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Unilateral
visual impairment in rural south India–Andhra Pradesh Eye Disease Study (APEDS)
Srinivas
Marmamula1,2,3, Rohit C Khanna1,2,3, Gullapalli N Rao1
1Allen
Foster Community Eye Health Research Centre, Gullapalli Pratibha Rao-International Centre
for Advancement of Rural Eye care, L V Prasad Eye Institute, Hyderabad 500034, India
2Brien
Holden Eye Research Centre, L V Prasad Eye Institute, Hyderabad 500034, India
3School
of Optometry & Vision Science, University of New South Wales, Sydney, New South Wales 2033, Australia
Correspondence
to: Srinivas Marmamula. Allen Foster Community Eye Health Research Centre, Gullapalli
Pratibha Rao-International
Centre for Advancement of Rural Eye care, L V Prasad Eye Institute, Road No.2, Banjara Hills,
Hyderabad 500034, India. srioptom@lvpei.org
Received: 2015-07-13
Accepted: 2015-09-25
Abstract
AIM:
To report the prevalence and causes of unilateral visual impairment (UVI) in
rural population of all ages in rural Andhra Pradesh, India.
METHODS:
A population-based cross sectional study
using a multi-stage cluster sampling methodology was carried out in West
Godavari, Adilabad and Mahbubnagar districts in south India. A comprehensive
eye examination that included presenting and best corrected visual acuity and
dilated fundus examination was conducted by trained professionals. UVI is
defined as presenting visual acuity ＜6/18
in one eye but ≥6/18
in other eye. Multiple logistic regression analysis was used to test
association of UVI
with socio-demographic risk factors.
RESULTS:
Data were analyzed for 6634/7771 participants after excluding those with
bilateral visual impairment. The mean age of the participants was 27.4y (standard deviation:
17.9y), 51.9%
were women and 49.1% were educated. The prevalence of UVI was 7.8% (95% CI: 7.2%-8.5%). Uncorrected
refractive error (60.8%), cataract (17.4%) and retinal causes (6.6%) were the
leading causes of UVI. On multiple logistic regression analyses, older age, not
having education, living in well-off district had significantly higher odds of
being associated with UVI. UVI was not associated with gender.
CONCLUSION:
UVI is common in rural south India. Most
of it is due to cataract and refractive errors, both of which can be addressed
at primary and secondary levels of eye care. Burden of UVI should also be
considered in planning eye care services.
KEYWORDS:
visual impairment; cataract; refractive errors; India; Andhra Pradesh Eye Disease
Study
DOI:10.18240/ijo.2016.05.23
Citation: Marmamula
S, Khanna RC, Rao GN. Unilateral visual impairment in rural south India–Andhra Pradesh Eye
Disease Study (APEDS). Int J Ophthalmol 2016;9(5):763-767
INTRODUCTION
Globally, over 32.4
million people are blind and another 191 million people have moderate to severe visual
impairment (VI)[1].
India is the home of over 8.3 million people with VI, the highest number in
the world. Typically these VI estimates are based on definition using
presenting visual acuity and/or visual field in the better eye; hence those
with unilateral VI
(UVI) are missed out in these estimates. The use of better eye in VI definitions
underestimates the true burden of VI in a given population. Studies have
shown the impact of UVI on visual function and health related quality of life
in different settings[2-3]. Studies have also
shown the benefits of second eye cataract surgery[4-8]. Data that
include both unilateral and bilateral VI would provide complete spectrum of VI in a given region.
The Andhra Pradesh Eye
Disease Study (APEDS) I was a large epidemiological study that was conducted
between 1996 and 2000 in which 10 293 participants were examined from one
urban and three rural locations in the south Indian state of Andhra Pradesh.
This study found the prevalence of 1.84% and 8.09% for blindness and moderate
VI respectively[9-10]. A review of major
findings from this study was reported[11]. This study also reported a
prevalence of UVI
of 3.8% in urban population of all ages where UVI was defined as
presenting distance visual acuity ＜6/18
in the worse eye and 6/12 or better in the better eye[12].
During 2010-2011, a feasibility study
(APEDS II) was carried out to assess the availability of the participants
examined in 1996-2000[13]. The results from this study
revealed that over 70% of the participants from the original cohort were
available in rural clusters and were willing to participate in a follow-up
study. However the participants from the urban cohort could not be traced due
to significant infrastructural changes. This feasibility study also found that
mortality is associated with VI[13]. As over 70% of the participants examined in
the initial cohort in rural areas were available, a follow-up study of the
surviving cohort was initiated in June 2012 (APEDS III) to understand the incidence
and progression of VI
in the surviving cohort. In this paper we report the prevalence and causes of
UVI in rural population aged ＞15y
in Andhra Pradesh, India, from the APEDS I as a baseline for the
follow-up study (APEDS III) that is currently being carried out. The urban data
on prevalence of UVI is published[12].
