Tuesday, April 28, 2015

Improving vision in older adults.

I'm now a Fort Lauderdale, Florida resident (except for 5 months of spring and summer in Madison WI.), and have several friends 85 and older still still driving on the death defying I-95 interstate that links Palm Beach, Fort Lauderdale, and Miami, even though their visual capabilities have clearly declined. This is an age cohort that is increasing by 350% between 2000 and 2050. One of the most obvious declines in their visual processing is with contrast sensitivity, resolving small changes in illumination and shape detail, especially at high spatial frequencies. DeLoss et al., in a study in the same vein as others reported in this blog (enter aging in the search box in the left column), show that doing simple discrimination exercises for 1.5 hr per day of testing and training over 7 days resulted in performance that was not statistically different from that of younger college age adults prior to training. (These were exercises of the sort currently available online (See Brainhq.com or Luminosity.com). Here is the abstract, followed by figures illustrating the test employed.
A major problem for the rapidly growing population of older adults (age 65 and over) is age-related declines in vision, which have been associated with increased risk of falls and vehicle crashes. Research suggests that this increased risk is associated with declines in contrast sensitivity and visual acuity. We examined whether a perceptual-learning task could be used to improve age-related declines in contrast sensitivity. Older and younger adults were trained over 7 days using a forced-choice orientation-discrimination task with stimuli that varied in contrast with multiple levels of additive noise. Older adults performed as well after training as did college-age younger adults prior to training. Improvements transferred to performance for an untrained stimulus orientation and were not associated with changes in retinal illuminance. Improvements in far acuity in younger adults and in near acuity in older adults were also found. These findings indicate that behavioral interventions can greatly improve visual performance for older adults.

Example of the task used in the study. In each trial, subjects saw a Gabor patch at one of two standard orientations—25° clockwise (shown here) or 25° counterclockwise for training and testing trials, 45° clockwise or 45° counterclockwise for familiarization trials. After this Gabor patch disappeared, subjects saw a second stimulus and had to judge whether it was rotated clockwise or counterclockwise in comparison with the standard orientation (the examples shown here are rotated 15° clockwise and counterclockwise off the standard orientation, respectively). 
Example of contrast and noise levels used in the experiment. Gabor patches are displayed at 75% contrast in the top row and at 25% contrast in the bottom row. Stimuli were presented in five blocks (examples shown from left to right). There was no noise in the first block, but starting with the second block, stimuli were presented in Gaussian noise, with the noise level increasing in each subsequent block.
A clip from the NY Times review:
...the subjects watched 750 striped images that were rapidly presented on a computer screen with subtle changes in the visual “noise” surrounding them — like snow on a television. The viewer indicated whether the images were rotating clockwise or counterclockwise. The subject would hear a beep for every correct response.
Each session took an hour and a half. The exercises were taxing, although the subjects took frequent breaks. But after five sessions, the subjects had learned to home in more precisely on the images and to filter out the distracting visual noise. After the training, the older adults performed as well as those 40 years younger, before their own training.

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