Search

To illustrate the interdependence between the solution of practical problems and the search for fundamental mechanisms, their relationship within the contexts of the history of night myopia and the problem of nighttime traffic accidents is discussed. Night myopia, or nearsightedness at night, which has been a problem since the late 18th century, was shown to be the result of a recently discovered oculomotor mechanism, the intermediate resting position of accommodation. With this knowledge, the handicap of nearsightedness at night (a major problem in nighttime viewing such as driving and military operations) is readily amenable to solution. Recent developments in our knowledge of the functional significance of the nervous system has led to an increased understanding of the cause and to amelioration of nighttime traffic accidents. These developments illustrate the symbiotic relationship between basic and applied research and the benefits to be gained by consideration of both objectives.

Assessment of the effects of alcohol consumption on contrast sensitivity to sine-wave gratings shows that, while most states in the US disallow driving at blood alcohol concentration (BAC) of 0.08-0.10% or higher, visual impairment can occur at levels a s low as 0.44%. Eight male volunteers took part in 3 testing sessions with different alcohol levels and a control session with no beverage. The mean BAC at which an impairment in contrast sensitivity was recorded was 0.043%. Reduced sensitivity to moving objects typically occurred before a reduction in sensitivity to stationary objects.

Despite the documented health hazards associated with stair descent, the mechanisms of falling on stairs remain relatively unexamined. The objectives of this study were to define kinematic variables that could be usd to describe foot-stair spatial relationships during the mid-stair phase of stair descent, and to investigate the effects of various visual and environmental conditions on those variables in a group of 36 healthy women between the ages of 55 and 70. Foot clearance and foot placement were measured through high-speed film analysis. Clearances between the foot and the stair during swing phase was small under all visual conditions. Degraded visual acuity had a significant effect on cadence, foot placement, and foot clearance, but visual surround conditions did not. The kinematic variables used in this experiment may be helpful in future studies to assess the results of interventions and aimed at reducing the frequency of falls on stairs., Most falls in public places occur while going down steps. In spite of this, there is very little information about the internal and external factors involved in falls. Safe stair descent depends on both proper visualization and proper sensory feedback about movement (kinesthesia). Thirty-six healthy women between the ages of 55 and 70, with normal sensory feedback and visual contrast sensitivity, were selected from a panel of volunteers to study foot-stair spatial relationships while descending the middle steps of a flight of stairs. The stairs were painted black to simulate low contrast, and subjects descended with and without blurring of their vision. A ''high-contrast'' effect was produced by painting a white stripe at the edge of each stair tread. The wall panels were modifiable so that half of the subjects were surrounded by vertical stripes and the other half by horizontal stripes as they descended. Very small foot clearance was found, indicating that small errors are more critical when descending stairs than on a level surface. The subjects slowed their pace when their vision was blurred, and increased their foot clearance, thereby adjusting for possible errors in foot placement. The wall patterns did not make a difference. The results underscore the importance of properly fitted footwear, better contrast definition on stairs, special attention to the needs of those who wear bifocals, and the use of slip-resistant surfaces. (Consumer Summary produced by Reliance Medical Information, Inc.)