Cataract Repair: 20-Year Outcomes In Diabetic Patients
Overview
This study aimed to assess the 20-year outcomes in terms of best-corrected visual acuity (BCVA) and subjective visual function, as measured by the VF-14 questionnaire, following cataract surgery in individuals with type 2 diabetes compared to those without diabetes.
A prospective, longitudinal, population-based cohort study included 109 individuals with type 2 diabetes and 698 non-diabetic individuals who underwent cataract surgery within a one-year period at a single institution. BCVA and VF-14 questionnaire responses were recorded both before and after surgery, and at five-year intervals for up to 20 years post-surgery. Retinopathy levels were assessed before the surgical procedure.
The study found no statistically significant difference in the change in BCVA between diabetic and non-diabetic individuals at 10, 15, and 20 years post-surgery (p=0.45, p=0.44, and p=0.83, respectively). Similarly, there were no significant differences in self-reported visual function (VF-14) between the two groups at any time following surgery (p=0.72, p=0.20, and p=0.78, for the 10 to 20-year period).
The study also revealed that there was no significant difference in BCVA based on retinopathy levels before surgery, even at the 20-year mark (p=0.1). However, a trend was observed from 10 years post-surgery onwards, where patients without retinopathy at baseline experienced fewer declines in vision over the 20-year period compared to diabetic patients with retinopathy. Furthermore, individuals with known type 2 diabetes at the time of surgery had a significantly lower survival rate compared to non-diabetic individuals at each follow-up (p=0.003).
In individuals with diabetes who survived, this study demonstrated that BCVA and subjective visual function remained largely stable for up to 20 years after cataract surgery. Therefore, cataract extraction appears to be an effective procedure for sustaining long-term improvements in visual function, even in individuals with type 2 diabetes. This knowledge is crucial when advising individuals with diabetes on the potential benefits of cataract surgery.
Introduction
Diabetes mellitus (DM) is a highly debilitating chronic disease with a rapidly increasing global prevalence and burden. Over the past decade (2005-2021), the number of diagnosed DM patients has surged from approximately 333 million to 537 million, and this number is projected to reach a staggering 783 million by 2045 (source: IDF Diabetes Atlas, 2021). Notably, there is a well-established connection between cataracts and late-onset type 2 diabetes, with diabetic individuals at a heightened risk of developing cortical and posterior subcapsular cataracts, often necessitating cataract surgery at an earlier age (references: Chang et al., 2011; Klein et al., 1995). It is estimated that up to 20% of cataract surgeries are performed on diabetic patients (source: Rossi et al., 2020).
Beyond improving visual acuity (VA), cataract surgery in diabetic patients serves another critical purpose—facilitating the screening and treatment of diabetic retinopathy (DR). Unlike older surgical methods like extracapsular cataract surgery, modern small-incision phacoemulsification (PE) has demonstrated favorable and safer outcomes in terms of postoperative DR progression and macular edema (references: Romero-Aroca et al., 2006; Squirrell et al., 2002).
Existing research has consistently shown that VA generally improves after cataract surgery in most diabetic patients (references: Danni et al., 2019; Han et al., 2020; Liu et al., 2019). However, our understanding of the long-term visual outcomes remains limited, primarily due to the relatively short follow-up periods in most prospective studies, which are typically less than a decade (reference: Lundqvist & Mönestam, 2012). Despite the fact that diabetic patients still have a higher mortality rate compared to the general population, their life expectancy has improved (reference: Laatikainen et al., 2016). Consequently, there is a pressing need for comprehensive, long-term data on visual function post-surgery in diabetic individuals.
This study’s primary objective is to prospectively assess the 20-year longitudinal outcomes in best-corrected visual acuity (BCVA) and subjective visual function following PE surgery in type 2 diabetic patients, with a comparative analysis against non-diabetic individuals. The evaluation of visual function will involve a questionnaire addressing the self-assessed ability to perform activities dependent on vision. This research aims to contribute vital insights into the extended-term consequences of cataract surgery in diabetic patients, thereby enhancing our knowledge of its efficacy in this population.
Method
This prospective, population-based study, whose study design and methods were previously detailed (references: Mönestam, 2016; Mönestam et al., 2005), aimed to examine a geographically defined cohort of cataract surgery patients over a 20-year period. The study received prior approval from the institutional review board/ethics committee of Umeå University, and informed consent obtained from all participants in accordance with the Helsinki Declaration.
The cohort comprised 810 patients aged 30 to 96 years who underwent surgery for senile and presenile cataract between June 1, 1997, and May 31, 1998. Only the first eye operated on was considered for patients who had surgery on both eyes during the study period.
All patients underwent a standardized, dilated eye examination, including best-corrected visual acuity (BCVA) assessments before and shortly after surgery. They also completed a visual function questionnaire (VF-14) that assessed their self-perceived difficulties in performing visually demanding tasks (reference: Steinberg et al., 1994).
