European Journal of Cardiovascular Medicine

Cataracts are a primary cause of global blindness and are predominantly a consequence of diabetes. Diabetic eye problems are prevalent, with up to 20% of cataract surgeries conducted on diabetic patients [1]. Diabetic retinopathy is characterized by the progressive impairment of retinal blood vessels due to persistent hyperglycaemia, leading to structural destruction of the neural retina. Microaneurysms are the initial ophthalmoscopically identifiable change in diabetic retinopathy and are regarded as the hallmark of non-proliferative diabetic retinopathy (NPDR) [2]. Cataracts in diabetic patients result in diminished visual acuity and complicate thorough retinal examination. Therefore, conducting cataract surgery is beneficial for both diagnostic and therapeutic purposes, despite the potential risk of exacerbating retinopathy. Historically, cataract surgery in diabetics faced challenges due to the rapid advancement of diabetic retinopathy and vision impairment resulting from an increased occurrence of postoperative complications [3]. Kim SJ et al. report that diabetic eyes have a significant prevalence of central foveal thickness following cataract surgery [4]. Research indicates that clinicians must maintain vigilance in diabetic patients following cataract extraction, even in the absence of central macular edema immediately before surgery, especially in eyes with a history of Diabetic Macular Edema (DME) treatment or non-central involved DME, which may be at elevated risk for the onset of central-involved Macular Oedema (ME) postoperatively [5,6]. Nonetheless, this condition is typically moderate and can be effectively managed with photocoagulation. Contemporary surgical methods, namely Small Incision Cataract Surgery (SICS) and phacoemulsification, offer advantages over traditional cataract procedures by facilitating expedited visual recovery and reducing post-operative inflammation. Contemporary cataract surgical procedures have enhanced outcomes [7,8]. Recent studies indicate improved visual acuity following cataract surgery in diabetes patients [9-11]. Cataract surgery in diabetic people yields favorable outcomes, with excellent dependability, albeit with a marginally elevated complication risk compared to non-diabetic individuals. Factors contributing to diminished visual acuity post-surgery include inadequate pre-operative visual acuity, severe diabetic retinopathy, and advanced age [12]. Measurement of central foveal thickness via OCT in diabetic patients post-cataract surgery revealed increased macular thickness, resulting in diminished visual recovery. Nevertheless, some investigations suggest that retinal edema after cataract surgery in diabetic patients may follow a benign course [13,14]. Pre-existing macular edema in diabetic patients undergoing cataract surgery typically does not resolve spontaneously; however, if macular edema develops after cataract surgery, it generally resolves spontaneously, particularly in cases of moderate non-proliferative diabetic retinopathy. The impact of Intra Ocular Lens (IOL) implantation on inflammation in diabetic eyes versus non-diabetic eyes is contentious, as is the question of whether IOL implantation in diabetic eyes results in a greater incidence of macular edema compared to aphakic eyes. Recent studies support lens implantation in diabetic eyes, as correcting aphakia with spectacles leads to further image distortion and narrowing of peripheral vision fields [15]. This study aims to determine the impact of glycaemic management on visual control to provide improved preoperative guidance for patients. The aim of this study was to evaluate and compare the visual outcomes after cataract surgery in diabetic and non-diabetic patients, including those with and without diabetic retinopathy. Additionally, the study assessed post-operative complications following cataract surgery in diabetic patients compared to non-diabetic patients. It also analyzed the increase in central foveal thickness using optical coherence tomography after cataract surgery.

This prospective observational clinical study was conducted at the Department of Ophthalmology, Government Medical College and Hospital, Bettiah, Bihar, India, over a study period of one year. This study included 50 patients with diabetes mellitus and 50 non-diabetic controls, who came for cataract surgery. A written informed consent was taken from all the patients.

Inclusion Criteria:

1. Patients aged 40 years or above undergoing cataract surgery.
2. Patients diagnosed with diabetes mellitus (type 1 or type 2) for at least one year before cataract surgery.
3. Non-diabetic patients serving as controls.
4. Patients with HbA1c levels recorded preoperatively to assess glycaemic control.
5. Patients with clear visualization of the fundus preoperatively (for OCT analysis subgroup).
6. Patients with no or mild non-proliferative diabetic retinopathy (NPDR) and no macular edema at baseline.
7. Patients undergoing phacoemulsification or small-incision cataract surgery (SICS) with posterior chamber intraocular lens (PCIOL) implantation.
8. Patients who provided written informed consent to participate in the study.

