Glossary of terms
Accommodation
Ability of the eye to change focus between distance objects and near objects
Age related macular degeneration (AMD)
Destructive changes in the centre of the retina (macula), resulting in loss of central vision
Amblyopia
An eye that appears healthy but is unable to see clearly under any circumstances.
This is a condition that develops during childhood, when the brain learns to interpret the information from the eyes. If something interferes with the ability of one eye to see clearly (eg astigmatism or hypermetropia) the image from the other eye is used preferentially by the brain and the eye with blurred vision is neglected. If not corrected early (before the age of 8 years) the ability of the brain to interpret visual information from this eye will be permanently lost
Angle
The thin groove between the iris and the cornea, where fluid drains from the eye
Anisometropia
A condition where the two eyes have unequal refractive power
Anterior chamber
The space between the clear cornea, at the front of the eye, and the coloured iris. This space contains aqueous humour
Aqueous humour
The clear fluid that fills the anterior chamber
Astigmatism
A condition where the surface of the eye is not perfectly round (like a soccer ball), but instead, is shaped more like a rugby ball. This shape does not allow an image to focus sharply on the retina.
Basal Cell Carcinoma
A type of skin cancer. It is the most common form of skin cancer and does not spread to other parts of the body (metastasis). However, it is locally destructive and will invade and destroy local tissues.
Binocular
Using both eyes together to see the same image
Blepharitis
Inflammation of the eyelid margin. It has numerous causes, each requiring its own, specific treatment.
Blepharoplasty
An operation that removes the excess skin (dermatochalasis) from the upper lids
Canaliculus
A thin tube located under the skin in the inner corner of the eye, which drains excess tears from the eyelids. There is a canaliculus in each lid
Canthus
A term that refers to the angle between the upper and lower lid of the eye. There is a canthus in the inner and outer corner of the eye
Cataract
The clear lens in the eye gradually loses its clarity as we age. When it becomes visibly opaque (cloudy), it is called a cataract. At this stage your lens and your cataract are simply two terms for the same thing
Ciliary body
This is a donut shaped structure that is attached to the inner wall of the eye directly behind the iris (coloured part of the eye). It produces fluid (aqueous humour) and is attached to the lens by a multitude of fine strands, called zonules (in the same way that a circular trampoline is attached to the framework by numerous springs).
It is able to alter the tension of the zonules in order to change the shape of the lens. Changes in the shape of the lens is how the eye changes focus between distance and near objects
Conjunctiva
This is the clear lining on the surface of the eye. It covers the entire globe (eyeball) with the exception of the cornea and extends into the fornix of both upper and lower lids. It then continues along the inside of the eyelids until it reaches the lashes at the lid margin, where it meets the skin
Cornea
The clear round window at the front of the eye, through which the coloured iris is visible
Cystoid macular oedema
Swelling of the central retina that results in blurred vision
Dacryocystorhinostomy
An operation that creates a passage for tears between the eye and the nose. It is performed when the natural connection (nasolacrimal duct) is blocked
Dermatochalasis
Excess skin in the upper lids
Diabetic retinopathy
Diabetes leads to a multitude of medical conditions, some of which affect the eye. Diabetic retinopathy refers to changes in the retina that may affect the vision. It results from changes to the blood vessels and usually becomes apparent only once diabetes has been present for several years. The disease varies in severity from mild changes that cause no symptoms to severe changes that result in vision loss. It can be treated and patients with diabetes need to be screened for evidence of retinopathy
Diplopia
Double vision
Dysphotopsia
Unwanted images that may be seen after cataract surgery. This is often in the form of a bright arc seen in the temporal part (outer corner of the eye) of the vision and is caused by light reflecting from the edge of the new intraocular lens. It is a phenomenon that usually resolves after a few months
Ectropion
An abnormal eyelid position that results in the margin of the lid rotating out, away from the eye. This causes exposure of the inner surface of the lid which may become red and inflamed. It is usually caused by age related laxity of the lid
Entropion
An abnormal eyelid position where the lid margin rotates in, towards the eye. The lashes of the lower lid are now directed toward the eye and rub against the cornea
Epiphora
Increased tears in the eye, eventually resulting in flow of tears over the eyelid
Epiretinal membrane
A thin layer of scarring that forms on the surface of the retina. It involves the macula and can vary from a very subtle membrane that causes no symptoms to a significant membrane that results in loss of central vision
Episcleritis
Inflammation on the surface of the eye, involving the layer between the sclera and conjunctiva
Fornix
The space between the eyeball and the eyelid
Glaucoma
An eye disease that results in gradual, progressive loss of vision. Initially, only the peripheral vision is affected, and it causes no symptoms. However, if the disease becomes advanced, which may take many years, the vision will become severely restricted and eventually result in vision loss.It is associated with the pressure in the eye but usually causes no symptoms until central vision becomes affected, at the end stage of the disease. The damage is progressive and irreversible, but treatment can slow it down and prevent vision loss
Hyperopic
Far sighted. Objects that are far away can be seen without glasses (but glasses are required for reading), unless the condition is very significant in which case glasses are needed for all distances
Intraocular Lens (IOL)
An artificial lens that is placed in the eye to perform the function of the natural lens that has been removed
Iris
The coloured part of the eye. It has a central hole called the pupil, that appears as a black dot. The iris controls the size of the pupil to regulate the amount of light that enters the eye, causing the pupil to enlarge when it is dark and constrict when it is bright
Keratitis
Inflammation of the cornea
Lacrimal Gland
The gland that produces tears. There is one in each eye and it is located inside the eye socket (orbit) roughly behind the outer part of the eyebrow
Lacrimal sac
A small sac that collects tears. It is located under the skin in the inner corner of the eye
Lagophthalmos
An inability to completely close the lids
Lash follicle
The structure that is located in the eyelid margin and gives rise to an eyelash
Lens
The lens is used to focus light onto the retina at the back of the eye. It is located in the eye, behind the iris.
