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ORIGINAL RESEARCH
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An institution-based cross-sectional study on the prevalence of diabetic retinopathy from Kolkata


1 Department of Ophthalmology, College of Medicine and Sagore Dutta Hospital, Kolkata, West Bengal, India
2 Department of Ophthalmology, R G Kar Medical College, Kolkata, West Bengal, India
3 Department of General Medicine, College of Medicine and Sagore Dutta Hospital, Kolkata, West Bengal, India
4 Department of Pharmacology, College of Medicine and Sagore Dutta Hospital, Kolkata, West Bengal, India

Date of Submission19-Apr-2020
Date of Decision04-Aug-2020
Date of Acceptance21-Sep-2020

Correspondence Address:
Prithwijit Banerjee,
Department of Pharmacology, College of Medicine and Sagore Dutta Hospital, Kamarhati, Kolkata - 700 058, West Bengal
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjdrdypu.mjdrdypu_197_20

  Abstract 


Background: Diabetic retinopathy (DR) is a microvascular complication as a consequence of prolonged hyperglycemia and other risk factors. It is seen in both types of diabetes mellitus (DM) and can lead to progressive vision loss. Many prevalence studies were undertaken in the past, but the eastern part of India was less explored. Aim: (1) The aim of this study is to determine the prevalence of DR among both types of DM patients in an institution-based population of Kolkata. (2) To compare the clinic-biochemical profiles of patients with and without DR. Materials and Methods: From January 2019 to December 2019, 313 patients with a history of DM were screened for DR using slit-lamp bio microscopy with +90D lens after dilating the pupils. Classification of DR was done on the basis of International Clinical classification of DR. Metabolic profile of all participants was noted. Results: The overall prevalence of DR was 16.60% (14.37% nonproliferative and 2.23% proliferative). The prevalence was 80% and 15.58% among Type 1 and 2 DM patients, respectively. Diabetic macular edema was observed in 2.54% of cases. Highest prevalence (38.46%) was observed in patients suffering for more than 20 years of DM. The duration of DM was significantly higher among DR patients (9.46 ± 5.23 years vs. 7.34 ± 5.57; P = 0.012). Patients with DR also displayed significantly higher levels of glycated hemoglobin, creatinine, and albumin-creatinine ratio in comparison to the patients without DR. Conclusion: The prevalence of DR from an institution of Eastern India is comparable to other institutional studies conducted in the various parts of the country. The prevalence is higher among Type 1 DM patients. Nonproliferative DR is the most common type. Comparatively, DR patients had a longer duration of DM. Glycemic control and renal statuses are poor in DR than non-DR patients.

Keywords: Albumin-creatinine ratio, diabetes mellitus, diabetic retinopathy, nonproliferative diabetic retinopathy



How to cite this URL:
Dutta Chowdhury MS, Bandyopadhyay S, Chakraborty S, Banerjee P. An institution-based cross-sectional study on the prevalence of diabetic retinopathy from Kolkata. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2021 Jun 13]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=316405




  Introduction Top


The overwhelming presence of diabetes mellitus (DM) is a worldwide health problem. Based on the estimate of International Diabetes Federation India, China and the USA harbor nearly half of the diabetic population in the world.[1] In India, the patients suffering from diabetes is likely to touch 79 million by the year 2030.[2] The disease is known for its wide ranges of systemic and ocular complications.[3] Diabetic retinopathy (DR) is common sight-threatening microvascular complication, occurring in both types of diabetes and is secondary to prolonged uncontrolled hyperglycemia and other risk factors.[4],[5] According to earlier estimates, within 15–20 years of diagnosis more than 75% diabetic patients develop DR.[6],[7]

In the past, regional and national studies were conducted in India to measure the prevalence of DR; however, the number of institutional studies was fewer. According to Ramavat et al., the prevalence of DR was 33.92% from a hospital-based population of Western India.[8] Nadarajan et al. found a very similar picture of 32.53% based on his observation at a rural primary health center of South India.[9] While another study from Goa Medical College revealed the prevalence to be 16.7%.[10] The authors from Sikkim documented 17.4% prevalence based on their study on patients attending a single tertiary care center.[11] However, in recent times, no such studies were reported from the eastern part of the country. The present study was, therefore, undertaken in an institutional-based population of eastern India to determine the prevalence of DR and to compare the clinical and biochemical profiles of patients with and without DR.


