Glossary Flashcards
Accommodation
Adjustment by the eye for focusing clearly on near targets, which is accomplished by changing the shape of the crystalline lens through the action of the ciliary muscle.
Anterior chamber
The aqueous-filled space in the forward portion of the eye, bounded in the front by the cornea and behind the iris.
Aqueous
Clear, watery fluid which fills the anterior chamber of the eye.
Blind spot
The natural sightless area of the visual field generated by the lack of photoreceptors where the optic nerve enters the eye.
Cataract
A clouding of the crystalline lens of the eye or its capsule, or both, with consequent loss of visual acuity.
Choroid
The vascular, intermediate layer of the eye, lying between the retina and the sclera, which furnishes nourishment to the other parts of the eyeball.
Ciliary body
A portion of the vascular layer between the iris and the choroid, which consists of ciliary processes and ciliary muscle
Conjunctiva
Mucous membrane which lines the eyelids and covers the front part of the eyeball
Contact lenses
Lenses that are placed on the corneal surface or sclera. They have either an optical, therapeutic, or cosmetic purpose
Cornea
The transparent, done-shaped tissue covering the iris and the pupil. The front “window” of the eye, approximately 12mm in diameter, responsible for approximately 2/3 of the refractive power of the eye
Crystalline lens
The transparent lens which is suspended inside the eye immediately behind the iris. It is responsible for 1/3 of the refractive power of the eye.
Fornix
The pocket formed where the bulbar conjunctiva meets the palpebral conjunctiva
Fundus
The back of the eye including the retina, optic nerve, macula and fovea
Iris
Coloured, circular muscle tissue behind the cornea and immediately in front of the crystalline lens. The iris regulates the amount of light entering the eye by hanging the size of the pupil.
Ophthalmologist
A medical doctor who specializes in diagnosis and treatment of defects and diseases of the eye, performs surgery when necessary or prescribing other types of treatment.
Optic disk
Head of the optic nerve in the eyeball where the retinal nerve fibres leave the eye; responsible for physiological blind spot.
Optician
One who dispenses frames and lenses, based on a prescription written by an optometrist or ophthalmologist; grinds lenses, fits them into frames, and adjusts the frame to wearer
Optic nerve
The nerve which carries visual messages from the retina to the brain
Optometrist
A primary health care provider specializing in diagnosing and treating diseases and optical disorders of the eye, prescribing lenses, vision training, medicines and other treatments.
Posterior chamber
The narrow space between the back of the iris and the front surface of the crystalline lens, bounded by the ciliary body and filled with aqueous.
Presbyopia
A condition common after age forty in which gradual lessening of the eye’s power of accommodation causes difficulty seeing near objects
Retina
A thin membrane lining the back of the eye where the optical images are received. The retina converts these images into electronic impulses and transmits them to the brain along the optic nerve
Rods and cones
These are two types of nerve cells which form a layer of the retina and act as light receiving media. Cones are concerned with visual acuity and colour discrimination; rods with motion and vision at low degrees of illumination (night vision)
Sclera
The white part of the eye - a tough covering which, with the cornea, forms the external protective coat of the eye.
Visual acuity
The resolving power of the eye, or ability to see two separate objects as separate. Ability if the eye to perceive shape of objects in the direct line of vision, usually measured in terms of a Snellen fraction eg 20/20
