Sarah R. Hatt

Development of a Quality-of-Life Questionnaire for Adults with Strabismus

PURPOSE We report the development of a patient-derived, health-related quality-of-life (HRQOL) questionnaire for adults with strabismus. DESIGN Cross-sectional study. PARTICIPANTS Twenty-nine patients with strabismus in a first phase, and 32 patients with strabismus, 18 patients with other eye diseases, and 13 visually normal adults in a second phase. METHODS Individual patient interviews generated 181 questionnaire items. For item reduction, we asked 29 patients with strabismus to complete the 181-item questionnaire, analyzed responses, and performed factor analysis. Two prominent factors were identified, and the 10 items with the highest correlation with each factor were selected. The final 20-item questionnaire (10 psychosocial items and 10 function items) was administered to an additional 32 patients with strabismus (22 with diplopia, 10 without diplopia), 13 visually normal adults, and 18 patients with other eye diseases. A 5-point Likert-type scale was used for responses (never = 100, rarely = 75, sometimes = 50, often = 25, and always = 0). Median overall questionnaire scores and psychosocial and function subscale scores, ranging from 0 (worst HRQOL) to 100 (best HRQOL), were compared across groups. MAIN OUTCOME MEASURES The HRQOL questionnaire response scores. RESULTS Median overall scores were statistically significantly lower (worse quality of life) for patients with strabismus (56) compared with visually normal adults (95; P<0.001) and patients with other eye diseases (86; P<0.001). Median scores on the psychosocial subscale were significantly lower for strabismus patients (69) compared with visually normal adults (99; P<0.001) and patients with other eye diseases (94; P<0.001). For the function subscale, median scores were again significantly lower for strabismus patients (43) compared with visually normal adults (91; P<0.001) and patients with other eye diseases (78; P<0.001). CONCLUSIONS We have developed a 20-item, patient-derived, HRQOL questionnaire specific for adults with strabismus, with subscales to assess psychosocial and function concerns. This 20-item, condition-specific questionnaire will be useful for assessing HRQOL in individual strabismus patients and also as an outcome measure for clinical trials. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

Development and initial validation of quality of life questionnaires for intermittent exotropia

PURPOSE The development and initial validation of patient-derived, health-related quality-of-life (HRQOL) questionnaires for intermittent exotropia (IXT). DESIGN Cross-sectional study. PARTICIPANTS In a development phase, 27 children (age, 2-17 years) with IXT and 1 of their parents. In an initial validation phase, 33 children with IXT and 49 control children (age, 5-17 years), along with 1 parent for each child. Children in the control group had no strabismus or amblyopia. METHODS Individual patient interviews generated 35 items for child and proxy (parental assessment of childs HRQOL) questionnaires and 46 items for a parent questionnaire. To reduce to a feasible number of items, questionnaires were administered to 5- to 17-year-old children with IXT (n = 15) and parents of 2- to 17-year-old children with IXT (n = 27). Responses were analyzed using standard item reduction methodology. Three final derived IXT questionnaires (IXTQ): child, proxy, and parent (12, 12, and 17 items, respectively) were administered to children with IXT and control children and to parents of IXT and control children. Likert-type scales ranging from never (100, best HRQOL) to almost always (0, worst HRQOL) were used. MAIN OUTCOME MEASURES Median scores for IXT and control groups, compared using Wilcoxon tests. RESULTS Median child scores were significantly lower (worse HRQOL) in the IXT group compared with the control group: 85 (quartiles, 73-92) versus 92 (quartiles, 79-96; P = 0.04). Median proxy IXTQ scores were significantly lower for IXT children than controls: 83 (quartiles, 75-94) versus 98 (quartiles, 92-100; P<0.0001). Median parent IXTQ scores also were significantly lower in the IXT group compared with the control group: 68 (quartiles, 56-79) versus 93 (quartiles, 87-99; P<0.0001). CONCLUSIONS A new 3-part patient-derived HRQOL questionnaire for children with IXT and their parents has been developed and validated, comprising child, proxy, and parent questionnaires. These questionnaires detect reduced HRQOL in children with IXT as reported by the children themselves and perceived by their parents (proxy report). Childhood IXT also seems to affect parent HRQOL. The IXTQ HRQOL questionnaires may prove useful in the clinical assessment of IXT and for clinical trials. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Comparison of Quality-of-Life Instruments in Adults with Strabismus

