Determination of Prevalence of
Diabetic Retinopathy & its
Relationship to Duration and the age
of Onset of Diabetes
Ashish Thapar, Neeraj Arora, Saramma
Jaison, SK Chopra
INTRODUCTION
Whilst pouring our knowledge and
efforts into the curing of the sick
let us not forget that our social
conscience would be better served by
preventing the sickness. With this
statement in mind the dedicated
ophthalmologist should make it a
part of this practice to participate
in research of the preventable cause
of blindness.
There is
an apparent epidemic of diabetes
amongst adult population of
disadvantaged communities, both in
developing countries and also in the
industrialized world. For every
patient who is known to have
diabetes, another has the disease
unawares (Diabetes 2000 Project
Leaflet, 2000). Thyle, Negrel,
Pararajasegram and Dadzie, (1995),
in their analysis of WHO Global Data
bank on Blindness, said that the
survey data on diabetic retinopathy
as cause of blindness is too limited
to reach an accurate figure.
However, it does seem that blinding
diabetic eye disease is now the 4th
major cause of blindness worldwide,
after cataract, glaucoma and
trachoma. Diabetes Mellitus (DM) is
one of the leading causes of
blindess in the industrialized
countries. It accounts for 10% of
all new cases of blindness in the
USA (Kahn & Hiller, 1974). In India,
the prevalence of retinopathy in
diabetic patients has been reported
from4-28% and a 6.7% prevalence of
retinopathy in patients of NIDDM at
initial diagnosis of diabetes.
The
affluent urban population of Punjab
which has a high rate of DM is a
vulnerable group with a high risk of
developing retinopathy. This study
was therefore, undertaken to find
out the prevalence of diabetic
retinopathy in this high risk group
and determine its relationship with
duration and age of onset of DM.
MATERIAL AND METHODS
This study was conducted on diabetic
patients attending the diabetic
clinic in the Department of
Medicine, Christian Medical College
and Hospital, Ludhiana from April
1st 1999 to March 31st 2000.
The
following patients were excluded
from the study: Patients in whom
dilatation of the pupil is contra
indicated e.g. angle closure
glaucoma. patients with hazy media,
thus impairing visualization of the
fundus e.g. macular/leucomatous
corneal opacities and cataracts.
Small children (10 or less years of
age) because of lack of cooperation
needed for funds visualization.
A
detailed history was elicited from
the patients as per the protocol. A
comprehensive ophthalmological
examination was carried out. Visual
acuity for distance and near vision
was recorded using Snellen's chart
and using near vision chart
respectively. Anterior segment
examination was done with slit lamp
biomicroscope and gonioscopy with
goldmann's three mirror gonioscope
to detect neovascularisation of
iris. Intraocular pressure was
recorded with applanation tonometer.
The
pupils of both eyes were dilated
with 5-10% Phenylephrine or 1%
Tropicamide and/or 1% Cyclopentolate
eye drops to achieve maximum
pupillary dilatation. Phenylephrine
was avoided in patients with history
of systemic hypertension. A
detailed fundus examination of both
eyes was made with binocular
indirect ophthalmoscope using +20D
condensing lens and also with
biomicroscopic indirect method using
+90D Volk's lens. Typical diabetic
retinopathic changes in patients
were documented with fundus
photographs and fluorescein
angiography.
Classification of diabetic
retinopathy was made according to
Modified Airlie House Classification
(Hykin PG 1996) as follows:
a) Mild
Non-Proliferative Diabetic
Retinopathy
b)
Moderate Non-Proliferative Diabetic
Retinopathy
c)
Severe Non-Proliferative Diabetic
Retinopathy
d) Very
Severe Non-Proliferative Diabetic
Retinopathy
e)
Proliferative Diabetic Retinopathy
f)
Maculopathy/Clinically significant
Macular Oedema
For
statistical analysis, Chi square
test was used for comparing the
numbers and percentages. Analysis of
vAriance (Anova) was used to
calculate means. Student's t-test
and F statistics were used for the
above purpose. Non parametric
statistics (Mann-Whitney) and
Kruskas-Wallis 'H' - Statistics were
used wherever required, especially
where the distribution of data was
not uniform.
