 |
|
Relative Contributions of Reduced Vision and General Health to NEI-VFQ Scores in Patients With Neovascular Age-Related Macular Degeneration
Päivi H. Miskala, PhD;
Neil M. Bressler, MD;
Curtis L. Meinert, PhD
Arch Ophthalmol. 2004;122:758-766.
ABSTRACT
| |
Objective To estimate the relative contributions of central vision loss and general health to vision-targeted quality of life as measured by the National Eye Institute Visual Function Questionnaire (NEI-VFQ).
Methods Data on quality of life (NEI-VFQ and the 36-Item Short-Form Health Survey [SF-36]) and visual acuity were collected as part of the Submacular Surgery Trials Pilot Study. Information on medical conditions was collected by patient chart review. Twenty-four–month data for 120 patients were analyzed using linear regression methods.
Results Median patient age at the 24-month examination was 77 years; 60% were women, and 98% were non-Hispanic whites. A 3-line decrement in visual acuity in the better-seeing eye was associated with a 5.1- to 17.1-point decrement in NEI-VFQ scores after adjustment for general health (SF-36 physical component summary [PCS] and mental component summary [MCS] scores). A 10-point decrement in the PCS score was associated with a 4- to 9-point decrement in NEI-VFQ scores after adjustment for visual acuity in the better-seeing eye and MCS score. A 10-point decrement in the MCS score was associated with a 4- to 8-point decrement in NEI-VFQ scores after adjustment for visual acuity in the better-seeing eye and PCS score. Diabetes, arthritis/rheumatism, and hypertension also had large effects on NEI-VFQ scores in the adjusted analysis.
Conclusions The NEI-VFQ is sensitive to differences in visual acuity in the better-seeing eye, as expected, and to differences in general health. Adjustment for general health should be considered when comparing NEI-VFQ scores between patient groups.
INTRODUCTION
Because most individuals with vision loss caused by age-related macular degeneration (AMD) are older than 65 years, they often have coexisting medical conditions. The National Health Interview Survey1 reported the following prevalences in individuals 65 years and older: high blood pressure, 36%; arthritis, 48%; heart disease, 27%; diabetes, 10%; and asthma, 5%. Psychological distress2 and depression3 also are common in patients with AMD. In one study,3 nearly one third of patients with advanced AMD screened positive for depression. Other sensory impairments, such as hearing loss, also may compound the effects of vision impairment and make day-to-day functioning more difficult. For example, in the white population of Beaver Dam, Wis, AMD and hearing loss were both present in 15% of individuals aged 48 to 92 years and in 40% of individuals 75 years or older.4
Since vision and other health problems disproportionately affect older people, it is important to understand how these conditions contribute to quality of life (QOL). The knowledge of possible effects that nonocular medical conditions may have on QOL is particularly important when trying to assess the effect of vision loss on daily activities in people older than 65 years. One measure of vision-related QOL is the National Eye Institute Visual Function Questionnaire (NEI-VFQ).5-8 Adjustment of NEI-VFQ scores for general health, among other factors, has been reported in the literature6, 8-10; however, no discussion has addressed the best way to measure general health or the magnitude of the effect that general health may have on NEI-VFQ scores. The purpose of this study is to estimate the relative contributions of reduced vision and general health to vision-targeted QOL as measured by the NEI-VFQ. This information may be valuable for investigators who are measuring and interpreting vision-targeted QOL outcomes using the NEI-VFQ and for physicians who care for people with AMD.
METHODS
STUDY POPULATION
The Submacular Surgery Trials (SST) Pilot Study consists of 4 randomized pilot trials undertaken to assess the feasibility of larger clinical trials to evaluate submacular surgery for subfoveal choroidal neovascularization associated with AMD and other conditions. Patients who enrolled in 2 SST pilot trials, Group N and Group B, were eligible for the present study.11 Group N pilot trial included persons with AMD who were 50 years or older, had new untreated subfoveal choroidal neovascularization, and had visual acuity in the affected eye of 20/100 through 20/800 (approximate Snellen equivalent).12 The subfoveal lesion could be either well-demarcated and large (3.5-9.0 Macular Photocoagulation Study13 [MPS] disc areas, whereby 1 MPS disc area12 corresponds to a circle with an area of 2.5 mm2) or poorly demarcated with no lower size limit ( 9.0 MPS disc areas). Group B pilot trial patients also were 50 years or older and had AMD but had a large, predominantly hemorrhagic lesion ( 3.5 MPS disc areas), with visual acuity in the study eye of 20/100 (approximate Snellen equivalent) or worse but at least light perception.12 In these pilot trials, eligible consenting patients were randomized equally to submacular surgery or observation of the study eye.
