Laser Eye Treatments | Lasik Treatment | Laser Eye Treatment UK

Aberrometer

A diagnostic device that measures the way light waves travel through the eye and any distortion the eyes optical system creates as the light passes through. Used in laser eye surgery to calculate wavefront guided treatments.

Ablation

The removal of tissue using an excimer laser in laser eye surgery to correct a refractive error. Used in LASIK and Epi-LASIK and the treatment of Keratoconus at AccuVision.

Accommodation disorder

Where the eyes ability to focus from distance to near ojects and from near to distance does not work correctly. Disorders can be caused by a number of symptoms such as: eye strain, headache, difficulty concentrating (especially reading), blurred visi

Age Related Macular Degeneration (AMD or ARMD)

Age Related Macular Degeneration is caused by damage to the retinal cones (the part of the eye that transfers images and colour to the brain). A gradual loss of central vision occurs leaving just the peripheral vision for seeing.

Allergy

The body's immune system is programmed to protect the body from foreign bodies e.g. pollen. Allergy symptoms can also affect the eyes, usually showing as redness of the eyes, tears, swollen eyelids or itching.

Amaurosis Fugax

This is sometimes described as an 'Eye Stroke'. It is caused when a blood clot restricts blood flow to the eyes causing temporary vision loss. It usually affects just one eye.

Amblyopia

Also known as Lazy Eye. If the central vision in one eye is less developed than the other, the brain becomes dependent on the information from the good dominant eye. An eye patch is used to help correct Amblyopia at an early age. The two main causes of lazy eye are Strabismus and Anisometroia. It can also be treated in adults using Neurovision.

Aniridia

A condition where the iris in the eye is either absent or partially absent. It is usually a congential defect in the eye and causes photophobia and poor vision.

Anisocoria

A condition where pupils are of unequal size. Causes are various including: a natural event in the population without a known cause, head or eye trauma, previous intraocular surgery, an infection of the membranes around the brain, an intercranial tum

Anisometropia

A common condition in people with impaired vision where the prescription needed for good vision is very different for each eye due to the differences in refractive power.

Antibody

This is a specific protien that is initiated by the body's immune system to help fight foreign substances, toxins and infections inside the body.

Antioxidant

Antioxidants are powerful compounds that protect your body's cells against free radicals, unstable molecules that can cause harm if their levels become too high. Think of antioxidants as your body's personal bodyguards, neutralising these potentially damaging particles.

Aqueous humor

This is the clear fluid filling the front of the eye, located between the cornea and the iris. It supplies nutrients to the cornea and the lens. The fluid is created by the ciliary body. If this fluid is not able to drain away freely, pressure builds up and can cause Glaucoma. If this is not overcome, damage to the optic nerve can occur resulting in loss of vision.

Arcus

This describes fatty/oily deposits causing an opaque ring around the periphery of the cornea. It is a condition of elderly people but can also occur in people under the age of forty and is an indication of excessive level of cholesterol in the blood

Aspheric

Meaning not quite a spherical shape. In vision terms people who suffer high perscriptions usually prefer aspheric glasses as they can be produced using thin lenses and lightweight frames and reduce eye magnification. Aspheric contact lenses are designed to overcome astigmatism and can also be used as a multi-focal lens.

Astigmatism

Where the curvature of the cornea has developed in an asymmetrical shape (shaped like a rugby ball instead of a football). Consequently light entering the eye is focussed on two points on the retina rather than just one, which causes blurred vision. Astigmatism also causes double vision, squinting, eyestrain, distorted vision and shadowing around letters.

Atopy

Used to describe an increase in the antibody immunoglobin E that leads to conditions such as asthma, hay fever, eczema and rhinitis.

Band keratopathy

Used to describe a loss of opacity in the corneal stroma and Bowman's membrane. It causes vision loss.

Best corrected visual acuity (BCVA)

This describes the best vision you can achieve using corrective glasses. It is a measure taken from the standard Snellen eye table. If you have bad eyesight with an uncorrrected reading of 20/300 but you are capable of seeing 20/20 using glasses then your Best corrected visual acuity is 20/20.

Bifocal

Where a lens is created with two focussing areas; one for close vision and one for distance vision. Lenses like this can be created for both glasses and contact lenses.

Biocompatible

A material that is able to be placed inside the body or organs and not cause any adverse reaction. Intra Ocular lenses for example are boicompatible as they can be inserted inside the eye without any reaction from the body.

Blepharitis

An inflammation of the eyelid(s), usually around the eyelashes. Blepharitis can be caused by a number of conditions including: rosacea, dermatitis and allergies. The usual symptoms are a pink or red, sore looking eyelid, eyelid pain, swelling or crus

Blepharoconjunctivitis

In addition to inflammation of the eyelid, the conjunctivitis also causes swelling with infection, tearing, burning around the eyes and severe discomfort.

Bowman’s membrane

This is the corneal layer found between the epithelium and the stroma.

Canaliculi

Very small channels found at the start of the tear ducts through which tears drain until they pass out into the nose.

Canaliculitis

An inflammation of a tear duct, usually caused by a bacterial infection. Symptoms for canaliculitis include a pink or red swollen eye, discharge from the eye and swollen eyelids close to the nose.