PURPOSE To compare two health-related quality-of-life (HRQOL) questionnaires in adults with strabismus: the new 20-item Adult Strabismus (AS-20) questionnaire (developed specifically for Adult Strabismus) and the 25-item National Eye Institute Visual Function Questionnaire (VFQ-25). DESIGN Cross-sectional study. METHODS Eighty-four adult patients with strabismus (median age, 53 years; range, 18 to 81 years) completed the AS-20 and VFQ-25 HRQOL questionnaires. Patients were categorized as diplopic (n = 65) or nondiplopic (n = 19). Subnormal HRQOL was defined as less than the fifth percentile for adults with no visual impairment. The proportion of patients below normal was compared overall and by diplopia status. RESULTS Overall, more patients scored below normal with the AS-20 than with the VFQ-25 (90% vs 29%; P < .0001). Nondiplopic patients more often were below normal on the AS-20 psychosocial subscale than on the function subscale (95% vs 42%; P = .002), whereas diplopic patients were more often below normal on the function subscale (85% vs 68%; P = .01). On the psychosocial subscale, more nondiplopic than diplopic patients scored below normal (95% vs 68%; P = .01); on the function subscale, more diplopic than nondiplopic patients scored below normal (85% vs 42%; P = .0005). The VFQ-25 seemed to be insensitive to nondiplopic strabismus: no patients scored below normal on composite score and no more than 11% scored below normal on VFQ-25 subscales. Of diplopic patients, 37% scored below normal on VFQ-25 composite score. No more than 38% scored below normal on VFQ-25 subscales. CONCLUSIONS The new AS-20 seems to be more sensitive than the VFQ-25 for detecting reduced HRQOL in Adult Strabismus, and therefore may be a more useful tool for clinical assessment and clinical trials.

Variability of Stereoacuity in Intermittent Exotropia

PURPOSE Distance stereoacuity is used to monitor deterioration of intermittent exotropia (IXT), but variability of stereoacuity has not been studied rigorously. The purpose of this study was to assess the variability of stereoacuity over one day in children with IXT. DESIGN Prospective cohort study. METHODS Twelve children with IXT were recruited. Stereoacuity was assessed using the Frisby Davis Distance test and the Distance Randot test at distance, and the Frisby and Preschool Randot tests at near. Tests were repeated three or four times over the day, with at least two hours between assessments. The main outcome measure was variable stereoacuity defined as a change by two or more log levels between any two time points over the day. RESULTS Variable stereoacuity at distance was found in five (42%) of 12 patients. Four (33%) of 12 patients demonstrated variable results using the Distance Randot test, three of whom also showed variable results using the Frisby Davis Distance test. One patient had variable results using the Frisby Davis Distance test only. Nine (75%) of 12 patients completed near stereoacuity testing; two (22%) of nine showed variable near stereoacuity. Two (22%) of nine showed variable results using the Preschool Randot test, one (11%) of whom also had variable results using the Frisby test. In some cases, stereoacuity changed from measurable stereoacuity on one assessment to nil on another. CONCLUSIONS Nearly half of children with IXT show marked changes in stereoacuity over the course of a single day. When based on isolated measures, an apparent change in distance stereoacuity between visits should be interpreted with caution.