The
prevalence of diabetic retinopathy
was calculated and its relationship
to duration of diabetes and the age
of onset of the disease was derived
and tabulated.
RESULTS
Various studies conducted in India
and abroad have reported variable
prevalence of diabetic retinopathy.
Khosla,
Tiwari & Bajaj
1976
4-28%
Khosla
et al 1976 (Referral retinal
clinic) 79.5%
Kahn and
Bradley,
1975
25%
Shanna
1996 (South Indian diabetic
patients) 37%
In the
present study the prevalence of
diabetic retinopathy was calculated
to be 41.6%. The prevalence of
diabetic retinopathy in the present
study was expectedly, found to be
higher than that amongst the studies
in South Indian Population and also
more than that seen in most other
studies.
Relationship between Prevalence of
Diabetic Retinopathy and Duration of
diabetes:
Both
longitudinal and cross sectional
studies show that duration of
diabetes mellitus is an excellent
predictor of diabetic retinopathy.
The
Wisconsin Epidemiological study on
diabetic retinopathy, 1984 found
that in patients with insulin
dependent diabetes melliltus,
prevalence of diabetic retinopathy
varied from 2% in patients with < 2
years of diabetes to 98% in patients
with 10 or more years of diabetes.
In a study amongst diabetic patients
in the Joslin Clinic, 1975, the
prevalence of diabetic retinopathy
was 7% in patients with diabetes for
<10 years, 26% in patients with 10
to 14 years of diabetes and 63% in
patients with diabetes for 15 or
more years.
In a
study among patients with noninsulin
dependent diabetes mellitus, Yanko
et al (1983), found that the
prevalence of diabetic retinopathy
11 to 13 years after the onset of
diabetes was 26% and after 16 or
more years, it was 63%.
In India
Mohan, Vijayprabha and Roma, (1996)
in their study of vascular
complications in South Indians with
non insulin dependent diabetes,
found that as the duration of
diabetes increased, the prevalence
of diabetic retinopathy also
increased. After 25 years of
diabetes the prevalence of diabetic
retinopathy was found to be 52%.
The
present study made the following
observations:
|
Duration |
Prevalence of Diabetic
Retinopathy |
|
<6 months |
3.4% |
|
7-12 months |
25% |
|
<1-5 years |
30% |
|
6-10 years |
58% |
|
11-20 years |
68.3% |
|
>20 years |
80% |
It was
hence concluded that as the duration
of diabetes mellitus increased, the
prevalence of diabetic retinopathy
also increased (P<0.05).
It has
also been seen in various studies
that the prevalence of more severe
grades of diabetic retinopathy
increases as the 'duration of
diabetes increases. Sharma (1996)
found that no retinopathy was found
in patients with mean duration of
diabetes 4.8 years or less.
Background diabetic retinopathy was
found in patients with mean duration
of diabetes 9.4 years,
preproliferative diabetic
retinopathy in patients with mean
duration of diseases 10.4 years and
proliferative diabetic retinopathy
in patients with mean duration of
diabetes 12.4 years.
In the
present study the following
observations were made:
1.
The prevalence of all grades of
diabetic retinopathy increased as
the duration of diabetes increased.
|
Duration of diabetes |
Proliferative Diabetic
retinopathy |
|
7-12 months |
0% |
|
<1-5 years |
2.3% |
|
6-10 years |
6.6% |
|
11-20 years |
11.7% |
Thus it
was seen that there was a
significant relationship between the
duration of diabetes and severity of
diabetic retinopathy (p<0.05). The
prevalence of clinically significant
macular oedema in different studies
was compared and its relationship to
duration of diabetes studied.
Gupta
and Chandrasekhar, (1998), reported
that as the duration of diabetes
increased, the risk of developing
clinically significant macular
oedema also increased.
The
following observations were made in
the present study:
1.
Prevalence of clinically significant
macular oedema in the population
group studied was 8.8% (22/250).
2. Of
the 22 patients with clinically
significant macular oedema, the
frequency was as follows:
|
Duration of diabetes |
Clinically significant
macular oedema
|
|
7-12 months |
4.5% |
|
<1-5 years |
18.2% |
|
6-10 years |
31.8% |
|
11-20 years |
45.5% |
From the
above observations, we can conclude
that the risk of developing
clinically signifiant macular oedema
increases significantly as the
duration of diabetes increases
(0<0.5).
