Longitudinal Observational Study of Diabetic Retinopathy Progression in Type 2 Diabetes Patients (IMPORTANT)

IMaging Pre-PrOlifeRative sTAge of Diabetic retiNopaThy to Guarantee Timely Treatment - IMPORTANT

The purpose of this clinical study is to explore imaging, functional and systemic biomarkers of diabetic retinopathy (DR) progression, in Type 2 Diabetes (T2D) patients with moderate to severe non-proliferative diabetic retinopathy (NPDR) and mild proliferative diabetic retinopathy (PDR) using state of the art methodologies, commonly applied in clinical practice, over a period of two years. This study will provide longitudinal data to better understand retinal changes in moderate to severe diabetic retinopathy and early proliferative diabetic retinopathy and help guide timely interventions to prevent vision loss.

Study Overview

• Status: Recruiting
• Conditions: Diabetes Mellitus, Type 2; Diabetic Retinopathy; Retinal Disease; Diabetic Complication

Detailed Description

Diabetes Mellitus (DM) is an important public health problem, affecting about 589 million people in the world, and expected to reach 853 million by 2050. Active screening for DR is important because most patients may be asymptomatic until the very late stages. Nonproliferative diabetic retinopathy (NPDR) itself may be associated with reduced visual function and quality of life measures (Willis et al., 2017).

The molecular pathophysiology of DR is complex, and a complete model of the disease is still being elucidated. The oxidative stress in diabetes upregulates multiple cytokines and chemokines, such as vascular endothelial growth factor (VEGF), angiopoietins, tumour necrosis factor (TNF), interleukins (ILs) and matrix metalloproteinases (MMPs) that leads to breakdown of the blood-retinal-barrier (BRB). Also, retinal capillary obstruction (leukostasis) or dropout (apoptosis of vascular cells) in diabetes leads to tissue ischemia and hypoxia causing increased retinal VEGF expression through transcriptional regulation by hypoxia-inducible factor 1 alpha (HIF-1α) (Arjamaa & Nikinmaa, 2006; Whitehead et al., 2019).

The risk of developing DR complications increases over time, with increasing areas of capillary nonperfusion underpinning progression to more severe forms and development of complications as PDR or diabetic macular edema (DME), driven by hypoxia and hyperexpression of proangiogenic growth factors. However, this risk varies widely, independently of metabolic control. Differentiating patients with higher risk of progression and development of vision-threatening complications (VTC; DME and PDR) is of paramount importance for efficient treatment of the disease in order to prevent vision disability and achieve better visual outcomes. Recent developments in terms of retina imageology, namely Optical Coherence Tomography (OCT) and OCT Angiography (OCTA), have improved the understanding of DR pathophysiology and evolution, with a better characterization of venous abnormalities including occlusion, tortuosity, dilatation, looping or beading. OCTA examination is faster and safer compared to examination with fluorescein angiography (FA), and it can visualise the retinal vasculature in any layer of the retina. OCTA has the potential to become the examination of choice to identify eyes at risk of progression and development of VTC.

The purpose of this observational, non-interventional, prospective, and longitudinal clinical study is to explore imaging, functional and systemic biomarkers of DR progression, in T2D patients with moderate to severe NPDR and mild PDR - Diabetic Retinopathy Severity Scale (DRSS) levels 43, 47, 53, and 61 - using state of the art methodologies, commonly applied in clinical practice.

Follow-up visits will be performed every 6 months for 2 years with a total of 5 visits. Participants will undergo the following assessments: multimodal retinal imaging, including OCT, OCTA, ultra-widefield (UWF) fundus fluorescein angiography (FFA) and fundus photography (FP), and color fundus photography (CFP); functional testing: best corrected visual acuity (BCVA) and microperimetry (Macular Integrity Assessment, MAIA); collection of systemic health variables, including glycated hemoglobin (HbA1c), blood pressure, diabetes duration, and relevant comorbidities.