Exclusion Criteria:

1. Patients with proliferative diabetic retinopathy (PDR) or diabetic macular edema at baseline.
2. Patients with severe cataracts cause media opacity that prevents proper fundus visualization.
3. Patients with other pre-existing ocular conditions that could affect visual outcomes, such as:

• Glaucoma
• Uveitis
• Retinal disorders (e.g., age-related macular degeneration, vein occlusions)
• Optic nerve diseases

1. Patients with a history of previous intraocular surgery in the study eye.
2. Patients with complicated cataract surgery (e.g., posterior capsular rupture, vitreous loss).
3. Patients with a history of systemic diseases affecting vision, such as uncontrolled hypertension or neurological conditions.
4. Patients who did not complete the postoperative follow-up period (6 weeks).
5. Pregnant or lactating women.

Pre-operative parameters recorded included glycaemic control as indicated by HbA1c (glycosylated haemoglobin) levels, diabetes classification (type 1 or type 2), duration of diabetes (in years), age, gender, diabetes medication type, oral hypoglycaemic agents (OHA)/insulin, visual acuity assessed via Snellen chart, and intraocular pressure measured with Goldmann’s applanation tonometer, which has a measurement range of 0 to 78 mmHg. Ophthalmic surgical procedure for cataract removal Phacoemulsification/Small Incision Cataract Surgery (SICS) with the insertion of a Posterior Chamber Intraocular Lens (PCIOL) was conducted. A superior fornix base conjunctival flap is elevated, followed by the creation of a 6 mm (or 3 mm for phacoemulsification) scleral incision, after which a corneoscleral tunnel is established. The nucleus is excised during anterior capsulotomy (emulsified by phacoprobe), and an intraocular lens (IOL) is subsequently implanted. A routine ophthalmological examination was conducted pre-operatively and on postoperative days 1, 2, and 6 weeks for all patients. The assessment encompassed Best Corrected Visual Acuity (BCVA), slit lamp biomicroscopy, and fundus examination using direct and indirect ophthalmoscopy. Slit lamp biomicroscopy determined the cataract grade, while fundus examination assessed the presence and grade of diabetic retinopathy. The patient is positioned comfortably at a slit lamp and instructed to focus on a distant location while maintaining a straight gaze. During direct ophthalmoscopy, the patient is positioned seated and instructed to gaze straight ahead. The ophthalmologist utilizes the left eye to assess the patient's left eye and the right eye to evaluate the patient's right eye. During indirect ophthalmoscopy, the patient is positioned supine and instructed to concentrate on a distant object while maintaining a direct gaze, with completely dilated pupils. An indirect ophthalmoscope is employed to obtain a sharper, more enlarged visualization of the fundus. Uncorrected visual acuity and best corrected visual acuity (BCVA) were assessed at each visit using Snellen's 6-meter charts.  The central foveal thickness was assessed with Optical Coherence Tomography (OCT) prior to and six weeks following cataract surgery in a cohort of 50 diabetics and 50 non-diabetics. The central foveal thickness was assessed in diabetics who fulfilled the specified criteria. 1) Diagnosis of diabetes mellitus at least one year prior to cataract surgery; 2) Surgery performed without complications; 3) Cases with impaired fundus visualization due to severe cataracts were excluded; 4) Absence of proliferative diabetic retinopathy or macular edema at baseline. This restricted the diabetic spectrum to eyes with no or mild non-proliferative diabetic retinopathy.

Statistical Analysis: The collected data was organized into a table using Microsoft Excel 2019. Next, the data was transferred to GraphPad version 8.4.3 for further statistical analysis. Qualitative data analysis was performed using the student’s unpaired t-test. Quantitative data analysis was performed using the Chi-square test. A P-value of less than 0.05 was considered statistically significant​.

