling the space between the lens and the cornea. It is not to be confused with vitreous humour, which is contained within the larger cavity of the eye. It is transparent so as to allow light to pass through it. It maintains intraocular pressure, and inflates the globe of the eye.

Astigmatism: Astigmatism is the result of an inability of the cornea to properly focus an image onto the retina. The result is a blurred image. Astigmatism can be caused by a number of things, including an irregularly shaped lens (elliptical rather than perfectly spherical). It can be caused by the weight of the upper eyelid resting on the eyeball creating distortion, surgical incisions in the cornea, trauma or scarring to the cornea, the presence of tumors in the eyelid, or a developmental factor. Irregular astigmatism can be caused by scarring or keratoconus.

Asthenopia: a condition in which the eyes tire easily because of weakness of the ocular or ciliary muscles. Symptoms include pain in or around the eyes, headache, dimness of vision, dizziness, and slight nausea.

Atoric: Atoric simply means 'not toric,' just as aspheric means not spherical. An atoric lens surface varies slightly from a toric surface (a surface containing cylinder) in order to provide optical compensation for lenses with sphere and cylinder powers.

Atropine: A drug obtained from belladonna that is administered via injection, eye drops, or in oral form to relax muscles by inhibiting nerve responses. Used to dilate the pupils and as an antispasmodic.

Autoimmune: Pertaining to autoimmunity, a misdirected immune response that occurs when the immune system goes awry and attacks the body itself.
 

Bacteria: Single-celled microorganisms which can exist either as independent (free-living) organisms or as parasites (dependent upon another organism for life).

Bacterial: Of or pertaining to bacteria. For example, a bacterial lung infection.

Binocular Dysfunction: The brain tends to use the stronger of the two eyes - ranging in a number of disorders from strabismus (squinting) to lazy eye.

Blepharitis: Inflammation of the eyelids. It may be classified as seborrhoeic, staphylocccal, mixed, posterior or meiobomitis, or parasitic.

Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension".

Blurred vision: Lack of sharpness of vision with, as a result, the inability to see fine detail. Blurred vision can occur when a person who wears corrective lens is without them. Blurred vision can also be an important clue to eye disease.

Brain: That part of the central nervous system that is located within the cranium (skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

Bulbar: Pertaining to a bulb, in medicine any rounded mass of tissue (that is shaped somewhat like a crocus or tulip bulb). The eyeball.

Bulbar conjunctiva: That part of the conjunctiva, a clear membrane of the eye, which covers the outer surface of the eye. see also Bulbar Sheath.
 

Chalazion: (plural chalazia) A cyst of the little glands in the eyelids that make a lubricant which they discharge through tiny openings in the edges of the lids. The lubricant is a fatty substance called sebum characteristic of sebaceous glands.

Chemical reaction: A process in which one substance is transformed into another. Thousands of different types of chemical reactions occur in the body and are essential to its structure and function.

Chloride: The major anion (negatively charged substance) in the blood and extracellular fluid (the body fluid that lies outside cells). Blood and other body fluids have almost the same concentration of chloride ion as sea water. The balance of chloride ion (Cl^-) is closely regulated by the body.

Choroid: The choroid lies between the retina and sclera. It is composed of layers of blood vessels that nourish the back of the eye. The choroid connects with the ciliary body toward the front of the eye and is attached to edges of the optic nerve at the back of the eye.

Ciliary Muscles Ciliary Zonules Ciliary Process

Complication: In medicine, an additional problem that arises following a procedure, treatment or illness and is secondary to it. A complication complicates the situation...

Congestion: An abnormal or excessive accumulation of a body fluid. The term is used broadly in medicine. Examples include nasal congestion (excess mucus and secretions in the air passages of the nose) seen with a common cold and congestion of blood in the lower extremities seen with some types of heart failure.

Conjunctiva: A thin clear moist membrane that coats the inner surfaces of the eyelids and the outer surface of the eye.

Conjunctivitis: Inflammation of the conjunctiva, the membrane on the inner part of the eyelids and the membrane covering the white of the eye. The conjunctival membranes react to a wide range of bacteria, viruses, allergy-provoking agents, irritants and toxic agents. Viral and bacterial forms of conjunctivitis are common in childhood. Conjunctivitis is also called pinkeye and red eye.