Capsulotomy

During cataract surgery the surgeon makes an incision into the capsule that holds the natural crystalline lens of the eye (a capsulotomy), which allows for the natual lens to be removed and substituted for an artificial intra ocular lens.

Cataract

A clouding over of the eyes' natural lens, the most common cause being age. Other causes are high exposure to the sun's ultra violet light. Smoking is also an identified cause. The symptoms are varied but can include: blurred vision, halos, glare around lights, cloudiness of vision and dimness of colour.

Cellulitis

An inflammation around the eye. There are a number of types. Orbital cellulitis affects the areas around the eyeball causing a bulging eye which should be dealt with immediately, while Pre-septal cellulitis affects the eye lid and other parts around

Central island

Used to describe a refractive laser eye surgery complication where a small area of cornal tissue is left untreated in the ablation zone. This can cause double vision and sight distortion.

Chemosis

A swelling on the conjunctiva that is usually caused by an allergy.

Choroid

The fine layers of blood vessels that are situated between the white of the eyes (sclera) and the retina. Their function is to maintain a supply of nourishment to the back to the eye.

Ciliary body

The ciliary body holds the natural lens inside the eye in place and also causes it to change shape so that fine focussing is possible (accomodation). It also produces aqueous humor.

Collagen

Collagen is a crucial protein that plays a vital role in eye health and function.

Colour blindness

The inability to distinguish specific colours from the colour spectrum. Colour blindness is an inherited condition and is prevalent in men more than women.

Computer vision syndrome

Symptoms of computer vision syndrome include headaches, shoulder and neck pain, eyestrain, dry eyes, blurred vision, pink or red eyes or even light sensitivity. It is important to get an assessment for these conditions as the symptoms are also common

Concentric

Having a common center; extending out equally in all directions from a common center.

Conductive Keratoplasty

Procedure in which a surgeon applies radio waves to the cornea to heat the collagen in the cornea's periphery. This causes it to shrink, thereby reducing hyperopia.

Cone

Found in the retina. A cone is a photosensitive receptor that helps a person differentiate colours and there are approximately 6,400,000 in the human retina.

Conjunctivitis

This is an inflammation of the conjunctiva, which causes redness of the eye and discharge from the eye. A burning sensation and itching can occur along with light sensitivity and eye pain. It can occur in one or both eyes.

Contact lens

What are contact lens?

Contact lenses are thin, curved lenses placed di

Contact lens solution

Used by contact lens wearers to help with the comfort of wearing contact lenses.

Contrast sensitivity

The ability of the eye to perceive differences between an object and its background, i.e. the ability to identify a blue object on a blue background.

Convergence

Where a person's eyes begin to turn inwards. Performing close up tasks like reading may cause eye strain and blurred vision.

Cornea

The transparent front part of the external structure of the eye covering the iris, the pupil and the sclera. The dome-like shape of the cornea delivers approximately two-thirds of the optical power of the eye. Light passes into the eye through the cornea. It is reflected back out of the eye, making the iris and pupil of the eye visible.

Corneal abrasion

A corneal abrasion, often described as a scratched eye, is one of the most common eye injuries. While usually not serious, it can be painful and potentially lead to complications if not properly treated.

Corneal dystrophy

A condition where the clear window at the front of the eye (the cornea) loses its transparency. The surface of the cornea is no longer smooth which causes blurred vision, light sensitivity, eye pain and vision loss.

Corneal edema

A swelling of the cornea that can be as a result of intra ocular surgery, high intra ocular pressure, contact lens problems, or other corneal dystrophies. Symptoms can include halos around bright lights, eye pain, foreign body sensation or vision los

Corneal erosion

Continuing breakdown of the corneal epithelium. Symptoms include blurred vision, foreign body sensation and eye pain or discomfort.

Corneal implants

Vision correcting elements like corneal rings or contacts that are placed inside the eye structure to correct vision.

Corneal opacity

Where a translucent or small cloudy area is found in the cornea caused by scarring or an infection. Sufferers can experience halos around lights, vision loss and a visible cloudy spot on the eye.

Corneal ring

These are used in corrective surgery. A surgeon inserts a clear plastic ring into the cornea which then reshapes it to help with focussing the light entering the eye on to the retina.

Corneal topography

This is measured using a corneal topographer which directs light onto the surface of the eye and then is able to accurately measure the light as it is reflected back into the device so that a detailed corneal map can be created showing it's curvature and any irregularities it may contain in its structure. The corneal topographer produces a coloured map that clearly shows the variations in shape and height of the cornea. Very good for consulting on astigmatism, laser eye surgery and specialist contact lens fitting.

Crossed eyes

This condition is where both eyes are misaligned and pointing inwards. It is a type of strabismus.

Cystoid macular edema

Cystoid Macular Oedema (CMO), also spelled Edema, is an eye condition characterised by the accumulation of fluid in cyst-like spaces within the macula, the central part of the retina responsible for sharp, d

Cytomegalovirus retinitis (CMV retinitis)

An eye infection associated with immune deficiency such as AIDS. Major symptoms include blind spots blurred vision, vision loss and floaters.

