May 13, 2021
Emily Y. Chew, MD1
Author
Affiliations Article Information JAMA Ophthalmol. Published online May 13, 2021.
doi:10.1001/jamaophthalmol.2021.0521
In
this issue of JAMA Ophthalmology, Flaxman et al1 reported the results of their
study designed to estimate the rates of visual acuity loss and blindness in the
US, including rates for each individual state. Prior published reports2,3 in 2010 and 2015 addressing this
issue used different data sets and statistical methodology, resulting in rates
for those 40 years and older only. Both studies2,3 suggested the number of
individuals older than 40 years affected with vision impairment was
approximately 4.2 million in the US. The results of the current study1 of the population of all ages
estimated the rate to be much higher, at 7.08 million people living in the US
with visual acuity loss, defined as 20/40 or worse, with 1.08 million of these
having blindness, defined as visual acuity of 20/200 or worse. These are
important data that need to be explored further.
Methods
The
current study1 analyzed a greater number of
studies, including the classic population-based studies and data from the US
Centers for Disease Control and Prevention’s Vision and Eye Health
Surveillance, which provide data on both national and state-specific rates of
visual acuity loss using insurance claims, registries of electronic health
records, and self-reported data from national surveys that included populations
of all ages and were stratified by race/ethnicity and sex. Flaxman et al1 recognized the importance of
analyzing more granular data found in state-reported rates because of the
differences found in population demographics and risk factors for visual acuity
loss, including comorbidities such as diabetes, health care access, social
determinants of health, and lifestyle factors, such as nutrition and smoking.
The
use of the bayesian meta-analysis methods in this study may be superior in
estimating between-study heterogeneity and pooled effects, especially when
there is a relatively small number of studies, as found by Flaxman et al.1 Summarizing using various sources
of data in a single meta-analysis is the innovative part of this approach. The
bayesian methods also allow the researchers1 to integrate prior knowledge and
assumptions when calculating the meta-analyses.
Other
Results
The
overall prevalence of visual acuity loss in the US was 7.08 (95% uncertainty
interval [UI], 6.32-7.89) million, translating to a crude prevalence rate of
2.17% (95% UI, 1.94%-2.42%).1 Not surprisingly, the prevalence
of visual acuity loss or blindness increased with age, from 0.74% (95% UI,
0.37%-1.10%) for those younger than 12 years, to 0.99% (95% UI, 0.80%-1.18%)
among those aged 50 to 54 years and 20.73% (95% UI, 17.71%-23.27%) among
persons 85 years and older. As expected, a range of rates of visual acuity loss
was found in different states. Interestingly, approximately 22.89% of those
with visual acuity loss or blindness were younger than 40 years. Similar to
previous analyses of the National Health and Nutrition Examination Survey data,
the current study1 estimated higher prevalence in
Black and Hispanic individuals compared with White individuals and women
compared with men. However, these probabilities of differences between sex and
race/ethnicity crossed zero and were not statistically significant.
Importance
of These Data
These
data1 underscore the burden of
blindness in the US. Visual acuity loss is considered one of the most dreaded
events that individuals in the US fear compared with loss of speech, hearing,
or memory.4 In addition, it is important to
obtain accurate prevalence and eventually incidence data on visual impairment
and blindness, because they have compelling public health implications. With
this large increase in the numbers of US individuals who will experience visual
acuity loss or blindness, we need to prepare to the health care systems to
serve affected individuals. These estimates will also help to promote potential
screening and public health education for select ocular diseases that have
effective therapies that may be given either as preventive therapy or active
treatment to preserve visual acuity.
Although
the study results1 were not statistically
significant, the trends are similar to other studies5 that have found women to have
increased burden of blindness. Data suggesting an increased rates of visual
acuity loss in women does elevate the alert level to consider conducting
important studies in assessing sex as a biological variable, as promoted by the
National Institutes of Health.6 Others have highlighted the
excessive burden on Black and Hispanic individuals,7 again similar to what was found
in this current study. The trends of these studies should serve as notice to
keep these issues central to future research.
If
indeed these rates are valid, 1 in 5 individuals with visual acuity loss
include those younger than 40 years. Although some might have uncorrected
refractive errors, for those with irreversible causes of blindness, it implies
a lifetime of vision burden. Again, the public health importance of this would
inform how to approach future investigations, such as screening.
Next
Steps
Some
of the limitations of this study1 include the lack of eye
examination–based data in some of the studies from which self-reports of visual
acuity loss were obtained. The collection of new, examination-based data on
best-corrected visual acuity in the better-seeing eye would offer a more
precise and comprehensive rate of visual acuity loss. Another limitation of
this study is the lack of diagnoses associated with visual acuity loss. This
was not a focus of this current meta-analysis. But knowing the main causes of
blindness would indeed be logical data to obtain to better understand the
burden of visual acuity loss.
The
classic population-based studies provided enormously important data on
prevalence and incidence of eye diseases and visual impairment by
race/ethnicity, sex, age, and other important risk factors. As noted by the
authors,1 these studies are now fairly
dated. The demographics of the population in the US have shifted markedly and
will continue to change over the next decades. The classic epidemiologic
studies may not be the answer. What would be the next appropriate step in the
studies of epidemiology of ocular diseases? No one researcher or institution
has the perfect solution to this problem. Perhaps collective brainstorming on
this topic may help us best design studies that can provide more precise
estimate of the burden of visual acuity loss, which remains an important concern
for US people. Guidance may also be provided by esteemed colleagues at the US
Centers for Disease Control and Prevention and their collaborators, who have
provided such important data on the public health importance of visual acuity
loss in the United States.
Corresponding
Author: Emily Y. Chew,
MD, Division of Epidemiology and Clinical Applications, National Eye
Institute/National Institutes of Health, 10 Center Dr, MSC 1204, Bldg 10, CRC
Room 3-2531, Bethesda, MD 20892-1204 (echew@nei.nih.gov).
Published
Online: May 13, 2021.
doi:10.1001/jamaophthalmol.2021.0521
Conflict
of Interest Disclosures: None
reported.
References
1.
Flaxman AD, Wittenborn JS, Robalik T, et al; the Vision and Eye Health
Surveillance System Study Group. Prevalence of visual acuity loss or
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