European Journal of Cardiovascular Medicine

Globally, approximately 45 million people suffer from blindness, much of which is preventable or treatable. In India, cataracts account for about 66.2% of blindness in individuals over 50 years of age, according to the National Blindness and Visual Impairment Survey (2015–19).[1,2] Diabetes mellitus, a known contributor to early cataract development, further complicates this burden.[3]

The cornea, crucial for visual acuity, relies on a healthy endothelium-a single layer of non-regenerating cells that maintains corneal transparency through fluid regulation. At birth, the ECD (Endothelial Cell Density) is approximately 3000 cells/mm² and gradually declines with age.[4] A minimum density of 400–500 cells/mm² is essential for normal function. Diabetes can accelerate endothelial damage due to metabolic stress, manifesting as reduced ECD, pleomorphism, and polymegathism. Specular microscopy allows noninvasive evaluation of endothelial morphology and function, making it indispensable in pre- and postoperative assessments.[5] While the systemic effects of diabetes on the eye have been well-studied,[6] fewer investigations have focused on how manual SICS uniquely impacts corneal endothelium in diabetic versus non-diabetic patients.[7,8]

Though phacoemulsification offers advanced surgical outcomes, it may not be viable in low-resource settings due to high equipment costs.[9] SICS provides a cost-effective alternative with comparable results, especially in managing dense cataracts common in India.[10,11] However, concerns remain regarding endothelial cell loss during surgery, particularly in diabetic patients with preexisting corneal stress.[9] This study aims to compare corneal endothelial changes in diabetic and non-diabetic patients undergoing SICS to better understand the differential impact of diabetes on postoperative corneal health and aid in surgical planning and prognosis.

Aims and Objectives

The aim of this study was to evaluate the changes in corneal endothelium and central corneal thickness in patients with and without diabetes following manual SICS. The objectives include assessing the effect of SICS on corneal endothelial cell morphology, cell density, and central corneal thickness in both diabetic and non-diabetic patients; comparing endothelial cell morphology and cell loss postoperatively between the two groups; and evaluating differences in central corneal thickness after surgery to understand the impact of diabetes on corneal healing and endothelial response.

Study Design

This prospective observational study was conducted over a period of 18 months at the Department of Ophthalmology, People’s College of Medical Science and Research Center, Bhopal (M.P.), with the aim of evaluating corneal endothelial changes in diabetic and non-diabetic patients undergoing manual SICS. A total of 100 patients aged above 40 years with senile cataracts were enrolled from the outpatient department.

Inclusion and Exclusion Criteria

Patients included were those above 40 years of age scheduled for SICS, with or without a diagnosis of diabetes mellitus, and who provided informed consent to participate. Patients were excluded if they were under 40 years of age, had undergone any previous ocular surgery, had complicated or eventful cataract surgeries, or declined to participate in the study.

Data Collection Tools

The primary tools used for data collection in this study included the Snellen chart for assessing BCVA (Best-Corrected Visual Acuity), a slit-lamp biomicroscope for anterior segment evaluation, and indirect ophthalmoscopy for fundus examination. A clinical specular microscope (TomeyEM 4000) was used to assess corneal endothelial parameters, including ECD, CV, hexagonality, and CCT. Non-contact pachymetry integrated into the specular microscope was used for measuring CCT. Additionally, patient records and intraoperative documentation sheets were used to record demographic data and surgical details.

Data Collection Procedure

Eligible patients who consented to participate were enrolled and underwent a comprehensive preoperative ophthalmological examination. This included recording demographic data and clinical evaluation of visual acuity, anterior segment, and fundus. Preoperative specular microscopy was conducted to document endothelial parameters. Intraoperative data, such as the extent of pupillary dilation, use of dyes, capsulotomy technique, IOL type, surgical duration, and any complications, were recorded by the operating surgeon. Postoperative evaluations were conducted at 1 week and 6 weeks, during which BCVA, slit-lamp examination, and repeat specular microscopy were performed to monitor changes in ECD, CV, hexagonality, and CCT. All assessments were carried out using standardized methods to ensure consistency and reliability of the data.