Dacryoadenitis

This condition describes the inflammation of the tear gland. The cause is usually a viral or bacterial infection. The resulting symptoms include red eyelids or swelling around the eyes.

Dacryocystitis (Tear Duct Infection)

Dacryocystitis is a painful infection of the tear sac (lacrimal sac) located at the inner corner of the eye. This condition occurs when the tear duct, which normally drains tears from the eye to the nose, becomes blocked or obstructed.

Dacryostenosis

This condition is where the tear duct becomes blocked, causing tears and some discharge.

Descemet’s membrane

Descemet's membrane is a thin, elastic layer located in the cornea, the clear front surface of your eye. It sits between the stroma (the thickest layer of the cornea) and the endothelium (the innermost layer of the cornea).

Diabetic maculopathy

Diabetic maculopathy is a serious eye condition that affects people with diabetes. It occurs when high blood sugar levels damage the blood vessels in the macula, the central part of the retina responsible for sharp, detailed vision. Left untreated, diabetic maculopathy can lead to significant vision loss or even blindness.

Diabetic retinopathy

A condition affecting long term diabetes sufferers. Retinal blood vessels begin to discharge which affects the functioning of the macula. Blurred vision may be the first symptom or a larger number of floaters but can progress to loss of vision.

Diabetic vitreous hemorrhage

Caused by weakening of blood vessels in the eye, the bleeding into the vitreous humor obscures clear vision and may require surgery.

Diopter

Used as a measure for refraction or bending of light through a substance. Opticians use diopter measurements to describe prescriptions for contact lenses and spectacles to provide clear vision for patients. A positive number would describe a long-sig

Diplopia

Diplopia is used to describe double vision. This occurs when one or both eyes percieve two images at the same time.

Disc hemorrhage

The optic disc at the back of the eye is where the optic nerve is attached to the back of the retina. Bleeding around the edge of the disc can occur and is one indication of glaucoma.

Disposable contact lenses

Some contact lenses are now produed so that they can be thrown away after a short period of wear. This time period can range from just a day to a couple of weeks.

Dk/t

Used to describe the permeability and thickness of a contact lens. The Dk value is the oxygen permeability of the contact lens material. The t value indicates its thickness which affects the transfer of oxygen through the contact lens.

Double vision

Also referrred to as diplopia. See diplopia.

Druse

Describes a deposit in the eye that can be white or yellow. Druse is sometimes linked to macular degeneration.

Dry eye

Dry eye is a common ocular condition characterized by insufficient tear production or rapid tear evaporation, leading to discomfort and potential vision problems. This chronic condition affects millions worldwide and can significantly impact quality of life if left untreated.

Dry eye syndrome

Dry eye can occur through aging or long term contact lens wear. It can also be part of a number of systemic diseases. Dry eye syndrome can cause eye pain, a burning sensation in the eyes, itching and frequent blinking.

Emmetropia

This describes the condition of an eye with normal vision where light is correctly focused on the right part of the retina at the back of the eye.

Enophthalmos

The recession of an eyeball into the orbit. Causes include developmental problems, trauma and inflammation.

Entropion

An abnormal inward turning of an eyelid (usually the lower lid), which causes the lashes to rub on the ocular surface; usually due to aging. Additional symptoms include eye or lid pain or discomfort, redness, itching, tearing and vision loss if there

Epiretinal membrane

Thin layer of scar tissue on the retina which forms as a result of changes in the vitreous gel. Also called a macular pucker. In its early stages, an epiretinal membrane is often asymptomatic, but some people have blurred vision. There may be symptom

Episcleritis

Inflammation of the episclera. The cause is usually unknown, but episcleritis may be associated with some systemic (e.g. autoimmune) diseases. Symptoms include a red eye, pain or discomfort, light sensitivity and tearing.

Epithelial in-growth

A LASIK complication in which epithelial cells migrate and grow under the LASIK flap; epithelial ingrowth does not usually affect vision. Reported incidence is low (0,1%).

Epithelium

The cornea's outer layer of cells. The only layer of the cornea that has the ability to replicate if damaged.

Esotropia

A form of 'squint' or strabismus where one or both eyes point inward, so the eyes are "crossed." Commonly erroneously referred to as 'lazy eye'. Management options include glasses, orthoptic exercises or surgery.

Excimer laser

An instrument that uses ultraviolet wavelength of light to vaporize and remove tissue from the eye's surface during vision correction procedures. 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.

Exotropia

A form of 'squint' or strabismus where one or both eyes point outward. Management includes orthoptic exercises or surgery.

Extended wear

Currently, these contact lenses are approved to be worn without removal from 1 week to 1 month, meaning some people will be comfortable sleeping with them in their eyes. Sometimes referred to as continuous wear. Known risks include corneal infection.

Eye Accommodation

In optics this means the capability of the eye to automatically focus from distance to near objects and from near to distance objects.