A total of one hundred eyes were included in this study, fifty from the known diabetic and fifty from the non-diabetic patients. Among them, 59% were male and 41% were female (Table 1). Only one eye of each of the diabetic patients was included. Among the fifty diabetics, seven eyes belonged to type 1 diabetics and forty-three eyes from type 2 diabetic patients. There were thirty-eight eyes with mild NPDR, ten with moderate, and the rest two with severe NPDR. The co-morbidities were comparable diseases in both study groups, hypertension being the most commonly associated co-morbidity in the two groups. Over 58% of diabetics with retinopathy changes had hypertension and no other co-morbidities. Pre-operative glycaemic control was assessed by their glycosylated haemoglobin levels. It was found to be well controlled (HbA1c<7) in thirty-six patients whereas it was elevated (HbA1c>7) in fourteen patients. Among the diabetic population, 40 patients (80%) were given oral hypoglycaemic agents,9 patients (18%) were on insulin and 1 (2%) was only advised diet modification.

The age and gender distribution, as well as type of cataract in diabetics and non-diabetics, were noted (Table 1). The majority of patients fell within the 60-69 years age group, accounting for 42% of the total, followed by 33% in the 50-59 years range. A smaller proportion of patients were aged 70-79 years (12%), while only 7% were between 40-49 years, and 6% were aged 80 years or above. In terms of gender distribution, diabetic males and females were nearly equally represented, with 29 males and 21 females, whereas the non-diabetic group had 30 males and 20 females. The occurrence of different types of cataracts was also analyzed. Nuclear cataracts were slightly more common in non-diabetics (32 cases) compared to diabetics (29 cases), while cortical cataract was observed more frequently in diabetic patients (21 cases) than in non-diabetics (18 cases). These findings suggest that the prevalence of cataracts, particularly cortical cataracts, tends to be higher in diabetic individuals, while nuclear cataracts are slightly more frequent in non-diabetics.

Table 1: Showing the different demographic profiles of the patients of both groups.

he intraocular pressure (IOP) findings were recorded in the study population (Table 2). In this study, the majority of patients showed IOP levels within the normal range, with 98% of diabetic patients and 94% of non-diabetic patients falling within these limits. Elevated IOP was found in 2% of diabetics and in 6% of non-diabetics.

Table 2: Showing the intraocular pressure (IOP) in the study population.

The comparison of pre-operative and post-operative visual acuity at different time points reveals a clear trend of improvement in both diabetic and non-diabetic patients after cataract surgery. Before surgery, severe visual impairment (worse than 6/60) was slightly more common in diabetics (41%) than in non-diabetics (39%), indicating that diabetic patients tended to have poorer baseline vision. A small proportion of both groups had moderate vision (6/60 to 6/24), with 7% of diabetics and 10% of non-diabetics falling within this range. Good pre-operative vision (6/18 to 6/6) was rare in both groups but slightly higher in non-diabetics (2% in diabetics vs. 1% in non-diabetics) (Table 3).

On postoperative day 1, a significant improvement in visual acuity was observed in both groups. The proportion of patients achieving 6/6 vision increased to 6% in diabetics and 7% in non-diabetics, while 6/9 vision was seen in 11% of diabetics and 12% of non-diabetics. Although a few patients still had vision ≤6/60 (2% diabetics, 3% non-diabetics), the majority had noticeable vision recovery. There was no significant difference between the two groups (p = 0.243) (Table 4).

By week 2, further improvement was seen, with 5% of diabetics and 7% of non-diabetics reaching 6/6 vision. The proportion of patients achieving 6/9 to 6/18 vision increased, while only 1% of diabetics and 2% of non-diabetics had vision ≤6/60. The difference remained statistically insignificant (p = 0.179), indicating similar recovery patterns (Table 5).

At week 6, the final visual outcomes showed that 6% of diabetics and 8% of non-diabetics attained 6/6 vision, with most patients achieving 6/9 to 6/18 vision. The proportion of patients with vision ≤6/60 was reduced to 1% in both groups, highlighting a successful post-operative recovery. The difference between the groups remained statistically insignificant (p = 0.263) (Table 6). Of the entire study population (n=100), most of the patients showed improvement in vision post-cataract surgery. When compared to pre-operative BCVA status, post-operative BCVA showed significant improvement at the postoperative day 1, 2 weeks, and 6 weeks follow-up (p=0.032).

