Diabetes mellitus (DM) has reached pandemic proportions globally. The International Diabetes Federation estimated that 536.6 million adults aged 20–79 years were living with diabetes in 2014, a figure projected to rise to 783.2 million by 2045 ¹. This sustained rise in the diabetic population has translated into a corresponding increase in the burden of diabetes-related microvascular complications, of which diabetic retinopathy (DR) is among the most visually disabling ². DR remains the leading cause of preventable blindness among working-age adults in many parts of the world and the fifth leading cause of moderate-to-severe vision impairment globally ³.

A systematic review and meta-analysis of population-based studies estimated the global prevalence of any DR among people with diabetes at approximately 22.3%, with vision-threatening DR (VTDR) affecting 6.2% and clinically significant macular edema (CSME) affecting roughly 4.1% of the diabetic population ². More recent imaging-based pooled estimates place the prevalence of any DR at around 23%, proliferative DR (PDR) at 6%, and sight-threatening DR at 9–14% across the seven IDF regions ⁴, confirming that DR continues to represent a substantial and evolving public health challenge despite advances in diabetes care.

Hospital-based studies, particularly those conducted in tertiary eye care settings, consistently report a higher prevalence of DR than community-based surveys, largely because such centers receive referrals of symptomatic patients or those with longstanding, poorly controlled diabetes ⁵. For instance, a descriptive cross-sectional study from a tertiary hospital reported that 27.0% of diabetic patients attending the ophthalmology department had retinopathy changes in at least one eye ⁵, while studies from tertiary centers in India have reported prevalence figures ranging from 18% to over 37% depending on patient selection and disease duration at presentation ⁶.

The pathogenesis and progression of DR are strongly influenced by a constellation of modifiable and non-modifiable risk factors. Longer duration of diabetes, poor glycemic control reflected by elevated glycated hemoglobin (HbA1c), coexisting systemic hypertension, dyslipidemia, and diabetic nephropathy have all been independently associated with both the development and severity of retinopathy ⁷. A tertiary-care evaluation found that patients with diabetes duration of ten years or more, and those with HbA1c levels of 8% or higher, had significantly higher rates of severe non-proliferative and proliferative disease, and that coexisting hypertension and nephropathy further amplified this risk ⁷.

Despite the well-documented global and regional epidemiology of DR, locally generated clinical profiles remain essential, since the distribution of risk factors, healthcare-seeking behavior, and stage of disease at presentation vary considerably across populations and healthcare systems ⁸. Many patients remain asymptomatic until relatively advanced stages of retinopathy, and a substantial proportion of diabetic patients have never undergone a dilated retinal examination prior to presentation at a tertiary eye center ⁸.

Against this background, the present study was undertaken to describe the demographic and clinical profile of patients with diabetic retinopathy attending the ophthalmology department of a tertiary care center, and to examine the association between disease severity and key systemic risk factors, including duration of diabetes, glycemic control, hypertension, and dyslipidemia. Such hospital-based clinical characterization is intended to inform local screening priorities and to strengthen the case for earlier, structured ophthalmic referral within diabetes care pathways.

Study Design and Setting This was a hospital-based, cross-sectional observational study conducted in the Department of Ophthalmology, in collaboration with the Department of Endocrinology, of a tertiary care teaching hospital, over a period of 12 consecutive months. The study was conducted in accordance with the tenets of the Declaration of Helsinki and was approved by the Institutional Ethics Committee prior to commencement. Written informed consent was obtained from all participants before enrolment. Study Population All consecutive patients with a confirmed diagnosis of type 1 or type 2 diabetes mellitus (as per American Diabetes Association criteria) attending the ophthalmology outpatient department, either directly or on referral from the endocrinology/medicine department, were screened for eligibility. Patients aged 18 years or older who provided informed consent and were able to undergo a complete dilated fundus examination were included consecutively until the desired sample size was achieved. Inclusion and Exclusion Criteria Patients with media opacities (dense cataract, vitreous hemorrhage, or corneal opacity) precluding adequate fundus visualization, those with retinal disease unrelated to diabetes (e.g., retinal vein occlusion, age-related macular degeneration, uveitis), pregnant women with gestational diabetes, and patients unwilling to provide consent were excluded from the study. Clinical Examination and Data Collection A structured proforma was used to record demographic details (age, sex, residence, socioeconomic status), duration of diabetes mellitus, type of diabetes, current treatment (oral hypoglycemic agents, insulin, or combination), and systemic comorbidities including hypertension, dyslipidemia, and diabetic nephropathy. Best-corrected visual acuity was measured using a Snellen chart. Anterior segment evaluation was performed by slit-lamp biomicroscopy, and intraocular pressure was measured by applanation tonometry. Dilated fundus examination was carried out using indirect ophthalmoscopy with a 20-diopter lens and slit-lamp biomicroscopy with a 90-diopter lens, supplemented by fundus photography in all cases and optical coherence tomography where clinically indicated to confirm macular edema. Grading of Diabetic Retinopathy DR severity was classified according to the International Clinical Diabetic Retinopathy Disease Severity Scale 9 into the following categories: no apparent retinopathy, mild non-proliferative DR (NPDR), moderate NPDR, severe NPDR, and proliferative DR (PDR). The presence of clinically significant macular edema (CSME) was assessed independently in each eye using slit-lamp biomicroscopy and OCT criteria. For analysis, the eye with the more severe grade of retinopathy was taken to represent the patient's overall disease status. Laboratory Investigations Venous blood samples were obtained for fasting and postprandial blood glucose, glycated hemoglobin (HbA1c), fasting lipid profile, serum creatinine, and urine albumin-to-creatinine ratio. Glycemic control was categorized as good (HbA1c <7%), fair (7–8%), or poor (≥8%). Hypertension was defined as a recorded blood pressure ≥140/90 mmHg or current use of antihypertensive medication, and dyslipidemia was defined per National Cholesterol Education Program Adult Treatment Panel III criteria. Statistical Analysis Data were entered into Microsoft Excel and analyzed using SPSS software (version 26.0). Continuous variables were expressed as mean ± standard deviation and categorical variables as frequencies and percentages. The Chi-square test was used to assess associations between categorical variables, and one-way ANOVA was used to compare means across DR severity groups. A two-tailed p-value of less than 0.05 was considered statistically significant throughout the analysis.