• Study Type: Observational
• Enrollment (Estimated): 100

Contacts and Locations

• Study Contact: Name: Joana Tavares, PhD; Phone Number: +351239480137; Email: jftavares@aibli.pt
• Study Contact Backup: Name: Liliana C Soares, MsC; Phone Number: +351239480105/131; Email: important_4c@aibili.pt

Study Locations

• Portugal
  • Coimbra, Portugal, 3000-548
    • Recruiting
    • AIBILI-CEC (AIBILI-Clinical Trial Centre)
    • Contact: Joana Tavares, PhD; Phone Number: +351 239 480 137; Email: jftavares@aibili.pt
    • Contact: Inês P Marques, MD PhD; Phone Number: +351 239 480 124; Email: ipmarques@aibili.pt

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Study Population: Patients with moderate to severe NPDR and mild PDR. Ideally, the distribution of participants will be as follows: 40 for Diabetic Retinopathy Severity Scale (DRSS) level 43, 40 for DRSS level 47, and 20 for DRSS levels 53-61

Description

Inclusion Criteria:

• Type 2 diabetes mellitus (T2D) according to 1985 World Health Organization (WHO) criteria.
• Age between 35 and 80 years.
• Best-corrected visual acuity (BCVA) ≥ 69 letters (20/40).
• Refraction with a spherical equivalent less than 5 diopters.
• Non-proliferative diabetic retinopathy (NPDR; DRSS levels 43, 47, 53) or mild proliferative diabetic retinopathy (PDR; DRSS level 61: Neovascularization Elsewhere (NVE) < ½ disc area in ≥ 1 quadrant, no Neovascularization of the Disc (NVD), no vitreous or sub-hyaloid hemorrhage), in which panretinal photocoagulation (PRP) and/or intravitreal anti-VEGF treatment can safely be deferred for at least 6 months, based on consensus between patient and investigator - using ETDRS criteria, 7-field equivalent area on ultra-widefield fundus imaging.
• Ability to understand and sign the written Informed Consent Form (ICF).

Exclusion Criteria:

• Central subfield thickness (CST) > 400 μm (fluid allowed if CST ≤ 400 μm and foveal contour is normal, as determined by the Central Reading Centre, and treatment is not immediately required).
• Any sign of retinal fibrovascular proliferation.
• Uncontrolled glaucoma (intraocular pressure > 25 mmHg regardless of concomitant IOP-lowering medications) or neovascular glaucoma.
• Any sign of iris neovascularization, vitreous, or pre-retinal hemorrhage.
• Other retinal vascular diseases (ocular ischemic syndrome, retinal arterial or venous occlusion, exudative age-related macular degeneration, etc.).
• Previous panretinal photocoagulation (PRP) or intravitreal injection treatment.
• Any eye surgery within 6 months prior to the inclusion visit.
• Significant media opacities including severe cataract, corneal scarring or edema, or vitreous hemorrhage that precludes fundus evaluation.
• Pupil dilation < 5 mm.

