Glossary

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Central Vision Loss(also: Central Field Loss, Central Scotoma)

Loss of vision in the central part of the visual field, typically caused by damage to the macula — the area of the retina responsible for sharp, detailed vision. People with central vision loss experience difficulty seeing fine details directly in front of them, often describing…

Cerebral Visual Impairment(also: CVI, Cortical Visual Impairment)

Cerebral visual impairment (CVI) is an umbrella term for visual deficits resulting from damage to the brain rather than the eyes. It affects visual perception, including visual acuity, cortical image processing, and pattern recognition. CVI is often associated with additional…

Clinical Dementia Rating(also: CDR, CDR Scale)

The Clinical Dementia Rating (CDR) is a five-point staging scale used to characterise the severity of dementia, originally developed by Hughes and colleagues at Washington University in 1982. A clinician rates the person across six domains — memory, orientation, judgement and…

Cochlear implant(also: CI, Bionic ear)

A surgically implanted electronic device that provides a sense of sound to a person with severe to profound sensorineural hearing loss by directly stimulating the auditory nerve, bypassing damaged hair cells in the cochlea. Unlike hearing aids, which amplify sound, cochlear…

Cognitive load(also: Mental load, Cognitive burden, Cognitive demand)

The total amount of mental effort required to complete a task, encompassing the processing of information, decision-making, remembering instructions, and managing attention. Cognitive load theory, developed by John Sweller in the 1980s, distinguishes between intrinsic load…

Cognitive-Communication Needs(also: CCN, Cognitive-Communication Disorders)

Difficulties in communication that arise from underlying cognitive deficits in areas such as attention, memory, organization, problem-solving, and executive function, rather than from primary language impairments. Cognitive-communication needs commonly result from traumatic…

Colour Vision Deficiency(also: CVD, Color Blindness, Colour Blindness)

A condition in which a person has difficulty distinguishing between certain colours due to differences in the cone cells of the retina. CVD affects approximately 1 in 12 men and 1 in 200 women worldwide. It is not typically a complete inability to see colour but rather a reduced…

Convergence Insufficiency(also: CI)

A binocular vision disorder in which the eyes have difficulty turning inward (converging) to focus on nearby objects, causing symptoms such as double vision, eye strain, headaches, difficulty reading, and blurred vision during close work. Convergence insufficiency affects an…

Cortical visual impairment(also: CVI, Cerebral visual impairment)

A neurological form of visual impairment caused by damage or atypical structures in the visual pathways and visual processing centres of the brain, rather than in the eyes themselves. CVI is now the most common cause of visual impairment in children in developed countries.…

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