Prevalence and Associated Risk Factors for Diabetic Retinopathy among in-patients Diagnosed with Diabetes Mellitus : A Retrospective Study Conducted in Nobel Medical College and Teaching Hospital , Biratnagar

Background: Diabetes mellitus (DM) being disease of modern world occurrence of Diabetic retinopathy (DR) has become more frequent. Knowledge on the prevalence and associated risk factors of diabetic retinopathy helps to detect the disease in its early course. The objective of the study was to establish the prevalence and to analyze the associated risk factors and help to screen the disease as early as possible so as to prevent and /or to delay the onset as well as progression of DR. Materials and Methods: A hospital based retrospective study conducted among 213 inpatients of Nobel Medical College, Biratnagar diagnosed with DM. Result: The prevalence of diabetic retinopathy was 32.39% and prevalence of mild NPDR, moderate NPDR, severe NPDR, very severe NPDR, proliferative diabetic retinopathy and clinically significant macular edema was 12.7%, 8.9%, 6.1%, 5%, 1.9% & 2.3% respectively. There was statistically significant relation of diabetic retinopathy with duration of diabetes (p value 0.004) and the mean duration was 8.704 years. Conclusions: The prevalence of diabetic retinopathy among in-patients was 32.39%. Though there was no significant relation with occurrence of DR with type of diabetes, age, sex, alcoholism, smoking and drug intake history, the duration of diabetes and hyperlipidemia, poor hyperglycemic control were highly significantly associated with DR while high BP showed marginally insignificant relation with the same.


Introduction
Diabetes mellitus is the emerging disease in the modern world.Diabetic retinopathy the most common micro vascular complication of DM is predicted to be principle reason of new blindness among working populations [1].425 million people have diabetes mellitus in the world, out of which 82 million people were from the South-East Asia only and it is estimated that this will rise to 151 million by the year 2045.There were 657,200 cases of diabetes mellitus reported in 2017 in Nepal [ [3,8,9,[11][12][13][14][15][16].There is 29 times higher risk to develop blindness due to diabetic retinopathy than non-diabetic of similar age and gender [4].
The aim of the study was to find the prevalence and to establish the associated risk factors for diabetic retinopathy among in-patients diagnosed with diabetes mellitus in Nobel Medical College and Teaching Hospital, Biratnagar so as to take measures to prevent and/or to delay the progression of potentially blinding diabetic retinopathy.

Result
Out of 213 diabetic patients, 144 (67.6%) were found to have no diabetic retinopathy whereas 12.7% had mild NPDR, 8.9% had moderate NPDR, 6.1% had sever NPDR, 0.5% had very severe NPDR, 1.9% had PDR and 2.3% had CSME [Table1] .Most of them (74.6%) have normal or mild visual impairments, whereas 21.6% had moderate visual impairment, 2.8% had severe visual impairment and 0.9% was blind according to WHO blindness classification [Table2] .Among total patients, 32.9% have multiple associated conditions followed by 21.6% with only cardiac and 11.3% with only renal problems while 18.3% patients have no other associated conditions with DM with/without DR [Table6] .Age of the patients varied from 19 years to 87 years with mean age of 56.51(±12.73)with majority of patients were in age group of (50 -59) years (34.7%) and minority of patients in the age group of ≥80 years (3.8%) and <40 years (9.4%).Diabetic retinopathy was found in highest frequency in the age group of (50 -59) years (34.8%) and in lowest frequency in age group of <40 years (8.7%).Of total diabetic patients with DR, 60.9% were male. [Table3,4]  Age was not found to be a significant risk factor for development of diabetic retinopathy (p=0.804).Similarly, other factors viz.sex, fasting blood sugar blood Triglyceride level, Blood pressure, family history, alcohol intake, smoking and drug intake (in the form of oral hypoglycemic agents or S/C insulin) were not found as statistically significant associated factors for development of diabetic retinopathy [Table7] .Among studied patients, 2.3% had type 1 DM while 97.7% had type 2 DM and its association with development of diabetic retinopathy was found statistically insignificant (p =0.095) [Table5] .However, the duration of diabetes was found highly statistically significant associated risk factor for development of retinopathy in diabetics (p=0.004).Majority of Diabetic patients with retinopathy had duration of 5-9 years (43.5%), and minority them had duration of <5 years (10.1%) [Table7] .Mean duration to develop diabetic retinopathy was found to be 8.7(±4.64)years.Similarly, poor glycemic control in diabetic patients as represented by high HbA1c was fond statistically highly significant (p=0.002) as well as serum total cholesterol level and LDL level also found to be highly significant associated risk factors for development of diabetic retinopathy with p -value of 0.001 each [Table7] .

Discussion
The prevalence of diabetic retinopathy in our study was 32.39% that is found to be lower than worldwide prevalence (34.6%) but much higher than its prevalence in Asians in general (19.9%) [8].But some studies have suggested that South Asians are more likely to have DR as compared to white Europeans, but Asians with DR are younger, the course of disease is short, blood pressure and plasma sugar level are higher [9].Although there is no ethnic difference among Asian countries, [10] the prevalence observed in our study is far higher than in other Asian countries such as India (21.7%) [11] and Bangladesh (21.6%)[12] but lower than Singapore(35%) [13].These differences among studies may be caused by the type of study population, the sample size, age of the patients, different methods of fundus evaluation and the average levels of various variables.
Our study also confirms commonly accepted risk factor for DR i.e. duration of diabetes.The glycemic control as indicated by HbA1C level was fond to be insignificant for association with DR.The high BP was found to be only marginally insignificant associated factor for DR.However, the present study showed that blood lipids were strongly associated with occurrence of DR that is also supported by American studies which fond that occurrence of hard infiltration in the fundus of the population with high TC and LDL was twice as much as that fond in normal population [14] but other studies could not establish this association [15].Hence further studies are needed for the relationship between serum lipid profile and DR.Although some studies indicated that Sr. Cr. was an independent risk factor for DR [10] , the result of this study did not reveal any association between Sr. Cr. and DR.As the prevalence of diabetes in developing countries is growing higher than that in developed countries, the prevalence of diabetes in Nepal is also steadily increasing and diabetes is diagnosed at younger age [16].Our study, in the similar way, found that the prevalence of diabetes and DR had the most important growth in younger age i.e. 60.9% diabetic patients with DR are younger than 60 years.The mean age of diabetics was fond to be 56.51 years with majority of patients were in age group of (50 -59) years for both diabetes and DR.Though the selection criteria and the limitations of the study could limit the generalization of our study, the screening programmes for patients with diabetes in general population and DR diabetic patients should be implemented especially in individuals who have risk factors for diabetes and diabetic complications like retinopathy (eg.high BP, dyslipidemia and diabetes of longer duration).

Table 7 : Association of different factors with DR
Akhter A, Fatema K, Ahmeed SF, et al, Prevalence and associated risk indicators of retinopathy in a rural Bangladeshi population with and without diabetes, Ophthalmic Epidemiol.20 (2013) 220-7.