SUBJECTS
AND METHODS
The study protocol was
reviewed and approved by Institutional Review Board of L V Prasad Eye
Institute, Hyderabad, India. The study followed the tenets of the Declaration
of Helsinki. All the participants provided written informed consent for
participating in the study. Data collection was accomplished from 1996 to 2000.
Details of the study
protocol and the findings of the APEDS were reported elsewhere[14]. In brief, a multi stage systematic cluster
random sampling methodology was used to select a representative sample from
three rural locations (West Godavari, Adilabad and Mahbubnagar districts) in
Andhra Pradesh[14]. Adilabad and Mahbubnagar
districts are now in the newly formed state of Telangana. The comprehensive eye
examination was conducted by trained professionals. The detailed eye
examination protocol is published elsewhere[14]. The
data collection included personal and socio-demographic details such as age, gender,
education, area of residence. In short, the clinical examination included
presenting distance and near visual acuity assessment using a logarithm of
minimum angle of resolution (logMAR) chart under standard testing conditions.
Best corrected visual acuity was recorded after refraction. Detailed anterior
segment assessment was conducted using a slit lamp biomicroscope. Fundus
examination through dilated pupils was done on all participants unless
contraindicated.
UVI is defined
presenting visual acuity worse than 6/18 in one eye but better than 6/18 in
other eye. Those with bilateral VI were excluded from analysis. UVI is included
moderate UVI (＜6/18 to 6/60) and
unilateral blindness (＜6/60).
A second definition of
UVI is also used to compare the prevalence estimates of this study with the
earlier published urban segment of the same study. As per this, UVI was defined
as presenting distance visual acuity ＜6/18
in the worse eye and 6/12 or better in the better eye[12].
Statistical Analysis Data
were analyzed using Stata statistical package for windows version 12 software.
Univariate analysis was done using a chi-square test. Multiple
logistic regression models were used to examine the association between UVI and
risk factors such as age, gender, education and area of residence.
Hosmer-Lemeshow goodness of fit test was used to assess the goodness of the
model fit. The odds ratio (OR) with 95% confidence intervals (CI) is presented. The
prevalence estimates were adjusted for the age and gender distribution of the
population of the three districts in year 2001.
RESULTS
Characteristics
of the Study Participants Data
were analyzed for 6634 participants after excluding those with bilateral VI.
The mean age of the participants was 27.4y (standard deviation
17.9y; ranged ＜1y to 90y), 44% (n=2922) participants were older than
30y, 51.9% (n=3443) were women, 50.9%
(n=3377) had no formal education.
About 31.5% (n=2091) participants
were from West Godavari district, 36.0% (n=2391)
from Adilabad and 32.4% (n=2152) were
from Mahbubnagar district.
Prevalence
of Unilateral Visual Impairment The
prevalence of UVI was 7.8% (n=518; 95% CI: 7.2%-8.5%), which included
unilateral blindness in 152 participants (2.3%; 95% CI: 2.0%-2.7%) and moderate UVI in
366 participants (5.5%;
95% CI: 5.0%-6.1%). The crude prevalence
of UVI stratified by age groups, gender, education and area of residence are
presented in Table 1. On univariate analysis, UVI was higher in older age
groups (P＜0.01), among those with no formal
education (P＜0.01), those residing in West Godavari
district (P＜0.01). The UVI was not associated with
gender (P=0.593).
Table
1 Characteristics
of the participants and prevalence of UVI (univariable analysis) n
(%)
|
Parameters |
Participants |
Prevalence of UVI |
P |
|
Age
groups (a) |
＜0.01 |
||
|
＜15 |
2178 |
27 (1.2) |
|
|
16-29 |
1359 |
27 (2.0) |
|
|
30-39 |
1358 |
78 (5.7) |
|
|
40-49 |
899 |
109
(12.1) |
|
|
50-59 |
489 |
114
(23.3) |
|
|
60-69 |
291 |
122
(41.9) |
|
|
≥70 |
60 |
41
(68.3) |
|
|
Gender |
0.593 |
||
|
M |
3191 |
255
(8.0) |
|
|
F |
3443 |
263
(7.6) |
|
|
Education |
＜0.01 |
||
|
Any education1 |
3257 |
210
(6.4) |
|
|
No education2 |
3377 |
308
(9.1) |
|
|
Area of
residence |
＜0.01 |
||
|
West Godavari |
2091 |
199
(9.5) |
|
|
Adilabad |
2391 |
170
(7.1) |
|
|
Mahbubnagar |
2152 |
149
(6.9) |
|
|
Total |
6634 |
518 (7.8) |
UVI: Unilateral visual
impairment. %: Row percentages presented; 1Any education is
defined as attending at least primary school among those aged 5y and older; 2Includes
597 participants who were aged ≤5y on whom data on education was not
collected.