Additional data collection for the present study was limited to 10 clinical centers that participated in Group N and Group B pilot studies and that also were participating currently in the larger randomized trials of submacular surgery sponsored by the NEI of the National Institutes of Health (the SST). This analysis is limited to cross-sectional data from 120 patients who underwent interviews using the NEI-VFQ and visual acuity measurements 24 months after enrollment in the SST Group N and Group B pilot trials (Figure 1). The institutional review board at each clinical center reviewed the SST Pilot Study protocol before patient enrollment began. Approval was obtained from the SST Operations Committee and the local institutional review boards at the 10 centers for the medical chart reviews conducted for the present study.
|
|
|
|
Figure 1. Flow chart of patients included and excluded from the analysis. NEI-VFQ indicates National Eye Institute Visual Function Questionnaire. *Patients at Submacular Surgery Trials (SST) Pilot Study clinical centers not participating in the SST were excluded. One clinical center that participated in the SST Pilot Study and in the SST was excluded because there were no patients with baseline interviews and only a few with 24-month interviews.
|
|
|
CLINICAL DATA
Information on baseline characteristics and best-corrected visual acuity was collected as part of the SST Pilot Study. Visual acuity was measured using modified Bailey-Lovie (Early Treatment Diabetic Retinopathy Study) charts14 and a standard protocol after careful refraction to obtain the best correction.12, 15 Visual acuity was measured monocularly at a 2-m test distance from the vision chart. Whenever a patient could read at least 15 letters correctly at this distance with the eye being tested, the final visual acuity score for that eye was the number of letters read correctly plus 30. However, when the patient could not read at least 15 letters, he or she was moved to 0.5 m from the chart and the measurement was repeated; the final visual acuity score for that eye was the number of letters read correctly at the 0.5-m distance. When the patient could not read any letters on the vision chart at the 0.5-m distance (visual acuity <20/1600), vision was coded as light perception or no light perception, as assessed by the vision examiner and confirmed by the ophthalmologist. For the purpose of SST Pilot Study data analysis, light perception was given a score of –10 (ie, 3 lines worse than 20/1600) and no light perception a score of –30 (ie, 7 lines worse than 20/1600). Scores were converted to lines of visual acuity by dividing visual acuity scores by 5 (5 letters per chart line).
During the 24-month follow-up examination, a traveling vision examiner, who was masked to treatment assignment and to study eye, measured the visual acuity of each patient at each clinical center whenever possible. Ninety-eight (82%) of 120 patients had masked visual acuity measurements 24 months after enrollment. For this analysis, those visual acuity measurements were used when available.
QOL INTERVIEW DATA
Interviews were conducted at baseline and 6, 12, and 24 months after enrollment in the SST Pilot Study. Initially, the 36-Item Short-Form Health Survey (SF-36)16-17 was administered in-person by a member of the clinical staff as part of baseline data collection in the SST Pilot Study for most of the patients enrolled. The QOL data collection was modified in January 1997 when the interview procedure changed from in-person local interviewer administration to masked central telephone administration. Also at that time, the NEI-VFQ was added to the interview. Because the NEI-VFQ was introduced in the course of the study, the number of patients with NEI-VFQ interviews was largest 24 months after enrollment. Thus, 24-month NEI-VFQ data were analyzed for this study to include the maximum number of patients.
Three versions of the NEI-VFQ have been published, containing 25 items, 39 items, and 51 items.5-7,18 For this analysis, a 37-item NEI-VFQ was created by excluding 2 general health items from the 39-item version. The 37 items are divided into 11 subscales: general vision, ocular pain, near activities, distance activities, social functioning, mental health, role difficulties, dependency, driving, color vision, and peripheral vision. Individual subscales consist of 1 to 6 questions, and each question is given a score of 0 to 100. One of the driving subscale questions (difficulty driving in difficult conditions) was added late to the NEI-VFQ interview, and, therefore, for 55% of individuals included in this analysis, the driving subscale was calculated from a maximum of 2 items instead of 3. A subscale score is an unweighted average of all questions for which a response was recorded. Subscale scores range from 0, which is the worst score (poorest function), to 100, which is the best possible score (best function). The overall score for the NEI-VFQ is an unweighted average of the 11 subscale scores.
The SF-36 interview scores were evaluated as a measure of general health status. The SF-36 consists of 8 subscales that can be combined to form 2 summary scales.16-17 Data analysis for this study concentrated on the 2 summary scales: the physical component summary (PCS) and the mental component summary (MCS) scores 24 months after enrollment.17 All 8 subscales contribute to each of the 2 summary scales, but they are weighted differently for each summary scale. A nonmissing value is required for all 8 subscale scores to create the summary scales. The summary scale scores are standardized to have a mean of 50 and an SD of 10 in the general US population.17 Theoretically, the worst possible value for the summary scale scores is 0, and the best possible value is 100, but these are highly improbable scores for individuals participating in an outpatient study.