Contact dermatitis: A skin condition caused by contact between skin and some substance. Includes irritant contact dermatitis (a rash brought on purely by repeated irritation from a substance such as water causing "dish pan hands") and allergic contact dermatitis (involving a specific sensitivity or allergy to a specific substance such as poison ivy).

Contact lenses: Lenses which fit directly on the eyeball under the eyelids.

Cornea: The clear front window of the eye that transmits and focuses light into the eye. Resembles the crystal on the front of a watch.

Corneal: Pertaining to the cornea, the clear front window of the eye that transmits and focuses light into the eye.

Corneal Topography: the detailed mapping or charting of the features of the cornea, important for fitting contact lenses and Orthokeratology lenses.

Cycloplegic Eye Examination: Eye drops are used to temporarily paralyze the ciliary muscle in order to determine the true refractive error of the lens. Especially accurate refractive error determination.
 

Decongestant: A drug that shrinks the swollen membranes in the nose and makes it easier to breath. Decongestants can be taken orally or by nasal spray. Decongestant nasal sprays should not be used for more than five days without the doctor's advice, and if so, usually only when accompanied by a nasal steroid. Many decongestant nasal sprays often cause a rebound effect if taken too long. A rebound effect is the worsening of symptoms when a drug is discontinued. This is a result of a tissue dependence on the medication. Decongestants should not be used by patients with high blood pressure (hypertension) unless under doctor's supervision.

Dermatitis: Inflammation of the skin, either due to direct contact with an irritating substance, or to an allergic reaction. Symptoms of dermatitis include redness, itching, and in some cases blistering.

Dilate: To stretch or enlarge. It comes from the Latin verb "dilatare" meaning "to enlarge or expand."

Dilation: The process of enlargement, stretching, or expansion. The word "dilatation" means the same thing. Both come from the Latin "dilatare" meaning "to enlarge or expand."

Diopters: A dioptre, or diopter, is a unit of measurement of the optical power of a lens, which is equal to the reciprocal of the focal length measured in metres (that is, 1/metres). see also Lens Prescriptions

Discharge: 1.The flow of fluid from part of the body, such as from the nose, eye or vagina.
2. The passing of an action potential, such as through a nerve or muscle fibre.
3. The release of a patient from a course of care. The doctor may then dictate a discharge summary.

Drain: A device for removing fluid from a cavity or wound. A drain is typically a tube or wick. As a verb, to allow fluid to be released from a confined area.

Drusen: Tiny yellow or white deposits in the retina of the eye or on the optic nerve head. The presence of drusen is one of the most common early signs of age-related macular degeneration (AMD). An Optometrist can see drusen during an eye examination. Their presence alone does not indicate disease, but it may mean that the eye is at risk for developing more severe AMD. (They are similar in molecular composition to plaques and deposits in other age-related diseases such as Alzheimer's disease and atherosclerosis.)

Dry eye: A deficiency of tears. The main symptom is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon. (see artificial tears)

Dry mouth: The condition of not having enough saliva to keep the mouth wet. This is due to inadequate function of the salivary glands. Everyone has dry mouth once in a while when they are nervous, upset or under stress. But if someone has a dry mouth most all of the time, it can be uncomfortable and lead to serious health problems.
 

Edema: The swelling of soft tissues as a result of excess water accumulation.

Electrolyte: An electrolyte is a substance that will dissociate into ions in solution and acquire the capacity to conduct electricity. The electrolytes include sodium, potassium, chloride, calcium and phosphate. Informally, called lytes. (The clue to the word electrolyte is in the lyte which comes from the Greek lytos meaning that may be dissolved.)

Eyelash: One of the familiar stiff hairs that project from the margin of the eyelid.

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Eyelid: The lid or cover of the eye, a movable fold of skin and muscle that can be closed over the eyeball or opened at will. Each eye has an upper and a lower lid. An eyelid is also called a palpebra.