Statistical Analysis

Data were analyzed using SPSS version 25.0 software. Continuous variables were presented as mean ± standard deviation. Paired t-tests and ANOVA were used to compare preoperative and postoperative endothelial parameters between diabetic and non-diabetic groups. A p-value of less than 0.05 was considered statistically significant, indicating a low probability that observed differences occurred by chance. However, while a significant p-value suggests statistical difference, it does not necessarily reflect clinical relevance, especially in large sample sizes where even small, potentially unimportant differences may appear significant.

Table 1 shows the age distribution among diabetic and non-diabetic patients. Both groups were comparable in age, with no statistically significant difference.

Table 2 compares the gender distribution between the groups, showing a female predominance in both, without significant difference.

Table 3 shows that endothelial cell loss increased with longer duration of diabetes, suggesting progressive endothelial vulnerability.

Table 4 presents baseline corneal parameters, showing statistically higher central corneal thickness in diabetics (p = 0.003), while other differences were not significant.

Table 5 shows a consistent decline in ECD in both groups post-surgery, with diabetics showing more loss, though not statistically significant.

Table 6 illustrates postoperative corneal thickening in both groups with delayed normalization in diabetics, though differences were not statistically significant.

Table 7 indicates higher postoperative morphological stress (increased CV, decreased 6A) in diabetics compared to non-diabetics, although none of the differences reached statistical significance.

The corneal endothelium plays an important role in maintaining corneal clarity, and its integrity can be challenged by intraocular procedures like Small Incision Cataract Surgery (SICS), particularly in patients with systemic conditions such as diabetes mellitus.^[12] This study aimed to compare the impact of SICS on corneal endothelial parameters in diabetic patients versus non-diabetic patients.

Preoperative Corneal Parameters

Our preoperative assessment revealed comparable age distributions and gender ratios between the diabetic and non-diabetic groups (p=0.5527 and p=0.3029, respectively), ensuring a baseline similarity for comparison. Regarding endothelial parameters, we found no statistically significant difference in preoperative mean ECD (p = 0.857), CV (p = 0.358), or percentage of hexagonal cells (6A) (p = 0.0742) between the groups. While our ECD finding aligns with Kudva et al.,^[13] it contrasts with Dhasmana et al.^[7] and Ahmed et al,^[14] who reported significantly lower preoperative ECD in diabetic patients. Our non-significant findings for CV and 6A preoperatively differ from studies focusing on postoperative changes where significance was sometimes observed.^[7,13,14]

Notably, our study found a statistically significantly higher mean CCT in diabetic patients compared to non-diabetic patients preoperatively (480.98 ± 15.07 µm vs. 460.24 ± 15.32 µm, p = 0.003). This finding suggests potential subclinical corneal alterations in the diabetic group even before surgery.

Postoperative Endothelial Cell Density and Loss

Following SICS, we observed a decrease in mean ECD in both groups at 1 week and further by 6 weeks, consistent with expected surgical trauma. The mean ECD remained lower in the diabetic group at both follow-up points, although the differences were not statistically significant (p = 0.6163 at 1 week, p = 0.6105 at 6 weeks). Correspondingly, the calculated percentage ECL was higher in the diabetic group compared to non-diabetic patients at both 1 week (5.64% vs. 2.21%) and 6 weeks (11.03% vs. 8.01%). However, these differences did not reach statistical significance (p = 0.072 at 1 week, p = 0.315 at 6 weeks).

This contrasts with several studies that reported significantly higher ECL in diabetic patients after SICS. Mathew et al.^[15] found higher ECL at 6 weeks (9.26% vs. 7.67%) and significantly higher ongoing loss by 3 months. Dhasmana et al.^[7], Raut et al.^[16], Kudva et al.^[13], and Ahmed et al.^[14] all reported significantly greater ECL or ECD reduction in diabetic patients. While our study aligns with the trend of greater ECL in diabetics, the lack of statistical significance might be related to our shorter follow-up period (6 weeks vs. 3 months in several cited studies), sample size, or specific nuances of the SICS technique employed.