INFORMATION ON COMORBIDITIES
A list of medical conditions was taken from the Medical Outcomes Study19 by the developers of the NEI-VFQ7 and was used as a model for collecting information on medical conditions. For the present study, the 16-item checklist of medical conditions was retained; items were added regarding clinic note dates, source of information (ie, medical history or examination), and information on prescription medications.11 Psychiatric disease was added to the list of conditions after data collection based on responses to an open-ended question on the questionnaire.
Information on medical conditions was extracted from the medical charts that were available to the ophthalmologist when study patients were examined. These medical charts typically were the total ophthalmology charts (6 centers) or the ophthalmology subspecialty charts (retina service charts) (2 centers); at 2 centers, the full outpatient medical record typically was available to the ophthalmologist. Differences reflected the variety of clinical center settings, that is, community-based centers and university-based centers. Charts at all 10 clinical centers were reviewed by one of us (P.H.M.); a physician (N.M.B.) provided advice regarding categorization of medical conditions, surgeries, procedures, and therapies. Information on prescription medications was used as a secondary source when the clinical notes were unclear as to whether a medical condition was present.
DATA ANALYSIS
Descriptive statistics were calculated for each variable of interest. The  2 test or the Fisher exact test was used to compare patient characteristics that were categorical. The Wilcoxon 2-sample rank sum test was used to compare patient characteristics that were continuous. An extension of the Wilcoxon rank sum test20 was used to evaluate trends in QOL scores across visual acuity categories.
Linear regression models were used to explore relations among visual acuity, general health, and QOL. The dependent variable in all regression models was the NEI-VFQ overall score or 1 of the 11 subscale scores 24 months after enrollment. The independent variables were visual acuity in the better-seeing eye and general health status measured by the presence of medical conditions or SF-36 PCS and MCS scores 24 months after enrollment. The NEI-VFQ and SF-36 scores were treated as continuous variables in the analysis. Visual acuity in the better-seeing eye, also a continuous variable, was defined to be that of the eye with the higher visual acuity score 24 months after enrollment. Medical conditions were treated as indicator variables and were coded as 0 when the condition was absent or when the disease status could not be determined and as 1 when the condition was definitely or probably present. Data analysis concentrated on the 5 most common medical conditions. Hearing problems were studied in detail to investigate how another sensory impairment contributes to NEI-VFQ scores. The number of medical conditions was categorized for some linear regression models: coding was 0 when the patient had less than 2 medical conditions other than AMD and 1 when the patient had 2 or more additional medical conditions. This categorization was based on our observation that there seemed to be a difference in the distribution of NEI-VFQ scores between individuals with less than 2 conditions and those with 2 or more conditions. Gender and age were evaluated as potential confounders, using linear regression methods, for the association between vision loss and QOL.
Power calculations (post hoc) were carried out. With a 5%  level (P.05) and a sample size of 120 for most scales, there was 11% to 33% power to identify 5-point differences in NEI-VFQ overall and subscale scores between individuals who had less than 2 medical conditions vs individuals who had 2 or more medical conditions and 30% to 86% power to identify 10-point differences. Unadjusted P.05 was considered statistically significant. Biological plausibility and clinical significance were considered when determining whether findings were meaningful. Data were analyzed primarily using SAS software (SAS Institute Inc, Cary, NC) on a UNIX platform.
RESULTS
DEMOGRAPHIC AND CLINICAL CHARACTERISTICS
A total of 197 of 206 patients were included in the study (Figure 1); 120 of these 197 patients underwent NEI-VFQ interviews and visual acuity measurements 24 months after enrollment and were included in this analysis. The median age of these patients was 77 years (Table 1). Most patients were non-Hispanic whites (98%), reflecting the underlying distribution of neovascular AMD in the US population. Median visual acuities in the better-seeing and worse-seeing eyes were 20/100 and 20/500, respectively. Twenty-eight percent (33/120) of the individuals included in the cross-sectional analysis of 24-month NEI-VFQ data were legally blind at that time (visual acuity 20/200 in the better-seeing eye). The most common medical conditions at 24-month follow-up were hypertension, arthritis or rheumatism, heart attack or angina, cancer, and diabetes (Table 2). Eighty-five percent of the patients had 1 or more medical conditions in addition to neovascular AMD (Figure 2). At 24 months, the median SF-36 PCS score was 46 (mean, 44; range, 18-60) and the median MCS score was 57 (mean, 55; range, 17-68) in the 120 patients included in the analysis (data not shown).
|
|
|
|
Table 1. Demographic and Clinical Characteristics of 120 Patients at 24 Months of Follow-up
|
|
|
|
|
|
|
Table 2. Prevalence of Nonocular Medical Conditions 24 Months After Enrollment
|
|
|
|
|
|
|
Figure 2. Prevalence of multiple nonocular medical conditions in 120 patients 24 months after enrollment.