Table 3: Showing the pre-operative visual acuity in the study population.

Table 4: Showing the best corrected visual acuity (BCVA) on postoperative day 1 in the study population.

Table 5: Showing the best corrected visual acuity (BCVA) at 2 weeks postoperative day in the study population.

Table 6: Showing the best corrected visual acuity (BCVA) at 6 weeks postoperative day in the study population.

In patients with diabetes, an uncontrolled baseline glycosylated hemoglobin (HbA1c) level was identified as a significant factor impacting postoperative visual recovery. Among the participants, 18 eyes with low pre-operative glycaemic levels (HbA1c levels of less than 7%) achieved a visual acuity of 6/9 or better, as shown in Table 7.

Table 7: Showing the postoperative visual acuity in diabetic patients who had HbA1c<7.

Complications after cataract surgery were noted more frequently in diabetics, with iritis and Descemet’s membrane folds being the most common complications. However, the difference was not statistically significant (p=0.301) (Table 8).

Table 8: Showing the postoperative complications in the study population.

The comparison of pre-operative and post-operative central foveal thickness (CFT) in diabetic and non-diabetic patients revealed a significant increase in CFT after cataract surgery in both groups (Table 9). Before surgery, the mean pre-operative CFT was 191.80±7.73 microns in diabetics and 192.30±7.01 microns in non-diabetics, indicating no substantial difference between the two groups. However, at six weeks post-operatively, there was a notable increase in CFT in both groups. In diabetic patients, the mean post-operative CFT increased to 241.70±8.38 microns, whereas in non-diabetic patients, it increased to 231.90±7.87 microns. The increase in CFT was more pronounced in diabetic patients compared to non-diabetics, and this difference was statistically significant (p < 0.0001). This suggests that diabetic patients are more prone to post-operative macular thickening, which could be indicative of early subclinical macular edema following cataract surgery. While both groups showed an increase in CFT, the greater increase in diabetics highlights the importance of monitoring potential retinal changes in diabetic individuals post-surgery.

Table 9: Showing the pre- and post-operative central foveal thickness (microns) in the study population.

