RELATIONSHIPS BETWEEN PRINT SIZE, PREFERRED VIEWING DISTANCE AND READING SPEED

Title RELATIONSHIPS BETWEEN PRINT SIZE, PREFERRED VIEWING DISTANCE AND READING SPEED
Author, Co-Author Bei Zhang, Connie Myong, Karen Lin, Ian Bailey
Topic
Year
2005
Day
Program Number
055169
Room
Affiliation
University of California Berkeley, School of Optometry
Abstract PURPOSE: Print size being too small is a common cause of patient complaints about legibility. Reading speed has been used as a key measure for reading efficiency and speed depends on angular size that is determined by the ratio between the height of the letters and the viewing distance. There are two approaches to determine the optimum print size: critical angular size (CAS) and preferred angular size (PAS). CAS is the smallest angular size at which maximum reading speed can be obtained. PAS is the angular size at which readers choose to hold the print as a function of print size. In this study, we compare the CAS and PAS exhibited by a group of 10 normally sighted adult subjects.

METHODS: Experiment I involved measuring reading speed as subjects read word charts and text charts at a fixed distance. In Experiment II the subjects could adjust their viewing distance as they read down charts with progressively smaller print sizes. PAS and CAS were then determined for each subject.

RESULTS: When averaging across the subjects, (1) the difference between PAS and CAS in VAR units was very small: 0.9 +/- 4.6 for word charts, 0.4 +/- 7.1 for text charts; (2) the difference between text and word charts: 0.4 +/- 2.1 for PAS, 0.0 +/- 7.2 for CAS; (3) reading speed was faster for text (ratio = 1.4x).

CONCLUSIONS: (1) PAS is an alternative to CAS in determining optimal print size in normal sighted adults. (2) Either word or text reading charts could be used, while the reading speed of text charts are faster than that of word charts. (3) Preferred angular size may be a more favorable method in evaluating a low vision patient, because there may be a series of points where the patient changes angular size when reading a print of different sizes. In addition, it is also possible to observe any change of reading speed with this method.
Affiliation of Co-Authors University of California Berkeley, School of Optometry, University of California Berkeley, School of Optometry, University of California Berkeley, School of Optometry
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