|
|
|
Thirteen of 77 patients who were included in the study but excluded from the cross-sectional analysis of 24-month data died before this point. No large differences were found on demographic characteristics (age, gender, and race) between the 120 patients who were included in the analysis and the remaining 64 patients who had reached 24 months of follow-up but were excluded from the analysis because of missing data (data not shown). However, patients who were included in the analysis less often had a major paralysis or neurologic problems (5.0% vs 21.9%; 2 P = .001) and hearing problems (5.8% vs 18.8%; 2 P = .006) at 24 months of follow-up than patients who were excluded from the analysis.
DISTRIBUTION OF NEI-VFQ SCORES BY VISUAL ACUITY
The NEI-VFQ overall score and 9 of the 11 subscale scores were sensitive to differences in visual acuity in the better-seeing eye (Table 3). That is, the NEI-VFQ overall and subscale scores were highest in the subgroup with best visual acuity and lowest in the subgroup with poorest visual acuity in the better-seeing eye. The exceptions were the peripheral vision and ocular pain subscales.
|
|
|
|
Table 3. NEI-VFQ Overall and Subscale Scores at 24 Months of Follow-up by Visual Acuity in the Better-Seeing Eye
|
|
|
RELATIVE CONTRIBUTIONS OF REDUCED VISION AND GENERAL HEALTH TO NEI-VFQ SCORES
Linear regression models that included 1 of 6 medical conditions (hypertension, arthritis or rheumatism, heart attack or angina, cancer, diabetes, or hearing problems) indicated that visual acuity in the better-seeing eye was the primary influence on the NEI-VFQ overall score and on 9 of the 11 subscale scores (Table 4). In the unadjusted analysis (data not shown) and the analysis adjusted for individual medical conditions, the ocular pain and peripheral vision subscale scores were not associated with visual acuity in the better-seeing eye. The effect of visual acuity in the better-seeing eye was consistent within each of the subscales and was independent of single medical conditions included in the linear regression model (ie, the slope for visual acuity in the better-seeing eye was stable). Visual acuity in the better-seeing eye had the greatest impact on the driving, near activities, dependency, and distance activities subscales, where 3- to 6-point differences were observed per 1-line difference in visual acuity in the better-seeing eye after considering each of the 6 medical conditions.
|
|
|
|
Table 4. Difference in 24-Month NEI-VFQ Scores Associated With a 1-Line Difference in Visual Acuity (VA) in the Better-Seeing Eye and With the Presence of Medical Conditions
|
|
|
Despite the dominant effect of visual acuity, some medical conditions had a large effect on some of the NEI-VFQ subscales: the dependency subscale scores were, on average, 10.7 points lower for patients who had arthritis or rheumatism, the distance activities subscale scores were 12.2 points lower for patients with diabetes, and the ocular pain subscale scores were 7.6 points higher for patients with hypertension after adjustment for visual acuity in the better-seeing eye (Table 4). The presence of less than 2 vs 2 or more medical conditions was considered in alternate regression models; findings are summarized in Table 5. Slopes for visual acuity in the better-seeing eye were nearly identical to those in Table 4. The presence of multiple medical conditions was related to scores on the role difficulties subscale. After taking into account visual acuity in the better-seeing eye, patients with 2 or more medical conditions averaged 7.6 points lower on the role difficulties subscale than patients with less than 2 medical conditions.
|
|
|
|
Table 5. Difference in 24-Month NEI-VFQ Scores Associated With a 1-Line Difference in Visual Acuity (VA) in the Better-Seeing Eye and With the Presence of Medical Conditions
|
|
|
Linear regression models also were constructed using the SF-36 PCS and MCS scores as measures of general health (Table 6). Although the relation between NEI-VFQ scores and visual acuity in the better-seeing eye remained unchanged before and after inclusion of SF-36 summary scale scores, the SF-36 PCS and MCS scores contributed substantially to most of the NEI-VFQ subscale scores. A 10-point decrement in the PCS score translated to a 4- to> 9-point decrement in the NEI-VFQ overall score and in 10 of 11 subscale scores after adjustment for visual acuity in the better-seeing eye and MCS score, and a 10-point decrement in the MCS score translated to a 4- to 8-point decrement in the NEI-VFQ overall score and in 7 of 11 subscale scores after adjustment for visual acuity in the better-seeing eye and PCS score.
|
|
|
|
Table 6. Difference in 24-Month NEI-VFQ Scores Associated With a 1-Line Difference in Visual Acuity (VA) in the Better-Seeing Eye and a 1-Point Difference in SF-36 Summary Scores
|
|
|
The SF-36 PCS and MCS scores were unrelated to visual acuity in this study (data not shown). Visual acuity in better-seeing and worse-seeing eyes explained 0.02% and 2.0% of variability in PCS scores, respectively, and 0.01% and 1.0% of variability in MCS scores, respectively.