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in capillary skeletonized vessel density (SVD)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in capillary non-perfusion using skeletonized vessel density (SVD) in the superficial and deep retinal vascular layers assessed with Optical Coherence Tomography Angiography.	Baseline to 24 months
Changes in capillary perfusion density (PD) using OCTA	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in capillary non-perfusion using binarized vessel density (VD) as perfusion density (PD) in the superficial and deep retinal vascular layers assessed with Optical Coherence Tomography Angiography.	Baseline to 24 months
Foveal Avascular Zone (FAZ) area	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in the area of the foveal avascular zone measured in square millimeters (mm²) using Optical Coherence Tomography Angiography automated segmentation tools across DRSS levels.	Baseline to 24 months
Foveal Avascular Zone (FAZ) perimeter	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in the perimeter of the foveal avascular zone measured in millimeters (mm) using Optical Coherence Tomography Angiography automated segmentation tools across DRSS levels.	Baseline to 24 months
Foveal Avascular Zone (FAZ) circularity	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in the circularity of the foveal avascular zone using Optical Coherence Tomography Angiography automated segmentation tools across DRSS levels.	Baseline to 24 months
Changes in retinal ischemic area using UWF FFA	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in retinal ischemic area (mm2) across DRSS levels.	Baseline to 24 months
Changes in central retinal thickness (CRT)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in Central Retinal Thickness (CRT) assessed using Optical Coherence Tomography (OCT) across DRSS levels.	Baseline to 24 months
Changes in central intraretinal fluid	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in intraretinal fluid (layer-specific) assessed using Optical Coherence Tomography (OCT) across DRSS levels.	Baseline to 24 months
Changes in Disorganisation of Retinal Inner Layers (DRIL)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in Disorganisation of Retinal Inner Layers (DRIL) assessed using Optical Coherence Tomography (OCT) across DRSS levels.	Baseline to 24 months
Changes in Disorganisation of Retinal Outer Layers (DROL)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in Disorganisation of Retinal Outer Layers (DROL) assessed using Optical Coherence Tomography (OCT) across DRSS levels.	Baseline to 24 months
Changes in Ganglion Cell Layer (GCL) + Inner Plexiform Layer (IPL) thickness	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in Ganglion Cell Layer (GCL) + Inner Plexiform Layer (IPL) thickness assessed using Optical Coherence Tomography (OCT) across DRSS levels.	Baseline to 24 months
DRSS severity level	Evaluate the DRSS score (range 10-85; higher scores indicate worse severity) in Ultra-widefield fundus photography (UWF-FP).	Baseline to 24 months
Changes in microaneurysm (MA) count	Evaluate baseline differences and longitudinal changes (from baseline to months 6, 12, and 24) in MA number in colour fundus photography (CFP field 2) across DRSS levels.	Baseline to 24 months
Changes in microaneurysm (MA) turnover	Evaluate baseline differences and longitudinal changes (from baseline to months 6, 12, and 24) in MA turnover in colour fundus photography (CFP field 2) across DRSS levels.	Baseline to 24 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in DRSS levels	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in DRSS classification, including one-step and two-step changes across DRSS levels.	Baseline to 24 months
Changes in Best Corrected Visual Acuity (BCVA)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in BCVA, measured on the Early Treatment Diabetic Retinopathy Study (ETDRS) chart at a starting distance of 4 meters.The BCVA letter score ranges from 0 to 100 (best score), and a gain in BCVA from baseline indicates an improvement in visual acuity.	Baseline to 24 months
Retinal sensitivity using MAIA Microperimetry	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in average macular sensitivity (dB), fixation indices P1 and P2 (%), and Bivariate Contour Ellipse Area (BCEA; 63% and 95%) across DRSS levels.	Baseline to 24 months
Changes in Intraretinal Microvascular Abnormalities (IRMAs)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in presence and area of IRMAs using Swept-Source-OCTA and FFA, including location-specific analysis across posterior pole and mid-periphery across DRSS levels.	Baseline to 24 months
Changes in neovascularization (NV)	Evaluate baseline differences and longitudinal changes (from baseline to month 24) in presence and area NV using Swept-Source-OCTA and FFA, including location-specific analysis across posterior pole and mid-periphery across DRSS levels.	Baseline to 24 months

Collaborators and Investigators

• Sponsor: Association for Innovation and Biomedical Research on Light and Image
• Collaborators: Fundação para a Ciência e a Tecnologia
• Investigators: Principal Investigator: Inês P Marques, MD PhD, AIBILI - Associação para a Investigação Biomédica e Inovação em Luz e Imagem

Publications and helpful links

General Publications

• Arjamaa O, Nikinmaa M. Oxygen-dependent diseases in the retina: role of hypoxia-inducible factors. Exp Eye Res. 2006 Sep;83(3):473-83. doi: 10.1016/j.exer.2006.01.016. Epub 2006 Jun 5.
• Willis JR, Doan QV, Gleeson M, Haskova Z, Ramulu P, Morse L, Cantrell RA. Vision-Related Functional Burden of Diabetic Retinopathy Across Severity Levels in the United States. JAMA Ophthalmol. 2017 Sep 1;135(9):926-932. doi: 10.1001/jamaophthalmol.2017.2553.
• Whitehead M, Osborne A, Widdowson PS, Yu-Wai-Man P, Martin KR. Angiopoietins in Diabetic Retinopathy: Current Understanding and Therapeutic Potential. J Diabetes Res. 2019 Aug 14;2019:5140521. doi: 10.1155/2019/5140521. eCollection 2019.

Study record dates

Study Major Dates

• Study Start (Actual): November 24, 2025
• Primary Completion (Estimated): December 1, 2027
• Study Completion (Estimated): June 1, 2028

Study Registration Dates

• First Submitted: February 26, 2026
• First Submitted That Met QC Criteria: March 5, 2026
• First Posted (Actual): March 9, 2026

Study Record Updates

• Last Update Posted (Actual): March 11, 2026
• Last Update Submitted That Met QC Criteria: March 9, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Disease biomarkers
• Additional Relevant MeSH Terms: Endocrine System Diseases; Vascular Diseases; Cardiovascular Diseases; Metabolic Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Eye Diseases; Diabetic Angiopathies; Nutritional and Metabolic Diseases; Retinal Diseases; Diabetic Retinopathy; Diabetes Mellitus, Type 2; Diabetes Complications
• Other Study ID Numbers: 4C-2025-17

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No