Study Overview
- Title: Comparing Stages of Diabetic Retinopathy with Systemic Vascular Status Using Finger Photoplethysmography
- Journal: *Retina*, February 2025
- DOI: 10.1097/IAE.0000000000004297
- Objective: Investigate the association between finger photoplethysmography (PPG) vascular markers and diabetic retinopathy (DR) severity to develop a noninvasive screening tool for early detection of severe DR.
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Key Findings
1. Diabetic Retinopathy (DR):
- DR is a leading cause of blindness in working-aged adults.
- Prevalence is higher in Type I diabetes (77.3%) than Type II (25.1%).
- In Malaysia, DR prevalence increased from 7.2% (2013) to 10.6% (2019).
2. Finger Photoplethysmography (PPG):
- PPG is a noninvasive, low-cost technique to measure blood volume changes in microvascular beds.
- PPG-derived indices include:
- PPG Fitness Index (PPGF): Measures vascular function and aging.
- Vascular Risk Prediction Index (VRPI): Predicts cardiovascular risk.
- Vascular Age (VascA): Assesses vascular performance relative to chronological age.
3. Need for Early DR Screening:
- Current DR screening methods (e.g., fundus photography) have limitations, including cataract interference and manual staging requirements.
- PPG offers a simple, noninvasive alternative for early detection of severe DR.
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Methods
1. Study Design:
- Cross-sectional observational study at Selayang Hospital, Malaysia (October 2020–May 2021).
- Included 141 Type II diabetic patients with DR.
- Excluded patients with ischemic heart disease, stroke, high blood pressure, or other retinal vascular diseases.
2. Data Collection:
- Clinical Parameters: Age, gender, blood pressure, HbA1c, visual acuity (logMAR), central macular thickness (CMT).
- PPG Parameters: PPGF, VRPI, VascA.
- DR severity classified into six stages: no DR, mild NPDR, moderate NPDR, severe NPDR, proliferative DR (PDR), and advanced diabetic eye disease (ADED).
3. Statistical Analysis:
- One-way ANOVA and Kruskal–Wallis tests for group comparisons.
- Pearson and Spearman correlations for parametric and nonparametric data.
- Multivariable linear regression to adjust for confounders.
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Results
1. Demographics:
- Mean age: 58.8 years; 56.4% female.
- Ethnic distribution: Malay (55%), Chinese (26.4%), Indian (18.6%).
- Mean HbA1c: 7.6%; mean systolic BP: 125.5 mmHg.
2. DR Severity and Clinical Parameters:
- HbA1c and systolic BP significantly higher in PDR and ADED groups.
- Visual acuity and CMT significantly worse in ADED group.
3. PPG Indices and DR Severity:
- PPGF: Significantly lower in PDR and ADED groups.
- VRPI: Significantly higher in PDR and ADED groups.
- VascA: Significantly higher in PDR and ADED groups.
- Multivariable regression confirmed strong associations between PPG indices and DR severity.
4. Correlations:
- Weak positive correlation between VRPI and HbA1c.
- No significant correlations between PPGF/VascA and age, BP, HbA1c, visual acuity, or CMT.
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Discussion
1. PPG as a Screening Tool:
- PPG indices (PPGF, VRPI, VascA) effectively differentiate severe DR (PDR, ADED) from milder stages.
- PPG is noninvasive, cost-effective, and suitable for primary care settings.
2. Clinical Implications:
- Early detection of severe DR using PPG can facilitate timely referral for treatments like laser therapy or anti-VEGF injections.
- PPG may complement existing screening methods, especially in resource-limited settings.
3. Limitations:
- PPG readings can be affected by temperature, movement artifacts, and skin pigmentation.
- Study limited to Type II diabetic patients; further research needed for Type I diabetes and other populations.
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### Conclusion
- Finger PPG markers (PPGF, VRPI, VascA) are significantly associated with DR severity.
- PPG can serve as a noninvasive screening tool to identify severe DR stages, enabling early intervention and improved patient outcomes.
- Further studies are needed to validate PPG's role in DR screening and explore its integration with other biomarker.