Eye tumor

An abnormal growth or mass that occurs in or next to the eye. Tumors can be both benign and malignant and primary or secondary (from other organs). They include the dermoid cyst, capillary hemangioma, cavernous hemangioma, choroidal melanoma, retinob

Far-sightedness

Far-sightedness, also known as hyperopia, is a common refractive error where distant objects appear clear, but nearby objects are blurry. This condition affects millions worldwide and can impact daily activities like reading, using smartphones, or wo

Femtosecond laser

A laser device that creates bursts of laser energy at an extremely fast rate measured in terms of a unit known as a femtosecond (one quadrillionth of a second). These ultra fast energy pulses precisely target and break apart tissue or other substances at a molecular level, without damaging adjacent areas. Commonly used in corneal refractive surgery e.g. to create LASIK flaps.

Fixation

The eye's ability to maintain gaze upon an object or target.

Floaters

Floaters are very common and may look like clouds, strands, webs, spots, squiggles, wavy lines or other shapes and often move in the field of vision. As the eye ages, the gelatinous vitreous humor begins to liquefy in the center of the gel. Floaters

Fluorescein angiography

An imaging test that involves injecting fluorescent yellow-green dye into the veins. When the dye reaches interior regions of the eye, it provides opportunity for high contrast photography or other imaging of blood vessels. This is particularly usefu

Foreign body (in the eye)

A foreign body refers to any object or substance that enters the eye from the outside environment. These can range from tiny particles like dust or eyelashes to larger objects such as metal shavings or wood

Fovea

A depression in the retina that contains only cones (not rods), and that provides acute eyesight. Ideally the area of the retina where light is focused to form an image.

Frequent replacement contact lenses

Also called planned replacement. Technically, this is any contact lens that is thrown away after a moderately short period of time. Among most eye care practitioners, "disposable" usage ranges from one day to two weeks, while "frequent replacement" l

Glaucoma

An eye disorder in which the optic nerve suffers damage, permanently impacting vision in the affected eye(s) starting with peripheral vision loss and progressing to complete blindness if untreated. It is often, but not always, associated with increas

Graves’ disease

An eye disorder associated with abnormalities of the thyroid gland; symptoms include eyelid retraction, bulging eyes, light sensitivity, eye discomfort, double vision, vision loss, a red or pink eye and a limited ability to move the eyes.

Hard contact lenses

Rarely worn now, hard lenses are made of PMMA material. Cannot transmit oxygen through the lens to the cornea and often cause warpage of the cornea's shape. Compared with modern soft and rigid lenses, they are less healthy to wear long-term.

Herpes eye infection

Typically causes infection in the corneal stroma with characteristic dendrite shaped lesions. Symptoms include pain, redness and reduced vision. The virus stays dormant and infection can be triggered by ill health or trauma.

Heterochromia

Condition where one iris of an eye is a different colour to the other, or where one eye is more than one colour.

High-index

Type of lens with a higher index of refraction, meaning that light travels faster through the lens to reach the eye than with traditional glass or plastic. It is denser, so the same amount of optical correction occurs with less material - so the lens

Higher-order aberration

Higher-order aberrations are visual problems that cannot be diagnosed using a traditional eye exam, which tests only for acuteness of vision. Severe aberrations can cause significant vision impairment. These aberrations include starbursts, ghosting,

Histamine

A protein that can be released as part of the body's immune system responses during an allergic reaction. Presence of histamine can lead to inflammation and swelling, which is why antihistamines often are prescribed for allergy symptoms.

Horner’s syndrome

Condition characterized by a small pupil, ptosis (drooping upper eyelid) and an abnormal lack of facial perspiration (all on the same side of the face); Horner's syndrome is caused by injury to the sympathetic nerves of the face.

Hyperopia

What is hyperopia?

Hyperopia, commonly known as farsightedness, is a re

Hypotony

Abnormally low intraocular pressure, often caused by eye surgery or trauma (e.g. open globe injury). Could indicate fluid leakage or deflation of the eyeball.

Intraocular lenses (IOL)

An artificial lens that is implanted in the eye, generally after the eye's natural crystalline lens (see Lens, Crystalline) has been removed. IOLs are used on patients suffering from Cataracts or as an alternative to Laser Eye Surgery to correct large visual prescriptions.

Intraocular pressure (IOP)

The fluid pressure of aqueous humor. Measuring the IOP is important in detecting for and monitoring of Glaucoma.

Iritis

Inflammation of the iris, a form of Anterior Uveitis. A number of causes and conditions are associated.

Keratectomy

Surgical removal of part of the cornea. See (PTK) Phototherapeutic Keratectomy.

Keratitis

An inflammation of the cornea, caused by an infection or inflammatory process. Causes can include any or a combination of the following : Bacterial, Amoebic, Viral, Fungal, Onchocercal, Exposure, PhotoUV (Snow Blindness, Arc eye), Ulcerative, Contact

Keratoconjunctivitis (vernal)

Seasonal inflammation of the conjunctiva. Also known as Warm Weather conjunctivitis or Spring Catarrh. Strong association with atopy (hayfever, asthma & eczema).

Keratoconus

A degenerative disorder of the cornea causing progressive thinning and conical curvature of the cornea leading to decreased vision. Kerataconus is the most common form of Corneal Ectasia. Without medical intervention, keratoconus often causes the perforation (Hydrops) of the cornea requiring a corneal transplant or graft. The exact cause or trigger mechanism is not known, however a strong autosomnal genetic link amongst environmental and cellular factors are indicated. LASIK refractive surgery has also induced keratoconus, see Post-LASIK Ectasia. Corneal Collagen Cross-linking is the only treatment shown to halt the progressive nature of the disorder.

