RecruitingACTRN12620000837921

Characterising ocular blood flow changes with an exercise stimulus using optical coherence tomography angiography (OCT-A).

Characterising ocular blood flow changes with an exercise stimulus using optical coherence tomography angiography (OCT-A) in healthy, normal tension glaucoma and diabetic retinopathy patients.

Sponsor

University of NSW, Rural Clinical School

Enrollment

27 participants

Start Date

Aug 31, 2020

Study Type

Interventional

Conditions

Diabetic Retinopathy Normal Tension Glaucoma

Summary

Glaucoma is a chronic, progressive degeneration of the optic nerve which results in visual loss from the peripheral visual field, creeping towards complete blindness. It is the leading cause of irreversible blindness worldwide and in Australia. There are many sight-saving treatments available, but identifying who is likely to worsen is a critical step to intervening for the right patients. Problems with the blood flow to the back of the eye have been identified as a significant contributing factor in glaucoma, and may occur early in the pathophysiology of diabetic retinopathy. A new imaging technique called optical coherence tomography angiography (OCT-A) allows rapid, non-invasive imaging of the blood flow of the optic nerve. The blood flow at the back of the eye changes in response to the blood pressure and the pressure inside the eye (IOP). Isometric exercise (a simple handgrip test) is a simple, yet reliable method to increase blood pressure temporarily. This study will help determine if we can detect the changes in blood flow using OCT-A, and whether the changes are different between healthy people and people with glaucoma or diabetes. In future, this research may help to generate clinical tests to detect glaucoma or diabetes earlier, or pick who will get worse and therefore would benefit from more treatment to prevent vision loss.

Eligibility

Sex: Both males and femalesMin Age: 18 YearssMax Age: 75 Yearss

Plain Language Summary

Simplified for easier understanding

Glaucoma is a leading cause of permanent blindness worldwide, involving progressive damage to the optic nerve — often without early warning symptoms. Problems with blood flow to the back of the eye are increasingly recognised as an important factor in glaucoma progression, and also in diabetic retinopathy (eye complications of diabetes). Early detection of abnormal blood flow patterns could help identify who is at greatest risk of vision loss and needs more aggressive treatment. This study uses a new non-invasive imaging technology called OCT-A (optical coherence tomography angiography) to photograph the tiny blood vessels at the back of the eye. Participants will perform a simple handgrip exercise that temporarily raises blood pressure, and researchers will use OCT-A to detect and measure the eye's blood flow response. The goal is to see whether these responses differ between healthy individuals, people with glaucoma, and people with diabetic retinopathy. You may be eligible if you are aged 18 to 75 and attend the Port Macquarie Eye Centre — either as a healthy control patient, or as someone with normal tension glaucoma or mild-to-moderate diabetic retinopathy without macular oedema. People taking blood pressure medications (particularly beta-blockers), those who are pregnant, or those with significant hand conditions that would prevent performing the grip test would not be eligible.

This summary was AI-generated to explain the trial in plain language. It is not medical advice. Always discuss eligibility with your doctor before enrolling in a clinical trial.

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Interventions

All participants (healthy controls, patients with normal tension glaucoma and diabetic retinopathy) will perform an isometric handgrip exercise for 3 minutes at 30% of their predetermined force of maximal voluntary contraction. Measurements of biological parameters; Systolic Blood Pressure, Diastolic Blood Pressure, Pulse Rate, and Intraocular Pressure, will be recorded with concurrent OCT-A scans of the macular and optic nerve head regions of one eye. These measurements will be taken at the following time points: Baseline 1: 20 minutes before sustained contraction Baseline 2: 10 minutes before sustained contraction Intra-Exercise Period: 2 minutes into sustained contraction Post-Exercise: 10 minutes after the cessation of exercise Intervention Name: (1) Optical Coherence Tomography Angiography (OCT-A) * OCT-A is a novel imaging technique which enables rapid, non-invasive, three dimensional imaging of the retinal and choroidal vasculature. * OCT-A will be performed using the DRI OCT Triton swept source OCT (DRI OCT Triton, TOPCON, Tokyo, Japan). * Performed by a medical student researcher with prior computer-based and face-to-face OCT-A training. * Administered four times during the study (two scans at each time point), taking approximately 1 minute for complete examination of one eye at each time point. * For healthy controls and diabetic retinopathy patients, the dominant eye will be selected, for patients with glaucoma the worse eye (as determined by visual field index) will be selected * OCT-A images will be evaluated for presence and severity of artefacts using a validated grading system, then processed using a custom approach to determine vessel density (as a surrogate measure for ocular blood flow). * Any urgent clinical considerations discovered on routine image review are discussed with the treating ophthalmologist. Intervention Name: (2) Hand Held Dynamometer * Isometric exercise (handgrip) induces a characteristic rise in systemic blood pressure, heart rate, and sympathetic activity. These parameters are determinants of ocular blood flow. * The handgrip exercise will be performed using a digital hand dynamometer (Jamar Plus+, Sammons Preston, Rolyon, Bolingbrook, IL) in accordance with the National Health and Nutrition Examination Survey (NHANES) protocol. * Patients will be taught the correct technique by a medical student researcher. * Maximal voluntary contraction (MVC) of the forearm will be performed 3 times (3 seconds each) prior to commencement of sustained contraction. Contraction will then be sustained at 30% of the MVC for 3 minutes. All contractions will be performed in a seated position.