The GLIDE study looks at how the small blood vessels of the eye respond during the first months of a new diabetes medicine. Two widely used classes of glucose-lowering drugs, GLP-1 receptor agonists and SGLT2 inhibitors, are compared in adults with type 2 diabetes who have no diabetic retinopathy or only early (mild) diabetic retinopathy.
When blood sugar (HbA1c) falls quickly after starting treatment, the retina can undergo a brief, temporary worsening before it stabilizes and benefits over the long term. This study asks whether it is the speed of that blood-sugar reduction, which we call "glycemic velocity," rather than the specific drug, that drives early changes in retinal and choroidal blood flow.
Participants are patients whose own physician has decided, independently of the study, to start one of these two drugs for the first time. The study does not choose, provide, or change any medicine; it adds only eye imaging, blood tests, and observation. Each participant is followed with specialized, non-invasive eye scans, optical coherence tomography angiography (OCT-A) and structural/choroidal OCT, together with HbA1c and other measurements, at the start of treatment and again over the following months.
The main measurement is the change, from the start of treatment to month 3, in the density of the tiny deep-layer capillaries at the center of the retina, measured on OCT-A. The study will test whether faster HbA1c reduction is linked to greater early change in these vessels and, using statistical mediation analysis, will estimate how much of any difference between the two drug groups is explained by glycemic velocity versus a direct drug effect.
If glycemic velocity, a factor physicians can influence by adjusting how quickly treatment is intensified, turns out to drive early retinal change, the findings could guide safer treatment strategies and help identify patients who need closer eye monitoring when starting these medicines.
Adults aged 18 years or older with a documented diagnosis of type 2 diabetes mellitus.
Clinical decision, made by the treating physician independently of the study, to initiate a first-ever GLP-1 receptor agonist or a first-ever SGLT2 inhibitor.
Baseline retinal status ranging from no diabetic retinopathy to mild non-proliferative diabetic retinopathy (NPDR) in the study eye(s), confirmed by fundus photography / ETDRS grading.
Baseline HbA1c within a range permitting a measurable subsequent change (e.g., 7.0% or higher), obtained within 30 days before or after the scheduled ophthalmic assessment.
Moderate-to-severe NPDR, proliferative diabetic retinopathy, or center-involving diabetic macular edema at baseline.
Prior or concurrent treatment for diabetic retinopathy or maculopathy: pan-retinal or focal/grid laser photocoagulation, intravitreal anti-VEGF or corticosteroid therapy, or vitreoretinal surgery.
Any prior exposure to a GLP-1 receptor agonist or SGLT2 inhibitor (to preserve the new-user design).
Type 1 diabetes, latent autoimmune diabetes of adults, or secondary diabetes.
Adults with type 2 diabetes attending the diabetes/endocrinology clinics of Thammasat University Hospital who are initiating, for the first time, a GLP-1 receptor agonist or an SGLT2 inhibitor on their treating physician's decision, and who have no diabetic retinopathy or only mild non-proliferative diabetic retinopathy at baseline.
Cohort
Prospective
GLP-1 Receptor Agonists
DrugFirst-ever GLP-1 receptor agonist initiated as routine clinical care; class and rate of titration are recorded but not controlled by the study. Mapped to Cohort 1.
SGLT2 inhibitor
DrugFirst-ever SGLT2 inhibitor initiated as routine clinical care; recorded but not controlled by the study. Mapped to Cohort 2.
Change in parafoveal deep-capillary-plexus (DCP) vessel density on OCT angiography
Vessel density (%) of the deep capillary plexus in the parafoveal ring on OCT angiography (fixed macular scan, validated quantification, pre-specified image-quality threshold, masked grading); primary metric is the change from baseline to Month 3.
Superficial capillary plexus (SCP) vessel density and perfusion density
SCP vessel density and perfusion density (%) in standardized macular sectors on OCT angiography.
Foveal avascular zone (FAZ) area
FAZ area (mm²) by automated or masked manual delineation on OCT angiography.
Subfoveal choroidal thickness
Vertical distance from the outer RPE to the chorioscleral interface at the fovea (µm) on EDI-OCT.
Choroidal vascularity index (CVI)
Ratio of luminal to total choroidal area (%) by standardized image binarization on EDI-OCT; indexes the choroidal / hypoxia arm of the mechanism.
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Thammasat University Hospital
Lead sponsor
Thammasat University
Collaborator
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