Diabetic retinopathy (DR) severity was clinically assessed using the International Clinical Diabetic Retinopathy Severity Scales (reference: Wilkinson et al., 2003). DR was categorized into four stages: no DR, mild non-proliferative DR (NPDR), moderate to severe NPDR, and Proliferative DR (PDR) past or present. Patients with a history of PDR before surgery were classified as having proliferative DR, even if it was not active at the time of cataract surgery.
Surviving patients who were willing to participate underwent repeat examinations and questionnaires at 5, 10, 15, and 20 years after surgery. In cases where patients could not travel to the clinic, they completed the questionnaire only.
Additionally, it was checked whether patients initially classified as non-diabetic developed diabetes during the 20-year follow-up period. Diabetes was defined as continuous treatment with insulin and/or oral glucose-lowering medications.
The VF-14 questionnaire, a well-established patient-reported outcome instrument in ophthalmology, assessed activity limitations in 14 vision-specific daily life tasks. Scores ranged from 0 to 100, with higher scores indicating better visual function. The same questionnaire was administered at multiple time points, enabling longitudinal comparisons of scores.
Ten years after surgery, 396 of the original 807 patients remained alive, with 35 of them having preoperatively known diabetes, 17 newly diagnosed with diabetes, and 344 having no diabetes. Twenty years after surgery, 133 patients from the original cohort were still alive, including 6 with preoperative diabetes, 20 new diabetes diagnoses in the 10-20 year postoperative period, and 107 without diabetes.
To refine the assessment of diabetes’s long-term impact on visual function after cataract surgery, two patient subsets were selected. The first group comprised patients who never had a diabetes diagnosis or any other ocular disease pre- or postoperatively and had a follow-up of 10 years or more (n=306, control group). The second group consisted of patients with a diagnosis of type 2 diabetes with or without DR at surgery but no other ocular disease and had a follow-up of 10 years or more (n=38, diabetic group).
Regarding the surgical procedure, most patients underwent standard sutureless clear corneal phacoemulsification (PE) with a 3.2mm temporal incision and the implantation of a posterior chamber foldable intraocular lens (IOL). The majority received an acrylic hydrophobic IOL (Alcon Acrysof® MA60BM) (95%).
Statistical Methods
In this study, various statistical methods were employed to analyze the data collected from patients who underwent cataract surgery. Here is a summary of the key statistical methods used:
- Measurement of Visual Acuity (VA):
– VA was assessed using ETDRS-charts, and the results were recorded as the total number of letters read correctly.
– VA measurements were then transformed into the logMAR (logarithm of the minimum angle of resolution) scale, a common method for quantifying visual acuity.
– Patients who could not read any letters were evaluated using alternative measures, such as counting fingers (CF), hand movements (HM), and light perception (P).
– Specific logMAR values were assigned to these alternative measures: CF in front of the eye = logMAR 2.2, HM = logMAR 2.5, and no light perception = logMAR 3. These values were applied in a manner consistent with prior research (reference: Mönestam, 2016).
- Postoperative Change in BCVA:
– The change in best-corrected visual acuity (BCVA) after surgery was calculated by subtracting the logMAR score obtained 1-2 months after surgery from the logMAR scores recorded at each subsequent follow-up.
– A positive value indicated an improvement in visual acuity compared to the initial postoperative assessment.
- Data Analysis:
– All collected data were examined for normality. If data did not follow a normal distribution, non-parametric analyses were utilized.
– For normally distributed continuous variables, mean values along with their standard deviations (SD) were reported. Skewed data were presented as medians, with corresponding minimum and maximum values.
– Categorical variables were presented as counts and percentages.
- Statistical Tests:
– Independent samples median test with Bonferroni correction was used for multiple comparisons in VA data analysis.
– Kruskal-Wallis tests were employed to analyze differences in VA data among groups.
– Independent sample t-tests were applied to compare age differences and differences in VF-14 scores (subjective visual function).
– For qualitative data presented in tables, Yates-corrected chi-square tests or Fisher’s tests were used.
– The chi-square for trend was used to assess the survival rates of non-diabetic and diabetic patients at the time of surgery.
– Repeated measures tests were utilized to compare changes in BCVA (logMAR) and VF-14 scores over the course of follow-up examinations.
- Significance Threshold:
– All statistical tests were two-sided, and a p-value of less than 0.05 was considered statistically significant.
- Software:
– Data analysis was performed using SPSS (Statistical Package for the Social Sciences for MS Windows, software version 27.0, SPSS Inc.).
These statistical methods allowed for the rigorous examination of visual acuity and subjective visual function data collected throughout the study, enabling researchers to draw meaningful conclusions and identify significant trends and differences among various patient groups.
Result
This study focused on the outcomes of cataract surgery in patients with type 2 diabetes and non-diabetic individuals, with a specific emphasis on visual acuity (VA) and subjective visual function, as assessed by the VF-14 questionnaire. Here’s a summary of the key findings:
- Diabetes Status at Surgery:
– Out of the 112 patients initially identified with diabetes, 109 (97%) had type 2 diabetes, while the remaining 3% had type 1 diabetes.
– Over the course of the study, the number of patients with type 2 diabetes at the 15-year follow-up decreased to 35 out of 359 (9.7%).