Eye Pressure: See Intraocular Pressure
 

Fingernail: A fingernail is produced by living skin cells in the finger. A fingernail consists of several parts including the nail plate (the visible part of the nail), the nail bed (the skin beneath the nail plate), the cuticle (the tissue that overlaps the plate and rims the base of the nail), the nail folds (the skin folds that frame and support the nail on three sides), the lunula (the whitish half-moon at the base of the nail) and the matrix (the hidden part of the nail unit under the cuticle).

Floaters: Floaters are deposits within the eye's vitreous humour, which is normally transparent. They may be of embryonic origin or acquired due to degenerative changes of the vitreous humour or retina. The perception of floaters is known as myodesopsia, or less commonly as myiodeopsia, myiodesopsia, or myodeopsia. Floaters are visible because of the shadows they cast on the retina or their refraction of the light that passes through them, and can appear alone or together with several others in one's field of vision. They may appear as spots, threads, or fragments of cobwebs, which float slowly before the observer's eyes.

Fungal: Pertaining to a fungus. For example, a fungal skin infection.

Fungi: Plural of fungus.

Fundus: The fundus of the eye is the interior surface of the eye, opposite the lens, and includes the retina, optic disc, macula and fovea, and posterior pole.

Fungus: A single-celled or multicellular organism. Fungi can be true pathogens (such as histoplasmosis and coccidioidomycosis) that cause infections in healthy persons or they can be opportunistic pathogens (such as aspergillosis, candidiasis, and cryptococcosis) that cause infections in immunocompromised persons (including cancer patients, transplant recipients, and persons with AIDS). An example of a common fungus is the yeast organism which causes thrush and diaper rash (diaper dermatitis). Fungi are also used for the development of antibiotics, antitoxins, and other drugs used to control various human diseases.
 

Gland: 1. A group of cells that secrete a substance for use in the body. For example, the thyroid gland. 2. A group of cells that removes materials from the circulation. For example, a lymph gland.

Glaucoma: A common eye condition in which the fluid pressure inside the eyes rises because of slowed fluid drainage from the eye. If untreated, it may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness. (See also Acute angle closure glaucoma and angle closure glaucoma)
 

Headache: A pain in the head with the pain being above the eyes or the ears, behind the head (occipital), or in the back of the upper neck. Headache, like chest pain or back ache, has many causes.

Heterophoria: A type of eye condition in which the directions that the eyes are pointing are not consistent with each other.

High blood pressure: Also known as hypertension, high blood pressure is, by definition, a repeatedly elevated blood pressure exceeding 140 over 90 mmHg -- a systolic pressure above 140 with a diastolic pressure above 90.

Histamine: Substance that plays a major role in many allergic reactions. Histamine dilates blood vessels and makes the vessel walls abnormally permeable.

Hyperopia: Hyperopia (farsightedness) is the condition of the eye where incoming rays of light reach the retina before they converge into a focused image. Typically, far off objects will be easy to see, but up close work (reading, computers) will require more effort to focus on. This effort can be mitigated with reading glasses.

ICD-9 codes: International Classification of Diseases, 9th revision. It is a standardized classification of disease, injuries, and causes of death, by etiology and anatomic localization and codified into a 6-digit number, which allows clinicians, statisticians, politicians, health planners and others to speak a common language.

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Infection: The growth of a parasitic organism within the body. (A parasitic organism is one that lives on or in another organism and draws its nourishment therefrom.) A person with an infection has another organism (a "germ") growing within him, drawing its nourishment from the person.

Inflammation: A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response.

Injury: Harm or hurt. The term "injury" may be applied in medicine to damage inflicted upon oneself as in a hamstring injury or by an external agent on as in a cold injury. The injury may be accidental or deliberate, as with a needle stick injury. The term "injury" may be synonymous (depending on the context) with a wound or with trauma.

INTACS:Trade name of an intracorneal implant consisting of two tiny half-ring segments, which are inserted into the cornea to reshape its curvature and correct ametropia. The method is presently used to flatten the cornea by a given amount (the thicker the ring segments the flatter the cornea) in order to correct low myopia. It is an outpatient procedure carried out under local anaesthesia, takes less than half an hour and is reversible. The ring segments are made of clear biocompatible plastic inserted into the stroma and around the optical zone of the cornea.

