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UTILITY VALUES ASSOCIATED WITH BLINDNESS IN AN ADULT POPULATION

Tyson, Sydney L. MD

Socioeconomic Studies
Free

Wills Eye Hospital, Jefferson Medical College

Philadelphia, PA

Brown M, Brown G, Sharma S, Kistler J, Brown H. Utility values associated with blindness in an adult population. Br J Ophthalmol 2001;85:327–331.

Original study reprint requests: Melissa M. Brown, Center for Evidence-Based Health Care Economics, Suite 210, 1107 Bethlehem Pike, Flourtown, PA.

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Research Objective

To ascertain utility values associated with varying degrees of legal blindness.

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Study Design

A cross-sectional study on three groups of patients.

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Locations

Retina Vascular Unit, Wills Eye Hospital, Jefferson Medical College, Philadelphia, PA.

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Funding Source

Supported in part by the Retina Research and Development Foundation, Philadelphia.

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Relevant Methodology

A cross-sectional study on three groups of patients. There were (i) 15 patients with complete absence of vision (no light perception) in at least one eye who were asked to assume a scenario of no light perception in the second eye as well, (ii) 17 patients with light perception to counting fingers in the better-seeing eye, and (iii) 33 patients with 20/200–20/400 vision in the better-seeing eye. Utility values were measured using the time trade-off and standard gamble methods in each of the three groups.

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Results

  1. The mean time trade-off utility value for the no-light-perception group with the theoretical scenario of bilateral absence of light perception was 0.26 (95% CI, 0.196–0.33). Thus, patients with no light perception in one eye, who were presented with the same scenario in the second eye as well, were willing to trade almost 3 of every 4 years of remaining life in return for perfect vision in each eye.
  2. The mean utility value for the light-perception to counting-fingers group was 0.47 (95%, CI 0.33–0.61), and the mean utility value for the 20/200–20/400 group was 0.65 (95% CI 0.58–0.72). Those with light perception to counting fingers would trade approximately 1 of 2 remaining years and those with 20/200–20/400 would trade approximately 1 of 3 remaining years
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Conclusions

There is a wide range of utility values associated with legal blindness. The utility value decreases dramatically with perceived total loss of vision (absence of light perception in each eye), compared with counting fingers to light perception vision, indicating that the preservation of even small amounts of vision in patients with legal blindness is critically important to their well-being and functioning in life.

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Comment

As clinicians, we are able to qualitatively recognize the severe impact legal blindness can have on the quality of life for such patients. What we may not have recognized is the profound difference in the perception of life quality within stratified groups of legally blind patients. Using utility analysis, this study attempts to quantitate the functional impact of varying degrees of blindness on the lifestyle and well-being of affected patients. The study reveals that there are clear differences in the perception of the quality of life depending on the severity of visual loss. Within the stratified study groups, patients with more severe visual loss in one eye had a greater fear of total loss of vision in the other eye and were willing to trade more of their remaining years of life in return for perfect vision in each eye. In short, as the vision in the better-seeing eye decreases, so does its corresponding utility value.

In evaluating this study, it is important to recognize possible study weaknesses:

  1. As the authors point out, the sample groups were not subdivided based on length of visual disability. The length of time with visual disability affects utility value. The longer a patient has a profound visual disability, the lower the utility value and perceived quality of life.
  2. The study points out that the type of disease causing legal blindness has little influence on utility values. One can't help but wonder if other factors such as age, level of education, gender, race, and other associated systemic comorbidities impact utility values. Perhaps a larger study using multivariate analysis could elucidate the impact of these factors.
  3. Although we realize that utility values allow better comparisons between different nonophthalmic disease states, it would be interesting to see how utility value analysis compares to vision-targeted questionnaires such as the VF-14 or VFQ when investigating the functional status and quality of life of patients with varying degrees of legal blindness.

The conclusions of this study make it clear that we cannot place a single utility value on legal blindness because there is a dramatic range of utility values (0.26 to 0.65) associated with varying degrees of legal blindness. As clinicians, we should not discount the substantial impact even a small improvement in visual acuity can have on the quality of life for our legally blind patients.

As an aside, the authors are also to be commended for their contribution in quantifying utility values for specific ophthalmic diseases that can cause legal blindness. 1,2 Once quantified, one can, for example, determine the change in utility value conferred by interventional therapy. In other words, does a particular therapy lead to an improvement in the quality of a patient's life? This type of valuable information has broader health care policy implications in that it creates a mechanism by which one can determine and justify the allocation of limited resources for disease-specific prevention and intervention strategies.

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References

1. Brown GC, Sharma S, Brown MM, et al. Utility values and age-related macular degeneration. Arch Ophthalmol 2000; 118:47–51.
2. Brown MM, Brown GC, Sharma S, et al. Utility values and diabetic retinopathy. Am J Ophthalmol 1999; 128:324–30.
© 2002 Lippincott Williams & Wilkins, Inc.