Vol.14
No. 1, Januray, 2004
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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-
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Address
for Correspondence
Dr.
Ashish Thapar, Deptt. of Ophthalmology,
Christian Medical College, Ludhiana