On multivariable analysis,
the odds of having UVI were higher in among those older than 30y compared to less than
30y age group. While gender showed no significant association (P=0.593), having no formal
education had higher OR for UVI (OR: 1.3; 95% CI: 1.0-1.6; P=0.02). Compared to relatively well-off, West Godavari
district, participants in poorer regions such as Mahbubnagar and Adilabad had a
lower odds (OR: 0.7; 95% CI: 0.6-0.9; P＜0.01) and (OR: 0.8; 95% CI: 0.6-1.0; P=0.03)
respectively (Table 2).
Table
2 Effect of demographic variables on UVI by multiple logistic
regression analysis
|
Parameters |
Odds ratio (95% CI) |
P |
|
Age groups (a) |
||
|
≤30 |
1.0 |
|
|
＞30 |
8.5 (6.4-11.2) |
＜0.01 |
|
Gender |
||
|
M |
1.0 |
|
|
F |
0.9 (0.7-1.1) |
0.29 |
|
Education |
||
|
Any education |
1.0 |
|
|
No education |
1.3 (1.0-1.6) |
0.02 |
|
Area of residence |
||
|
West Godavari |
1.0 |
|
|
Adilabad |
0.8 (0.6-1.0) |
0.03 |
|
Mahbubnagar |
0.7 (0.6-0.9) |
＜0.01 |
Hosmer-Lemeshow test
for goodness of fit for the regression model: P=0.66, variance inflation factor for the
multiple logistic regression model:
P=1.23.
Using the definition
two for UVI,
the prevalence of UVI was 3.6% (n=239; 95% CI: 3.2%-4.1%), which included
unilateral blindness in 106 participants (1.6%; 95% CI: 1.3%-1.9%) and moderate UVI in
133 participants (2.0%;
95% CI: 1.7%-2.4%).
Causes
of Unilateral Visual Impairment Table
3 shows the causes of UVI by categories of VI. Refractive errors
were the leading cause of moderate UVI (82.2%); cataract was the leading cause
of unilateral blindness (43.4%).
Table
3 Causes of moderate UVI
and unilateral blindness n (%)
|
Causes of
UVI |
Moderate UVI |
Unilateral blindness |
All UVI |
|
Refractive error |
301
(82.2) |
14 (9.2) |
315
(60.8) |
|
Cataract |
24 (6.6) |
66
(43.4) |
90
(17.4) |
|
Corneal disease1 |
7 (1.9) |
22
(14.5) |
29 (5.6) |
|
Glaucoma |
0 (0.0) |
7 (4.6) |
7 (1.4) |
|
Amblyopia |
6 (1.6) |
11 (7.2) |
17 (3.3) |
|
Retinal disease2 |
18 (4.9) |
16
(10.5) |
34 (6.6) |
|
Others |
10 (2.7) |
16
(10.5) |
26 (5.0) |
|
Total |
366 (100) |
152 (100) |
518 (100) |
UVI: Unilateral visual
impairment. 1Corneal
disease includes corneal scars due to infection or trauma; 2Retinal
disease includes age related macular degeneration, other retinal degenerations
and other retinal conditions such as vascular occlusions.
Table 4 shows the main
causes of moderate UVI and unilateral blindness stratified by age, gender,
education and area of residence. While the proportion of causes of moderate UVI
and blindness varied across the age groups (P＜0.001), it was similar among the
genders, education status and area of residence.
Table
4 Main causes of moderate UVI
and unilateral blindness stratified by personal and demographic characteristics
of the study population
|
Parameters |
Moderate UVI |
Unilateral blindness |
||||||
|
(%, n=301) |
Cataract (%, n=24) |
Other causes (%, n=41) |
P |
Refractive error (%, n=14) |
Cataract (%, n=66) |
Other causes (%, n=72) |
P |
|
|
Age
groups (a) |
<0.001 |
0.001 |
||||||
|
＜40 |
64 |
1 |
34 |
11 |
21 |
68 |
||
|
41-59 |
90 |
3 |
7 |
10 |
54 |
36 |
||
|
≥60 |
81 |
16 |
3 |
7 |
58 |
35 |
||
|
Gender |
0.59 |
0.79 |
||||||
|
M |
83 |
7 |
10 |
9 |
41 |
50 |
||
|
F |
82 |
6 |
13 |
10 |
46 |
44 |
||
|
Education |
0.24 |
0.15 |
||||||
|
Any education |
77 |
10 |
14 |
12 |
35 |
53 |
||
|
No education |
85 |
6 |
9 |
12 |
35 |
53 |
||
|
Area |
0.87 |
0.41 |
||||||
|
West Godavari |
82 |
7 |
10 |
8 |
51 |
41 |
||
|
Adilabad |
83 |
5 |
12 |
7 |
43 |
51 |
||
|
Mahbubnagar |
81 |
7 |
12 |
15 |
35 |
50 |
||
UVI: Unilateral visual
impairment. %: Row
percentages presented.