EVALUATION OF POTENTIAL CONFOUNDERS
In the unadjusted analysis and after adjustment for visual acuity in the better-seeing eye, distribution of the ocular pain subscale scores only were statistically significantly different between men and women (data not shown). Men had, on average, 7.6-point higher ocular pain subscale scores (ie, less ocular pain) than women (P = .02) in the unadjusted analysis and after adjustment for visual acuity in the better-seeing eye. Of the 16 medical conditions, women had higher prevalences of arthritis and rheumatism (35% vs 15%; 2 P = .02) and back problems (11% vs 0%; Fisher exact test P = .02) than men. However, adjustment for either of these conditions and visual acuity in the better-seeing eye did not diminish the association of ocular pain with gender. Adjustment of ocular pain subscale scores for visual acuity in the better-seeing eye and general health status measured by the SF-36 PCS and MCS resulted in a gender difference of 5.7 points (P = .06).
We observed apparent gender differences for other NEI-VFQ subscales; however, none of these differences reached statistical significance. After taking into account visual acuity in the better-seeing eye and PCS and MCS scores, men's scores, on average, were 7.7 points higher than women's scores on the peripheral vision subscale (P = .13), 4.6 points lower on the general vision subscale (P = .12), 4.5 points lower on the distance activities subscale (P = .19), and 3.8 points lower on the role difficulties subscale (P = .31). The distribution of visual acuity in the better-seeing eye was not different between men and women.
Age was independently associated with 3 of 11 NEI-VFQ subscale scores: role difficulties, ocular pain, and driving (data not shown). A 1-year increment in age resulted, on average, in a 0.7-point decrement in role difficulties subscale score (P = .02), a 0.5-point increment in ocular pain subscale score (P = .03), and a 1.1-point decrement in driving subscale score (P = .02). However, age was associated only with the ocular pain subscale scores when the relationship between age and NEI-VFQ scores was adjusted for visual acuity in the better-seeing eye or for visual acuity in the better-seeing eye and SF-36 PCS and MCS scores. A 1-year increment in age was associated with a 0.5-point increment in ocular pain subscale scores in both of these adjusted analyses (P = .03). Age distributions of men and women were similar.
COMMENT
The results of this study show that a 37-item version of the NEI-VFQ is sensitive to differences in visual acuity in the better-seeing eye and to differences in general health. Visual acuity in the better-seeing eye was consistently associated with NEI-VFQ scores before and after adjustment for general health, whether measured by individual medical conditions or by SF-36 PCS and MCS scores. A 3-line decrement in visual acuity in the better-seeing eye was associated with a 5.1- to 17.1-point decrement in the NEI-VFQ overall score and in 9 of the subscale scores. Ocular pain and peripheral vision subscale scores were unrelated to visual acuity in the better-seeing eye in this group of patients.
Although NEI-VFQ scores were mostly driven by the level of visual acuity in the better-seeing eye, physical and mental aspects of general health also contributed to the NEI-VFQ scores: a 10-point decrement in the PCS score was associated with a 4- to 9-point decrement in NEI-VFQ scores after adjustment for visual acuity in the better-seeing eye and MCS score, and a 10-point decrement in the MCS score was associated with a 4- to 8-point decrement in NEI-VFQ scores after adjustment for visual acuity in the better-seeing eye and PCS score. All 6 of the medical conditions studied in detail had an impact on 1 or more subscales of the NEI-VFQ after adjustment for visual acuity in the better-seeing eye, although many of the associations did not reach statistical significance, perhaps because of the small sample size. However, 3 large associations were observed: the dependency subscale scores were affected by the presence of arthritis or rheumatism, the distance activities subscale scores by diabetes, and the ocular pain subscale scores by hypertension after accounting for visual acuity in the better-seeing eye. Hip and knee replacements were included in the arthritis or rheumatism category and may explain some of the effect on the dependency subscale. Patients with more severe diabetic retinopathy were excluded from the SST Pilot Study at baseline, but some patients with diabetes and no diabetic retinopathy or less severe diabetic retinopathy were included. It is possible that some of these patients developed visually impairing diabetic retinopathy by 24 months after enrollment, when this cross-sectional analysis was performed, which could explain the association between diabetes and distance activities subscale scores. Other potential explanations could be the presence of retinal ischemia, reduced peripheral vision, diminished capacity of visual pathways due to some disease process associated with diabetes or AMD, or chance alone. We cannot formulate a biologically plausible hypothesis for the association of hypertension with higher ocular pain subscale scores (ie, less ocular pain), which may represent a chance finding.
