Eye movements and reading with simulated visual impairment

Area of Science:

• Ophthalmology
• Visual Science
• Human Factors

Background:

• Reading speed is crucial for information acquisition.
• Visual impairment can significantly impact reading performance.
• Understanding the effects of visual impairment on reading is essential for developing effective visual aids and strategies.

Purpose of the Study:

• To investigate the impact of simulated visual impairment on reading speed.
• To analyze changes in reading eye movements under simulated visual impairment.
• To determine optimal print size and contrast for reading under impaired visual conditions.

Main Methods:

• Utilized afocal diffusing filters (Ryser occlusion foils) to simulate visual impairment at three distinct levels.
• Employed a spectacle-mounted, infra-red limbal reflection system to record eye movements during reading tasks.
• Measured reading speed and analyzed parameters of reading eye movements, including fixation duration and saccade characteristics.

Main Results:

• A significant decrease in reading speed was observed as the level of simulated visual impairment increased (P < 0.01).
• Key factors contributing to reduced reading speed included prolonged fixation durations and shorter saccades, leading to more forward saccades per line.
• Increased time for page navigation was also identified as a contributing factor to slower reading.

Conclusions:

• Simulated visual impairment adversely affects reading speed and eye movement patterns in normally-sighted individuals.
• Print size should be at least four times the acuity threshold for optimal reading.
• Print contrast should be at least twenty times the contrast threshold to ensure efficient reading, even with mild visual impairment.