Quality of Life Assessment in Diabetic
A BARBAZETTO, MD, & HOWARD F FINE, MD, MHSc
impairment due to diabetic retinopathy (DR) and other eye diseases is associated
with a significant decrease across all domains of quality of life (QoL). It has
an impact comparable to that of major medical conditions. Although the direct physical
impairment may be minor, the effect on the patient's psychological well-being can
be severe and the reduction of independence is often overlooked when assessing disability.1
Increasingly, researchers and clinicians
are trying to quantify the impact of DR and its treatments on patients' QoL. The
measurement of patient-reported health outcomes is a discipline aimed at exploring
the effect of disease on QoL from the patient's perspective.2 Health-related
quality of life (HRQoL) is how people's own health affects their satisfaction with
and enjoyment of living, including physical, psychological, and social functioning.
HRQoL offers information that is complementary to other biophysical measures in
evaluating the impact of disease on a patient and may aid not only in optimizing
patient care but also in allowing one to analyze the cost-effectiveness of various
HEALTH RELATED QUALITY
Studies commonly measure HRQoL
by means of utility value. Utility theory in health care sprang from economic theories
introduced by von Neumann and Morgenstern3 in 1944 to deal with quantification
of uncertainty and was later modified by Weinstein and Sasson4 in the
1970s to facilitate cost-effectiveness analysis in health care. A utility value
of 1 is defined as perfect health and 0 as death. Disease states fall somewhere
between 0 and 1. Several methods exist to measure health state preferences. Four
methods more commonly used are standard gamble, time trade-off, willingness to pay,
and rating scale methods.5
The standard-gamble method asks
patients how willing they would be to risk a worse health state in hopes of achieving
an improved health state. The time trade-off method asks how much life expectancy
in years they would give up for a better health state. The willingness-to-pay technique
asks subjects to evaluate their health state in monetary terms. Rating-scale methods
offer them graphical or numeric scales on which to rate their health state.
HRQOL FOR VISUAL DISORDERS
Utility values in ophthalmology
are usually highly correlated with the acuity of the better-seeing eye. Several
vision-specific HRQoL measures have been introduced over the years. Commonly used
tests include the Visual Functioning Index (VF-14) and the National Eye Institute
Visual Function Questionnaire (NEI-VFQ) and its variations.
The VF-14 is a functional assessment
14 questions designed to elicit how patients function with their
current vision. Here is an example of one question:
K Do you have any difficulty, even
A Reading small print such as labels
on medicine bottles, a telephone book, food labels?
A Writing checks or filling out
Respondents who answer affirmatively
must then rate the difficulty as "little," "moderate," "a great deal," or "unable
to do the activity." The VF-14 was validated for patients with retinal disease in
1999.6 It addresses functional limitations but does not specifically
elicit how visual decline affects patients' overall sense of well-being.
The NEI-VFQ investigates visual/functional
limitations and how they have an impact on a patient's overall social and emotional
functioning. This 51-item metric was validated in 1998 on patients with cataract,
macular degeneration, DR, glaucoma, cytomegalovirus retinitis, and low vision.7
The areas tested (number of questions) were: general health (2), general vision
(2), ocular pain (2), near vision (7), distance vision (7), vision-specific social
functioning (4), vision-specific mental health (8), expectations for visual function
(3), vision-specific role functioning (5), dependency due to vision (5), driving
(4), peripheral vision (1), and color vision (1). This comprehensive metric is commonly
employed in large ophthalmic trials. A drawback is that questionnaires with numerous
items can be unwieldy, time consuming, and expensive to administer.
