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DISCUSSION
In our study, the overall prevalence of diabetic retinopathy was 28% which is comparable to prevalence of 21.9%28.8% reported in other studies [5,12,13] . Some studies had prevalence rate as low as 5% [14]to as high as 48.6% [3].
This may have been the difference in the criteria of selection of the patients into the study. There were more male diabetic patients with retinopathy than female patients, which corresponds to the higher number of male patients overall. The distribution of retinopathy among the ethnic groups was proportionate to their representation in Malaysia. There was no statistically significant association between gender, age, socioeconomic status, alcohol consumption, type of diabetes BMI, and prevalence of retinopathy. This observation was similar to van Leiden et al[15]. However, incidence of retinopathy was found to be inversely associated with BMI.
This finding is compatible with the notion that obese older onset NIDDM has a milder form of the disease and the leaner NIDDM patients are more likely to be insulin deficient[5]. However, no definite scientific or clinical explanation is currently available for this.
More than half of the smokers had retinopathy. The effect of smoking on macrovascular disease is well recognized but evidence of its impact on microvascular disease has not always been consistent [3]. Duration of disease had significant association with prevalence of retinopathy. Diabetics of less than 2year duration had 12.5% incidence and those with more than 10 years had 55.6% incidence. The patients between 2 to 10 years duration had 30.9% incidence rate. These findings were comparable with other studies showing incidence of retinopathy varied from 2.0% to 3.0% for those with diabetes less than five years and up to 15.5% to 47% for diabetes more than ten years [5,6,16]. Segato et al[17] reported that duration of diabetes alone accounts for increasing prevalence of retinopathy. In the analysis of frequency of distribution of retinopathy with associated medical conditions, there was statistically significant association between incidence of retinopathy and neuropathy ( 75%) and also nephropathy ( 90%) which was noted in other studies as well[18,19].
In looking at the association between various comorbid factors and biochemical parameters with the prevalence of retinopathy, many interesting significant findings have surfaced. Those with poor control of blood pressure ( blood pressure of more than 130/85 on treatment)[10]and poorly controlled diabetes ( fasting blood sugar more than 6.1mmol/L and HbA1c more than 6.4% on treatment ) definitely showed higher prevalence of retinopathy， which has been proven by other studies [15,2022]. Hypertension has been linked with increased retinal blood flow and retinopathy [23,24]. Poorly controlled blood pressure acts as an independent risk factor for the onset and progression of retinopathy [25,26]. The severity of retinopathy is parallel with the severity of nephropathy and these chronic diabetic complications may occur even in newly diagnosed diabetics[19]. Patients with poor renal function, which was detected by high blood urea and serum creatinine levels, have proportionately higher incidence of retinopathy[14,27] .
Triglycerides and high density lipoprotein levels had a significant association with retinopathy in our study, which is contrary to Tzeng and colleagues observation [19]. From previous studies done, it is interesting to note that the association between the prevalence of retinopathy and hyperlipidemia have been variable. van Leiden et al[20] had reported in a populationbased study done between 1989 to 1992 that prevalence of retinopathy was positively associated with elevated serum cholesterol and triglycerides. The same group of researchers later found no consistent or statistically significant association between retinopathy and serum lipids in another study[15]. Proteinuria and microalbuminuria indicate the poor integrity of the renal vascular system and may be signs of early renal impairment. Eightythree percent of patients with proteinuria and 85.7% of patients with microalbuminuria had retinopathy, which reflects on the pathophysiology of microvascular angiopathy in these endorgans [5].
The major limitation of this study was the small number of patients and single centre cohort which will not be representative to the true scenario of the whole population in Malaysia.
In conclusion, the incidence of diabetic retinopathy among the diabetic population at our centre was 28%. Diabetic retinopathy is a multifactor microvascular complication, which apart from poor blood sugar control, is also associated significantly with duration of the disease, smoking, neuropathy, nephropathy, hyperlipidemia and poor blood pressure control. As clinicians, the presence of even a small number of patients having retinopathy among the newly diagnosed IDDM alerts us not to miss this group during screening. Baseline screening for retinopathy in diabetic patients is desirable as early detection, regular followup, prompt referral to ophthalmologists and effective management will reduce and avoid severe vision loss for these patients.
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