Diabetes in primary care optometry
PhD.BSc.FCOptom.FAAO.DipCLP.DipClinOptom.
Diabetic care forms an increasingly important part of general optometric practice with optometrists in some areas of the UK, and indeed across the world in the USA, Canada, Australia and some EC countries such as the Netherlands, examining the majority of diabetics seen for their eye care.
In certain Area Health Authorities in the UK there are formal "Shared Care" schemes where the optometrist is paid an additional fee for just carrying out fundoscopy on diabetics.
1% of the 60 million population in the UK suffers from Diabetes. The prevalence increases with age to 3 to 4% of the population over the age of 40 years.
Norway, with a population of 4.5 million inhabitants has approximately 130,000 people with diabetes. This amounts to some 2.9% of the population. About 0.45% have IDDM and 1.8% suffer from NIDDM. It is estimated that a further 0.65% of the population are undiagnosed.
In the UK there are 1500 new cases of blindness per year.
Non-Insulin Diabetes Mellitus (NIDDM)
These patients can survive without exogenous insulin although many eventually require insulin to improve control. The prevalence in the UK is approximately 1% in UK and in Norway 1.8 %.
The prevalence in elderly and some groups in the UK, for example Asian communities are higher at around approximately 3 to 5%.
The prevalence in Lima Indians of Arizona is reportedly 50%.
Migrants to western world seem to be particularly susceptible.
NIDDM is correlated with a combination of relative insulin deficiency and insulin resistance. The latter may be exacerbated by obesity.
There is a strong genetic predisposition with twin concordance for NIDDM being 90% compared to only 40% for IDDM.
NIDDM accounts for about 75 to 80% of the diabetic population.
NIDDM gives high risk of macrovascular complications and usually presents as a syndrome of anomalies including hypertension, hyperlipidaemia, obesity, and insulin resistance.
Very often optometrists will hear from their patient that " I have a just a little sugar" or "I have mild diabetes". In fact, there is no such thing as "mild diabetes". Whatever the control required, if not adhered to, the disease will lead to retinal and other damage.
Insulin-Dependent Diabetes Mellitus (IDDM)
These patients cannot survive without insulin. In the UK the prevalence is about 0.2% with an incidence of 15/100,000/year aged < 21. Most cases present before 30 years and there is a peak incidence at 11-13 years.
A possible cause is destruction of the β cells of the Islets of Langerhans perhaps through an autoimmune response.
Retinopathy is unusual before puberty and usually only presents after at least 10 years.
Mortality in < 50 age group is about 5 x higher than non-diabetics.
Ocular manifestations of diabetes
Although we often think of retinal changes, it must not be forgotten that other parts of the eye and visual system may be affected including the anterior segment with changes occurring to the iris and lens. Changes in the iris include micro aneurysms and neovascularisation, the latter leading to a secondary glaucoma.
The classic "diabetic snowflake cataract" that occurs in acute diabetes is rarely seen. If the patient is swiftly treated, the cataract substantially resolves. Diabetics tend to develop prematurely age related lens changes.
The optometrist is often the first person to suspect diabetes in a patient because of apparent fluctuations in refraction, along with reported symptoms of an unusual thirst and possible a general feeling of malaise or repeated illnesses.
The visual pathway may be affected in a variety of ways with, for example, haemorrhages producing visual field defects. Similarly diabetics are more prone to suffering lesions of the ocular motor system with consequent gaze palsies and incomitant strabismus.
Retinal signs may be categorised into:-
Let us look at each of these.
Background diabetic retinopathy
This manifests as:
Pre-proliferative diabetic retinopathy
This manifests as
Proliferative diabetic retinopathy (PDR)
The term proliferation describes the appearance of "new vessels" or "neovascularisation". These vessels emanate from retinal venules..
These vessels are fragile and are prone to bleed into the sub-hylaoid space, giving
It is necessary to dilate diabetics’ and before doing so the optometrist should check the anterior chamber angle with the slit lamp (Van Herrick technique) and, if the angle appears narrow, with gonioscopy.
Drugs of choice to dilate are the anti-muscarinic, Tropicamide 0.5% or 1% and
The sympathomimetic, phenylephrine hydrochloride 2.5%. These can be used synergistically to produce maximum dilatation.
However, patients with advance diabetic disease, with signs such as peripheral neuropathy, may be "super-sensitive" to sympathomimetics. Phenylephrine should be avoided in these cases because of the risk of adversely affecting the cardiovascular system.
As a rule, the optometrist should check the systemic blood pressure of all patients over 40 years of age before using phenylephrine.
Advantages of indirect versus direct ophthalmoscopy
The best way of examining the diabetic fundus is with a slit lamp lens such as the
Volk 66, 70 or 90 D or with contact fundus lens. The direct ophthalmoscope may be used but really is quite inferior.
Whilst the direct opthalmoscope gives a field of view of about 10 degrees, this compares with the better field of view around 120 degrees with some slit lamp fundus lenses. Similarly indirect provides stereopsis and better illumination.
Retinal photography is also invaluable for screening for and recording changes.
Guidelines of the European Working Party for Screening for diabetic retinopathy
Informing the GP & Diabetic Physician
In the UK it is mandatory to write a report the patient’s GP following an eye examination. A copy sent to the diabetic physician will be useful/.
It should be remembered that although ophthalmological attention may not be necessary, modifications to the general diabetic regime of therapy are sometimes required.
Dr Simon Barnard
e-mail sb@eye-spy.co.uk
January 2002