Along with the widespread use of computers have come growing fears that working in front of video display terminals (VDTs) can irritate and even damage the eyes. Separating scientific fact from popular opinion, this report takes a critical look at the link between VDT use and eye discomfort and disease as well as at changes in visual performance and oculomotor function. Drawing on information from ergonomics, illuminating engineering, and industrial and organizational psychology, the report gives practical advice on optimal workstation design to improve the comfort, performance, and job satisfaction of VDT users.
- Video Displays, Work, and Vision
- Copyright
- Preface
- Contents
- Executive Summary
- 1 Summary of Findings
- INTRODUCTION
- Background
- Focus of the Study
- Organization of the Report
- The Literature Base
- The Nature of VDT Work
- FIELD STUDIES OF VDT WORKERS AND WORKSTATIONS
- Studies of Radiation Emission from VDTs
- Cataracts
- Field Surveys Based on Self-Reports of VDT Operators
- EQUIPMENT AND WORKSTATION DESIGN
- VDT Design and Display Quality
- Lighting and Reflections
- Human Factors
- THE CONCEPT AND STUDY OF ''VISUAL FATIGUE"
- JOB DESIGN AND PSYCHOSOCIAL STRESS
- DESIGN, PRACTICE, AND STANDARDS
- Principles of Good Design and Practice
- Public Education
- Standards and Guidelines for VDT Use
- RESEARCH NEEDS
- 2 Critique of Survey Methodology
- INTRODUCTION
- SURVEYS OF VDT USERS
- Adequacy of Theory
- Adequacy of Research Design
- Adequacy of Measurement
- Adequacy of Sampling
- Unanswered Questions
- RESEARCH DESIGN CONSIDERATIONS
- Control and Choice in Studies of VDT Physical Parameters
- Practical Considerations
- 3 Radiation Emissions and Their Effects
- TYPES AND LEVELS OF RADIATION EMITTED BY VDTS
- Studies of Emission Levels
- The 1977 NIOSH Study
- The Bell Telephone Laboratories Study
- A Collaborative Study
- Two European Studies
- The 1981 NIOSH Study
- The Bureau of Radiological Health Study
- Radiation Safety Standards
- VDT Emissions and Ambient Radiation
- BIOLOGICAL EFFECTS OF RADIATION
- Ionizing Radiation
- Nonionizing Radiation
- Ultraviolet Radiation
- Visible and Infrared Radiation
- Radio Frequency Radiation
- Skin Rashes
- VDT USE AND CATARACTS
- Prevalence and Causes of Cataracts
- The Evidence Regarding VDT Use and Cataracts
- The Claims
- Response to the Claims
- Methods of Studying Whether There Is a Relationship Between VDT Use and Cataracts
- Concurrent Longitudinal Study
- Nonconcurrent Longitudinal ("Cohort") Study
- Case-Control Study
- Two Ongoing Studies
- The NIOSH Baltimore Sun Study
- The Mt. Sinai Study
- Conclusions About Radiation Hazards
- 4 Display Characteristics
- EFFECTS OF CRT DISPLAY VARIABLES
- Luminance
- Effects on Visual Acuity
- Effects on Flicker Threshold
- Effects on Visual Task Performance
- Luminance Uniformity
- Contrast and Contrast Polarity
- Raster Structure
- Resolution
- Jitter and Temporal Instability
- Refresh Rate and Persistence
- Color
- Reflection Characteristics
- A Summary Measure: Modulation Transfer Function
- DISPLAY MEASUREMENT: TECHNIQUES AND PROBLEMS
- Measurement Techniques
- Measurement of Various Parameters
- Character Luminance
- Character Contrast
- Blur, Resolution, and MTF
- Reflection Characteristics
- Standardization
- FLAT-PANEL DISPLAYS
- Dot-Matrix Display Variables
- Character Size Effects
- Character Formation
- Contrast
- Font
- Luminance Uniformity
- Information Density
- Dot-Matrix Display Quality Measures
- Advantages and Disadvantages of Flat-Panel Displays Compared with CRTs
- FILTERS FOR VDTS
- Kinds of Filters
- Circular Polarizer with Antireflection Coating
- Neutral Density Filters
- Notch or Color Filters
- Directional Filters
- Evaluation of Filters
- General Comments
- Effectiveness of Filters
- 5 Lighting and Reflections
- ILLUMINATION
- Transient Adaptation
- Reflections
- Glare
- REVIEW OF VDT STUDIES
- Field Surveys of VDT Workers
- Field Surveys Comparing VDT and Non-VDT Work
- Laboratory Studies
- 6 Anthropometry and Biomechanics in VDT Applications
- POSTURAL STRAIN
- OVERVIEW OF BIOMECHANICAL FACTORS
- Work Posture
- Muscular Load
- Joint Angles
- Anthropometry
- WORKSTATION DESIGN
- Effects of Chair Design Features on the Spine
- Effects of Working Height on Postural Strain
- Effects of Display Position on Postural Strain
- 7 Visual Tasks, Functions, and Symptoms
- VISUAL ISSUES IN VDT STUDIES
- Field Surveys
- Visual Complaints
- Measurements of Visual Status
- Experimental Field and Laboratory Studies of Visual Functions in VDT Work
- The Need for Job and Task Analysis
- Are There Unique Features of VDT Tasks?
