Repeated visual acuity measurement: Establishing the patient's own criterion for change
We measured visual acuity in 10 young subjects, 10 times each over a period of approximately 3 weeks, using Bailey-Lovie charts. We used a consistent end-point criterion and scored each letter read on the chart. We derived the mean and standard deviation of visual acuity measures for each subject, and for the group. The standard deviation for the group was about 3 times that of the individuals in the group. We calculated the criterion for reduction of visual acuity for the group, as group mean plus 1.96 group standard deviations; use of this criterion would consistently fail to detect patients with clinically significant reductions in visual acuity. We recommend that visual acuity be measured to threshold for every patient. Measuring visual acuity between three and five times provides an estimate of the patient’s variability and allows a criterion for reduction of visual acuity to be established for the individual patient. Use of this criterion will enhance the sensitivity of visual acuity measurement as a diagnostic tool.
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|Item Type:||Journal Article|
|Additional Information:||Self-archiving of the author-version is not yet supported by this publisher.
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|Keywords:||Snellen acuity, visual acuity, logMAR, variability, referral criterion|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 1993 Lippincott Williams & Wilkins|
|Deposited On:||01 Dec 2006 00:00|
|Last Modified:||15 Jan 2009 07:16|
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