to streamline the NEI-VFQ, a shorter version with 25 items was validated in 2001,
the 25-Item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). It
can be administered in 5 minutes.8 The Table shows a comparison of the
Brown and colleagues published
a 1999 study exploring the general relationship between QoL and vision loss from
DR using the time trade-off method. They found that the average person with 20/40
vision in the better-seeing eye was willing to trade 2 of every 10 years of life
in return for perfect vision (utility value of 0.8), while the average person with
counting fingers vision in the better eye was willing to trade approximately 5 of
every 10 years (utility value of 0.52) in return for perfect vision.9
Subsequent analyses in DR patients not only confirmed these findings but also
showed that these results were independent of gender, formal education, and duration
of visual loss. Notably, the utility value in this study directly depended on the
degree of visual loss due to the disease.10
Klein and colleagues examined the
association of the NEI-VFQ-25 questionnaire and diabetes-related symptoms and comorbidities
in patients with type 1 diabetes. In their study, lower total NEI-VFQ-25 scores
were independently associated with poorer visual acuity (VA), more severe retinopathy,
older age, a history of loss of tactile sensation, and more total pack-years of
cigarettes smoked.11 However, the association of lower scores in HRQoL
tests with severe visual impairment is not specific for DR. When they were stratified
for VA loss, DR and age-related macular degeneration seemed to have comparable visual
The assessment of QoL is test-dependent
but is also affected by environmental and socioeconomic factors. For example, the
loss of driving ability may have less impact in an environment with a supportive
infrastructure. Using the RetDQoL test, a diabetic-specific 4-phase iterative approach
incorporating qualitative and quantitative methods, European researchers demonstrated
that, although many patients were able to cope with and adjust to the loss of driving,
the concerns and worries of visual impairment due to diabetes had a significant
impact on QoL.13
The impact of visual impairment
is not only significant for QoL but also for life expectancy. A study by Knutdson
and colleagues showed that persons with visual impairment from DR had greater mortality
than persons without.14
HOW TREATMENTS AFFECT
Changes in QoL after intervention
for sight-threatening retinopathy have also been subject to investigation and the
results to date have been somewhat controversial. Tranos and colleagues evaluated
55 patients before and
3 months after focal photocoagulation for diabetic maculopathy.
Using the NEI-VFQ questionnaire, they found a significant improvement after treatment
in QoL associated with many aspects of vision and vision-related functions, such
as near and distance vision, vision-specific social functioning, vision-specific
mental health, and expectations for visual function and dependency due to vision.15
and colleagues conducted a cost-effectiveness analysis for grid laser treatment
for diabetic macular edema (Figure) based on the data of the ETDRS study group.
In their analysis, patients with a 40-year life expectancy experienced an increase
in QoL after laser treatment corresponding to an additional 3 months of life.16
More recently, Scanlon and colleagues
evaluated 240 patients with DR before and 2 weeks after laser photocoagulation.
They found a pronounced reduction of QoL after the first laser treatment but an
improvement as patients progressed to receive multiple treatments. This may be explained
by treatment-related diminution in visual field and from progression of disease.
Many patients felt that their expectations were met, but the treatment had less
of an impact than they had hoped for. Yet patients stated that they were willing
to repeat laser treatment if needed.17
It should be kept in mind that
poor vision often is correctable and visual recovery can reduce the risk for injury
and improve the QoL for diabetics. A recent study by the Centers for Disease Control
showed a prevalence of 7.2% of correctable visual impairment among US diabetics
aged 20 years or older. The authors conclude that the proper prescription for glasses
or contact lenses would have restored normal VA to 65.5% of visually impaired diabetics.18
To improve diabetic care and to
serve patients better, ophthalmologists will need to pay more attention to the patient's
perspective. Currently no data are available regarding QoL measures for surgical
interventions, injections of triamcinolone or anti-VEGF substances, or the use of
protein kinase C inhibitors. Detailed analysis could help not only to better address
patients' expectations but also to provide more individualized treatments. In the
future, newer and potentially less destructive treatments may aid us not only to
better control patients' diseases but also to better address their specific needs
and to improve their QoL. RP
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18. Correctable visual impairment
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A. Barbazetto, MD, and Howard F. Fine, MD, MHSc, are both ophthalmologists with
the E.S. Harkness Eye Institute at Columbia Presbyterian Hospital in New York. Dr.
Barbazetto can be reached at (212) 305-9535 or at firstname.lastname@example.org. The authors
have no financial interest in the topics discussed. This manuscript was supported
by the Heed Ophthalmic Foundation.
Retinal Physician, Issue: January 2007