In our study, the male-to-female ratio was 1.44:1, closely aligning with the Wisconsin Epidemiologic Investigation of Diabetic Retinopathy, which reported a ratio of 1.5:1 [16]. The slightly higher proportion of male patients in our cohort may be attributed to the lower overall turnout of female patients at healthcare facilities, a trend observed in various healthcare settings. Despite this gender disparity, our findings indicate that neither age nor sex exerted a significant influence on postoperative visual outcomes or complication rates following cataract surgery. The majority of patients (86%) in our study had Type 2 diabetes mellitus (DM), and the duration of diabetes was directly correlated with the prevalence of baseline diabetic retinopathy at the time of presentation. Our findings align with the Chennai Urban Rural Epidemiology Study (CURES) Eye Study [17], which documented a significantly higher prevalence of diabetic retinopathy (DR) among individuals with a diabetes duration exceeding 15 years. Similar observations have been reported in previous studies [18], emphasizing the progressive nature of diabetic retinopathy with prolonged disease duration. Within the diabetic cohort, 40 patients (80%) were managed with oral hypoglycemic agents, while 9 patients (18%) required insulin therapy, and 1 patient (2%) was managed solely through dietary modifications. Glycosylated hemoglobin (HbA1c), a well-established metabolic marker of diabetes control, demonstrated a strong association with the severity of diabetic retinopathy at baseline. Patients with an HbA1c level exceeding 7% exhibited a significantly higher grade of diabetic retinopathy compared to those with optimal glycemic control (HbA1c <7%). Before surgery, 36 patients (72%) had adequate glycemic control (HbA1c <7%), whereas 14 patients (28%) exhibited suboptimal glycemic levels (>7%). Several studies have highlighted the benefits of stringent metabolic control in reducing the incidence of diabetic complications. A pivotal trial reported that lowering HbA1c levels significantly reduced the occurrence of microvascular complications by approximately 25% [3]. Furthermore, the Diabetes Control and Complications Trial (DCCT) demonstrated that intensive glucose management in Type 1 diabetics decreased the overall risk of retinopathy progression by nearly 76% [19]. Effective preoperative glycemic control has been associated with a reduction in postoperative complications, including the progression of diabetic retinopathy and macular edema, leading to improved visual outcomes. Our study determined that diabetic patients, irrespective of the severity of diabetic retinopathy, can anticipate significant improvements in visual acuity following cataract surgery. This holds true even for patients with advanced stages of diabetic retinopathy, provided there is no pre-existing proliferative diabetic retinopathy or clinically significant macular edema at the time of surgery. The study population consisted of 100 eyes that underwent cataract surgery, none of which exhibited proliferative diabetic retinopathy or clinically significant macular edema preoperatively. Preoperative visual acuity demonstrated a positive correlation with postoperative visual outcomes, while the severity of diabetic retinopathy showed a negative correlation, reinforcing the importance of early intervention in optimizing surgical results. Our findings are consistent with prior research, which has identified preoperative diabetic retinopathy status as a key prognostic factor influencing postoperative visual outcomes in diabetic patients undergoing cataract extraction [7,10]. Dowler JG et al. reported that the presence of macular edema during cataract surgery negatively impacts postoperative visual results [10]. However, in our study, none of the diabetic patients exhibited retinal edema at the time of surgery, precluding an analysis of this potential association. Comorbid conditions were comparable between diabetic and non-diabetic groups, with hypertension being the most prevalent. Notably, over 60% of diabetic patients presenting with retinal changes also had hypertension, a finding corroborated by multiple studies that have established a strong link between hypertension and the development of diabetic retinopathy [17,18]. Previous research by Squirrell D et al. indicated that diabetes status did not significantly influence the progression of diabetic retinopathy or retinal edema following cataract surgery, with preoperative glycemic control (HbA1c) being the primary determinant [7]. In our study, an increase in central foveal thickness was observed in both diabetic and non-diabetic groups six weeks post-cataract surgery. However, the thickening was more pronounced in diabetic patients, with an average increase of 49.9 μm compared to 39.6 μm in non-diabetics. This difference was statistically significant (p<0.0001), suggesting a heightened susceptibility of diabetic eyes to postoperative macular changes. Nevertheless, our findings indicate that cataract surgery in diabetic patients is associated with favorable visual outcomes and a reduced risk of macular edema progression when preoperative glycemic control is maintained. Surgeons should not hesitate to perform cataract surgery in diabetic patients, provided that there is no evidence of untreated macular edema or proliferative diabetic retinopathy preoperatively. Although macular edema may develop postoperatively, its occurrence is often part of the natural progression of diabetic retinopathy rather than a direct consequence of the surgical procedure. In most cases, postoperative diabetic macular edema follows a benign course, reinforcing the importance of proactive management and regular monitoring to optimize visual outcomes in diabetic patients undergoing cataract surgery.

Limitations of the study: The limitations of this study included a small sample size and a short follow-up period. The study could be enhanced by extending the duration of follow-up.

Cataract surgery with intraocular lens implantation shows favorable outcomes for diabetic patients. While post-operative visual acuity was better in non-diabetic patients compared to diabetics, this difference was not statistically significant during the trial. Complications following cataract surgery were more frequently observed in diabetic patients, with iritis and Descemet's membrane folds being the most common issues. However, the differences were still not statistically significant. Poor glycaemic control and the presence of diabetic retinopathy were linked to a noticeable decline in visual outcomes. After cataract extraction surgery, diabetic patients experienced a slightly greater increase in central foveal thickness as measured by OCT. Despite this, post-surgery visual acuity remained comparable between diabetic and non-diabetic patients. In conclusion, the pre-operative condition of diabetic retinopathy significantly impacts postoperative visual recovery. Evaluating changes in the severity of diabetic retinopathy after uncomplicated intraocular lens implantation may lead to improved visual results.

