Issue 3: Diabetic Retinopathy (June 2011)

Welcome

Professor Michael Kalloniatis, Director
Diabetes is the fastest growing chronic disease in Australia. Around 275 people develop the disease every day. Whilst nearly one million Australians are currently diagnosed, it is estimated that another 1.2 million are living with the disease but don’t know it yet.

All of these people are at-risk of vision loss due to diabetic retinopathy (DR), a serious ocular condition which can occur regardless of the type of diabetes, age or blood glucose levels.

Optometrists are now expected to identify and manage patients with early DR, although this can be challenging because patients can be asymptomatic, with good visual acuity.

Advanced imaging techniques, such as optical coherence tomography (OCT), are increasingly being utilised to ensure the earliest possible detection and to monitor changes over time.

Unfortunately, however, such state-of-the-art instrumentation is not accessible for many people in our community, who can suffer irreversible vision loss because of delays in diagnosis and intervention.

CFEH is here to assist in such cases, providing advanced imaging and assessment, at no-charge. The additional information helps you to appropriately triage patients, and establishes a baseline to monitor changes over time. The patient does not incur unnecessary fees, but can be referred to a specialist if and when it is required.

We encourage all optometrists to offer appropriate patients a referral to CFEH.

Prof. Michael Kalloniatis

Centre Director

WHO TO REFER

CFEH is a no-charge advanced imaging and assessment service most suitable for patients who are:

  • At-risk or suspected of eye disease, or who require ongoing monitoring of a known condition; and
  • Financially or geographically disadvantaged (e.g. low-income earners, pensioners or those in remote or low-serviced areas).

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Case Report

Monitoring progression of diabetic retinopathy

Carol, a 60-year-old female, with a nine-year history of Type 2 diabetes, was referred to Centre for Eye Health (CFEH) and diagnosed with mild to moderate non-proliferative diabetic retinopathy. At the four-month follow up with her optometrist, Carol said that her blood glucose control had deteriorated due to stress. During her dilated eye examination, the optometrist noticed an increased number of intraretinal haemorrhages and a small decrease in best-corrected visual acuity to 6/7.6 in each eye. As a result, Carol was referred back to CFEH for further evaluation.

Issues to consider

1. Which instruments are useful in monitoring the progression of diabetic retinopathy?

2. What are the established risk factors for progression of diabetic retinopathy?

Results and Discussion

Figure 1: Right macula at baseline (A) and at follow-up (B) showing a mild increase in the number of intraretinal haemorrhages within the macula.
Figure 1: Right macula at baseline (A) and at follow-up (B) showing a mild increase in the number of intraretinal haemorrhages within the macula.
Figure 1: Right macula at baseline (A) and at follow-up (B) showing a mild increase in the number of intraretinal haemorrhages within the macula.
Figure 2: Left macula at baseline (A) and at follow-up (B) showing a slight increase in the number of intraretinal haemorrhages within the macula.
Figure 2: Left macula at baseline (A) and at follow-up (B) showing a slight increase in the number of intraretinal haemorrhages within the macula.
Figure 2: Left macula at baseline (A) and at follow-up (B) showing a slight increase in the number of intraretinal haemorrhages within the macula.

At Carol’s second appointment at CFEH, retinal photography showed a mild increase in the number of intraretinal haemorrhages in the posterior pole of each eye (Figures 1A, 1B, 2A and 2B) and partial resolution of a larger blot haemorrhage in the inferior macula of the right eye.

Figure 3: Cystoid spaces (white arrows) in the outer nuclear layer and intraretinal haemorrhage (red arrow) in the inner retina within the inferior macula of the right eye.
Figure 3: Cirrus OCT images of the lesion on the left optic nerve (A identifies location of OCT image, B cross-section showing highly reflective nature of lesion and shadowing).

Line scans through the inferior macula of the right eye revealed intraretinal cystoid spaces approximately 1000µm from centre of the fovea, consistent with early diabetic macular oedema (Figure 3). There were no signs of macular oedema in the OCT images obtained of the left eye.