Keratometer

An instrument that measures the curvature of the cornea. Keratometry is relevant to laser and IOL refractive surgery, Keratoconus and contact lens fitting.

Keratoplasty

Any of several types of corneal transplantation or graft. These are either complete transplants (penetrating keratoplasty) or part grafts (lamellar keratoplasty).

LASEK (Laser Epithelial Keratomileusis)

LASEK is an advanced laser eye surgery technique designed to correct vision problems such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. This procedure is particularly beneficial for patients with thin corneas who may not b

LASIK (Laser-Assisted In Situ Keratomileusis)

The most popular form of elective refractive treatment. A corneal flap is cut using either a Microkeratome or Femtosecond laser. The flap is folded back before an excimer laser ablates the desired correction. The flap is folded back into position prior to completing treatment. Wound healing is quick, with the epithelium sealing within 24-48 hours. Visual recovery can take from as little as 24hrs up to 2 weeks in some cases. The treatment is popular due to the pain free recovery and quick visual rehabilitation.

Lacrimal plug see Punctal plug

Made either of collagen (temporary) or silicone (permanent), punctual plugs are sometimes inserted into the puncta (tear duct) of the lower lid to stop tear drainage.

Laser photocoagulation

A procedure using a laser, normally to cauterise blood vessels on the retina. Most commonly used in providing therapeutic treatment for Diabetic Retinopathy and more recently age related macular degeneration.

Lens (crystalline)

A structure in the eye that along with the cornea focuses light on the retina. The lens unlike the cornea does this by changing shape. The shape change allows for a change in focal point (accommodation). As the lens ages (38-45 yrs), it starts to los

Lens (optical)

Any optical device that transmits and refracts light.

Lens dislocation (Ectopia lentis)

Full or partial displacement of the eye's lens. Dislocation is commonly associated with a number of systematic syndromes as well as trauma.

Leukocoria

An abnormal (white) reflection of the eye. Commonly noted in photos taken with a flash (as opposed to the usual red reflection). While noted in a number of other conditions, Leukocoria is most prominently associated with the eye cancer retinoblastoma

Limbal relaxing incisions

Are surgical incisions of the corneal edge or limbus, often performed during cataract surgery. As opposed to Radial Keratotomy (RK), these incisions are not particularly deep or near the visual field of the eye. These incision are typically made to c

Limbus

The border of the cornea and sclera.

Lupus (systematic lupus erythematosus)

Is a systematic auto-immune disease that causes inflammation and tissue destruction. Lupus is more prevalent in non-europeans and is found much more commonly in women. While Lupus is more noticeable on the dermus, it can have optical symptoms such as

Macula

A small area near the centre of the retina which has the greatest density of cone receptor cells necessary for good visual acuity and colour vision.

Macular degeneration

Definition: Age-Related Macular Degeneration (AMD) is a degenerative eye disease primarily affecting individuals over 50. It impacts the macula, a small area in the retina responsible for central visio

Macular edema

This condition occurs when fluid leaking from retinal blood vessels causes the macula to become swollen. It causes temporary vision loss which may become permanent if untreated.

Maculopathy

Any deterioration of the macular tissue. Symptoms include blurring, distortion or loss of central vision.

Meibomian gland

Situated at the base of the eyelashes this gland secretes a lipid substance which constitutes part of the tear film.

Meibomianitis

This condition occurs when the meibomian glands become inflamed resulting in redness and swelling of the eye. In addition, vision may be blurred and there may be a burning sensation due to poor tear film.

Melanin

Naturally occurring pigment present in skin and hair as well as the iris of the eye thereby defining eye colour.

Melanosis

Deposits of melanin.

Meridian

The angles relative to the horizontal plane through the centre of the pupil at which the cylindrical powers needs to be set to correct astigmatism.

Metamorphopsia

Distortion of vision whereby straight lines may appear to be curved, objects may be magnified or minified, and depth perception may be impaired.

Microcornea

A cornea that is unusually small in diameter and has steep curvature.

Microkeratome

Semi-automated device with an oscillating blade which creates the flap of tissue on the front of the cornea in the LASIK procedure.

Microphthalmia

Abnormal development of the eye where the eye does not grow to its full size resulting in one or both eyes being abnormally small.

Minification

Concave lenses in spectacles to correct myopia cause objects to appear reduced resulting in minification.

Mixed astigmatism

Where the curvature of the two main meridians of the cornea differ so that one meridian is hyperopic and the other myopic. This results in blurred vision both distance and near.

Monochromatic

A source of light made up of one wavelength only.

Monovision

Refers to monofocal correction in each eye where the dominant eye is corrected for distance vision and the other eye is corrected to a shorter focal length for near vision. Monovision is often used for patients who have presbyopia to reduce the need for separate reading glasses.

Mucin

A glyco-protein which forms part of the tear film. It increases viscosity of the tear film necessary for effective lubrication of the eye.

Multifocal

Lenses which are designed to have a transition of varying power from the centre of the lens so that presbyopes focus at different distances through different parts of the same lens.

