The Effect of Age on Dark Focus Distance and Visual Information Transfer Rate

Details

• Personal Author:
  Yodpijit N
• Description:
  Although the static measure of accommodation is well documented, the dynamic aspect of the resting state (dark focus) of accommodation is still unknown. Previous studies suggest that refractive error is minimal at the intermediate resting point of accommodation - i.e., at the dark focus distances. Additionally, aging is closely linked to increased refractive error. In order to assess the effects of age on dark focus distance and its utility in enhancing the visual information transfer rate, two experiments were conducted under nighttime condition (scotopic vision) in a laboratory setting. A total of forty participants with normal vision or corrected to normal vision were recruited from four different age groups (younger: 26.9 +/- 5.0 years; middle-aged: 50.7 +/- 4.8 years; young-old: 64.6 +/- 2.8 years; and old-old: 79.8 +/- 6.1 years). Each age group included ten participants. In Experiment I, the accommodative status of dark focus at the fovea was assessed objectively using the modified autorefractor, a newly developed method to continuously monitor the accommodation process. The mean dark focus distances for younger, middle-aged, young-old, and old-old adults were 64.5 +/- 6.6, 73.4 +/- 20.6, 84.4 +/- 29, and 92.1 +/- 33.4 cm, respectively. There was a significant difference between the dark focus distances among different age groups. Post-hoc analysis indicated that there were statistically significant differences among young and old-old, young and young-old, and middle-aged and old-old age groups. In Experiment II, the information transfer rate was determined while viewing a target at three different distances: 52 cm, 73 cm (current recommended reading distances) and the individual's dark focus. A set of randomized alphabet characters were presented on a visual display with a luminance level of 20 cd/m2 and ambient illumination level of 4 lux. To assess the information transfer rate, participants were asked to read a set of characters aloud with their fastest rate for three seconds. Three measurements of inforamtion transfer rate at each viewing distance at random were made. Results obtained from each viewing distance were collected and averaged. The results showed that the mean visual information transfer rate for younger, middle-aged, young-old, and old-old adults were 14.27 +/- 1.43, 10.58 +/- 2.25, 9.35 +/- 2.13, and 7.73 +/- 2.36 bits/sec, respectively. There were statistically significant differences at a< 0.05 in means and standard deviations of visual information transfer rate in young and old-old, young and young-old, young and middle-aged, and middle-aged and old-old age groups. The mean visual information transfer rate at 52 cm, 73 cm and individual dark focus were 11.08 +/- 3.10, 10.14 +/- 2.97, and 10.22 +/- 3.42 bits/sec, respectively. There were statistically significant differences at a< 0.05 in means and standard deviations of visual information transfer rate at different viewing distances at 52 cm and 73 cm, and 52 cm and individual's dark focus. However, there were no statistically significant differences in the interaction between age and viewing distance (F = 1.6818, P = 0.1378) on the amount of visual information transfer rate. In summary, the visual information transfer rate was not greater when presenting visual stimulus at the individual's dark focus as compared with two fixed recommended viewing distances (52 cm and 73 cm). The greatest amount of visual information gained was at 52 cm. Actual and potential applications of this study including specifications for designs were also discussed. [Description provided by NIOSH]
• Subjects:
  Aging Eye Occupational Health Safety Sense Organs Vision Disorders
• Keywords:
  Age Groups Author Keywords: Age Autorefractor Dark Focus Eye Function Tests Eyesight Vision Disorders Visual Information Transfer Rate Visual Motor Performance
• Publisher:
  Virginia Polytechnic Institute and State University
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Dissertation
• Place as Subject:
  OSHA Region 3 ; Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-80
• NIOSHTIC Number:
  nn:20055484
• Citation:
  Blacksburg, VA: Virginia Polytechnic Institute and State University, 2010 Oct; :1-80
• Federal Fiscal Year:
  2011
• NORA Priority Area:
  Construction ; Services
• Performing Organization:
  Virginia Polytechnic Institute and State University
• Peer Reviewed:
  False
• Start Date:
  20090901
• Source Full Name:
  The effect of age on dark focus distance and visual information transfer rate
• End Date:
  20140831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:9bb1bf7d04f68302a96fd0bc2aab2d5203a010a4d667874a429ee5355451a8b06ef9a13ad8721f324f4bc4437db87f04a14bc3b6322c5b57c045bee5d333e6ff
• Download URL:
  https://stacks.cdc.gov/view/cdc/213322/cdc_213322_DS1.pdf
• File Type:
  [PDF - 3.39 MB ]