1. Li L, Wan XH, Zhao GH. Meta-analysis of the risk of cataract in type 2 diabetes. BMC Ophthalmol. 2014;14:94.
2. Yanoff M(ed), Duker J.S.(ed) Ophthalmology. Fourth edition. Elsevier Inc, 2014. [2]Pp. 541.
3. Chang LK, Sarraf D. Current and future approaches in the prevention and [3]treatment of diabetic retinopathy. Clin Ophthalmol. 2008;2(2):425-33.
4. Kim SJ, Equi R, Bressler NM. Analysis of macular edema after cataract surgery in patients with diabetes using optical coherence tomography. Ophthalmology. 2007;114(5):881-89.
5. Diabetic Retinopathy Clinical Research Network Authors/Writing Committee, Baker CW, Almukhtar T, Bressler NM, Glassman AR, Grover S, et al. Macular edema after cataract surgery in eyes without pre-operative central-involved diabetic macular edema. JAMA Ophthalmol. 2013;131(7):870-79.
6. Yang J, Cai L, Sun Z, Ye H, Fan Q, Zhang K, et al. Risk factors for and diagnosis [6]of pseudophakic cystoid macular edema after cataract surgery in diabetic patients. J Cat and Refractive Surg. 2017;43(2):207-14.
7. Squirrell D, Bhola R, Bush J, Winder S, Talbot JF. A prospective, case controlled study of the natural history of diabetic retinopathy and maculopathy after uncomplicated phacoemulsification cataract surgery in patients with type 2 diabetes. Br J Ophthalmol. 2002;86(5):565-71.
8. Romero-Aroca P, de la Riva-Fernandez S, Valls-Mateu A, Sagarra-Alamo R, Moreno-Ribas A, Soler N. Changes observed in diabetic retinopathy: eight-year follow-up of a Spanish population. Br J Ophthalmol. 2016;100(10):1366-71.
9. Zaczek A, Olivestedt G, Zetterstrom C. Visual outcome after phacoemulsification and IOL implantation in diabetic patients. Br J Ophthalmol. 1999;83(9):1036-41.
10. Dowler JG, Hykin PG, Lightman SL, Hamilton AM. Visual acuity following extracapsular cataract extraction in diabetes: a meta-analysis. Eye (Lond). 1995;9(Pt 3):313-17.
11. Krepler K, Biowski R, Schrey S, Jandrasits K, Wedrich A. Cataract surgery in patients with diabetic retinopathy: visual outcome, progression of diabetic retinopathy, and incidence of diabetic macular oedema. Graefes Arch Clin Exp Ophthalmol. 2002;240(9):735-38.
12. Ostri C. Intraocular surgery in a large diabetes patient population: risk factors and surgical results. Acta Ophthalmol. 2014;92 Thesis1:1-13.
13. Pollack A, Leiba H, Bukelman A, Oliver M. Cystoid macular oedema following cataract extraction in patients with diabetes. Br J Ophthalmol. 1992;76(4):221-24.
14. Dowler JG, Hykin PG, Hamilton AM. Phacoemulsification versus extracapsular cataract extraction in patients with diabetes. Ophthalmology. 2000;107(3):457-62.
15. Kokame GT, Flynn HW Jr BG. Posterior chamber intraocular lens implantation during diabetic pars plana vitrectomy. Ophthalmology. 1989;(5):603-10.
16. Klein R, Klein BE, Moss SE, Davis MD, DeMets DL. The Wisconsin epidemiologic study of diabetic retinopathy. III. Prevalence and risk of diabetic retinopathy when age at diagnosis is 30 or more years. Arch Ophthalmol (Chicago, Ill 1960). 1984;102(4):527-32.
17. Rema M, Premkumar S, Anitha B, Deepa R, Pradeepa R, Mohan V. Prevalence of diabetic retinopathy in urban India: The Chennai Urban Rural Epidemiology Study (CURES) Eye Study, I. Investig Ophthalmol Vis Sci. 2005;46(7):2328-33.
18. Gella L, Raman R, Kulothungan V, Saumya Pal S, Ganesan S, Sharma T. Retinal sensitivity in subjects with type 2 diabetes mellitus: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SN-DREAMS II, Report No. 4). Br J Ophthalmol. 2016;100(6):808-13.
19. Nathan DM. The diabetes control and complications trial/epidemiology of diabetes interventions and complications study at 30 years: Overview. Diabetes Care. 2014;37(1):9-16.