DISCUSSION
UVI is common in rural
south India affecting eight out of every hundred individuals after excluding
those with bilateral VI. The reports on UVI are important as
several causes such as corneal scars post infectious keratitis, and other
consequences of trauma get excluded when VI definition are based on better eye
are used. For example, we found that corneal blindness contributed to over
14.5% in the unilateral blindness. Ocular trauma is also common and mostly
reported to be unilateral in this population[15].
Using a similar
definition, the prevalence of UVI in our study was similar to that reported
from urban population[12]. Similar
to bilateral VI, UVI
was more common in older age groups. This was expected as VI has been shown to
be associated with older age in earlier studies done elsewhere and in Andhra
Pradesh[9,10,16]. It is
possible that the older individuals do not seek eye care services for UVI due
to several barriers. A recent study from the same state has shown that “one
vision adequate and no need felt” were leading person-related barriers that
prevented people seeking services[17].
Contrary to bilateral
VI earlier reported from this study, we did not find an association between
gender and UVI both on univariable
and multivariable analysis[9-10]. The urban segment of this study that was
published earlier also did not find an association between gender and UVI[12]. The association between gender and VI are not
very consistent across the studies done in India. While few studies found a
positive association between VI and gender while other recent studies
did not find any association[9-10,16,18]. This could possibly be attributed to the regional
variations in availability and uptake of eye care services among women.
Education is often
linked with socio-economic status. We found a lower prevalence of UVI among
those with any education. This finding is similar to that of bilateral VI
earlier reported from the same state[19]. This may be due to higher
visual demands among those with any education; better economic status and then
seeking care to get rid of their VI. Lower prevalence of UVI in
comparatively poorer areas such as Mahbubnagar and Adilabad compared to
well-off West Godavari district was a surprise finding. Both the blindness and
moderate VI were also reported to be higher in this district[9-10]. This could be due to differences in life style
and family support structure in these districts. This phenomenon needs to be
investigated further.
Refractive errors were
the largest cause of UVI followed by cataract both of which can be corrected
using spectacles and surgery respectively. Refractive errors can be detected
and corrected at the primary eye care level such as vision centres while
cataract surgeries can be performed at secondary eye care facilities. Cataract
and refractive errors can also be detected through door to door surveys and
community screening programmes. Apart from development of infrastructure such
as vision centres and secondary centres, emphasis should also be laid on
increasing the awareness levels in the community, as recent studies have found
predominance of “person-related” barriers that prevent
the uptake of services. These may be applicable to UVI as well. One can presume
that barriers would be even more common in cases of UVI as impact of UVI is
comparatively less compared to bilateral VI.
Our study involved a
large representative sample and achieved a high response rate. A comprehensive
eye examination was conducted to ascertain the causes of VI. Our definition of UVI included only visual
acuity loss and not the visual field loss. This may have resulted in under
estimation of the prevalence of UVI. The results of the study reflect the
UVI
situation 16y ago and it is possible that the prevalence must have changed over
the years. Only the results from the APEDS III which is being carried can
provide insights in the incidence and progression of UVI in the state. In
conclusion, this paper supplements the earlier reports on bilateral VI and
urban component of UVI published earlier[9-10,12] and will be a
baseline for comparison of results from APEDS III.
ACKNOWLEDGEMENTS
The
authors acknowledge the contributions of Dr. Lalit Dandona and Dr. Rakhi
Dandona who conducted the detailed study and Prof. Hugh R. Taylor and Dr.
Catherine A. McCarty for their guidance in the study design. The authors thank
the participants of APEDS for their participation in the study. The authors
also thank the entire APEDS team including Dr. Pyda Giridhar, Dr. Kovai
Vilas and Mr.Mudigonda N. Prasad for their involvement in data
collection in the field. Dr. Sreedevi Yadavalli is acknowledged for her
language inputs on earlier versions of the manuscript.
Foundation:
Supported by Hyderabad Eye Research Foundation, India and Christoffel-Blindenmission
(CBM), Bensheim, Germany.
Conflicts of Interest: Marmamula S, None; Khanna RC, None; Rao
GN, None
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