BACKGROUND Vision impairment, resulting in vision difficulties, is a leading cause of disability, and hence one of the key barriers for people to access education and employment, which may force them into poverty. OBJECTIVES The objective of this study was to determine the prevalence of self-reported vision difficulties as an indicator of vision impairment in economically disadvantaged region...

We used a new method to measure the perceived quality of contrast-enhanced motion video. Patients with impaired vision (n=24) and normally sighted subjects (n=6) adjusted the level of MPEG-based enhancement of 8 videos (4 min each) drawn from 4 categories. They selected the level of enhancement that provided the preferred view of the videos, using a decreasing-step-size staircase procedure. Mos...

Intraspecific color vision variation is prevalent among nearly all diurnal monkeys in the neotropics and is seemingly a textbook case of balancing selection acting to maintain genetic polymorphism. Clear foraging advantages to monkeys with trichromatic vision over those with dichromatic "red-green colorblind" vision have been observed in captive studies; however, evidence of trichromatic advant...

In this study, we evaluated observers' ability to compare naturally shaped three-dimensional (3-D) objects, using their senses of vision and touch. In one experiment, the observers haptically manipulated 1 object and then indicated which of 12 visible objects possessed the same shape. In the second experiment, pairs of objects were presented, and the observers indicated whether their 3-D shape ...

All RDs are accompanied by some loss of visual function but this will vary depending upon the type of detachment, its size, and retinal location, making it difficult to ascribe one set of symptoms to the condition (Box 71.3). Diagnosing RD is complex with many qualifications. Abnormal vision is the only reliable symptom of RD. But the types of abnormal vision are large and varied: light flashes...

The term“tetrachromacy” describes the physiological possession of four different classes of simultaneously functioning retinal photopigments (also called “weak tetrachromacy”). From an empirical standpoint, tetrachromatic color vision (or “strong tetrachromacy”) additionally requires demonstrating that mixtures of four independent appropriately chosen primary lights will simulate all distinctio...

To perform a more complete diagnosis on the effect of color vision deficiency on visual performance we measured luminance and color contrast threshold functions. Measurements were carried out on CRT for a range of spatial frequencies on color deficient and normal color vision individuals. Luminance and color contrast threshold is a measure of the recognition limits of low luminance and color co...

Background/aims: Disturbances of colour vision are a frequently reported sign of digoxin toxicity. The aim of this study was to investigate the incidence of acquired colour vision deficiency in elderly hospitalised patients receiving maintenance digoxin therapy. Methods: 30 patients (mean age 81.3 (SD 6.1) years) receiving digoxin were tested using a battery of colour vision tests (Ishihara, AO...

Day vision and night vision are two separate modes of visual perception and the visual system shifts from one mode to the other based on ambient light levels. Each mode is primarily mediated by one of two photoreceptor classes in the retina, i.e., cones and rods. In day vision, visual perception is primarily cone-mediated and perceptions are chromatic. In other words, color vision is present in...