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Prospective Study (UKPDS)21 : Clinical has confirmed that good glycaemic control in Type 2 non-insulin dependent Findings and Management diabetes mellitus is also beneficial and delays the onset of retinopathy. 3. . Reports have indicated recent study of diabetic patients in Pakistan K Viswanath MS DO MSc that high diastolic blood pressure in indicated that and uncorrected Head of the Department of young individuals8 and higher systolic were more common causes blood pressures in older individuals 21 of than retinopathy.7 Osmania Medical College can worsen the retinopathy. The VISION 2020 protocol projects Deputy Medical Superintendent 4. Pregnancy in women can be associated diabetic retinopathy and the Regional Institute of Ophthalmology with worsening of the retinopathy. as the ‘emerging’ causes of blindness in Sarojini Devi Eye Hospital 5. Hyperlipidaemia. Some studies have developing countries. Hyderabad – 500 028 indicated that high levels of serum cho- Andhra Pradesh lesterol and/or triglycerides are signifi- Epidemiological Studies in Diabetic India cant risk factors for retinopathy. Retinopathy D D Murray McGavin However, it is yet to be clearly proved MD FRCSEd FRCOphth Epidemiological studies such as the that therapy to reduce serum lipids E d i t o r ,J o u r n a l o fC o m m u n i t y Ey e He a l t h Wisconsin Epidemiological Study on affects any retinopathy. Cigarette smok- Medical Director Diabetic Retinopathy,8 the Diabetic ing may or may not be an additional risk International Resource Centre Retinopathy Study (DRS),9,10,11 the Early factor as its effect on cardiovascular International Centre for Eye Health Treatment of Diabetic Retinopathy Study disease is well documented. London School of Hygiene and (ETDRS),12,13,14,15,16,17 the Diabetes Control 6. Age. In younger onset diabetes, diabetic Tropical Medicine, Keppel Street and Complications Trial (DCCT),18 the retinopathy is uncommon before the age London WC1E 7HT Diabetic Retinopathy Vitrectomy Study of 13 years. The onset of puberty may UK (DRVS), 19,20 and the UK Prospective influence retinopathy – although the Diabetic Survey 21 have established the duration of diabetes is a significant Diabetes Mellitus various risk factors and provided guide- factor. In those with older onset diabetes lines for the management of diabetic there is an increased frequency of Diabetes mellitus is a metabolic abnormal- retinopathy. retinopathy in those younger than 50 ity in which there is a failure to utilise glu- years. 7. Ethnicity. The variety of study designs cose and hence a state of hyperglycaemia General Risk Factors for Diabetic make comparisons difficult, but Afro- can occur. If hyperglycaemia continues Retinopathy uncontrolled over time, it will lead to American blacks do seem to have more significant and widespread pathological 1. Type of Diabetes and its Duration. retinopathy than whites. changes, including involvement of the Tables 1 and 2 show the relationships , brain and kidney. between the type, duration of diabetes Clinical Types of Diabetic In industrialised countries, approxi- mellitus and retinopathy. Retinopathy mately 1% of the population is diabetic, 2. Control of Diabetes Mellitus. The Clinical classification is as follows: and at least another 1% are undiagnosed Diabetes Control and Complications diabetics. Insulin dependent diabetes Trial (DCCT)18 has shown that in Type • Non-proliferative diabetic retinopathy (IDDM), accounts for approximately 10– 1 insulin dependent diabetes mellitus • Proliferative diabetic retinopathy. 15% of cases, the remainder being maturity (IDDM), good control of metabolic onset or non-insulin dependent diabetics status will reduce the risk of progression Non-Proliferative Diabetic Retinopathy (NIDDM). Diabetes mellitus is an interna- of diabetic retinopathy and delays the (NPDR) tional public health problem with estimated onset of retinopathy in patients who do prevalences ranging from 2.0% to 11.7% in not have retinal changes at the time of The lesions in the retina at this stage are studied populations across the world.1 presentation. The United Kingdom within the retina and include micro- aneurysms, small ‘dot and blot’ haemor- Prevalence of Diabetic Retinopathy rhages, ‘splinter’ haemorrhages, intrareti- Table 1: Any Retinopathy nal microvascular abnormalities (IRMA) Diabetic retinopathy is increasingly (Viswanath K, unpublished data) becoming a major cause of blindness and ‘cotton wool’ spots. < 2 years > 15 years The presence of these lesions in various throughout the world in the age group of IDDM 2% 95% 2,3,4 degrees determines whether the NPDR 20–60 years. Loss of productivity and NIDDM 10% 58% quality of life for the patient with diabetic is ‘mild’, ‘moderate’, ‘severe’ and ‘very retinopathy will lead to additional socio- severe’. economic burdens on the community. Diabetic retinopathy is the cause of 1. Mild Non-Proliferative Diabetic blindness in approximately 2.5 million of Table 2: Proliferative Retinopathy Retinopathy the estimated 50 million blind people in the (Viswanath K, unpublished data) At least one microaneurysm, and also dot, world. However, diabetic retinopathy, as a < 4 years > 15 years blot or flame-shaped haemorrhages in all cause of blindness, is less common in India IDDM 0% 26% four fundus quadrants. according to population-based studies.5,6 A NIDDM 3% 4%