Figure 4A: Cirrus Macular Change Analysis (right eye) shows thickening of the central and inner inferior subfield compared with baseline.
Figure 4B: Cirrus Macular Change Analysis (left eye) shows thickening of the central and parafoveal subfields compared with baseline.
Figure 4A: Cirrus Macular Change Analysis (right eye) shows thickening of the central and inner inferior subfield compared with baseline.
(View larger version of Figure 4A)
Figure 4B: Cirrus Macular Change Analysis (left eye) shows thickening of the central and parafoveal subfields compared with baseline.
(View larger version of Figure 4A)

A Macular Thickness Change Analysis was conducted using the Cirrus OCT. It revealed that in the right eye, there was an 8µm increase in the patient’s central ETDRS (Early Treatment Diabetic Retinopathy Study) subfield between CFEH appointments. There was also a 12µm increase in the inner inferior subfield, corresponding to the area of cystoid macular oedema (Figure 4A).

Advanced imaging techniques such as OCT are particularly useful in the early diagnosis of vision-threatening The left eye also demonstrated a 16µm increase in the central subfield at follow-up (Figure 4B).

The absence of cystoid spaces in the left eye is consistent with a more diffuse macular oedema, affecting the majority of the macular ETDRS subfields.

Carol was referred to a retinal specialist to assess and consider treatment options.

She also returned to her endocrinologist and diabetes educator for assistance with improving her glycaemic control.

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Eye Condition Spotlight: Diabetes

Diabetic retinopathy (DR) is one of the leading causes of blindness in working-aged adults.

Current National Health and Medical Research Council (NHMRC) management guidelines recommend that patients with Type 1 or Type 2 diabetes have a dilated fundus examination (DFE) at the time of diagnosis, and at least every two years thereafter.

In higher-risk patients, such as those with sub-optimal blood glucose or blood pressure control, it is recommended that a DFE take place at least every year(1).

In Australia, only 50% of people with diabetes are managed in accordance with these recommendations, and around 33% have never had a DFE at all(2).

Managing patients with early signs of diabetic retinopathy is within the scope of practice of optometrists. These patients should be examined every 3-12 months depending on the level of non-proliferative DR.

NHMRC guidelines recommend urgent referral to an ophthalmologist if there is any unexplained decrease in visual acuity, any suspicion of diabetic macular oedema or proliferative DR.

Figure 5: Eyes of three individual patients (A, B, C) with diabetic macular oedema presenting with 6/6 entering visual acuity.
Figure 5: Eyes of three individual patients (A, B, C) with diabetic macular oedema presenting with 6/6 entering visual acuity.
Figure 5: Eyes of three individual patients (A, B, C) with diabetic macular oedema presenting with 6/6 entering visual acuity.
Figure 5: Eyes of three individual patients (A, B, C) with diabetic macular oedema presenting with 6/6 entering visual acuity.

In its early stages, diabetes affects the inner retina. This means that significant retinopathy may be present in an asymptomatic patient with good visual acuity (Figures 5A, 5B, 5C).

Advanced imaging techniques, such as optical coherence tomography (OCT), are particularly useful in the early diagnosis of vision-threatening macular oedema that may be difficult or sometimes impossible to detect with ophthalmoscopy.

Systemic risk factors for the onset and progression of DR in patients with both Type 1 and Type 2 diabetes include longer duration of diabetes(3), (4, 5), systemic hypertension(6), elevated serum lipid levels(7), renal disease and pregnancy(8).The results of a recent Australian study suggest that obesity is also an independent risk factor for DR(9).

Multiple studies have shown that more intensive blood glucose control, based on measurements of glycosylated haemoglobin A1c (HbA1c), can reduce the risk of diabetes-related eye complications. The Diabetes Control and Complications Trial (DCCT) demonstrated for patients with Type 1 diabetes that intensive blood glucose control reduced the rate of development of DR by 76%, the progression of DR by 54% and the need for laser photocoagulation surgery by 56%.

The United Kingdom Prospective Diabetes Study (UKPDS) demonstrated similar findings in patients with Type 2 diabetes and also confirmed the importance of optimal blood pressure control on reducing the progression of retinopathy. After 8.4 years of follow-up, it was found that patients with good blood pressure control had a 34% reduction in progression of retinopathy.

