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From the Jaeb Center for Health Research, Tampa, Florida.
| Abstract |
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METHODS. The NEIVFQ was administered to 244 patients 5 to 8 years after treatment for an episode of acute optic neuritis as part of the Optic Neuritis Treatment Trial. Visual acuity, visual field, contrast sensitivity, and color vision were measured at the same time as questionnaire completion.
RESULTS. The NEIVFQ scores generally were lower than those reported for a disease-free group. Reported dysfunction was greater when multiple sclerosis was present and when visual acuity was abnormal, supporting the construct validity of the NEIVFQ. Rank correlations between the NEIVFQ subscales and clinical measures of visual function were moderate at best. Internal consistency reliability was generally high for most of the NEIVFQ subscales.
CONCLUSIONS. These findings add support to the use of the NEIVFQ as a valuable measure of self-reported visual impairment.
| Introduction |
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The Optic Neuritis Treatment Trial (ONTT), a multicenter randomized trial funded by the National Eye Institute, found that (1) treatment with intravenous corticosteroids can accelerate visual recovery but does not have an effect on the degree of permanent visual loss and (2) treatment with oral prednisone does not improve vision and may be associated with an increased risk of recurrence.5 6
Measurement of health-related quality of life (HRQL) has become recognized as an important adjunct to clinical outcome measures in clinical trials. HRQL is the subjective self-assessment of ones health status, often partitioned into several relevant domains, such as physical functioning, emotional well-being, and social relations. The National Eye Institute supported the development of the Visual Functioning Questionnaire (NEIVFQ), an instrument to assess self-reported visual impairment in studies of vision. Prior studies have reported results from the NEIVFQ among patients with age-related cataracts, age-related macular degeneration, diabetic retinopathy, primary open-angle glaucoma, cytomegalovirus retinitis, low vision from any cause,7 and glaucoma.8 9
As part of the ONTT, we administered the NEIVFQ to a subset of patients 5 to 8 years after study entry. Herein we report the following: (1) a description of HRQL, measured with the NEIVFQ, of patients several years after optic neuritis, according to their neurologic and visual status; (2) the relationship between the NEIVFQ subscales and clinical measures of visual function; and (3) the internal consistency reliability of the NEIVFQ subscales.
| Methods |
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Vision tests, all performed with correction of refractive error from a
standardized refraction protocol, included the following: (1) visual
acuity with a retro-illuminated ETDRS chart, (2) contrast
sensitivity with the PelliRobson chart, (3) color vision with the
Farnsworth Munsell 100-hue test, and (4) visual field with the Humphrey
Field Analyzer, program 30-2. The normal ranges for visual acuity
(logMar value < 0.0 (better than 20/20) and contrast sensitivity
(
line 15) were based on normative data collected by the ONTT clinical
centers on subjects in the age range of the ONTT
patients14
for color vision (error score
110)
based on published data,15
and for visual field mean
deviation (
-3.00) based on unpublished normative data collected by
the ONTT Visual Field Reading Center at the University of California,
Davis (Johnson C, unpublished observations, January 1991). Each
patient was classified as having zero, one, or two eyes abnormal with
respect to visual acuity.
A diagnosis of clinically definite MS (CDMS) was made when a patient
reported new neurologic symptoms consistent with demyelination, other
than recurrent optic neuritis, lasting more than 24 hours that were
confirmed by the presence of a new neurologic abnormality on
examination.16
Neurologic disability was assessed using
the Expanded Disability Status Scale (EDSS).17
Each
patient was classified as follows: no CDMS, CDMS with EDSS < 3,
or CDMS with EDSS
3.
Between April 1996 and March 1997 (58 years from study entry), the 51-item field-test version of the NEIVFQ was included as part of the testing at the annual examination of 244 patients who had a study visit during this 1-year period at one of the study clinical centers. The major reason for noninclusion of patients (for 167 [78%] of the 213 nonincluded patients) was that they did not have a visit at a study clinic in the time window in which the NEIVFQ was administered: 13 of the patients had moved and had ongoing follow-up by a nonstudy ophthalmologist, 50 patients discontinued follow-up before the inclusion of the NEIVFQ, and 104 were still in follow-up but did not have a visit during the 12 months it was administered (visit window for annual visits spanned 16 months). Forty-six (22%) patients had an examination at a study clinic during the time window of the NEIVFQ but did not complete the NEIVFQ; we did not collect data on whether the patient refused or the clinic neglected to give the questionnaire to the patient to complete. The 213 patients who were not included were similar to the 244 who were included in gender (75% versus 79% female, P = 0.31) but were slightly younger in age at the time of entry into ONTT (mean 31 ± 6 versus 33 ± 7, P < 0.01) and were slightly less often white (82% versus 88%, P = 0.05).