Community Eye Health Vol 16 No. 46 2003 21 Diabetic Retinopathy

visual impairment. All these back- ground diabetic retinal changes are due to pathology occurring at the microvascular level of the reti- na, including dilatation of the cap- illaries, destruction of the capillary walls and closure of the capillaries resulting in hypoxia and micro- infarcts. The Early Treatment of Diabetic Retinopathy Study (ETDRS) classified patients who were given macular focal laser Fig. 1: Moderate non-proliferative diabetic therapy, based on whether ‘clini- Fig. 2: Diabetic retinopathy cally significant macular oedema’ Photo: K Viswanath Photo: K Viswanath was present or not.12,13,15 This was 2. Moderate Non-Proliferative Diabetic classified as: detachment, which may or may not involve Retinopathy the macula. Vitreous haemorrhage may • Retinal thickening at or within 500µ (one require B-scan ultrasonography to deter- Intraretinal microaneurysms and dot and third of the diameter of the optic disc) at mine if a tractional or rhegmatogenous blot haemorrhages of greater severity, in the centre of the macula (retinal break or hole) is one to three quadrants. Cotton wool spots, • Hard exudates at or within 500µ of the present. Neovascularisation of the anterior venous calibre changes including venous centre of the macula, if there is thicken- segment of the eye may cause intractable beading, and intraretinal microvascular ing of the adjacent retina painful blindness due to neovascular glau- abnormalities are present but mild. • An area of retinal thickening greater than coma. 3. Severe Non-Proliferative Diabetic one optic disc area in size, at least a part Retinopathy of which is within one disc diameter of Screening for Diabetic Retinopathy the centre of the macula. At least one of the following should be Diabetic retinopathy does not reduce vision present: a) ‘severe’ haemorrhages and The following photographs show non- in its early stages, when treatment is most microaneurysms in all four quadrants of the effective. Preventing blindness from fundus, b) venous beading, which is more proliferative and macular diabetic retinopathy. retinopathy relies on early detection of marked in at least two quadrants, and c) asymptomatic disease by fundus examina- intraretinal microvascular abnormalities, 1. Moderate non-proliferative diabetic tion. The fundus may be examined by which are more severe in at least one ophthalmoscopy, using a slit lamp and quadrant. retinopathy (Figure 1). 2. Diabetic maculopathy (Figure 2). either a contact lens or a 78D lens, or by 4. Very Severe Non-Proliferative retinal photography, which may use Diabetic Retinopathy Proliferative Diabetic Retinopathy (PDR) conventional film or a digital camera. It has been shown that fundus photography is the Two or more of the criteria for severe Micro-vascular pathology with capillary most accurate means of screening for non-proliferative diabetic retinopathy, but closure in the retina leads to hypoxia of tis- retinopathy. The photos allow an ophthal- without any proliferative diabetic retino- sue. The hypoxia leads to release of vaso- pathy. mologist to examine a large number of eyes proliferative factors which stimulate new very quickly. Digital fundus photography blood vessel formation to provide better Diabetic Maculopathy is expensive initially, but has very low run- oxygenation of retinal tissue. These new ning costs as it does not require film or Diabetic retinopathy situated in and around vessels growing on the retina are called developing the pictures. The images are the macula is described as diabetic macu- neovascularisation elsewhere (NVE) and available instantly. The quality of digital lopathy, which can result in significant those on the optic disc are called neovascu- photos is not as good as conventional film, larisation of the disc (NVD). These new vessels can bleed and produce haemorrhage into the vitreous.