As a result, optimal management of diabetes and comorbid conditions is essential to minimise the risk of diabetes-related vision loss. The general practitioner (GP) is central to the diabetes care team and is supported by a range of health care practitioners, which may include an endocrinologist, nephrologist, optometrist, ophthalmologist, diabetes educator, dietician, podiatrist, dentist and exercise physiologist.

It is important that optometrists understand their role in the multidisciplinary diabetes team and communicate the eye exam findings directly to their patient’s GP.

This edition prepared by Paula Katalinic, Principal Optometrist.

Names and details of patients have been changed to protect privacy.

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INSTRUMENT PROFILE

Using The Optomap P200MA

Optomap P200MA

Optomap P200MA
In early 2010, Centre for Eye Health (CFEH) published a profile of the three optical coherence tomographers (OCTs) that are on-site. Since this time, the Spectralis OCT has been upgraded and now offers some significant additional features.

OCT is used to obtain cross-sectional images of the retina, but imaging of deeper tissue structures, such as the choroid, is often difficult(1) due to pigment from the Retinal Pigment Epithelium (RPE) and light scattering from the dense vascular structure of the choroid(2).

Enhanced Depth Imaging (EDI) is a new imaging modality(3) on the Spectralis OCT that provides an enhanced visualisation of the choroid (Figure 1). The EDI mode is particularly useful for imaging pigmented lesions in the choroid such as naevi and melanomas.

The Posterior Pole Asymmetry Analysis is a new function of the Spectralis software that combines mapping of the posterior pole retinal thickness with asymmetry analysis between eyes and between hemispheres of each eye(3).

Click here for full profile >>

See entire equipment list for the Centre >>

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Next Issue

Detection, diagnosis and management of optic nerve head drusen in a 39-year-old Caucasian female.

More issues of Image >>

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References

  1. National Health and Medical Research Council. Guidelines for the Management of Diabetic Retinopathy, 2008.
  2. Eye Research Australia and Access Economics. Clear Insight Report, 2004.
  3. Klein R, Klein BE, Moss SE, Davis MD, DeMets DL. The Wisconsin epidemiologic study of diabetic retinopathy. III. Prevalence and risk of diabetic retinopathy when age at diagnosis is 30 or more years. Arch Ophthalmol. 1984 Apr;102(4):527-32.
  4. The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The New England Journal of Medicine. Sept 30, 1993 No. 14, Vol 329.
  5. UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet. 1998 Sep 12;352(9131):837-53. Erratum in: Lancet 1999 Aug 14;354(9178):602.
  6. UK Prospective Diabetes Study Group. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes: UKPDS 38. BMJ. 1998 Sep 12;317(7160):703-13. Erratum in: BMJ 1999 Jan 2;318(7175):29.
  7. Chew EY, Klein ML, Ferris FL 3rd, Remaley NA, Murphy RP, Chantry K, Hoogwerf BJ, Miller D. Association of elevated serum lipid levels with retinal hard exudate in diabetic retinopathy. Early Treatment Diabetic Retinopathy Study (ETDRS) Report 22. Arch Ophthalmol. 1996 Sep;114(9):1079-84.
  8. Aiello LP, Cahill MT, Wong JS. Systemic considerations in the management of diabetic retinopathy. Am J Ophthalmol. 2001 Nov;132(5):760-76.
  9. Dirani M, Xie J, Fenwick E, Benarous R, Rees G, Wong TY, Lamoureaux EL. Are Obesity and Anthropometry Risk Factors for Diabetic Retinopathy? The Diabetes Management Project (DMP).Invest Ophthalmol Vis Sci. 2011 Apr 11. [Epub ahead of print]

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Disclaimer: This newsletter is not intended to provide or substitute advice through the appropriate health service providers. Although every care is taken by CFEH to ensure that this newsletter is free from any error or inaccuracy, CFEH does not make any representation or warranty regarding the currency, accuracy or completeness of this newsletter.

Copyright: © 2011, Centre for Eye Health Limited. All images and content in this letter are the property of Centre for Eye Health Limited and cannot be reproduced without prior written permission of the Director, Centre for Eye Health Limited.

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