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See also AIHW glossary  

Accommodation
The adjustment of the eye to variations in distance, especially when focusing on an object as it moves towards the eye.
Adnexa
Appendages of an organ.
Astigmatism
An optical defect, whereby vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina.
Blindness
There is no set definition for blindness. Usually, it is either a total loss of vision, or when there is no possibility of correcting vision through medical intervention. In Australia legal blindness is defined as best corrected visual acuity of 6/60 or below in the better eye.
Cataract
A mostly degenerative condition in which the lens of the eye clouds over, obstructing the passage of light to cause vision loss and, potentially, blindness. Cataract surgery involves the removal of the lens, replacing it with a plastic one.
Conjunctiva
A clear membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids.
Conjunctivitis
An infection (bacterial, viral or allergic) causing inflammation of the conjunctiva. Also referred to as pink eye.
Cornea
The transparent front part of the eye that covers the iris, pupil and anterior chamber.
Diabetic retinopathy
A disorder of the retinal blood vessels (such as microaneurysms or haemorrhaging), most often found in persons with long-standing diabetes.
Glaucoma
A condition in which there is elevated pressure within the eye caused by obstruction of the outflow of aqueous humour. The acute form may quickly cause blindness if untreated. The chronic form may progress slowly over a number of years, producing gradual loss of peripheral vision. Glaucoma is a leading cause of blindness worldwide.
Hyperopia
The inability of the eye to focus on nearby objects due to the rays of light entering the eye being brought to focus behind the retina. Also called long-sightedness or far-sightedness.
Lacrimal
Pertaining to the tear ducts and connected structures.
LASIK (laser-assisted in situ keratomileusis)
A type of refractive laser eye surgery which reshapes the cornea. It is usually performed in order to treat short-sightedness, although may also be used to treat other disorders such as astigmatism.
Low vision
A visual impairment which cannot be corrected with glasses or contact lenses, and which affects the ability to perform everyday activities. Usually excludes blindness.
Macular degeneration
A progressive deterioration of the macula of the retina (the central inner-lining of the eye). It is often positively related to old age (usually referred to as 'age-related macular degeneration'), and results in a loss of central vision.
Myopia
A type of refractive error whereby distant objects appear blurred, usually due to light rays entering the eye being focused in front of the retina. Also called short-sightedness or near-sightedness.
Ophthalmology
The branch of medicine concerned with the study of the eye and the diagnosis and treatment of disorders of the eye.
Optometry
The practice of primary eye care, including testing for visual acuity and prescribing treatments for eye disorders.
Presbyopia
An age-related condition in which the loss of elasticity of the lens leads to a shift to long-sightedness.
Refractive error
The inability of the lens of the eye to focus on an image correctly, such as occurs in far- and near-sightedness.
Strabismus
A disorder whereby the visual axes of the eye are not directed at the same point.
Trachoma
An infectious disease of the eye caused by Chlamydia trachomatis. If left untreated, follicles form on the upper eyelids and grow larger until the granulations invade the cornea, eventually causing blindness.
Visual acuity
The ability to see clearly and at a distance. It is measured using an eye chart, and is usually expressed as a fraction. e.g. 6/60 describes the ability to see objects at 6 metres that the normal eye sees at 60 metres.
Visual impairment
A significant limitation of visual capacity, including those with low vision or blindness, usually brought about by degenerative or congenital disorders, or through trauma.