Relationship between Prevalence of
Diabetic Retinopathy and age of
onset of Diabetes:
According to the Wisconsin
Epidemiological Study of Diabetic
Retinopathy 1989 the older onset
diabetic patients with less than 2
years of disease had higher rates of
diabetic retinopathy (25% in those
taking insulin and 20% in those not
taking insulin) than among younger
onset diabetic (2%).
Jerneld
and Peep, (1986), found that the
highest prevalence of diabetic
retinopathy was found amongst
patients with age of onset of
diabetes less than 20 years and the
lowest when diabetes was diagnosed
after the age of 60 years. Also,
prevalence of proliferative diabetic
retinopathy was 28% in patients with
age of onset of diabetes less than
20 years and 5% in patients with age
of onset more than 60 years. Caird
et al (1969), however estimated that
the risk of blindness for a given
duration of diabetes increases with
the age of the patient at the time
of diagnosis of disease.
Thus we
can see that there have been
discrepancies in the prevalence of
diabetic retinopathy according to
the age of onset of diabetes in
different studies.
The
present study made the following
observations;
-
The
prevalence and severity of
diabetic retinopathy is highest
when the age of onset of
diabetes is 20 years or less.
This result is similar to that
found in Wisconsin
Epidemiological study of
diabetic retinopathy, 1989.
However, the number of such
patients was only 10 out of 250,
hence this result cannot be
statistically significant.
-
Prevalence and severity of
diabetic retinopathy in patients
with age of onset of diabetes 21
years or more increase as the
age of onset of diabetes
increases.
-
Relationship between age of
onset of diabetes and clinically
significant macular oedema was
not found to be significant.
-
Other risk variables studied
were:
-
Gener- for a given duration of
diabetes no significant
relationship existed between sex
and prevalence of diabetic
retinopathy.
-
Treatment: 80.4% patients on
irregular treatment had diabetic
retinopathy only, 34.2% patients
on regular treatment had the
same (p<0.05). Also, it was
found that patients on insulin
or combined treatment were at a
greater risk of developing
retinopathy than on oral
hypoglycaemics alone.
-
Positive family history, d)
Hypertension and e) diabetic
nephropathy were found to be
strongly associated with the
prevalence and severity of
diabetic retinopathy.
CONCLUSION
Of the 250 patients examined, 104
had diabetic retinopathy. The
prevalence of diabetic retinopathy
was hence calculated to be 41.6%
which is higher then that found in
most other studies, leading us to
conclude that the urban population
of Punjab is indeed at a
considerably higher risk of
developing diabetic retinopathy.
The
prevalence of diabetic retinopathy
was seen to increase as the duration
of diabetes increased.
Prevalence of diabetic retinopathy
was found to be high in patients
with age onset of diabetes 20 years
or less (60%). All these patients
had insulin dependent diabetes
mellitus. From the age of onset of
diabetes 21 years onwards, the
prevalence of diabetic retinopathy
gradually increased as the age of
onset increased.
However,
it was also seen that the increase
in prevalence and severity of
diabetic retinopathy was much
steeper with increasing duration of
diabetes than with increase in age
of onset of diabetes. Duration of
diabetes mellitus therefore, remains
the best predictor of prevalence and
severity of diabetic retinopathy.
Patients
with 11-20 years duration of
diabetes and age of onset of
diabetes 31-40 years were seen to
have the highest prevalence of
diabetic retinopathy and hence form
a high risk group, which required
regular monitoring.
We would
like to emphasis that ignorance of
patients about diabetes and its
complications was identified as the
most important contributor towards
higher prevalence of diabetic
retinopathy.
Patient
education, physician and primary
health care personnel orientation,
application of research,
comprehensive ophthalmological
examination, mass media utilization
and prompt referrals would go a long
way in curbing the menace of this
blinding diabetic eye disease.
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Address for Correspondence
Dr.
Ashish Thapar, Deptt. of
Ophthalmology,
Christian Medical College, Ludhiana
