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VOLUME 7 NUMBER 3 • SEPTEMBER 2010
Various studies have investigated the relationship between diabetic
retinopathy and glucose control in diabetics. These include the Diabetes
Control and Complications study and the UKPDS.
12,13
Both these studies
demonstrated that initially, when tight blood sugar control was instituted,
the proliferation worsened, but after one year the outcome was better in
those with tight control. There is inevitably a group of patients that will
continue to worsen. This is referred to as retinopathic momentum.
Starting a screening programme for diabetic retinopathy
The non-mydriatic
camera
The advantage of this camera is that there is no waiting time for the test
and the patient is able to drive immediately afterwards. The risks of dilata-
tion are small but significant.
There are numerous studies comparing the efficacy of identifying dia-
betic retinopathy (DR) using photography through a dilated pupil, indirect
fundoscopy through a dilated pupil and photography through an undilated
pupil. These studies indicate that photography through the undilated pupil
is comparable as a screening tool.
14-16
These studies, however, used cameras that are no longer manufactured
and the results may have compared even more favourably if current tech-
nology had been used. In one of the studies, no patients were missed who
needed urgent referral for laser or surgery for treating proliferative DR. In
the absence of macular exudates or haemorrhages, macular oedema may
be difficult to identify but in the above study no patients were missed due
to concurrent retinopathy needing referral.
15
The camera should be used in a dark room to optimise the natural dilata-
tion of the pupil but with adequate lighting to ensure quick thoroughfare of
thepatients.Patients should ideally be in thedark roomor adarkenedwaiting
area for at least a minute prior to the testing. The minimal pupil size is be-
tween 3.2 and 3.8 mm and this allows one to take 45-degree photographs
of the retina. Some models have an internal fixation device, which enables
one to make a collage of the retina extending further into the periphery.
Any dense opacities of the media in front of the retina would preclude
the use of the camera. The most common of these is cataract but may in-
clude corneal opacities and vitreous haemorrhage. It may not be possible
to take photographs in those with pinpoint pupils. In one large study it was
not possible to take images due to small pupils and media opacities in
7% of patients.
14
If the photographer is also trained as a reader/screener
these problems may be identified at the time of imaging.
Modern cameras are digital, which allows one to view images in real
time. The images can be viewed, repeated if improvement in image qual-
ity is possible, and read at the screening centre, or stored and sent to a
distant reading centre on an appropriate storage device or via the Internet.
There are commercially available packages to send many images in a
compressed format. These one can buy with the camera.
In California there is a non-propriety-based Internet system called EYE-
PACS, which allows for the distant reading of photographs.
16
There are also
various commercially available proprietary-based systems. These systems
have security measures to allow controlled access and patient privacy.
Photographers and readers
The staff that are trained for these tasks should preferably not be medical-
ly qualified. Screening programmes would create a new career direction
for interested people. A programme would have to be created to train and
certify the personnel. For example, in the USA the EYEPACS system re-
quires photographers to take 10 photographs of readable quality in order
to be certified. They also offer a training programme where photographs
are sent in and suggestions are made to improve the quality.
For each patient screened as part of EYEPACS, four photographs are re-
quired. One photograph is an external image to verify the size of the pupil,
the presence of cataract and corneal clarity. The other three photographs
are retinal and include one centred on the disc, a second including the
macula and disc, and the third includes the macula and the temporal retina.
One proposed model is that the photographers be trained to also read
the images. The alternative would be for eye specialists to perform the
screening. One would have to set up local guidelines for referral and fol-
low up. The grading of diabetic retinopathy for a screening programme
could be devised as part of a pilot project so that the most pragmatic
system is adopted. This would have to take into consideration the limited
human resources and other constraints in South Africa. The grading for a
screening programme would differ considerably from the ETDRS grading
since the photographs would be different and it would be a screening test.
A screening programme would employ a considerable number of peo-
ple if it were decided to train personnel for this task. In the south-west
region of the UK a screening programme was proposed which would serve
a population of 4.9 million people. This programme would employ 21 pho-
tographers/screeners if their only tasks were to take photographs and
screen patients.
17
If their work included education, the number of staff
would increase to 30 people.
A follow-up and referral pattern
A question that could only be answered by a pilot project is whether the
ophthalmology services in a specific region would be able to manage the
increased workload. For example, in the region of South Africa where I
lived, there is a large Indian population. Among the Indian people in this
region, the prevalence of diabetes is 15%. This percentage is much higher
than the prevalence quoted from the literature for developed nations.
The majority of patients would be referred for cataracts and retinopathy.
SA JOURNAL OF DIABETES & VASCULAR DISEASE
Hands On