- The Special Task of Reading
- The Problematic Concepts of "Visual Fatigue" and "Eyestrain"
- Refractive Errors and Visual Difficulties
- Myopia
- OCULOMOTOR FACTORS AFFECTING VISUAL PERFORMANCE
- Eye Movements
- Saccadic Trajectory
- Dual Mode Tracking Eye Movements
- Higher-Level Eye Movement Patterns
- Gaze and the Vestibulo-Ocular Reflex
- Blinking
- Triadic Near Reflex: Combined Focusing, Convergence, and Aperture Mechanisms
- Accommodation
- Dynamic Factors in Accommodation
- Fatigue and Accommodation
- Vergence
- Pupil
- Pupil as a Regulator of Light Level
- Pupillary Constriction Associated with Prolonged Visual Work
- Pupil as a Factor in Visuomotor Discomfort
- Pupillary Hippus in Relation to Habituation and Sleepiness
- Synkinesis of Accommodation, Vergence, and Pupillary Constriction
- SUMMARY AND CONCLUSIONS
- 8 Job Design and Organizational Variables
- INTRODUCTION
- Workers' Complaints and Job Structures
- Defining Psychosocial Stress and Strain
- A FRAMEWORK FOR STUDYING PSYCHOSOCIAL STRESSORS IN VDT WORK
- Person-Environment Fit
- Objective and Subjective Fit
- STRESSORS FOR STUDY IN VDT WORK
- Control
- Opportunity to Control: E
- Need for Control: P
- Participation
- Opportunity to Participate: E
- Need to Participate: P
- Predictability and Controllability
- Unpredictable Events: E
- Tolerance of Unpredictability: P
- Complexity
- Role Ambiguity
- Threat of Unemployment
- Quantitative Workload
- Prescription for Overload—Deadline Plus Delay
- Responsibility for Persons
- Responsibility: E
- Responsibility: P
- Role Conflict
- Social Support
- DISCUSSION AND CONCLUSIONS
- 9 Design, Practice, and Standards for VDT Equipment and Work
- PRINCIPLES OF GOOD DESIGN AND PRACTICE
- Image Quality and Display Design
- Lighting and Reflections
- Minimizing Problems Caused by Direct Glare and Transient Adaptation
- Minimizing Reflected Glare and Veiling Reflections
- Systematic Design of VDT Workstations
- General Considerations
- Specific Design and Use Guidelines
- Job Design and Organizational Variables
- Variation in the Task and Task Environment
- Other Strategies for Good Employee Management
- STANDARDS AND GUIDELINES FOR VDT DESIGN
- 10 Research Needs
- EFFECTS OF DISPLAYS ON VISUAL ACTIVITY
- Objective Correlates of Visual Complaints
- Relating Display Characteristics to Workplace Conditions
- Effects of Image Instability
- Distinguishing Specific Effects of VDTs
- PSYCHOSOCIAL STRESSORS
- Appendix A A Review of Methodology in Studies of Visual Functions During VDT Tasks
- Appendix B Review of a Preliminary Report on a Cross-Sectional Survey of VDT Users at the Baltimore Sun
- SUMMARY OF THE NIOSH STUDY
- REVIEW OF THE NIOSH STUDY
- Study Approach and Methods
- Introduction and Background
- Design
- Measures
- Analyses
- Conclusions
- Substantive Conclusions
- Methodological Conclusions and Limitations
- Appendix C Dissent
- Appendix D Biographical Sketches of Panel Members and Staff
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