Changes in Health-Related Quality of Life 1 Year Following Strabismus Surgery

PURPOSE To report changes in health-related quality of life (HRQOL) 1 year following strabismus surgery. DESIGN Retrospective cohort study. METHODS Seventy-three adults undergoing strabismus surgery in a single clinical practice completed the Adult Strabismus-20 (AS-20) HRQOL questionnaire preoperatively and at 6 weeks and 1 year postoperatively. All included adults were successfully aligned at 6 weeks postoperatively. Success was defined based on clinical criteria. Change in AS-20 psychosocial and function scores was evaluated as: 1) difference in scores between 6 weeks and 1 year postoperatively and 2) proportions exceeding previously published limits of agreement at 6 weeks and 1 year. RESULTS For patients successfully aligned at both 6 weeks and 1 year (n=51), further improvement in median scores was seen from 6 weeks to 1 year for both the psychosocial scale (83.8 vs 93.8; P<.0001) and the function scale (72.5 vs 77.5; P=.007). Also, a greater proportion exceeded limits of agreement at 1 year than at 6 weeks (psychosocial: 48% vs 30%; P=.007, function: 67% vs 51%; P=.01). For patients who became partial success (n=18) or failure (n=4) at 1 year there was a numerical decrease in scores at 1 year. CONCLUSIONS Adult strabismus patients who remain successfully aligned show continued improvement in both psychosocial and function scores from 6 weeks to 1 year postoperatively, indicating that improvement in HRQOL is long-lasting. Evaluation of HRQOL should be considered when reporting strabismus surgery outcomes in clinical trials, and may prove helpful in assessing outcomes in clinical practice.

Test-retest reliability of health-related quality-of-life questionnaires in adults with strabismus.

PURPOSE 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. DESIGN 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.

The Effect of Bangerter Filters on Optotype Acuity, Vernier Acuity, and Contrast Sensitivity

PURPOSE Bangerter filters are designed to cause progressive degradation of distance optotype acuity to predicted levels (density label indicating expected decimal acuity) and are used to treat amblyopia and diplopia. Few authors have reported data regarding induced acuity deficits. We investigated the effect of Bangerter filters on distance and near optotype acuity, vernier acuity, and contrast sensitivity. METHODS Fifteen subjects with best-corrected optotype acuity of at least 20/25 in each eye were blurred sequentially in one eye with 7 Bangerter filters (densities <0.1, 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0). At each filter level, distance and near optotype acuity (LogMAR), vernier acuity, and contrast sensitivity were assessed. Mean log acuities were compared using generalized estimating equation methods. RESULTS The 1.0, 0.8, and 0.4 filters degraded distance optotype acuity to a similar degree (mean 0.22, 0.23, and 0.28 logMAR). Subsequent filters progressively degraded acuity: 0.44, 0.57, 0.93, and 1.69 logMAR. Near optotype acuity was reduced in a similar pattern. Vernier acuity was minimally degraded by 1.0, 0.8, and 0.4 filters (18, 19, and 20 arcsec), followed by progressive degradation with subsequent filters (31, 35, 113, and 387 arcsec). Contrast sensitivity was minimally reduced with filters 1.0 through 0.2 and then precipitously degraded with 0.1 and <0.1 filters. CONCLUSIONS The 1.0, 0.8, and 0.4 filters cause similar, minimal degradation of distance and near optotype and vernier acuity, whereas subsequent filters cause progressive degradation. Contrast sensitivity is not markedly reduced until the 0.1 filter. These results have important implications for the use of Bangerter filters therapeutically.

Stability of near stereoacuity in childhood intermittent exotropia

PURPOSE To investigate the course of near stereoacuity in a cohort of children with untreated intermittent exotropia. METHODS A total of 95 children ages 2-16 years with untreated intermittent exotropia were identified who had measurements of near stereoacuity using the Preschool Randot (PSR) test on at least 2 successive examinations, with no intervening treatment. Deterioration was defined as a drop of at least 3 octaves, as determined by test-retest data. Alternative secondary analyses were performed defining deterioration as a drop of at least 2 octaves or as a transition from normal to subnormal. The main outcome measure was the deterioration rate calculated at 1 and 2 years using a Kaplan-Meier survival analysis. RESULTS For near stereoacuity, the rate of decreasing 3 or more octaves was 2% (95% CI, 0%-6%) at 1 year and 7% (95% CI, 0%-16%) at 2 years. The alternative secondary analyses revealed similar low deterioration rates. In most cases of apparent deterioration, near stereoacuity returned to baseline levels without treatment. CONCLUSIONS For children with untreated intermittent exotropia, deterioration in near stereoacuity at 1 and 2 years is infrequent. Therefore, performing surgery for intermittent exotropia to proactively prevent deterioration of near stereoacuity cannot be justified. Retesting stereoacuity is critical to determine whether any measured decrease in stereoacuity is real.