Postoperative Central Corneal Thickness

Consistent with surgical inflammation and edema, CCT increased in both groups at 1 week post-operation and subsequently decreased by the 6th week. Throughout the follow-up, mean CCT remained higher in the diabetic group, reflecting the significantly higher preoperative baseline. However, the differences in CCT between the groups at 1 week (p = 0.5107) and 6 weeks (p = 0.8431) were not statistically significant.

This finding differs from several studies^[7,13,14,16] that reported significantly greater increases or persistently higher CCT in diabetic patients postoperatively, suggesting slower edema resolution. Mathew et al.^[15] noted a significantly greater reduction in CCT between weeks 2 and 6 in diabetics, indicating different recovery dynamics. While our study showed higher CCT values in diabetics postoperatively, the lack of a significant difference compared to non-diabetic patients might again be influenced by the follow-up duration or the significant preoperative difference.

Postoperative Endothelial Morphology (CV and Hexagonality)

Changes in CV (polymegathism) and 6A (pleomorphism) reflect endothelial stress and repair. In our study, mean CV increased progressively in the diabetic group over 6 weeks, while it decreased initially and then stabilized in the control group. Despite this diverging trend, the difference between groups was not statistically significant at any time point (p = 0.134 pre-op, p = 0.521 at 1 week, p = 0.851 at 6 weeks). This aligns partially with Dhasmanaet al.^[7] who found no significant difference in CV change, but contrasts with Kudva et al.^[13] and Ahmed et al.^[14] who reported significantly increased CV in diabetics postoperatively.

The percentage of hexagonal cells (6A) decreased postoperatively in both groups, remaining lower in diabetic patients. The difference between groups was not significant at any time point (p = 0.9018 pre-op, p = 0.3676 at 1 week, p = 0.5091 at 6 weeks). This finding aligns with Raut et al.^[16] but differs from Dhasmana et al.^[7] (significant detrimental change) and Kudva et al.^[13] (significant difference at 3 months). The lack of significant morphological changes in our study might suggest less pronounced stress or slower manifestation within the 6-week timeframe.

Overall, our study observed trends towards greater endothelial cell loss, higher central corneal thickness, and increased polymegathism in diabetic patients compared to non-diabetic patients following SICS. However, unlike several previous reports^[7,13,14,16] these differences generally did not achieve statistical significance within our 6-week follow-up period, with the exception of preoperative CCT.

The consistent direction of these trends, nonetheless, aligns with the broader literature suggesting that the diabetic corneal endothelium possesses less functional reserve and is more vulnerable to surgical stress.^[15,16] The lack of statistical significance in our postoperative comparisons could be attributed to factors such as the limited follow-up duration compared to studies extending to 3 months, the specific sample size, inherent variability within the diabetic population (e.g., glycemic control duration, although often found uncorrelated^[13,14]), or subtle differences in surgical execution. Morya et al.^[17] highlighted the impact of technique variations (OVD vs. BSS) on endothelial outcomes, underscoring the multifactorial nature of ECL.

Limitations of this study include its single-center design, the 6-week follow-up which may be insufficient to capture longer-term endothelial remodeling or loss, and the sample size, which might limit the power to detect smaller differences as statistically significant.

Despite these limitations, the observed trends reinforce the clinical consideration that diabetic corneas may respond differently to SICS. While statistical significance was not uniformly demonstrated postoperatively in this cohort, the tendency towards greater endothelial compromise warrants careful surgical technique and supports the recommendation for preoperative endothelial evaluation in diabetic patients undergoing cataract surgery, as advised by numerous authors.^[7,13]

  Limitations

Limitations of this study include its single-center design, small sample size, and short follow-up period of 6 weeks, which may be insufficient to capture longer-term endothelial remodeling or loss. These limitations might have affected the power to detect smaller differences as statistically significant. It is recommended to conduct more research with larger sample sizes and longer follow-up periods to validate the conclusions proposed in this study.

