Validity of the University of Waterloo's near visual acuity charts

Purpose: We investigated the validity of the University of Waterloo's (UW) near visual acuity (VA) test card that consists of seven charts: the paragraph (PAR), illiterate (ILL) tumbling E, high contrast vertical (HCV), high contrast horizontal (HCH), low contrast vertical (LCV), and low contrast horizontal (LCH) charts, and the LEA chart that consists of a series of four optotypes - a circle, square, house, and heart. Methods: The VA of the right eyes of 31 patients, aged 15 to 30 years, with near VA of 6/30 or better, were determined using the seven charts. The charts were presented at 0.4 meters (with a luminance level of 95 to 115 cd/m²). Performance was scored using Kitchin and Bailey's per letter scoring method. Results: There was a positive agreement between the HCV and HCH charts. A ceiling effect was found with the PAR chart - the highest resolution, where the logarithm of the minimum angle of resolution (log MAR) is 0.0 units, was inadequate to measure the limit of near acuity. The ILL and LEA charts, for children and patients who are illiterate, were found to be valid only when the VA was close to 0.0 log MAR units. For patients with poor, uncorrected near acuity, both the ILL and LEA charts slightly overestimated VA. No statistically significant difference between the vertical and horizontal line charts was found. The difference in acuity between LCV and HCV, and between LCH and HCH, was constant over the entire measured acuity range. Conclusion: The seven near VA charts generally rendered valid measurements of near VA, in spite of some limitations.