To ease the implementation of the NEIVFQ in the study, the questionnaire was self-administered. Clinic staff described the questionnaire and how it was to be completed. This was reiterated in written instructions, which preceded the questions.
Subscales, scored 0 to 100 (with 100 indicating highest function), were generated for overall health, overall vision, difficulty with near vision activities, difficulty with distance vision activities, limitations in social functioning due to vision, role limitations due to vision, dependency due to vision, mental health symptoms due to vision, future expectations for vision, driving difficulties, limitations with peripheral and color vision, and pain or discomfort in or around eyes. For analysis, when one or more items from a subscale were missing, the subscale was considered missing. Analyses using all available data (i.e., a subscale score was generated when the subject responded to one or more items from the subscale) provided similar results (data not shown). In addition to the 51-item field test version of the NEIVFQ, we calculated scores for the 25-item version and present limited results using this abbreviated version.
Statistical Methods
For each NEIVFQ subscale, we computed a mean and SD, as well as
level-specific mean values and standard deviations by gender, race
group, occupation, and the 3-level ordered categorical variables for
MS/neurologic disability and visual acuity in the two eyes. We assessed
the mean differences in these ordered categorical variables by a test
for trend, as well as using ANOVA with Dunnetts multiple comparisons
test, which compares each successive level to the
lowest.18
Due to the skewed distributions for the clinical
visual function measures, Spearmans rank correlation coefficient,
rs,19
was used to assess
the association of these measures with the NEIVFQ subscales for the
better eye. Internal consistency reliability was assessed with
Cronbachs alpha (
)20
for each multi-item subscale.
All analyses were carried out using SAS version 6.1221
on
a UNIX platform.
| Results |
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With the exception of the NEIVFQ expectations subscale, scores among the recovered optic neuritis patients were generally lower than a disease-free comparison group (Table 3) . This disease-free comparison group consisted of 75 women and 47 men with a mean age of 59 (±14) years who were seen for a screening dilated eye examination or correction of refractive error.7 The majority of NEIVFQ subscales showed more dysfunction with increased neurologic disability, with the majority of the probability values for trend < 0.01 (Table 4) . For the majority of the subscales demonstrating a significant trend, the association was driven by the highest category of neurologic disability. This is demonstrated by the significant Dunnetts multiple comparison test (which compares each category to the lowest disability group, Table 4 ). Similar trends were observed between several NEIVFQ subscales and the combined visual acuity variable, with the majority of the probability values for trend < 0.01 (Table 4) . However, the ocular pain, social, and expectations subscales did not demonstrate a linear trend with the combined visual acuity variable. For the combined visual acuity variable, there was no distinct pattern of the associations being driven by the highest category of visual dysfunction.
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= 0.46), all multi-item subscales demonstrated a moderately
strong internal consistency reliability (general health,
=
0.87; general vision,
= 0.74; ocular pain,
= 0.72;
near activities
= 0.89; distance activities,
= 0.89;
social functioning,
= 0.91; mental health,
= 0.90;
role difficulties,
= 0.90; dependency,
= 0.92;
driving,
= 0.86). The average reliability over the 10
multi-item subscales (omitting the visual expectation subscale) was
0.86.
Abbreviated 25-Item NEIVFQ
The 25-item abbreviated version of the NEIVFQ correlated well
with the full 51-item field test version. Spearman rank correlations
between the two versions were as follows: general health = 0.94;
general vision = 0.84; near activities = 0.96; distance
activities = 0.95; social functioning = 0.96; mental
health = 0.92; role difficulties = 0.96; dependency =
0.88; driving = 0.90. The ocular pain, color, and peripheral
vision subscales are equivalent on the two versions. The internal
consistency reliability attenuated slightly, with an average
coefficient alpha of 0.78 for the eight computable subscales. The
coefficient alphas for the 25-item version were as follows: ocular
pain = 0.72; near activities = 0.85; distance activities = 0.73; social functioning = 0.78; mental health = 0.82; role
difficulties = 0.75; dependency = 0.92; driving = 0.65.
Coefficient alphas are not available for the single-item subscales
(general health, general vision, color, and peripheral vision).
We assessed the usefulness of the abbreviated NEIVFQ by
comparing the rank correlations between this abbreviated version and
the clinical visual function measures to those found with the 51-item
NEIVFQ field test version. In short, the abbreviated version provided
remarkably similar rank correlations (data not shown), only
distinguishable by very slight attenuation on some subscales for some
of the clinical measures.
| Discussion |
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Self-reported dysfunction was greater when MS was present and when visual acuity was abnormal, supporting the construct validity of the NEIVFQ. Internal consistency reliability was high for most of the subscales. However, correlations between the NEIVFQ subscales and clinical measures of visual function were moderate at best.
