Published in:
Open Access 01-12-2003 | Research
A new measure of patient satisfaction with ocular hypotensive medications: The Treatment Satisfaction Survey for Intraocular Pressure (TSS-IOP)
Published in: Health and Quality of Life Outcomes | Issue 1/2003
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Purpose
To validate the treatment-specific Treatment Satisfaction Survey for Intraocular Pressure (TSS-IOP).
Methods
Item content was developed by 4 heterogeneous patient focus groups (n = 32). Instrument validation involved 250 patients on ocular hypotensive medications recruited from ophthalmology practices in the Southern USA. Participants responded to demographic and test questions during a clinic visit. Standard psychometric analyses were performed on the resulting data.
Sample
Of the 412 patients screened, 253 consented to participate, and 250 provided complete datasets. The sample included 44% male (n = 109), 44% Black (n = 109) and 57% brown eyed (n = 142) participants, with a mean age of 64.6 years (SD 13.1) and a history of elevated IOP for an average of 8.4 yrs (SD 7.8). A majority was receiving monotherapy (60%, n = 151).
Results
A PC Factor analysis (w/ varimax rotation) of the 31 items yielded 5 factors (Eigenvalues > 1.0) explaining 70% of the total variance. Weaker and conceptually redundant items were removed and the remaining 15 items reanalyzed. The satisfaction factors were; Eye Irritation (EI; 4 items), Convenience of Use (CofU; 3 items), Ease of Use (EofU; 3 items), Hyperemia (HYP; 3 items), and Medication Effectiveness (EFF; 2 items). Chronbach's Alphas ranged from .80 to .86. Greater distributional skew was found for less common experiences (i.e., HYP & EI with 65% & 48.4% ceilings) than for more common experiences (i.e., EofU, CofU, EFF with 10.8%, 20.8% & 15.9% ceilings). TSS-IOP scales converged with conceptually related scales on a previously validated measure of treatment satisfaction, the TSQM (r = .36 to .77). Evidence of concurrent criterion-related validity was found. Patients' symptomatic ratings of eye irritation, hyperemia and difficulties using the medication correlated with satisfaction on these dimensions (r = .30-.56, all p < .001). Clinicians' ratings of IOP control, severity of side effects and problematic medication use correlated with patients' satisfaction scores on these dimensions (r = .13-.26, all p < .01).
Conclusions
This study provides initial evidence that the TSS-IOP is a reliable and valid measure, assessing patients' satisfaction with ocular hypotensive medications.