Diabetic patients undergoing cataract surgery exhibit greater corneal endothelial damage, including reduced cell density, increased corneal thickness, decreased hexagonality, and higher variation in cell size, indicating a lower functional reserve. These morphological abnormalities suggest the need for thorough preoperative corneal assessment and careful surgical techniques to protect the endothelium in diabetics.

1.       Pizzarello L, Abiose A, Ffytche T, et al. VISION 2020: The Right to Sight: a global initiative to eliminate avoidable blindness. Arch Ophthalmol 2004;122(4):615-20.

2.       Vashist P, Senjam SS, Gupta V, et al. Blindness and visual impairment and their causes in India: Results of a nationally representative survey. PLoS One 2022;17(7):e0271736.

3.       Saeedi P, Petersohn I, Salpea P, et al. Global and regional diabetes prevalence estimates for 2019 and projections for 2030 and 2045: Results from the International Diabetes Federation Diabetes Atlas. Diabetes Research and Clinical Practice 2019;157:107843.

4.       Vaiciuliene R, Rylskyte N, Baguzyte G, Jasinskas V. Risk factors for fluctuations in corneal endothelial cell density. Experimental and Therapeutic Medicine 2022;23(2):129.

5.       Krachmer JH, Mannis MJ, Holland EJ. Cornea E-Book. Elsevier Health Sciences 2010. https://books.google.co.in/books?id=eR0PDQAAQBAJ.

6.       Shih K, Lam KS, Tong L. A systematic review on the impact of diabetes mellitus on the ocular surface. Nutrition & Diabetes 2017;7(3):e251.

7.       Dhasmana R, Singh IP, Nagpal RC. Corneal changes in diabetic patients after manual small incision cataract surgery. J Clin Diagn Res 2014;8(4):VC03-6.

8.       Yang C, An Q, Zhou H, et al. Research progress on the impact of cataract surgery on corneal endothelial cells. Adv Ophthalmol Pract Res 2024;4(4):194-201.

9.       Fahmi A, Bowman R. Administering an eye anaesthetic: principles, techniques, and complications. Community Eye Health 2008;21(65):14-7.

10.    Gurnani B, Kim J, Tripathy K, et al. Iritis. Treasure Island (FL): StatPearls Publishing 2025. https://www.ncbi.nlm.nih.gov/books/NBK430909/.

11.    Venkatesh R, Veena K, Ravindran RD. Capsulotomy and hydroprocedures for nucleus prolapse in manual small incision cataract surgery. Indian J Ophthalmol 2009;57(1):15-8.

12.    Yanoff M, Duker JS, Augsburger JJ. Ophthalmology. An expert consult title online + print. Mosby Elsevier 2009. https://books.google.co.in/books?id= u43MTFr7-m8C.

13.    Kudva AA, Lasrado AS, Hegde S, et al. Corneal endothelial cell changes in diabetics versus age group matched nondiabetics after manual small incision cataract surgery. Indian J Ophthalmol 2020;68(1):72-6.

14.    Ahmed Z, Ahmed SM, Tasneem AF, et al. Endothelial cell changes after small incision cataract surgery in diabetic and non-diabetic patients: a cohort study. Int J Med Ophthalmol 2022;4(1):23-9.

15.    Mathew PT, David S, Thomas N. Endothelial cell loss and central corneal thickness in patients with and without diabetes after manual small incision cataract surgery. Cornea 2011;30(4):424-8.

16.    Raut N, Sonarkhan S, Chauhan R. Corneal endothelial cell loss after small incision cataract surgery in diabetic verses non diabetic patients. Med Res Chron 2016;3(1):146-55.

17.    Morya AK, Gurnani B, Mishra D, et al. Comparison of corneal endothelial cell loss during manual small-incision cataract surgery using viscoelastic-assisted nucleus removal versus continuous balanced salt solution plus technique - Randomized controlled trial. Indian Journal of Ophthalmology 2022;70(11):3960-6.