PREVALENCE OF DIABETIC RETINOPATHY IN A PRIMARY CARE SETTING USING DIGITAL RETINAL IMAGING TECHNOLOGY
Keah Say Hien FRACGP, Elizabeth Medical Centre, Muar,
Chng Kooi Seng FRACGP AM, Klinik Chng, Johor Bahru, Johor.
The advantages of digital retinal imaging were many. Firstly, the image can be viewed immediately and when the image is not clear another can be taken. Secondly, there is increased comfort to the patient compared with the closed-up viewing in routine ophthalmoscopy. The intensity of the flash is much less discomforting. Three-quarters of our patients do not need mydriatic eyedrops. Thirdly, the images can be stored for further review, consultation and comparison with another image at a later date. Finally the potential for patient education is great. As the saying goes, a picture paints a thousand words. After viewing the photograph personally, the patient can be made aware that changes have begun to occur in his eyes. He can then be made to understand that these changes may not be permanent, as lesions like microaneurysms, blot haemorrhages, hard and soft exudates come and go and that attempts should be started without delay to improve glycaemic and blood pressure control. Every 1% reduction in updated mean HbA1C was associated with reduction in risk of 37% for diabetic retinopathy (UKPDS).6 Despite the advantages, there is a need for validation studies to demonstrate the equivalence in diagnostic quality of digital images produced by individual systems compared with the gold standard 35 mm photography. On top of that, the sensitivity and specificity of the system will be affected by the skills of the provider in reading the images. Chia SY and co-worker showed that the use of retinal photographs to screen for diabetic eye disease achieved a high sensitivity by capturing diabetic retinal lesions and was comparable to an examination performed by the ophthalmologist.7
Epidemiological study of diabetic retinopathy in Malaysia is still lacking. Mafauzy reported in a primary care setting, presumably by direct ophthalmoscopy, 23.5% of the studied population had background retinopathy and 5.3% had advanced eye disease.8 To our knowledge, there are no published studies from Malaysia using retinal photography. The high prevalence of diabetic retinopathy in our study was of great concern, especially the significantly high rates of STED, but perhaps not too surprising in view of the equally alarming high prevalence of diabetic nephropathy in Asian Type 2 diabetes reported in the Microalbuminuria Prevalence Study.9 It was also noted that good vision was found in the majority of patients in our study. Only 12% of the respondents had visual acuity of 6/12 or worse in the better eye but approximately 3 times of that (40.8%) had STED. Hence many of the diabetics may not be inclined to seek early treatment for diabetic retinopathy.
The new international grading system used in the study is a more evidence-based approach to the classification of the disease and it incorporates data found in excellent trials such as the ETDRS and the WESDR. The main classification looks at the visible vascular events from the earliest changes (i.e. microaneurysms) to the blot haemorrhages, venous beading, intraretinal microvascular abnormalities (IRMA) and finally the advance preretinal and vitreous haemorrhages. The second part looks at the problem of exudative maculopathy which consist of macular hard exudates and macular oedema. It should be noted that macular oedema can only be appreciated if the digital imaging system has stereoscopic capabilities. However, the best method for looking at retinal thickening is still by indirect ophthalmoscopy or slit-lamp biomicroscopy. It is important also to note that any stage of diabetic retinopathy can be associated with diabetic macular oedema based on the findings of hard exudates. We realise that the classification was based on “dilated ophthalmoscopy” but our retinal photography was taken through the undilated pupils (in most patients). Since the camera we used was able to capture a clear central view of the fundus in the majority of cases, we think further dilatation of the pupils is unnecessary. Generally speaking, we find that the classification has assisted us in the early referral of STED to the specialists.
The prevalence of diabetic retinopathy in our community is predictably high. Early identification and treatment of diabetic retinopathy through screening is a cost effective strategy for improved health care in diabetic populations.10 Digital retinal imaging has offered a new range of imaging possibilities with comparable sensitivity and specificity as the gold standard. Thus avenues exist for more organised screening and referral programme in our country.
We would like to thank the Malaysian Primary Care Research Group (MPCRG) for their guidance and encouragement. We thank our clinic assistant, Miss Chng Hui Kian for secretarial help.
- Wilson C, Horton M, Cavallerano J, Aiello LM. Addition of primary care-based retinal imaging technology to an existing eye care professional referral program increased the rate of surveillance and treatment of diabetic retinopathy. Diabetes Care. 2005 Feb;28(2):318-22 [PubMed] [Full text]
- Klein R, Klein BE, Moss SE, et al. 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. [PubMed]
- Wilkinson CP, Ferris FL 3rd, Klein RE, et al. Proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. Ophthalmology. 2003 Sep;110(9):1677-82 [PubMed]
- Early Treatment Diabetic Retinopathy Study Research Group. Fundus photographic risk factors for progression of diabetic retinopathy. ETDRS report no 12. Ophthalmology. 1991 May;98(5 Suppl): 823-33 [PubMed]
- Aiello LM, Cavallerano J, Cavallerano A, et al. The Joslin Vision Network innovative telemedicine care for diabetes: preserving human vision. Ophthalmol Clin North Am. 2000:13(2):213-24 [Link]
- Stratton IM, Adler AI, Neil HAW, et al. Association of glycemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. BMJ. 2000 Aug 12;321(7258):405-12 [PubMed] [Full text]
- Chia SY, Yap EY. Comparison of the effectiveness of detecting diabetic eye disease: Diabetic retinal photography versus ophthalmic consultation. Singapore Med J. 2004 Jun;45(6):276-9 [PubMed] [Full text]
- Mafauzy M. Diabetes control and complications in private primary healthcare in Malaysia. Med J Malaysia. 2005 Jun;60(2):212-217 [PubMed]
- Wu AYT, Kong NCT, De Leon FA, et al. An alarming high prevalence of diabetic nephropathy in Asian type 2 diabetic patients: the Microalbiminuria Prevalence (MAP) Study: Diabetologia. 2005 Jan;48(1):17-26 [PubMed]
- Javitt JC, Aiello LP, Chiang Y, et al. Preventive eye care in people with diabetes is cost-saving to the federal government. Implications for health-care reform: Diabetes Care. 1994 Aug;17(8):909-17 [PubMed]