A total of 420 diabetic patients attending the ophthalmology outpatient department were screened during the study period, of whom 168 (40.0%) were found to have diabetic retinopathy in at least one eye and constituted the final study group analyzed in detail below.

Demographic Profile

Table 1. Demographic and baseline characteristics of patients with diabetic retinopathy (n = 168)

SD: standard deviation.

The mean age of patients with diabetic retinopathy was 58.6 ± 9.4 years, with the highest proportion of cases occurring in the 60–69 year age group (36.3%), followed by the 50–59 year group (34.5%). Males constituted a modest majority of cases (56.5%) compared to females (43.5%). The majority of patients resided in urban areas (61.9%). Type 2 diabetes mellitus accounted for the overwhelming majority of cases (91.7%), with type 1 diabetes contributing only 8.3%, reflecting the typical adult-onset demographic seen in tertiary ophthalmology clinics.

Severity Distribution of Diabetic Retinopathy

Table 2. Distribution of diabetic retinopathy by severity grade (n = 168)

*CSME was assessed independently and may coexist with any NPDR or PDR grade; percentage is calculated out of total DR eyes. NPDR: non-proliferative diabetic retinopathy; PDR: proliferative diabetic retinopathy; CSME: clinically significant macular edema.

Non-proliferative diabetic retinopathy (NPDR) was the predominant pattern, accounting for 70.8% of all cases, with moderate NPDR being the single most frequent grade (30.4%). Proliferative diabetic retinopathy (PDR), the sight-threatening end of the disease spectrum, was present in 29.2% of patients. Clinically significant macular edema was identified in 23.8% of eyes with retinopathy, frequently coexisting with both moderate-to-severe NPDR and PDR.

Systemic Risk Factor Profile

Table 3. Distribution of systemic and clinical risk factors among patients with diabetic retinopathy (n = 168)

HbA1c: glycated hemoglobin; DM: diabetes mellitus.

Nearly half of all patients (46.4%) had been diabetic for more than 10 years, and a similar proportion (49.4%) had poor glycemic control, defined as HbA1c ≥8%. Hypertension was the most common systemic comorbidity, present in 63.7% of patients, followed by dyslipidemia (53.0%) and diabetic nephropathy (27.4%). Slightly less than half of the patients (42.9%) were on insulin therapy, either alone or in combination with oral hypoglycemic agents.

Association Between Risk Factors and Severity of Retinopathy

Table 4. Association between systemic risk factors and severity of diabetic retinopathy

*Statistically significant (p<0.05), Chi-square test. Mild–Moderate NPDR and Severe NPDR–PDR groups were compared for each risk factor.

On comparing patients with mild-to-moderate NPDR against those with severe NPDR or PDR, statistically significant associations were observed for duration of diabetes exceeding 10 years (p=0.001), poor glycemic control with HbA1c ≥8% (p<0.001), coexisting hypertension (p=0.002), dyslipidemia (p=0.041), diabetic nephropathy (p=0.003), and insulin therapy (p=0.029). Each of these factors was disproportionately represented in the more severe disease category, indicating a cumulative relationship between systemic metabolic burden and the severity of retinal microvascular damage.