Comparing Outcome Criteria Performance in Adult Strabismus Surgery

PURPOSE To evaluate the performance of motor, diplopia, and health-related quality of life (HRQOL) criteria when analyzing outcomes of adult strabismus surgery. DESIGN Cohort study. PARTICIPANTS We studied 159 adults undergoing 171 strabismus surgeries. METHODS All patients underwent clinical assessment preoperatively and 6 weeks postoperatively, including completion of Adult Strabismus-20 HRQOL questionnaires. Preoperatively, strabismus was classified as either diplopic (n = 117), nondiplopic (n = 38), or atypical diplopic (n = 16). To assess performance of motor, diplopia, and HRQOL criteria, success was defined a priori and applied separately and in combinations. For success: (1) motor criteria, <10 prism diopters by simultaneous prism cover test; (2) diplopia criteria, none or only rare in primary distance and for reading; (3) HRQOL criteria, exceeding previously reported 95% limits of agreement (LOA). MAIN OUTCOME MEASURES Surgical success rate when applying motor, diplopia, and HRQOL criteria alone and in combinations. RESULTS Overall, success rates were 90% for motor criteria, 74% for diplopia criteria, and 60% for HRQOL criteria. Combining criteria, the highest success rate was for motor plus diplopia criteria (67%) and the lowest success rate was when combining motor, diplopia, and HRQOL criteria (50%). CONCLUSIONS Applying motor criteria alone yields the highest success rates when evaluating outcomes in adult strabismus surgery, but motor criteria do not fully represent the patients postoperative status. Combining diplopia criteria with motor criteria provides a more clinically relevant standard for judging the success of adult strabismus surgery. For HRQOL criteria, exceeding 95% LOA at 6 weeks postoperatively seems to be a difficult hurdle to clear for some individual patients, and evaluating change in HRQOL score may be more useful in cohort studies.

Comparison of quality-of-life instruments in childhood intermittent exotropia.

PURPOSE To compare 2 health-related quality-of-life (HRQOL) instruments: the condition-specific Intermittent Exotropia Questionnaire (IXTQ) and the generic Pediatric Quality of Life Inventory (PedsQL) in children with intermittent exotropia. METHODS Fifty-one children with intermittent exotropia (median, 7 years; range, 5-16 years) were recruited from outpatient clinics with one of their parents. All children completed age-appropriate Child IXTQ (12 items) and Child PedsQL (23 items). Parents completed parallel Proxy IXTQ and Proxy PedsQL (parent assessment of childs HRQOL). Possible scores ranged from 0 to 100 (worst to best HRQOL). Normal thresholds were defined using the 5th percentile in a control group of 47 normal nonstrabismic children. Proportions scoring below normal on each questionnaire were compared. Median scores in intermittent exotropia and control groups also were compared. RESULTS More scores were subnormal using Proxy IXTQ than Proxy PedsQL (55% vs 18%, p = 0.0004). When Child questionnaires were used, we found that similar proportions scored below normal (IXTQ 8% vs PedsQL 14%, p = 0.3). Median scores were lower for intermittent exotropia children compared with control patients for Child IXTQ (83 vs 92; p = 0.04), Proxy IXTQ (81 vs 98; p < 0.0001), and Proxy PedsQL (p = 0.04) but not for Child PedsQL (p = 0.3). CONCLUSIONS The Proxy IXTQ detects reduced HRQOL related to intermittent exotropia more often than the Proxy PedsQL. There were few subnormal scores on Child IXTQ and Child PedsQL. Children with intermittent exotropia scored, on average, lower than control patients on the IXTQ, but most individual scores fell within the normal range. The IXTQ may prove useful for clinical assessment of intermittent exotropia.