The following photographs show examples of proliferative diabetic retinopathy (PDR).

1. PDR with NVE (Figure 3). 2. PDR with NVD (Figure 4).

Advanced Proliferative Diabetic Retinopathy The unchecked progression of pro- Fig. 3: Proliferative diabetic retinopathy with liferative diabetic retinopathy can Fig. 4: Proliferative diabetic retinopathy with neovascularisation elsewhere neovascularisation on the disc Photo: K Viswanath lead ultimately to tractional retinal Photo: K Viswanath 22 Community Eye Health Vol 16 No. 46 2003 Diabetic Retinopathy however, they are quite adequate for macular photocoagulation. Diffuse or focal orrhage – performed early for insulin retinopathy screening. leakage can be identified by fundus dependent diabetics and after six months in In most developing countries there fluorescein angiography (FFA). FFA is non-insulin dependent diabetics if the are too few ophthalmologists for every done with black and white retinal photog- haemorrhage does not clear. diabetic to be examined annually by an raphy using the contrast dye, sodium ophthalmologist. If retinal photography is fluorescein, injected into the blood. Prevention of Blindness due to not possible, then the fundus may be If ‘clinically significant macular oedema’ Diabetic Retinopathy examined by the diabetic physician, an is present this may include: optometrist, or an ophthalmic assistant. Prevention of blindness due to diabetic Screening for diabetic retinopathy is • Focal leaks greater than 500µ from the retinopathy requires information on the only effective if it achieves high coverage centre of the macula, causing retinal prevalence of diabetic retinopathy in the (at least 80% of known diabetics). It is thickening or hard exudates general population, identifying the high essential that the screening process should • Focal leaks 300µ–500µ from the centre risk groups amongst diabetics, using cost be made as convenient as possible for of the fovea, without significant damage effective screening methods such as diabetic patients. It should also be free. to the perifoveal capillary network ophthalmoscopy or fundus photography. • Areas of diffuse leakage on fluorescein Treatment facility centres require photoco- Insulin-dependent/juvenile-onset diabetes angiography within the macular area agulators. Continuing medical education • Avascular areas within the macular area. for diabetic care physicians, training oph- • Dilated fundus examination every year thalmologists in photocoagulation and beginning 5 years after diagnosis, from Pan-retinal Photocoagulation (PRPC) health education amongst diabetic patients puberty onwards should be established. It should be kept in • Examinations more frequently once dia- Photocoagulating the posterior betic retinopathy is diagnosed. 45°–60° of the retina, away from the vascular arcades of the macula, with Non insulin-dependent/maturity-onset graded burns – to reduce the oxygen diabetes demand of the hypoxic retina in diabet- ic retinopathy – converts the hypoxic • Dilated fundus examination every year zones of the retina into anoxic zones, once diabetes diagnosed thereby reducing the release of va s o - • Examination more frequently once dia- proliferative factors (Figure 5). PRPC, betic retinopathy diagnosed. therefore, prevents new vessels appear- ing and can result in the regression of Diabetics are at significantly increased risk already existing new vessels on the of cataract. All diabetics should have an retina or optic disc. annual measurement of , and those with vision of less than 6/18 in either PRPC is indicated for the following eye should have a full eye examination, as clinical findings: Fig. 5: Laser pan-retinal photocoagulation they may have cataract, refractive error, or • Proliferative retinopathy Photo: K Viswanath . • New vessels of the iris. Treatment mind that diabetic patients in certain popu- Follow-up Management lations may have visual impairment or Diabetic Control Patients with diabetic retinopathy, whether blindness due to other causes, such as As previously mentioned, good glycaemic treated or untreated, need periodic follow- refractive error or cataract. control significantly reduces the risk up. Patients with diabetic maculopathy of diabetic retinopathy developing and should be reviewed 3 to 4 months after Acknowledgements subsequently progressing. The importance treatment to check if the macular oedema and Further Reading of good control should be emphasised. has subsided. Patients who receive PRPC The authors are very grateful to Ian should be reviewed in 3 months to check Murdoch FRCS FRCOphth and David Laser Photocoagulation for the regression or closure of new vessels Yorston FRCS FRCOphth who kindly and for the presence of any new vessels. The advent of laser photocoagulation of the reviewed this article. retina has dramatically changed the man- Our particular thanks to Philip Hykin Surgery in Diabetic Retinopathy agement of diabetic retinopathy. The pho- FRCS FRCOphth who has written previ- tocoagulation of non-proliferative diabetic Non-resolving vitreous haemorrhages and ously for this Journal and whose articles retinopathy with clinically significant mac- tractional retinal detachment, due to fibro- were a source of both guidance and content ular oedema is called macular photocoagu- vascular proliferation involving the macu- for this article. lation, and widespread photocoagulation lar region, require surgical procedures such Hykin P. Diabetic Retinopathy: Clinical for proliferative diabetic retinopathy is as vitrectomy, pealing of epi-retinal mem- Features and Management. J Comm Eye called pan-retinal photocoagulation. branes, endo-laser photocoagulation during Health 1996; 9: 58–62. surgery and vitreous replacement with sili- Hykin P. Diabetic Retinopathy: Clinical Macular Photocoagulation cone oil or perfluorocarbons. Features and Management. In: Community Photocoagulation for diffuse leakage Eye Health: Selected and Updated Articles. Vitrectomy around the macula may be applied in a Ed. McGavin DDM, International Centre ‘grid’ fashion to prevent leakage – grid Vitrectomy is indicated for vitreous haem- for Eye Health, London: In press.