With advancing age, the lens loses its clarity and is called a cataract.
Lid margin
The thin, flat part of the eyelid directly behind the eyelashes. It forms the junction between the front of the lid and the back of the lid. The lid margin of top and bottom lids meet when the eyes are closed
Limbus
The area at the front of the eye where the clear cornea changes to white sclera. This is also where the conjunctiva fuses with the sclera
Macula
The central part of the retina. It is the most sensitive area and responsible for detailed vision
Macular hole
A condition resulting in formation of a small hole in the centre of the retina. It leads to variable degrees of vision loss but only affects the very centre of the vision
Meibomian Gland
A gland found in the back of the eyelid (in the tarsal plate). It produces oil that is released onto the margin of the eyelid, which helps to stabilize the tear film (thin layer of tear on the surface of the cornea). There are about 30 of these glands in each lid
Melanoma
A type of skin cancer. It is caused by abnormal growth of cells called melanocytes. However, although most melanocytes are found in the skin, there are also melanocytes in the iris and behind the retina. These structures may also give rise to melanoma although it is rare
Monocular
Referring to only one eye
Myopic
Short sighted. Only near object, a short distance away, can be seen without wearing glasses
Naevus
A mole. Commonly found on the skin but can also occur in the back of the eye, behind the retina, where it is known as a choroidal naevus
Nasolacrimal duct
A narrow passage that leads from the lacrimal sac into the nasal cavity allowing the tears to drain into the nose
OCT
Optical coherence tomography (OCT) is a non-invasive imaging modality that can provide high resolution images of the retina and other structures in the eye. It has become essential in accurate monitoring of eye disease
Ocular surface squamous neoplasia
An abnormal or cancerous growth on the surface of the eye
Optometrist
An eye care professional, who provides primary eye care and screens for eye disease. They prescribe glasses and contact lenses
Optometry
A profession that involves examining the eye and visual function and prescribes corrective glasses or contact lenses
Ophthalmologist
A medical doctor that has specialised in eye disease. They diagnose and treat medical problems and operate on surgical conditions related to the eyes
Ophthalmology
A branch of medicine and surgery that deals with the treatment of eye disorders
Optic Nerve
The nerve that connects the eye with the brain
Orbit
The eye socket
Palpebral aperture
The opening between the upper and lower eyelid
Phacoemulsification
The technique used during cataract surgery to remove the lens
Photopsia
Perceived flashes of light in the visual field. Frequently caused by posterior vitreous detachment
Posterior vitreous detachment
A process that results in separation of the vitreous (gel) in the eye from the retina that lines the back wall. It is an age-related process that results from gradual degeneration of the vitreous structure
Pterygium
An abnormal growth of conjunctival tissue across the limbus, onto the cornea
Ptosis
Droopy upper lids. This refers specifically to the position of the eyelid margin and lashes. It is caused by ineffective muscle action when attempting to open the eyes. It should not be confused with dermatochalasis
Punctum
The small opening in the margin of each lid, located near the inner canthus. It represents the start of a thin tube (canaliculus) that runs under the skin, towards the nose and opens into the lacrimal sac
Pupil
The small, black hole in the centre of the iris that allows light into the back of the eye
Rectus muscles
The muscles in the orbit that are responsible for eye movement
Refraction
The bending of light that occurs when it passes from one transparent medium to another. It is responsible for the focus of light onto the back of the eye. It also describes the technique that optometrists use to prescribe glasses
Retina
The light sensitive layer at the back of the eye
Retinal artery occlusion
A blockage in an artery that supplies blood to the retina
Retinal detachment
A process that results in the retina separating from the back wall of the eye
Retinal vein occlusion
A blockage in a vein that drains blood from the retina
Sclera
The main structural component of the eye wall. It is the white part of the eye
Scleritis
Inflammation of the sclera
Skin crease
The crease that forms in the top eyelid when the lid opens. The crease runs parallel to the margin of the eyelid
Skin fold
The skin fold that forms when the top lid opens. If the amount of skin is excessive it is referred to as dermatochalasis and it may interfere with vision
Squamous cell carcinoma
A type of skin cancer
Syneresis
The process that results in degeneration of the vitreous
Tarsal plate
The firm structure at the back of the eyelid that helps to define and maintain its shape
Tear film
The thin layer of tear on the surface of the eye that protects the surface and optimises vision
Trabecular meshwork
A component of the angle (between the iris and the cornea). It has a structure similar to a fine sponge and allows fluid to slowly drain from the eye into the blood vessels
Uvea
The layer in the wall of the eye that lies between the white sclera and the inner retina
Uveitis
Inflammation of the uvea
Vitreous
The gel that fills the large space behind the lens in the eye
Zonules
Fine strands that suspend the lens in the visual axis. They connect the lens to the ciliary body, like springs on a trampoline