The vision-specific role difficulties subscale was found to be associated with the presence of multiple nonocular medical conditions. Patients who had 2 or more medical conditions had, on average, 7.6-point lower role difficulties subscale scores than individuals with less than 2 medical conditions. A possible explanation for this could be that many patients who had only 1 nonocular medical condition had hypertension only; however, patients who had more than 1 medical condition often had potentially debilitating conditions in addition to hypertension, such as heart problems, arthritis, cancer, diabetes, or serious lung problems. Several other NEI-VFQ subscales also seemed to be affected by the presence of multiple medical conditions, although these values did not reach statistical significance.
With respect to determining whether another sensory impairment in addition to vision loss would have an impact on NEI-VFQ scores, we noted that individuals who had hearing problems had 11-point lower social functioning subscale scores, 12-point lower mental health subscale scores, and 14-point lower color vision subscale scores, on average, than individuals without hearing problems after taking into account visual acuity in the better-seeing eye. Although these values were not statistically significant, they indicate that hearing problems may lower several of the NEI-VFQ subscales scores more than would be expected based on the level of visual acuity alone. Second, these data suggest that physicians may need to pay particular attention to the needs of vision- and hearing-impaired patients with AMD, for whom several domains of QOL seem to be affected.
It is possible that some of the effect of vision impairment on NEI-VFQ scores may be eliminated when adjusting NEI-VFQ scores for SF-36 PCS and MCS scores. The SF-36 has been reported in some studies21-23 to be associated with aspects of vision, whereas other studies9, 24-26 have shown small or insignificant associations. Visual acuity of better- or worse-seeing eyes was not associated with SF-36 PCS or MCS scores in our study of patients with central vision loss due to AMD. Therefore, we would not expect to eliminate vision-related disability from the NEI-VFQ scores by adjusting for SF-36 PCS and MCS scores. In other studies, we recommend careful examination of association between clinical vision of interest and SF-36 PCS and MCS scores before adjustment is applied.
A potentially important finding from this study was that gender was associated with the ocular pain subscale of the NEI-VFQ, with women having worse scores than men, on average. This association could not be explained by any gender difference in random treatment assignment in the SST Pilot Study or in the presence of medical conditions. This finding prompted an analysis of the bodily pain subscale scores of the SF-36. A similar finding was observed, with women having bodily pain scores that were 9 points lower (ie, worse), on average, than men. This finding also agrees with published findings for individuals 65 years and older.16 Consistency of the result in 2 different, but related, scales and the similarity of the results to what has been reported elsewhere argues against a chance association. There also was some evidence that gender differences may exist in other domains of the NEI-VFQ; however, this area needs further investigation.
A limitation of the present study was that information on medical conditions was collected retrospectively. It is possible that the clinic charts infrequently may have included information for conditions that are not common or life threatening or that do not require surgical intervention. Any missing information on medical conditions, and on severity and duration of conditions, may have caused residual confounding when the association of interest, in this case QOL and vision, was adjusted imperfectly. Thus, incomplete information on coexisting medical conditions could be another potential explanation, in addition to the small sample size, for the few statistically significant associations of the NEI-VFQ scores with individual medical conditions. However, general health measured by the SF-36 PCS and MCS scores, which were collected prospectively, had a substantial effect on most NEI-VFQ subscale scores. There are inherent problems in collecting and summarizing information on individual medical conditions; perhaps the SF-36 is a more accurate and reliable way to assess the impact that a particular condition or multiple medical conditions have on an individual.
It is likely that patients enrolled in the SST Pilot Study were healthier than "typical" patients with AMD and choroidal neovascularization because of the outpatient setting and the eligibility and exclusion criteria imposed. It also is possible that patients with hearing problems may have less often participated in a study that included an interview. Thus, results regarding QOL cannot be generalized to all patients with neovascular AMD. Furthermore, patients who were not interviewed during follow-up had a worse health status more often than those who were interviewed.
The main strength of the study was that QOL and clinical information was collected prospectively using standard protocols and trained and certified personnel. The telephone interviewers, the traveling vision examiners, and the individual who retrieved information on medical conditions did not have any other relationship with the patients that could have biased data collection. Furthermore, patients with choroidal neovascularization secondary to AMD came from 10 clinical centers in different parts of the United States, yielding a more heterogeneous study population than if all the patients had been identified and followed at a single clinical center.
In conclusion, NEI-VFQ scores were associated with the level of visual acuity in the better-seeing eye. Physical and mental aspects of general health contributed to NEI-VFQ scores. The extent to which general health contributed to NEI-VFQ scores was surprising since the questionnaire is supposed to measure vision-related disability. Thus, adjustment for general health should be considered when comparing NEI-VFQ scores between groups of patients.