Intraocular Pressure: Intraocular pressure (abbreviated as IOP) is the measurement of the amount of fluid inside the eyes. This fluid is called aqueous humour and provides nourishment to the cornea, iris and lens and allows the eyes to maintain their spherical shape.

Iris: The iris is the circular, collared curtain of the eye. Its opening forms the pupil. The iris helps regulate the amount of light that enters the eye.

Itching: An uncomfortable sensation in the skin that feels as if something is crawling on the skin or in the skin, and makes the person want to scratch the affected area.
 

Keratitis: Inflammation of the cornea (the transparent structure in the front of the eye).

Keratoconjunctivitis: Inflammation of the eye involving both the cornea and the conjunctiva.
 

Lacrimal: Pertaining to tears, as in lacrimal gland (tear gland). From the Indo-European dakru meaning a tear (from a weeping eye) which gave rise to the Greek dakry and the Latin lacrima.

Lacrimal gland: A small almond-shaped structure that produces tears. The lacrimal gland is located just above the outer corner of the eye. The lacrimal gland is part of the lacrimal apparatus, the system that forms tears, conveys them through the lacrimal (tear) duct to the eye, and drains the tears.

Lens: The transparent structure inside the eye that focuses light rays onto the retina (the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain). The lens was named after the lentil bean because it resembled it in shape and size.

Lens Prescriptions: The values indicated in the sphere and cylinder columns of an eyeglass prescription specify the optical power of the lenses in diopters, abbreviated D. The higher the number of diopters, the more the lens refracts or bends light. A diopter is the reciprocal of the focal length in metres. If a lens has a focal length of ¹⁄₃ metres, it is a 3 diopter lens.

Lubricant: An oily or slippery substance. Some synthetic tears eye drops could be called eye lubricants.

Lutein: A carotenoid that is found in yellow and orange fruits and vegetables, green leafy vegetables and egg yolks. Eating a diet rich in lutein may help to prevent cardiovascular disease and age-related eye diseases such as macular degeneration.
 

Macula: The macula or macula lutea is an oval yellow spot near the center of the retina of the human eye. It has a diameter of about 1.5 mm. Near its center is the fovea, a small pit that contains the largest concentration of cone cells in the eye and is responsible for central vision. Whereas loss of peripheral vision may go unnoticed for some time, damage to the macula will result in loss of central vision, which is usually immediately obvious.

Membrane: A very thin layer of tissue that covers a surface.

Mucus: A thick slippery fluid produced by the membranes lining certain organs such as the nose, mouth, throat, etc. Mucus is the Latin word for "a semi fluid, slimy discharge from the nose." Note that mucus is a noun while the adjective is mucous.

Myopia: Myopia is the medical term for short-sightedness or nearsightedness. People with myopia see objects more clearly when they are close to the eye, while distant objects appear blurred or fuzzy. Reading and close-up work may be clear, but distance vision is blurry.
 

Nasal: Having to do with the nose. Nasal drops are intended for the nose, not (for example) the eyes. The word "nasal" came from the Latin "nasus" meaning the nose or snout.

Nausea: Nausea, is the urge to vomit. It can be brought by many causes including, systemic illnesses, such as influenza, medications, pain, and inner ear disease. When nausea and/or vomiting are persistent, or when they are accompanied by other severe symptoms such as abdominal pain, jaundice, fever, or bleeding, a physician should be consulted.

Nerve: A bundle of fibres that uses chemical and electrical signals to transmit sensory and motor information from one body part to another.

Nodule: A small solid collection of tissue, a nodule is palpable (can be felt). It may range in size from greater than 1.0 cm (3/8 inch) to somewhat less than 2 cm (13/16 inch) in diameter. A nodule may be present in the epidermis, dermis or subcutis (at any level in the skin).

Nose: The external midline projection from the face.
 

Obstruction: Blockage of a passageway.

Ocular: Having to do with the eye.

Ointment: A medication preparation that is applied topically (onto the skin). An ointment has an oil base whereas a cream is water-soluble. (The word ointment comes from the Latin ungere meaning anoint with oil).