Myasthenia gravis

An auto-immune disease which causes voluntary muscles to weaken. Symptoms associated with the eye include diplopia and drooping of one or both eyelids.

Myopia

Medical term for short-sightedness. It occurs when the axial length of the eye is too long relative to the curvature of the cornea and the power of the lens within the eye. Distant images are focussed in front of the retina and therefore blurred.

Nanometer

A unit of measure used to define wavelength of different types of light.

Near-sightedness

Another term for myopia (see definition).

Neovascularization

Formation of micro-vascular network of new blood vessels from pre-existing ones. It can be associated with over-wear of contact lenses in response to reduced oxygen transmission to the cornea resulting in encroachment of blood vessels into the cornea

Neurons

Cells which transmit information by electrical or chemical stimulation. They form the core components of the peripheral and central nervous systems and are responsible for stimulus of the sensory organs.

Nickel

A metal commonly used as an alloy in metal spectacle frames.

Nose pad

Small supports attached to a spectacle frame to rest frame comfortably on the nose.

Nystagmus

Uncontrolled movement of the eye that is rapid and repetitive. The eyes may swing side to side, up and down or in a circular motion. It is often associated with poor visual acuity.

OD

Abbreviation for Oculus Dexter which means Right Eye in Latin.

OS

Abbreviation of Oculus Sinister, which means Left Eye in Latin.

Ocular herpes

Herpes of the eye occurs when herpes simplex virus infects the eye. It usually affects the cornea causing inflammation of the tissue. If it occurs in the superficial layers of the cornea it may heal without scarring but if it affects the deeper layer

Ocular hypertension

Abnormally raised Intraocular pressure in absence of damage to the optic nerve or reduction in the field. Patients with ocular hypertension have a greater tendency to develop glaucoma.

Ocular migraine

Visual disturbances characteristic of migraine without developing the actual headache.

Ophthalmologist

Specialist in medical eye conditions and eye surgery.

Ophthalmoplegia

Paralysis or weakness of the eye muscles. It is often caued by neurological disorders. It causes limitation of muscle function which can in turn result in diplopia, ptosis and nystagmus.

Optic nerve

Transmits information from the retina to the brain. Photoreceptor cells in the retina respond to light stimulation sending electrical impulses along the optic nerve to the visual cortex where they are interpreted as vision.

Optic nerve head

Pale disc shaped area on the retina where the ganglion cells exit the eye to form the optic nerve. It is also referred to as the optic disc. As it does not contain any photoreceptors it is the source of the blind spot which naturally occurs in our fi

Optical coherence tomography

3D imaging of biological tissue using near infra-red light. It is used in ophthalmology to obtain detailed images within the retina.

Optician

Generally refers to somone who dispenses spectacles and contact lenses.

Optics

Study of maths and physics of properties of light.

Optometrist

Health care professional concerned with vision, the eye and related structures.

Orbit

The cavity or socket in the skull in which the eyeball is located.

Orthokeratology (ortho-k)

Correction of myopia using rigid contact lens worn overnight to reshape the cornea.

Overconvergence

Eye muscle imbalance where there is excessive convergence of one or both eyes which can result in diplopia and suppression of image from one eye.

Overflow tearing

Occurs due to impaired drainage of tears away from the eye through the lacrimal duct as new tears are produced by glands in the eyelids. This overflow can be due to a blocked duct, loss of tension in the eyelids, or poor tear quality.

PMMA (polymethyl methacrylate)

A transparent thermoplastic which was the original material used to produce rigid contact lenses referred to as hard contact lenses.

PRK (Photorefractive Keratectomy)

A form of refractive surgery in which the epithelial cells are abraded from the corneal surface and then an excimer laser is used to reshape the underlying corneal tissue. Recovery is slow and painful. There is a significant risk of haze developing i

Papilla

Small elevation at the optic disc.

Papilloedema

Swelling of the optic disc usually occurs bilaterally and is due to raised intracranial pressure. It does not normally affect visual acuity in acute phase but can damage peripheral field of vision.

Papilloma

Benign epithelial growth on the skin which projects outwards in frond-like appearance.

Pars plana

It is part of the ciliary body forming the area where sclera and the iris meet on the inside of the eye.

Penetrating keratoplasty

This is a surgical procedure whereby damaged or diseased corneal tissue is replaced by donated tissue as a graft.

Peripheral vision

Peripheral vision, also known as side vision or indirect vision, refers to the ability to see objects and movement outside of your direct line of sight. It's the vision you use to detect things "out of the corner of your eye."

Phacoemulsification

The lens in the eye is broken down within the capsule in which resides an ultra-sonic device. The lens pieces are then removed by an aspirator which suctions them out. The lens can then be replaced by injecting a new synthetic lens in its place.

Phakic

An eye which retains a natural crystalline lens.

Phoropter

An instrument containing different lenses in graduated powers which can be turned in place in mixture of spherical and cylindrical powers to refract the eye and determine correction needed.

Photoablation

The vaporization of tissue by a laser using ultra-violet light.

Photochromic

Lenses that darken in the presence of UV light.