AUTHOR INFORMATION
| |
Corresponding author and reprints: Päivi H. Miskala, PhD, Wilmer Clinical Trials and Biometry, The Johns Hopkins University, 550 N Broadway, Ninth Floor, Baltimore, MD 21205 (e-mail: pmiskala{at}jhmi.edu).
Submitted for publication September 12, 2002; final revision received July 22, 2003; accepted August 14, 2003.
The SST Pilot Study was funded through numerous private and public sources that have been published previously (Am J Ophthalmol. 2000;130:408). Funding for the additional data collection and analysis for this ancillary study was provided by the Michael B. Panitch Stop AMD Fund (Baltimore).
We thank Barbara S. Hawkins, PhD, Michael X. Repka, MD, Marie Diener-West, PhD, and Barbara Martin, PhD, for their advice on this project; Barbara S. Hawkins, PhD, for her review of this manuscript and editorial comments; and the SST principal investigators and clinic coordinators at the following clinical centers for providing access to the medical records: Emory University Eye Center, Atlanta, Ga; The Wilmer Ophthalmological Institute, Baltimore; Barnes Retina Institute, St Louis, Mo; Cole Eye Institute, Cleveland, Ohio; Retina Vitreous Associates of Kentucky, Lexington; the Department of Ophthalmology, Duke University Medical Center, Durham, NC; Associated Retinal Consultants, Royal Oak, Mich; Schatz, McDonald, Johnson & Ai, San Francisco, Calif; Retina Vitreous Consultants, Pittsburgh, Pa; and Jules Stein Eye Institute, Los Angeles, Calif.
A complete listing of the SST investigators has been published elsewhere (Am J Ophthalmol. 2000;130:405-406).
The authors of this article assume authorship responsibility and had complete access to the data.
From the Department of Ophthalmology, The Johns Hopkins School of Medicine (Drs Miskala and Bressler), and the Departments of Epidemiology and Biostatistics, The Johns Hopkins Bloomberg School of Public Health (Dr Meinert), Baltimore, Md. The authors have no relevant financial interest in this article.
REFERENCES
1. Adams PF, Hendershot GE, Marano MA. Current estimates from the National Health Interview Survey, 1996. Vital Health Stat 10. 1999;200:81-82.
2. Williams RA, Brody BL, Thomas RG, Kaplan RM, Brown SI. The psychosocial impact of macular degeneration. Arch Ophthalmol. 1998;116:514-520.
FREE FULL TEXT
3. Brody BL, Gamst AC, Williams RA, et al. Depression, visual acuity, comorbidity, and disablity associated with age-related macular degeneration. Ophthalmology. 2001;108:1893-1901.
FULL TEXT
|
ISI
| PUBMED
4. Klein R, Cruickshanks KJ, Klein BEK, Nondahl DM, Wiley T. Is age-related maculopathy related to hearing loss? Arch Ophthalmol. 1998;116:360-365.
FREE FULL TEXT
5. Mangione CM, Berry S, Spritzer K, et al. Identifying the content area for the 51-item National Eye Institute Visual Function Questionnaire: results from focus groups with visually impaired persons. Arch Ophthalmol. 1998;116:227-233.
FREE FULL TEXT
6. Mangione CM, Lee PP, Pitts J, et al. Psychometric properties of the National Eye Institute Visual Function Questionnaire (NEI-VFQ). Arch Ophthalmol. 1998;116:1496-1504.
FREE FULL TEXT
7. Mangione CM, Lee PP, Gutierrez PR, et al. Development of the 25-item National Eye Institute Visual Function Questionnaire. Arch Ophthalmol. 2001;119:1050-1058.
FREE FULL TEXT
8. Submacular Surgery Trials Research Group. Responsiveness of the National Eye Institute Visual Function Questionnaire to changes in visual acuity: findings in patients with subfoveal choroidal neovascularization—SST Report No. 1. Arch Ophthalmol. 2003;121:531-539.
FREE FULL TEXT
9. Gutierrez P, Wilson MR, Johnson C, et al. Influence of glaucomatous visual field loss on health-related quality of life. Arch Ophthalmol. 1997;115:777-784.
FREE FULL TEXT
10. Globe D, Varma R, Azen SP, et al. Psychometric performance of the NEI VFQ-25 in visually normal Latinos: the Los Angeles Latino Eye Study. Invest Ophthalmol Vis Sci. 2003;44:1470-1478.
FREE FULL TEXT
11. Miskala PH. Associations Among Comorbidities, Visual Acuity, and Quality of Life in Patients With Age-Related Macular Degeneration and Central Vision Loss [dissertation]. Baltimore, Md: Johns Hopkins University; 2002.
12. Submacular Surgery Trials Research Group. Submacular Surgery Trials (SST) Manual of Procedures. Springfield, Va: US Dept of Commerce, National Technical Information Service; June 1998. NTIS technical report PB98-166648.