The ability of the NEIVFQ to distinguish among the subgroups based on
visual acuity in both eyes was impressive, considering that even when
visual acuity was reduced in both eyes it was generally only a mild
decrease (30 of the 38 with visual acuity worse than 20/20 in both eyes
had acuity
20/40 in each eye and only 3 had acuity worse than
20/40 in each eye). The fact that most of the patients had normal or
only mildly abnormal measured visual function may have attenuated the
correlations between the NEIVFQ subscales and the clinical measures
of visual function. The only two subscales that appeared to be
uninformative with respect to the clinical measures of visual function
were the ocular pain and the vision expectations subscales. Because
optic neuritis was not active at the time of completion of the
NEIVFQ, the ocular pain subscale would not be expected to be
meaningfully associated with severity of disease. Furthermore, that
these subscales are unrelated to visual function does not imply that
the subscales do not capture important independent information that may
be predictive of future disease. The vision expectations subscale also
performed poorly in another recent test of the psychometric properties
of the NEIVFQ.7
The results must be considered in the context of the characteristics of the patients who were included in the study. The subset of included patients appears to be representative of the full ONTT cohort. Although statistically those included were slightly older and more often white than those excluded, the magnitude of the differences was small and not consequential. Patients entered into the ONTT were experiencing their first episode of optic neuritis in the study eye (although the fellow eye could have had prior optic neuritis) and either did not have MS or if it was diagnosed it had not been treated (which in effect excluded patients who had more than minimal MS at the time of entry). Visual recovery from optic neuritis occurs fairly rapidly, with almost all recoverable vision achieved in the first few months after the episode of optic neuritis. Thus, when the NEIVFQ was administered, 5 to 8 years after study entry, the episode of optic neuritis at enrollment was long resolved. During this period, a substantial proportion of the patients had developed MS (45%) and many (27%) had experienced at least one recurrence of optic neuritis. Even when either of these had occurred, there was generally no or only mild neurologic disability at the time of NEIVFQ completion, and, as indicated above, visual function in both eyes was usually determined to be normal or near normal.
Gutierrez et al.8 reported on the influence of glaucomatous visual field loss on HRQL among 147 glaucoma patients and 44 normal-vision reference subjects and found that greater visual field defect (as measured by the Advanced Glaucoma Interventional Study score) in the better eye was significantly associated with lower NEIVFQ subscale scores, with correlations in the -0.2 to -0.35 range. As can be expected, our estimates among recovered optic neuritis patients were weaker, ranging from 0.12 for rank correlation between visual field and the NEIVFQ near activities subscale to 0.23 for the rank correlation with the general vision subscale. Gutierrez et al. also reported internal consistency reliabilities ranging from 0.67 (expectations subscale) to 0.93 (distance vision subscale), with 9 of the subscales greater than 0.78, similar to our findings. Parrish et al.9 also reported on the HRQL among these same 147 glaucoma patients, finding Pearson correlations as large as -0.60 between the NEIVFQ subscales and Humphrey visual field, and as large as -0.61 between the NEIVFQ subscales and the AMA visual acuity impairment score. Our largest rank correlation was between visual acuity and the NEIVFQ general vision subscale (-0.30).
Mangione et al.7 reported on the psychometric properties (reliability and validity) of the NEIVFQ among 598 patients with 1 of 5 chronic eye diseases (age-related cataracts, age-related macular degeneration, diabetic retinopathy, primary open-angle glaucoma, and cytomegalovirus retinitis) or low vision from any cause. Internal consistency reliability estimates range from 0.66 (expectations) to 0.94 (near vision), with the majority greater than 0.70, again similar to our results among recovered optic neuritis patients. There was a trend toward lower mean NEIVFQ subscale scores among cataract and low vision patients compared with the normal-vision reference group, similar to our finding of lower mean NEIVFQ subscale scores among those with greater MS disability or combined visual acuity.
Although we used the 51-item field-test version of the NEIVFQ, similar results were observed when we computed scores for the 25-item abbreviated version of the NEIVFQ. Our findings add support for the use of the NEIVFQ as a valuable measure of self-reported visual impairment. Although it is unlikely that the NEIVFQ will have use for diagnosing optic neuritis or determining how it should be treated, it nevertheless has value for patient management by providing the clinician with a comprehensive overview of a patients functioning in everyday life.
| Acknowledgements |
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| Footnotes |
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Submitted for publication April 27, 1999; revised August 27 and October 21, 1999; accepted October 27, 1999.
Commercial relationships policy: N.
Corresponding author: Roy W. Beck, Jaeb Center for Health Research, Suite 9, 3010 E. 138th Avenue, Tampa, FL 33613. rbeck{at}jaeb.org
| References |
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