Community Eye Health Vol 16 No. 46 2003 23 Diabetic Retinopathy

References 9 Four risk factors for severe visual loss in dia- thy. ETDRS report number 9. Early Treatment betic retinopathy. The third report from the of Diabetic Retinopathy Study Research Group. 1 Dwivedi RN, Krishna G. Epidemiology of Diabetic Retinopathy Study. The Diabetic Ophthalmology 1991; 98 (5 Suppl): 766–785. Diabetes in India; Indian Journal of Com- Retinopathy Research Group. Arch Ophthalmol 17 Grading diabetic retinopathy from stereoscopic munity Medicine 1999; XXIV: 40–44. 1979; 97: 654–655. color fundus photographs – an extension of the 2 Thylefors B, Negrel A D, Pararajasegaram R, 10 Diabetic Retinopathy Study Report No. 7: A modified Airlie House classification. ETDRS Dadzie K Y. Global data on blindness. Bull modification of the Airlie House classification report number 10. Early Treatment Diabetic World Health Organ 1995; 73: 115–121. of diabetic retinopathy. Invest Ophthalmol Vis Retinopathy Study Research Group. 3 Global initiative for the elimination of avoid- Sci 1981; 21: 210–226. Ophthalmology 1991; 98 (5 Suppl): 786–806. able blindness. An informal consultation. 11 Photocoagulation treatment of proliferative dia- 18 The effect of intensive treatment of diabetes on World Health Organization, Geneva, 1997. betic retinopathy. Clinical application of the development and progression of long-term WHO/PBL/97.61. Diabetic Retinopathy Study (DRS) findings, complications in insulin-dependent diabetes 4 NPCB – Government of India. Vision 2020: DRS Report Number 8. The Diabetic Retino- mellitus. The Diabetes Control and Complica- The Right to Sight. Plan of Action, 2001, page pathy Study Research Group. Ophthalmology tions Trial Research Group. New Engl J Med No.7, 5.2.1.1. 1981; 88: 583–600. 1993; 329: 977–986. 5 Dandona L, Dandona R, Naduvilath T J, 12 Early Treatment of Diabetic Retinopathy Study 19 Early vitrectomy for severe proliferative dia- McCarty C A, Rao G N. Population based Report No.1: Photocoagulation for diabetic betic retinopathy in eyes with useful vision. assessment of diabetic retinopathy in an urban . Arch Ophthalmol 1985; 103: Clinical application of results of a randomized population in southern India. Br J Ophthalmol 796–806. trial. Diabetic Retinopathy Vitrectomy Study 1999; 83: 937–940. 13 Treatment techniques and clinical guidelines Report 4. The Diabetic Retinopathy Vitrectomy 6 Narendran V, John R K, Raghuram A, for photocoagulation for diabetic macular Study Research Group. Ophthalmology 1988; Ravindran R D, Nirmalan P K, Thulasiraj R D. edema. Early Treatment of Diabetic Retino- 95: 1331–1334. Diabetic retinopathy among self reported dia- pathy Study Report Number 2. Early Diabetic 20 Early vitrectomy for severe vitreous hemor- betics in southern India: a population based Study Research Group. Ophthalmology 1987; rhage in diabetic retinopathy. Four-year results assessment. Br J Ophthalmol 2002; 86: 94: 761–774. of a randomized trial. Diabetic Retinopathy 1014–1018. 