Ophthalmic: Pertaining to the eye. An ophthalmic ointment is designed for the eye.

Ophthalmologist: An eye doctor. A physician practicing ophthalmology. An ophthalmologist is a Medical Doctor.

Optic: Having to do with vision.

Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images. Using an ophthalmoscope, the head of the optic nerve can be easily seen. It can be viewed as the only visible part of the brain (or extension of it).

Optometrist: A health care professional who is licensed to provide primary eye care services:

Orbital: Relating to the orbit, in anatomy the bony cavity that contains the eyeball.
 

Pain: An unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibres that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.

Palpebral conjunctiva: The part of the conjunctiva, a clear membrane, that coats the inside of the eyelids.

Parasite: An organism that lives in or on and takes its nourishment from another organism. A parasite cannot live independently.

Phosphate: A form of phosphoric acid. Calcium phosphate makes bones and teeth hard.

Photophobia: Painful oversensitivity to light. For example, there is photophobia in measles (rubeola). Keeping the lights dim or the room darkened may be useful. Sunglasses may also help.

Posterior Pole: In ophthalmology, the posterior pole is the back of the eye, usually referring to the retina between the optic disc and the macula. (see eye diagram below)

Presbyopia: Generally believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye due to aging. Likely to be first noticed as a difficulty to focus up close. 

Pupil: The opening of the iris. The pupil may appear to open (dilate) and close (constrict) but it is really the iris that is the prime mover; the pupil is merely the absence of iris. The pupil determines how much light is let into the eye. Both pupils are usually of equal size. If they are not, that is termed anisocoria (from "a-", not + "iso", equal + "kore", pupil = not equal pupils).
 

Radiation: 1. Rays of energy. Gamma rays and X-rays are two of the types of energy waves often used in medicine. 2. The use of energy waves to diagnose or treat disease. See also: Sunglasses.

Rebound: Return of the original symptoms when manoeuvres or treatment is discontinued.

Recurrent: Back again. A recurrent fever is a fever that has returned after an intermission: a recrudescent fever.

Reflex: A reaction that is involuntary. The corneal reflex is the blink that occurs with irritation of the eye. The nasal reflex is a sneeze.

Refractive Errors: When light rays don't properly refract from the cornea to the retina, it is a refractive error. This can take the form of myopia (short sightedness) or hyperopia (farsightedness) or astigmatism. The light rays are unable to focus on a single point.

Restasis: Ciclosporin is an immunosuppressant drug widely used in post-allogeneic organ transplant to reduce the activity of the immune system, and therefore the risk of organ rejection. It is commonly prescribed in the US as an ophthalmic eyedrop for the treatment of dry eyes

Retina: The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. There is a small area, called the macula, in the retina that contains special light-sensitive cells. The macula allows us to see fine details clearly. See Macula Degeneration

Retinal detachment: is 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.

Rosacea: A chronic skin disease that affects the middle third of the face with persistent redness over the areas of the face and nose that normally blush: mainly the forehead, the chin and the lower half of the nose. The tiny blood vessels in these areas enlarge (dilate) and become more visible through the skin, appearing like tiny red lines (called telangiectasias). Pimples can occur that look like teenage acne.
 

Scaling: Abnormal shedding or accumulation of an upper layer of skin (the stratum corneum).

Schlemm's canal: also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins.

Sclera: The tough white outer coat over the eyeball that covers approximately the posterior five-sixths of its surface. The sclera is continuous in the front of the eye with the cornea and in the back of the eye with the external sheath of the optic nerve.

Seborrhoeic dermatitis: (also known as "seborrheic eczema" & "seborrhea") is an inflammatory skin disorder affecting the scalp, face (can be around the eyes), and torso.

Sensitivity: 1. In psychology, the quality of being sensitive. As, for example, sensitivity training, training in small groups to develop a sensitive awareness and understanding of oneself and of one’s relationships with others. 2. In disease epidemiology, the ability of a system to detect epidemics and other changes in disease occurrence. 3. In screening for a disease, the proportion of persons with the disease who are correctly identified by a screening test. 4. In the definition of a disease, the proportion of persons with the disease who are correctly identified by defined criteria.

