Test-retest reliability of health-related quality-of-life questionnaires in adults with strabismus.
OBJECTIVE
To report the test-retest variability of two health-related quality-of-life instruments: the new Adult Strabismus 20 (AS-20) and the National Eye Institute 25-item Visual Function Questionnaire (NEI VFQ-25), in adults with strabismus.


METHODS
Prospective case series.


METHODS
Fifty-five adult patients in a clinical practice with stable strabismus completed the AS-20 and the NEI VFQ-25 at 2 visits, without intervening treatment. Questionnaires were completed the second time either at a subsequent office visit, immediately before surgery, or by mail. Intraclass correlation coefficients were calculated. Ninety-five percent limits of agreement and 95% confidence intervals around the 95% limits of agreement also were calculated.


RESULTS
There was excellent agreement of overall questionnaire scores for the AS-20 (intraclass correlation coefficient, 0.92) and NEI VFQ-25 (intraclass correlation coefficient, 0.94). The 95% limits of agreement for overall scores were 14.3 points (95% confidence interval, 10.9 to 17.7) for the AS-20 and 11.1 points (95% confidence interval, 8.5 to 13.8) for the NEI VFQ-25. The lower test-retest variability of the VFQ-25 seemed to be partly the result of ceiling effects with many scores at the normal end of the range.


CONCLUSIONS
The new AS-20 and the NEI VFQ-25 show excellent test-retest reliability in adults with strabismus. Change exceeding 95% limits of agreement (14 points on the AS-20 and 11 points on the VFQ-25) is indicative of real change in an individual patient. The AS-20 may be more useful than the VFQ-25 because it is less prone to ceiling effects in adults with strabismus.
Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
David A
DA
Leske
Sarah R
SR
Hatt
Jonathan M
JM
Holmes
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004172:Diplopia / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D015203:Reproducibility of Results; D018434:Sickness Impact Profile; D013285:Strabismus / Q000175:diagnosis / Q000503:physiopathology*; D011795:Surveys and Questionnaires