Photocoagulation

The clotting of tissue using a laser which emits light in a specific wavelength. Haemoglobin, a pigment in blood, selectively absorbs light from the visible green wavelength. Lasers which emit light of this wavelength are used to seal off blood vesse

Photophobia

Excessive sensitivity to light causing tearing, pain or discomfort in presence of natural or artificial light.

Photopsia

Sparks or flashes of light which are not visual in origin but in fact are due to mechanical stimulation of the light receptors in the retina. It is often associated with post vitreous detachment or retinal detachment. It is also a feature of visual d

Photoreceptor

Specialized nerve cell found in the retina able to convert light into an electrical impulse. The two principal photoreceptors are the rods and cones.

Phytochemicals

Chemical compounds that naturally occur in plants that appear to help protect humans against disease and cancer.

Pinguecula

A common benign growth on the conjunctiva. It often appears as a yellowish, nodular, thickened lesion on the sclera near the cornea.

Placebo

A treatment that has no intrinsic value in itself but is used in trials to compare effectiveness of actual treatment to the "pretend treatment".

Plano

Literally meaning "flat" this term is used to describe an optical lens that has no focussing power.

Polarized lenses

Lenses which filter light which is oscilliating in a given direction. This principle is used to filter light from sources such as bodies of water to reduce reflections which would cause glare.

Polycarbonate

A thermo-plastic polymer used in the manufacture of optical lenses and spectacle frames.

Porphyria

A relatively uncommon condition whereby an over production of chemicals called porphyrin accumulate in the body. Symptoms include urine appearing red in colour, abdominal pain, and damage to the skin as it comes to sunlight and more prone to injury.

Posterior chamber

The space in the eye between the posterior surface of the iris and ciliary body and anterior to the lens.

Presbyope

Patient who has reduced ability to read due to loss of accommodation.

Presbyopia

A common age-related condition where the eye gradually loses the ability to focus on close objects. It typically becomes noticeable in your early to mid-40s and continues to worsen until around age 65. Blended vision correction, or LASIK, can be a

Prescription lenses

Prescription lenses are corrective lenses that compensate for refractive errors in your eyes. These lenses are crafted based on a prescription provided by an eye care professional, typically an optometrist or ophthalmologist, following a comprehensive eye examination.

Prism

Prisms are incorporated in to spectacle lenses to correct muscle imbalances between the eyes. The prism is used to deflect light to alter the position of the image source with respect to the visual axis. They are often used to correct diplopia.

Progressive lenses

Also referred to as varifocal or multifocal lenses. They are characterized by a gradient of increasing power with correction for distance vision at the top of the lens gradually changing in power to correction for near at the bottom part of the lens.

Proliferative vitreoretinopathy (PVR)

A complication that commonly develops secondary to retinal detachment. It causes scar tissue to form in sheets which contracts and distorts the retina.

Prosthetic

Refers to an artificial device which replaces a body part e.g. "a glass eye".

Protective eyewear

Spectacles or goggles designed to from special materials to protect the eyes from injury.

Protein

Biochemical compounds found in the body necessary for cell growth and repair. Protein can be deposited by the tears onto contact lenses causing discomfort in lens wear.

Pseudoexfoliation syndrome

Characterized by deposits of white fibrillogranular material on the anterior lens capsule at the pupil margin. It is considered to be one of the most common causes of glaucoma due to accumulation of pseudoexfoliate material in the trabecular meshwork

Pseudotumor cerebri

A neurological condition characterized by raised intra-cranial pressure in the absence of a tumour. Common symptoms include nausea, headaches, vomiting and tinnitus. Untreated it can cause vision loss due to swelling of the optic disc. It most common

Pterygium

A benign wedge-shaped growth of the conjunctiva on the sclera. It may cause no symptoms or become inflamed causing itchiness and burning sensation. It is most commonly found in people who are more exposed to sunlight and wind. If it grows into the co

Ptosis

Condition in which one or both eyelids droop. It may be due to weakness of the muscle in the upper eyelid, damage to the nerves controlling this muscle or loosening of the tissue in the lid. It can be caused by the aging process, a congenital abnorma

Puncta

Minute openings located nasally on the lid margins. Tears are drained through these openings into the lacrimal duct.

Punctal plugs

Small collagen or silicone plugs designed to be inserted in the puncta to block the tear duct. They are used to treat moderate to severe dry eye problems on the basis that they keep tears in the eye for longer periods of time.

Pupil

Aperture at the centre of the iris which controls light entering the eye.

RGP

Or Rigid Gas Permeable lenses, are a type of contact lens manufactured from oxygen permeable polymers. They are made to custom specifications for each individual eye and when correctly fitted, they encourage the cornea to take up a more regular shape

Reading glasses

Glasses that magnify for close work or reading. Reading glasses are prescribed for people who are presbyopic.

Refraction

The change in direction of light rays as they strike the interface between two materials of different refractive index. A measurement of the focusing power of the eye; to determine what power of optical aids are necessary to fully correct an ametrope

Refractive Error

An assessment of the degree of ametropia that results in light being focused away from the retina, by the refractive elements of the eye. Measured in dioptres, it is an indication of the severity of myopia, hypermetropia or astigmatism in an eye.

