Development of an instrument to measure glaucoma medication self-efficacy and outcome expectations.
OBJECTIVE
The purpose of this study was to develop and evaluate the psychometric properties of (a) a glaucoma medication self-efficacy scale and (b) a glaucoma outcome expectations scale.


METHODS
Two instruments were developed: a glaucoma medication self-efficacy scale and a glaucoma outcome expectations scale. Packets containing (a) the instruments and patient demographic questions and (b) a letter explaining the study were distributed to 225 glaucoma patients from three ophthalmology practices between August and December 2007. The instrument was completed by 191 patients for a response rate of 85%. Principal components factor analysis with a varimax rotation and Cronbach's alpha reliability were used to analyse the data. To assess discriminant validity, we administered the scales and two self-reported measures of adherence in a separate sample of 43 glaucoma patients who were currently using at least one glaucoma medication.


RESULTS
Our results yielded a 21-item self-efficacy in overcoming barriers that might interfere with the use of glaucoma medications scale, a 14-item self-efficacy in carrying out specific tasks required to use eye drops correctly scale, and a four-item glaucoma outcome expectations scale. Results of the Cronbach's alpha reliability indicated that the scales are internally consistent. The self-efficacy scales were both significantly associated with two patient self-reported measures of glaucoma medication adherence, which show discriminant validity.


CONCLUSIONS
Eye care providers and researchers can use these scales to identify patients with low self-efficacy in using their glaucoma medications and patients who do not believe that following their eye care providers' advice can help their vision.
Sleath
B
B
Cecil G. Sheps Center for Health Services Research, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599-7590, USA. betsy_sleath@unc.edu
Blalock
S J
SJ
Robin
A
A
Hartnett
M E
ME
Covert
D
D
DeVellis
B
B
Giangiacomo
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005901:Glaucoma / Q000188:drug therapy*; D006801:Humans; D008297:Male; D055118:Medication Adherence / Q000523:psychology*; D008875:Middle Aged; D009883:Ophthalmic Solutions / Q000627:therapeutic use*; D011594:Psychometrics; D015203:Reproducibility of Results; D020377:Self Efficacy; D012651:Self Medication / Q000523:psychology*; D011795:Surveys and Questionnaires / Q000592:standards*; D016896:Treatment Outcome; D055815:Young Adult
D009883:Ophthalmic Solutions