Visual Acuity at Presentation

Table 5. Best-corrected visual acuity in the worse eye at presentation (n = 168)

Visual acuity recorded using Snellen chart; blindness defined per WHO criteria as BCVA <3/60 in the better eye equivalent category, applied here to the worse eye for descriptive purposes.

At presentation, nearly half of the patients with diabetic retinopathy (45.2%) retained good to mildly impaired vision (6/6–6/18) in the worse eye. However, a clinically significant proportion already had moderate (32.1%) or severe (15.5%) visual impairment, and 7.1% met criteria for blindness in the worse eye, underscoring the substantial proportion of patients presenting late in the disease course.

In the present hospital-based study, 40.0% of diabetic patients attending the ophthalmology department of a tertiary care center had diabetic retinopathy in at least one eye. This figure is higher than the 27.0% reported in a descriptive cross-sectional study from a tertiary hospital ophthalmology department 5, and considerably higher than the pooled global prevalence of approximately 22.3% reported among diabetic individuals in a large systematic review and meta-analysis 2. This pattern is consistent with the well-recognized referral bias inherent to tertiary eye-care settings, where patients are frequently referred specifically because of visual symptoms, longstanding diabetes, or poor metabolic control, rather than being drawn from the general diabetic population as in community-based surveys 5. The predominance of non-proliferative disease (70.8%) over proliferative disease (29.2%) in our cohort mirrors the natural history of DR, in which most patients pass through progressively advancing non-proliferative stages before developing neovascularization. This distribution is broadly comparable to other tertiary-care series from South Asia, where studies have reported wide-ranging DR prevalence figures, from 18% in early South Indian surveys to over 37% among newly detected diabetics at a Madurai-based tertiary hospital, with proliferative disease generally constituting a minority but clinically critical subset of cases 6. The mean age of our DR cohort (58.6 ± 9.4 years) and the male predominance (56.5%) are consistent with findings from a central rural Indian tertiary-care cohort, which reported a mean age of 56.4 ± 11.2 years among diabetic patients evaluated for retinopathy 6, reflecting the typical age of onset and diagnosis of type 2 diabetes mellitus, which constituted 91.7% of our cases. This is in keeping with global epidemiological trends, in which type 2 diabetes accounts for the vast majority of the diabetic burden, while type 1 diabetes, despite an earlier age of onset, contributes a comparatively small proportion of cases in adult ophthalmology clinics. Our finding that longer duration of diabetes, poor glycemic control, hypertension, dyslipidemia, and nephropathy were significantly associated with more severe grades of retinopathy reinforces a now well-established body of evidence on DR risk factors. A tertiary-care evaluation of factors associated with DR severity similarly found that diabetes duration of 10 years or more and HbA1c levels of 8% or higher were strongly associated with severe NPDR and PDR, and that hypertension and nephropathy independently contributed to disease progression, suggesting shared microvascular pathophysiology across renal and retinal beds 7. Similarly, a study from Ethiopia identified longer diabetes duration, insulin use, and systolic hypertension as independent predictors of DR presence 8, findings that align closely with our own observations. The proportion of patients presenting with moderate-to-severe visual impairment or blindness (22.6% combined) in our study highlights a persistent gap in early detection. This is consistent with literature suggesting that a substantial fraction of diabetic patients have never undergone a dilated retinal examination before presenting to tertiary eye care, often only after symptomatic visual decline has already occurred 8. Population-based estimates indicate that roughly one-third of diabetic individuals show some sign of retinopathy at any given time, while around 10% experience vision-threatening disease 8, underscoring that a meaningful proportion of disease remains undetected until advanced stages in real-world clinical settings. This study has certain limitations. As a single-center, hospital-based cross-sectional study, the findings are subject to referral bias and cannot be generalized to the broader community-dwelling diabetic population. The cross-sectional design also precludes establishing temporal or causal relationships between risk factors and DR severity. Longitudinal, multi-center studies incorporating standardized screening protocols would help validate and extend these findings.

Diabetic retinopathy remains a substantial clinical burden among diabetic patients attending tertiary eye care, affecting two in five patients screened in this cohort, with nearly a third already at the proliferative, sight-threatening stage at presentation. Severity of retinopathy was significantly associated with longer duration of diabetes, poor glycemic control, hypertension, dyslipidemia, and nephropathy, reaffirming the multifactorial and systemic nature of this microvascular complication. A meaningful proportion of patients presented with moderate-to-severe visual impairment, reflecting delayed detection in routine practice. These findings support the integration of regular, structured retinal screening into standard diabetes care pathways, particularly for patients with long-standing disease and poor metabolic control, alongside coordinated multidisciplinary management of blood pressure, lipids, and renal function to reduce the burden of vision-threatening diabetic retinopathy.

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