Refractive Lens Exchange

Or Clear Lens Extraction, also known as Refractive Lens Exchange, is a procedure in which the natural crystalline lens in the eye is removed and replaced with an artificial, silicon, intraocular lens of specific power, to correct the refractive error

Refractive surgery — The route to vision freedom

Refractive surgery has transformed millions of lives worldwide, offering a safe and effective path to clearer vision. Consult with an experienced eye surgeon to determine if you're a candidate for this life-changing procedure.

Regression

Post refractive surgery, natural changes in the eye can induce a refractive error. In most cases an enhancement procedure can be performed to return the eye to an emmetropic state.

Retina

A complex structure of multiple layers of various types of cells, found on the inner, back surface of the eye. Photoreceptors are responsible for detecting light incident on the retina. Various other cells and processes are involved in converting lig

Retinal Pigment Epithelium (RPE)

A single layer of hexagonally shaped, pigmented, epithelium cells, forming a boundary between the sensory retina and the choroid. The pigmented cells absorb stray light, preventing any further scattering in the eye. They phagocytose dead and damaged

Retinal detachment

A condition in which the neurosensory layers of the retina separate from the retinal pigment epithelium (RPE), allowing vitreous fluid to enter the sub-retinal space. The cells in the detached part of the retina are no longer able to derive nutrients

Retinitis Pigmentosa

The term given to a large group of hereditary conditions that are characterized by progressive retinal degeneration, also known as rod-cone dystrophies. It is believed that abnormal production of photoreceptor proteins are the root cause. Most common

Retinopathy of Prematurity

A disease affecting prematurely born infants, characterized by abnormal, disorganized growth of retinal vasculature. It is most commonly asymptomatic but can result in permanent loss of vision.

Retinoschisis

Abnormal splitting of the retinal layers. Classified as either acquired or juvenile Retinoschisis. The former being a degenerative process characterized by separation of the inner nuclear and outer plexiform layers. The latter, a congenital process c

Rheopheresis

An experimental treatment for Age Related Macular Degeneration (ARMD) based on apheresis, in which the blood of the subject is filtered to remove large proteins and cholesterol to improve the blood circulation to cells in the macula of the eye.

Rheumatoid Arthritis

An inflammatory disorder of the joints. Symptoms vary but include pain and swelling in joints and stiffness. It is an autoimmune disease which can have complications requiring treatment with an Ophthalmologist and is associated with Sjogren syndrome.

River Blindness

Also known as Onchocerciasis or Robles' Disease, is a parasitic disease where the Onchocerca volvulus infects the patient through the bites of the blackflies of Simulium species which are carriers of its larvae. According to the WHO, it is prevalent

Rod

A type of photoreceptor cell found in the retina, that facilitates the detection of light in scotopic (low light) conditions.

SPF

The Sun Protection Factor is a measurement used to represent how much protection a product such as sun-screen provides when applied to skin.

Sarcoidosis

Idiopathic multisystem disease which forms in the lymph nodes, lungs, skin and other areas including eyelid skin, lacrimal gland and sac and nasolacrimal duct. Symptoms include fatigue, weight loss, fever, coughing, uveitis, cranial nerve palsies and

Schlemm’s Canal

A porous channel at the iridocorneal angle into which the aqueous humour flows via a network of trabeculae. The canal empties into exrtaocular veins. It is itself a vein with thin walls and a very porous endothelial membrane and extends all around th

Sclera

The fibrous layer forming the outermost covering of the eye is composed of connective tissue and has two regions - the cornea and the sclera. The sclera forms the posterior region of this dense avascular tissue and is seen as the opaque white of the

Scleritis

Inflammation of the sclera which can occur both in anterior or posterior regions. It is known to be associated with systemic disease in about half of patients. Symptoms include pain, swelling, red eyes, photophobia and decreased vision and it is foun

Scotoma

A region of visual field loss (blind spot) within outer relatively normal vision. It is commonly seen after a stroke or brain injury and can be indicative of optic nerve damage. There are different types of pathological scotomas such as central, hemi

Seborrheic Dermatitis

A common skin condition which is inflammatory and results in the formation of 'scales' on oily areas of the scalp and inner ear. It is present with redness and itching. It is linked to blepharitis where there can be bacterial growth around the eyelid

Segment

A 'part' such as the near-vision hemispheric portion of a pair of bifocal lenses in frames.

Sinusitis

An inflammation of the mucosal lining of the sinuses of which humans have four pairs - the frontal, maxillary, ethmoid and sphenoid. It is often a result of an infection and can be termed acute or chronic. Symptoms include pressure and pain around th

Sjorgen Syndrome

An autoimmune disorder involved with a type of dry eye disease termed 'aqueous deficient dry eye'. It leads to lacrimal gland dysfunction and a reduced tear production. Symptoms are dry eyes, dry mouth and usually includes an inflammatory component.

Skin Cancer

Skin cancer is the abnormal growth of skin cells, typically caused by excessive sun exposure. While it's commonly associated with areas like the face and arms, many people are unaware that skin cancer can also affect the delicate skin around the eyes and even the eyes themselves.

Glossary

What are contact lens?

What is hyperopia?