Glossary

Search results

Parallax(also: Visual Parallax, Binocular Parallax)

Parallax is the apparent displacement or difference in position of an object when viewed from two different vantage points. In human vision, binocular parallax — the slight difference between the images seen by each eye due to their spatial separation — is a primary cue for…

Pelli-Robson Chart(also: Pelli-Robson Contrast Sensitivity Chart)

The Pelli-Robson chart is a clinical tool used to measure contrast sensitivity — the ability to detect objects at low-to-moderate contrast levels. The chart consists of a series of letter-charts composed of different contrasts, mapping a contrast-sensitivity function for the…

Point Spread Function(also: PSF)

A mathematical description of how a single point of light is spread or blurred by an optical system such as the human eye. The point spread function characterizes the degree and pattern of distortion introduced by optical aberrations. In accessibility research, PSFs are used to…

Presbyopia(also: Age-Related Farsightedness, Loss of Accommodation)

An age-related vision condition in which the eye gradually loses the ability to focus on nearby objects, typically becoming noticeable after age 40. Presbyopia affects the vast majority of older adults and is caused by the hardening of the eye's lens, reducing its flexibility.…

Prosopagnosia(also: Face Blindness)

A neurological condition characterised by the inability to recognise familiar faces, despite otherwise intact visual and cognitive abilities. People with prosopagnosia may fail to recognise family members, friends, or colleagues by face alone, instead relying on alternative cues…

Pupil Diameter(also: Pupil Size, Aperture Size)

The width of the opening in the iris through which light enters the eye, typically ranging from about 2mm in bright light to 8mm in darkness. Pupil diameter significantly affects visual quality because it determines how much of the eye's optical aberrations influence the image…

6 results.