  Materials and Methods Top


The present study was an observational cross-sectional evaluation of outpatient department (OPD)-based patients at a Government Medical College Cum Hospital of Kolkata. After obtaining ethical approval, all the diabetic patients who attended the ophthalmology OPD from January to December 2019 were screened for DR. Many of the cases were referred from other departments such as Internal Medicine, General Surgery, and Pediatrics. A total of 359 patients underwent thorough ocular examination by ophthalmologists during the aforesaid time period, out of which 313 were ultimately selected. The cases in which the laboratory reports data were either missing or older than a month were excluded for the analysis. Those who did not want to participate in the study were also excluded. First, Snellen chart was used to assess the visual acuity of all participants. Then after dilating the pupils with Tropicamide 0.8% and 5% Phenylephrine hydrochloride eye drops, slit-lamp biomicroscopy with +90D lens was performed to detect any evidences of DR. “International Clinical Classification of DR”[12] was adopted for the grading of retinopathy, if present. The demographic details of all patients, other relevant medical history, and concomitant medication details were clearly noted in a specifically predesigned case record form. Body mass index (BMI) was calculated by the formula kg/m2, where kg represented patient's weight in kilograms, whereas m2 meant height in meter squared. A standardized weighing machine was deployed to calculate the weight in kilograms, whereas a fixed wall-mounted height measuring scale was used to find out the heights in meters. Finally, all the necessary bio-chemical test reports were meticulously documented.

For statistical analysis, the relevant clinical findings as well as biochemical details of all these patients were tabulated in Microsoft Excel in a specially designed format. Continuously distributed variables were expressed in the form of mean with standard deviations. The Student's t-test was performed to determine the significance of differences between the means of two independent samples. Fischer's exact test was used for the comparison of categorical variables. P ≤ 0.05 was considered statistically significant. GraphPad Prism (Develpoed by GraphPad Software, Inc; San Diego; California, USA) was employed for the analysis.


  Results Top


At the end of the observation period, the demographic data and baseline clinical parameters of all 313 participants were compiled. Only five cases of Type 1 DM were included in this study, whereas the rest were Type 2 DM. The prevalence of DR and its various types are shown in [Table 1]. Overall, eight cases of diabetic macular edema were also observed. The overall prevalence of DR was 80% in Type 1 and 15.58% in Type 2 DM patients at the end of the analysis.
Table 1: Demographic and baseline clinical details of the study population

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The prevalence of DR in different age groups is shown in [Table 2]. The highest prevalence was found in the age group of 10–20 years. In rest of the groups, there was a gradual rise in the prevalence of DR with advancement of age which peaked at 21.05% after 81 years of age.
Table 2: Prevalence of diabetic retinopathy in different age groups of the study population

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The detailed distribution of different types of DR in relation to the duration of DM is depicted in [Table 3]. There was a gradual increase in the prevalence of all types of DR with the progression of the disease. The highest overall prevalence (38.46%) was found in the group who had been suffering from the DM beyond 20 years. The same rate declined to 32.35% in 16–20 years group and 18.9% in 11–15 years group. Further reduction was noted to 13.72% in 6–10 years group and only to 3.9% in up to 5 years category.
Table 3: Comparison of the prevalence of different sub-types of diabetic retinopathy in relation to duration of diabetes mellitus

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In [Table 4], the demographic details and various clinical parameters were statistically compared between the two groups of patients; who developed DR and who did not. DR group consisted of 52 patients while the non-DR group had the rest 261. In DR group patients were slightly older comparatively, which was statistically insignificant. Male proportion was also higher in DR group, which was again statistically insignificant. Higher proportion of smokers, hypertensive patients, and patients with positive family history of DR was also found with the DR category. None of those two could make significant differences in the analysis. However, duration of diabetes was found to be significantly higher among the patients of DR group in comparison to the non-DR. Statistically significant differences were also observed in terms of glycated hemoglobin (HbA1c), creatinine, and albumin-creatinine ratio (ACR) between the two groups. The proportion of patients suffering from Type 1 DM was found to be higher in the DR category, which was again statistically significant.
Table 4: Comparison of demographic and clinical features between diabetic retinopathy and nondiabetic retinopathy groups

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  Discussion Top


DR is one of the most serious microvascular complications of Type 2 DM and the leading cause of vision loss among adults.[13],[14] Nearly, 65 million Indian adults are presently affected by DM, and therefore, there is already a substantial disease burden which is likely to be higher in future.[15] Since there was no recent data on DR from the eastern part of the country, this study was conducted to provide some insight regarding the disease burden and metabolic profiles of those who were suffering from DR. A hospital-based population was selected for the analysis in which the mean duration of DM was 8.15 ± 6.92 years with average HbA1c of 7.92 ± 3.19.