13. Macular Photocoagulation Study Group. Subfoveal neovascular lesions in age-related macular degeneration: guidelines for evaluation and treatment in the Macular Photocoagulation Study. Arch Ophthalmol. 1991;109:1242-1257.
FREE FULL TEXT
14. Ferris FL, Kassoff A, Bresnick GH, Bailey I. New visual acuity charts for clinical research. Am J Ophthalmol. 1982;94:91-96.
ISI
| PUBMED
15. Submacular Surgery Trials Pilot Study Investigators. Submacular Surgery Trials randomized pilot trial of laser photocoagulation versus surgery for recurrent choroidal neovascularization secondary to age-related macular degeneration, I: ophthalmic outcomes: Submacular Surgery Trials Pilot Study Report Number 1. Am J Ophthalmol. 2000;130:387-407.
FULL TEXT
|
ISI
| PUBMED
16. Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 Health Survey: Manual & Interpretation Guide. Boston, Mass: Health Institute, New England Medical Center; 1993.
17. Ware JE, Kosinski M, Keller SD. SF-36 Physical and Mental Health Summary Scales: A User's Manual. Boston, Mass: Health Institute, New England Medical Center; 1994.
18. RAND Health Web site. VFQ-50. Available at: http://www.rand.org/health/surveys/vfq25. Accessed December 1, 2003.
19. Stewart AL, Greenfield S, Hays RD, et al. Functional status and well-being of patients with chronic conditions: results from the Medical Outcomes Study. JAMA. 1989;262:907-913.
FREE FULL TEXT
20. Cuzick J. A Wilcoxon-type test for trend. Stat Med. 1985;4:87-90.
ISI
| PUBMED
21. Schiffman RM, Jacobsen G, Whitcup SM. Visual functioning and general health status in patients with uveitis. Arch Ophthalmol. 2001;119:841-849.
FREE FULL TEXT
22. Wilson MR, Coleman AL, Yu F, et al. Functional status and well-being in patients with glaucoma as measured by the Medical Outcomes Study Short Form-36 Questionnaire. Ophthalmology. 1998;105:2112-2116.
FULL TEXT
|
ISI
| PUBMED
23. Musch DC, Farjo AA, Meyer RF, Waldo MN, Janz NK. Assessment of health-related quality of life after corneal transplantation. Am J Ophthalmol. 1997;124:1-8.
ISI
| PUBMED
24. Submacular Surgery Trials Pilot Study Investigators. Submacular Surgery Trials randomized pilot trial of laser photocoagulation versus surgery for recurrent choroidal neovascularization secondary to age-related macular degeneration, II: quality of life outcomes: Submacular Surgery Trials Pilot Study report number 2. Am J Ophthalmol. 2000;130:408-418.
FULL TEXT
|
ISI
| PUBMED
25. Mangione CM, Gutierrez PR, Lowe G, Orav EJ, Seddon JM. Influence of age-related maculopathy on visual functioning and health-related quality of life. Am J Ophthalmol. 1999;128:45-53.
FULL TEXT
|
ISI
| PUBMED
26. Parrish RK II, Gedde SJ, Scott IU, et al. Visual function and quality of life among patients with glaucoma. Arch Ophthalmol. 1997;115:1447-1455.
FREE FULL TEXT
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter
What's this?
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
|
Responsiveness of NEI VFQ-25 to Changes in Visual Acuity in Neovascular AMD: Validation Studies from Two Phase 3 Clinical Trials
Suner et al.
IOVS 2009;50:3629-3635.
ABSTRACT
| FULL TEXT
Validity of using vision-related quality of life as a treatment end point in intermediate and posterior uveitis
Murphy et al.
Br J Ophthalmol 2007;91:154-156.
ABSTRACT
| FULL TEXT
Quality of life and visual function in patients with intermediate uveitis
Murphy et al.
Br J Ophthalmol 2005;89:1161-1165.
ABSTRACT
| FULL TEXT
Health- and Vision-Related Quality of Life Among Patients With Ocular Histoplasmosis or Idiopathic Choroidal Neovascularization at Enrollment in a Randomized Trial of Submacular Surgery: Submacular Surgery Trials Report No. 5
Submacular Surgery Trials Research Group
Arch Ophthalmol 2005;123:78-88.
ABSTRACT
| FULL TEXT
Surgical Removal vs Observation for Subfoveal Choroidal Neovascularization, Either Associated With the Ocular Histoplasmosis Syndrome or Idiopathic: II. Quality-of-Life Findings From a Randomized Clinical Trial: SST Group H Trial: SST Report No. 10
Submacular Surgery Trials Research Group
Arch Ophthalmol 2004;122:1616-1628.
ABSTRACT
| FULL TEXT
|
