ABSTRACT
The influence of various polarised glasses on visual performance is crucial due to their widespread. This study measured the visual contrast sensitivity (CS) of dominant eyes by quick contrast sensitivity function (qCSF) procedure at 10 spatial frequencies and 3 noise levels under nonglare, steady glare, steady glare with night lenses, and steady glare with day&night lenses, respectively. Later, the second experiment measured the subjects' subjective feelings under these four viewing conditions. The results showed that there was no significant difference in the CS between the two conditions with polarised glasses and the steady glare. However, the subjects reported greater comfort with glasses than without them. These results suggest that there was an underlying bias when people rated the polarised glasses, and the qCSF procedure was a useful tool for evaluating visual performance.
Whether polarised glasses can relieve the impairment of steady glare on contrast sensitivity over multi-spatial frequency and external noise levels is unaddressed. Using the quick CSF method, we revealed that CS declines with steady glare but polarised lenses don't significantly relieve it. However, subjects reported increased comfort, suggesting a perceptual bias.
ABSTRACT
The improvements due to small incision lenticule extraction (SMILE) in vision, e.g., in spherical equivalent (SE) and visual acuity (VA), has been widely recognized. However, the contrast sensitivity (CS) change after SMILE was not certain. Here, we investigated the effect of SMILE on CS before, 1 day after and 7 days after surgery and then clarified the corresponding mechanism by using a perceptual template model (PTM). In addition, the relationship among SE, VA, and CS was discussed. The quick contrast sensitivity function (qCSF) was applied to measure CS with high precision and accuracy. We found that (1) CS was significantly improved 1 day after SMILE and was also increased 7 days after the surgery, (2) CS improvements were dependent on spatial frequency and external noise, (3) the increase in CS was due to the decreased internal additive noise and an enhanced perceptual template, and (4) Greater SE improvements predicted better VA improvements 1 day after SMILE, and a positive correlation between SE improvements and AULCSF improvements 7 days after SMILE was observed. These findings help us better understand the effect of SMILE and provide effective indicators for future visual research.
ABSTRACT
Potential cognitive and physiological alterations due to space environments have been investigated in long-term space flight and various microgravity-like conditions, for example, head-down tilt (HDT), confinement, isolation, and immobilization. However, little is known about the influence of simulated microgravity environments on visual function. Contrast sensitivity (CS), which indicates how much contrast a person requires to see a target, is a fundamental feature of human vision. Here, we investigated how the CS changed by 1-h -30° HDT and determined the corresponding mechanisms with a perceptual template model. A quick contrast sensitivity function procedure was used to assess the CS at ten spatial frequencies and three external noise levels. We found that (1) relative to the + 30° head-up tilt (HUT) position, 1-h -30° HDT significantly deteriorated the CS at intermediate frequencies when external noise was present; (2) CS loss was not detected in zero- or high-noise conditions; (3) HDT-induced CS loss was characterized by impaired perceptual template; and (4) self-reported questionnaires indicated that subjects felt less pleasure and more excitement, less comfort and more fatigued by screen light, less comfort in the area around the eye, and serious symptoms such as piercing pain, blur acid, strain, eye burning, and dizziness after HDT. These findings improve our understanding of the negative effects of simulated microgravity on visual function and elucidate the potential risks of astronauts during space flight.