– At the 20-year follow-up, only 6 out of 133 (5.3%) patients had known type 2 diabetes at surgery, and an additional 20 patients received a new diagnosis of diabetes post-surgery.
– Patients with known type 2 diabetes at surgery had significantly lower survival rates compared to non-diabetic patients at all follow-up points (p=0.003).
- Visual Acuity Changes:
– Preoperatively, there was no significant difference in median BCVA between patients with type 2 diabetes and non-diabetics (0.7 vs. 1.0; p=0.83).
– However, postoperatively, non-diabetic patients had significantly better BCVA (0.15 vs. 0.097; p=0.007).
– The improvement in BCVA (preoperative VA – postoperative VA) was not statistically different between diabetics and non-diabetics (p=0.29).
– Longitudinal analysis over 20 years showed that, from 10 years or more after surgery, the BCVA of diabetics was slightly, but not significantly, better than that of non-diabetics (p = 0.45, p = 0.44, and p = 0.83 at 10, 15, and 20 years, respectively).
- “Best Cases” of Visual Acuity Changes:
– Among the selected “best cases” with or without diabetes, there were no significant differences in median BCVA at any examination point, including preoperatively, postoperatively, and at 10 and 20 years after surgery.
– Interestingly, at 10 and 20 years after surgery, participating diabetics had lost fewer letters in BCVA compared to non-diabetics, but this difference was not significant.
- Subjective Visual Function (VF-14 Questionnaire):
– There was no significant difference in self-perceived visual function between diabetics and non-diabetics at any time, including before surgery.
– Both diabetics and non-diabetics reported significant improvements in VF-14 scores after cataract surgery (p < 0.001).
– Longitudinal analysis over 20 years showed that, although mean VF-14 scores were slightly better in diabetics at 10, 15, and 20 years after surgery, these differences were not statistically significant.
- Visual Acuity in Relation to Diabetic Retinopathy Severity:
– Among patients with type 2 diabetes at the time of surgery, those with no diabetic retinopathy (DR) at baseline tended to lose fewer letters in BCVA over the 20-year period compared to those with retinopathy.
– Surviving patients with DR had only a small decline in BCVA at 20 years.
In conclusion, this study found that cataract surgery generally resulted in improved visual acuity and subjective visual function for both diabetic and non-diabetic patients. While there were some variations in visual outcomes, especially in the long term, the differences between diabetics and non-diabetics were not statistically significant in most cases. Furthermore, the presence of diabetic retinopathy did not seem to have a significant impact on visual outcomes in the context of cataract surgery.
Conclusion
This study investigated the 20-year visual outcomes following cataract surgery in diabetic patients compared to non-diabetic individuals. The key findings are as follows:
– Positive Visual Outcomes: The majority of diabetic patients, similar to non-diabetics, experienced significant improvements in best-corrected visual acuity (BCVA) after cataract surgery.
– Long-Term Comparability: The long-term results in terms of BCVA and subjective visual function, as assessed by the VF-14 questionnaire, were comparable between diabetic and non-diabetic patients, extending up to 20 years post-surgery.
– Consistency with Previous Research: These findings align with prior research indicating favorable visual outcomes in diabetic patients, especially those without retinopathy.
– Impact of Retinopathy: Studies have shown that postoperative BCVA and visual acuity gain can be negatively affected by the severity of diabetic retinopathy. Vision-threatening stages of diabetic retinopathy can have a substantial impact on overall visual function.
– Study Design and Limitations: The study evaluated diabetic retinopathy status at the time of cataract surgery but was not designed to assess the influence of cataract surgery on postoperative diabetic retinopathy. It’s noted that many individuals with type 2 diabetes are initially undiagnosed, and the duration of diabetes plays a significant role in the development of diabetic retinopathy.
– Diabetes Care Advancements: The study acknowledges improvements in diabetes care over the years, including enhanced screening programs and advancements in eye care for diabetic complications. This likely contributed to the relatively good visual outcomes observed in the diabetic cohort.
– Survival and Diabetic Complications: The study found that a smaller percentage of diabetics diagnosed before cataract surgery were alive at various time points (10, 15, and 20 years) compared to non-diabetics. Diabetes-related complications can affect survival rates, with healthier diabetics potentially having better outcomes.
– Macular Edema: Pseudophacic macular edema (ME) remains a common cause of reduced visual acuity after cataract surgery. However, the study did not specifically assess the impact and development of ME following cataract surgery.
– Strengths: The study’s strengths include its prospective, long-term, longitudinal design, high follow-up rates, and a large number of patients. Additionally, the surgical techniques used were comparable to modern cataract surgery methods.
– Limitations: Limitations include small sample sizes for long-term follow-up in diabetic patients, potential selection bias, and the possibility of unmeasured confounding factors.
In conclusion, this study provides valuable insights into the long-term outcomes of cataract surgery in diabetic patients. It highlights that timely cataract surgery can be beneficial for most diabetics, with the potential for sustained positive visual outcomes for up to 20 years post-surgery. These findings are important for surgical decision-making and counseling of diabetic patients facing cataract surgery, though further research may be needed to explore additional factors influencing surgical outcomes in type 2 diabetics.
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