CES Office & Computer Ergonomics 2 — Questions and Answers
Question 1: What does the 20-20-20 rule recommend for computer workers?
- Every 20 minutes, look at something 20 feet away for 20 seconds to reduce eye strain (Correct answer)
- Take a 20-minute break every 20 hours of working
- Adjust monitor brightness by 20% every 20 minutes
- Perform 20 stretches every 20 minutes for 20 seconds each
Correct answer: Every 20 minutes, look at something 20 feet away for 20 seconds to reduce eye strain
The 20-20-20 rule reduces computer vision syndrome by giving the eyes periodic rest from near-focus by looking at a distant object, relaxing the ciliary muscles.
Question 2: What is 'computer vision syndrome' and which ergonomic factors contribute to it?
- Eye discomfort and visual fatigue from prolonged screen use, worsened by glare, poor lighting, and incorrect screen distance (Correct answer)
- A permanent visual impairment caused by blue light exposure
- An OSHA-recognized occupational illness requiring mandatory medical leave
- A condition requiring prescription eyewear for all computer users
Correct answer: Eye discomfort and visual fatigue from prolonged screen use, worsened by glare, poor lighting, and incorrect screen distance
Computer vision syndrome encompasses eye strain, dry eyes, headaches, and blurred vision from prolonged screen use, exacerbated by glare, improper viewing distance, and poor lighting.
Question 3: When should a sit-stand workstation be recommended as an ergonomic intervention?
- When a worker must remain seated for extended periods without opportunity for postural variation (Correct answer)
- As a replacement for all seated workstations in an office
- Only for workers already diagnosed with back injuries
- When monitor height cannot be adjusted
Correct answer: When a worker must remain seated for extended periods without opportunity for postural variation
Sit-stand workstations are most beneficial when workers are required to sit for prolonged periods without opportunity for postural variation, reducing static loading on the spine.
Question 4: Which mouse design feature most effectively reduces ulnar deviation during cursor control?
- A vertical or angled mouse that keeps the forearm in a handshake orientation (Correct answer)
- A larger mouse requiring a wider grip
- A mouse with extra buttons on the side
- A wireless mouse with extended range
Correct answer: A vertical or angled mouse that keeps the forearm in a handshake orientation
Vertical and angled mice position the forearm in a neutral pronation posture, eliminating the forearm pronation and ulnar deviation associated with standard flat mice.
Question 5: What seat pan depth is recommended to avoid pressure on the back of the knees in a properly adjusted office chair?
- 2-3 inches clearance between the front edge of the seat and the back of the knees (Correct answer)
- Seat pan extending to touch the back of the knees
- Maximum seat depth regardless of leg length
- Seat pan shorter than thigh length by 6 inches
Correct answer: 2-3 inches clearance between the front edge of the seat and the back of the knees
A 2-3 inch gap between the seat front edge and the popliteal area prevents pressure on the popliteal nerves and blood vessels while still providing adequate thigh support.
Question 6: Which lighting condition in an office is most likely to cause glare on computer monitors?
- Windows or overhead lights positioned in front of or behind the monitor creating direct or reflected glare (Correct answer)
- Dimly lit offices with no natural light
- Task lighting positioned below the monitor level
- Use of monitor privacy screens
Correct answer: Windows or overhead lights positioned in front of or behind the monitor creating direct or reflected glare
Light sources in the same field of view as the monitor or behind the monitor reflecting into the worker's eyes create both direct and veiling glare, reducing visual comfort.
CES Office & Computer Ergonomics 2
What does the 20-20-20 rule recommend for computer workers?