Sensory: Relating to sensation, to the perception of a stimulus and the voyage made by incoming (afferent) nerve impulses from the sense organs to the nerve centres.

Sleep: The body's rest cycle.

Slit-Lamp: A lamp that emits a narrow but intense beam of light that enables an ophthalmologist, using a microscope, to view the retina and optic nerve

Sodium: The major positive ion (cation) in fluid outside of cells. The chemical notation for sodium is Na⁺. When combined with chloride, the resulting substance is table salt.

Squint: (see strabismus)

Staphylococcus: A group of bacteria that cause a multitude of diseases. Under a microscope, Staphylococcus bacteria are round and bunched together. They can cause illness directly by infection, or indirectly through products they make, such as the toxins responsible for food poisoning and toxic shock syndrome. The best known member of the Staphylococcus family is Staphylococcus aureus. Staphylococcus are the main culprit in hospital-acquired infections, and cause thousands of deaths every year.

Strabismus: A visual defect in which one eye cannot focus with the other on an object because of imbalance of the eye muscles. (Also called squint).

Substance: 1. Material with particular features, as a pressor substance.
2. The material that makes up an organ or structure. Also known in medicine as the substantia.
3. A psychoactive drug as, for example, in substance abuse.

Syndrome: A set of signs and symptoms that tend to occur together and which reflect the presence of a particular disease or an increased chance of developing a particular disease.
 

Taste: Taste belongs to our chemical sensing system, or the chemosenses. The complicated process of tasting begins when molecules released by the substances stimulate special cells in the mouth or throat. These special sensory cells transmit messages through nerves to the brain where specific tastes are identified.

Tear: A drop of the salty secretion of the lacrimal glands which serves to moisten the conjunctiva and cornea.

Therapeutic: Relating to therapeutics, that part of medicine concerned specifically with the treatment of disease. The therapeutic dose of a drug is the amount needed to treat a disease.

Toric lenses: Toric contact lenses are special lenses that are used to correct astigmatism. Toric contact lenses are designed to give your eyes more power in one direction and less power in the opposite direction.

Trauma: Any injury, whether physically or emotionally inflicted. "Trauma" has both a medical and a psychiatric definition. Medically, "trauma" refers to a serious or critical bodily injury, wound, or shock. This definition is often associated with trauma medicine practiced in emergency rooms and represents a popular view of the term. In psychiatry, "trauma" has assumed a different meaning and refers to an experience that is emotionally painful, distressful, or shocking, which often results in lasting mental and physical effects.

Tricyclic antidepressants (TCAs): One of a class of medications used to treat depression. The tricyclic antidepressants (TCAs) are also used for some forms of anxiety, fibromyalgia, and the control of chronic pain.
 

UV radiation: Ultraviolet radiation. Invisible rays that are part of the energy that comes from the sun, can burn the skin, and cause skin cancer. UV radiation is made up of three types of rays -- ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC).

Uveitis: Inflammation of the uvea, the part of the eye that collectively refers to the iris, the choroid of the eye, and the ciliary body. The uvea provides most of the blood supply to the retina. Uveitis as a rule signifies inflammation involving the iris, choroid, and ciliary body -- all three components of the uveal tract.
 

Virus: A microorganism smaller than a bacteria, which cannot grow or reproduce apart from a living cell. A virus invades living cells and uses their chemical machinery to keep itself alive and to replicate itself. It may reproduce with fidelity or with errors (mutations)-this ability to mutate is responsible for the ability of some viruses to change slightly in each infected person, making treatment more difficult.

Viruses: Small living particles that can infect cells and change how the cells function. Infection with a virus can cause a person to develop symptoms. The disease and symptoms that are caused depend on the type of virus and the type of cells that are infected.

Visual Acuity: Clarity of vision, with corrective glasses.

Vitreous humour: A clear, jelly-like substance that fills the middle of the eye. Also called the vitreous, "humor" in medicine referring to a fluid (or semi-fluid) substance.
 

Zeaxanthin: an isomer of lutein occurring especially in fruits and vegetables (as spinach and corn)