In the past two decades, many Indian authors have published their data on DR from different parts of the country involving the variety of populations. The comparison of the results of few earlier observations with that of the present study is summarized in [Table 5].
Table 5: Prevalence of diabetic retinopathy in previous Indian studies

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Significant variation in the result was evident among these studies owing to the differences in their designs, sample size, and geographical location. Such variation of data was often confusing and might be overestimating the prevalence at times. Substantially, the high prevalence was attributed to referral bias and inclusion of relatively older population in one study.[8]

The findings from the current study closely resembles with earlier observations made by Rema et al.,[5] Ankush et al.,[10] and Kulkarni et al.[17] Similar data were also reported by Vaz et al. (15.4%)[18] and Bhutia et al. (17.4%);[11] though both studies included mostly rural population. The distinctive point of the current observation is the inclusion of both types of DM in the sample population. Mahesh et al. nevertheless reported the prevalence rate of 20.12% with a similar population of south India back in 2005.[19]

Higher proportions of nonproliferative diabetic retinopathy (NPDR) are consistent in all the previous studies which also matched with the present one.[5],[8],[11],[16] Interestingly, the proportions of proliferative diabetic retinopathy (PDR) varied depending upon the geographical location. The prevalence of PDR of the present study is found to be somewhat similar with the cohort of urban South Indian population.[5] On the other hand, studies conducted in Western India[8] as well as North India[16] exhibited higher prevalence rates. Asian young diabetes research study showed that the DR prevalence is comparatively lower among Indians than other Asians groups and suggested the role of genetic preponderance.[20] The extent of genetic susceptibility to DR among different ethnic classes shall remain a topic of future research.

Based on the present data, the prevalence of DR gradually increased with increase in age as well as with duration of DM. This finding is in concurrence with the fact that the duration of DM remained the strongest predictor of the development, progress, and severity of DR as described by the multiple authors.[21],[22],[23] Rema et al. predicted that for every 5-year increase in duration of diabetes, the risk for DR was increased by 1.89-fold, whereas a 2% increase in HbA1c resulted in a 1.7-fold increase in risk for DR.[5] This explains the significant differences both in the duration of DM and HbA1c values between the DR and non-DR categories in the present observation.

The overall prevalence was much higher among the Type 1 DM patients. Due to earlier onset and substantial hyperglycemia, these patients are more vulnerable to develop DR. However, the present study overestimated the prevalence owing to the small sample size. Two previous studies from Chennai, including the Type 1 DM population, exhibited 53.3%[24] and 37.1%[25] prevalence rates of DR.

Like most of the earlier studies,[5],[26],[27],[28] men were found to be more frequently affected by DR in the present one; though statistical significance was lacking. Mowatt nevertheless reported a contrarian view on this issue and documented female vulnerability to DR.[29]

The scientific basis of such gender-related difference is yet to be established. Reluctance to undergo regular medical check-up among women in this country might be one of the reasons of such lower prevalence.

No conclusive statement could be drawn in terms of the role of family history, smoking habit and BMI in the development of DR from the current analysis. Higher proportion of smokers was present in both the study groups was possibly due to the inclusion of more number of male patients. Patients receiving anti-hypertensive medications were also higher in the category of DR, but the statistical difference could not be derived probably due to relatively smaller sample size.

DR and diabetic kidney disease go hand in hand as they share common pathophysiological pathways.[30] In the current study, patients from the DR group showed poor renal status in the form of significantly higher ACR and serum creatinine values. Prolonged duration of the disease associated with Type 2 DM and substantial hyperglycemia in case of type 1 DM is to be blamed for this. Hence, raised ACR in diabetic patients warrants immediate retinal check-up.

It is noteworthy that many of the DR patients did not have any visual complaints during the time of screening in the present study. According to the report of Gadkari et al., 22.8% patients with visual acuity 6/18 or better had some form of clinically detectable DR.[2] It further reiterates the importance of regular retinal check-up of all patients with a history of DM.

The result from single-center-based cross-sectional observational studies with relatively smaller sample size cannot be extrapolated in the general population. This remains the most important drawback of the present study. Retinal photographs could only be taken in minority of cases. However, the study provides an estimate about the current burden of DR in the urban eastern India for the first time. The inclusion of both types of DM in the sample makes the observation more realistic. Metabolic profiles of such patients are also highlighted in detail in the analysis.


  Conclusion Top


The overall prevalence of DR is 16.60% among the patients suffering from DM based on the available data from a tertiary care cum teaching hospital in Kolkata. It matches with the previous institution-based studies reported from the other parts of India. Among Type 1 DM patients, the prevalence is comparatively higher. NPDR appears to be the most common type overall. Patients suffering from DM for more than 20 years are most vulnerable. Glycemic control and renal status are poor among DR patients in comparisons to the patients without DR.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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