14 Techniques for scatter and local photocoagula- Vitrectomy Study Report 5: Arch Ophthalmol 7 Yorston D, Farid N. Causes of visual impair- tion treatment of diabetic retinopathy: Early 1990: 108: 958–964. ment in diabetics in Pakistan. Personal commu- Treatment of Diabetic Retinopathy Study 21 Kohner E M, Stratton I M, Aldington S J. nication, 2003. Report no. 3. Int Ophthalmol Clin 1987; 27: Prevalence of Diabetic Retinopathy at 8 Klein R, Klein B E K, Moss S E, Davis M D, 254–264. Diagnosis of Non-Insulin Dependent Diabetes DeMets D L. The Wisconsin epidemiologic 15 Photocoagulation for diabetic macular edema: in the United Kingdom Prospective Diabetes study of diabetic retinopathy II. Prevalence and Early Treatment of Diabetic Retinopathy Study Study. Invest Ophthalmol Vis Sci 1993; 34: 713 risk of diabetic retinopathy when age at diagno- Report no. 4. Int Ophthalmol Clin 1987; 27: (Abstract). sis is less than thirty years. Arch Ophthalmol 265–272. ✩ ✩ ✩ 1984; 102: 520–526. 16 Early photocoagulation for diabetic retinopa- Letters updated. Suppose my selection of patients Monitoring Cataract Surgical Outcomes needs to be bettered. Where do I turn for Moses C Chirambo (J Comm Eye Health 2002; 15: 58–59) help? Improvement is not going to happen simply by doing an audit. lf my results are Dear Editor in an isolated hospital. Suppose I have the mediocre then I need a non-threatening intellectual honesty and humility to begin helping hand. But from where and from Dr Chirambo paints a realistic picture of the process of auditing my results. Suppose whom? African cataract surgery where the result I find that 50% or more of my post- Dr Andrew Potter of the average cataract operation is not operative cataract patients fail to attain MRCOphth reaching the WHO recommended visual 6/18 or better vision. Who will help me to Hôpital deBOKO outcome. improve? Parakou Suppose I am a cataract surgeon working Suppose my surgical skills need to be Benin Republic

Monitoring Cataract Surgical Outcomes Hans Limburg (J Comm Eye Health 2002; 15: 56–57) Monitoring Cataract Surgical Outcomes: Computerised Systems David Yorston (J Comm Eye Health 2002; 15: 51–53)

Dear Editor if possible, the relevant files are made point presentations, photographs from the available to others who perhaps already teaching slide sets, leaflets, etc.) might be I read with interest the articles by Hans have the hardware and software necessary, made avail-able in this way. This would Limburg and David Yorston. Both men- but lack the technical expertise to adapt the help to avoid already hard pressed person- tion using software to help with monitor- software for this purpose. This would also nel ‘re-inventing the wheel’ on a regular ing and the production of reports. David have the advantage that information could basis. Yorston goes on to say ‘. . . the design be readily shared between Eye Units and of the database and the reports do need that, at a National, or Regional level, Stephen Allford input from someone with the necessary reports could be easily produced. Perhaps CBM Country Coordinator for expertise.’ This expertise was obviously one means of disseminating these files Cameroon available at Kikuyu (Kenya) but will not would be by making them available to Promhandicam Association necessarily be available to everyone. download from the JCEH website. In the BP 4018, Yaounde I would therefore like to suggest that, future, perhaps other resources (power- Cameroon

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