The effect on Signal Quality using the Isometric Hand-Grip Test to maximize Vascular Flow in patients with macular disease

Interventions = 1) Optical Coherence Tomography Angiography (OCTA) without Isometric Hand Grip Test, and 2) OCTA with Isometric Hand grip test. *OCTA enables in vivo, non-invasive visualisation of retinal and choroidal vascular flow. *OCTA will be performed via the Cirrus HD-OCT v11.0.0.29946 Zeiss Cirrus Angioplex (Carl Zeiss Meditec; Jena, Germany) 6 × 6 mm en face macular cube scan protocol, by a research assistant. The research assistant is an optometrist who will be trained for use of this OCTA protocol. The scan involves the patient looking through an eyepiece and focussing on a centrally lit spot without blinking for approximately 10 seconds. *Isometric Hand Grip Test induces transient elevations in systemic blood pressure and heart rate. This can subsequently alter retinal and choroidal vascular flow. *Isometric Hand Grip Test will be performed using a digital hand dynamometer (Constant, Scale Manufacturer Camry; Zhongshan, China), by the patient. The test involves the patient sitting upright, elbow 90° in free space, shoulder adducated, and squeezing the dynamometer at 50% of the maximum voluntary contraction for approximately 90 seconds. *All study patients will have a random eye selected to be the study eye. *All study patients will be randomly allocated to one of two interventions sequences, i.e.: A) OCTA without Isometric Hand Grip Test then OCTA with Isometric Hand Grip Test, or B) OCTA with Isometric Hand Grip Test then OCTA without Isometric Hand Grip Test. *The research assistant will explain the OCTA and Isometric Hand Grip Test protocol prior to use. *For sequence A), patients will have two OCTA scans without Isometric Hand Grip Test acquired by the research assistant. Patients will then rest for two minutes. *Patients will squeeze the dynamometer as hard as they can without undue stress or pain for up to three seconds. This will be noted as the maximum voluntary contraction. Patients will then rest for 15 seconds. *Patients will squeeze the dynamometer at 50% maximum voluntary contraction for one minute. At one minute, the patient will continue squeezing while two OCTA scans with Isometric Hand Grip Test are acquired by the research assistant. Patients can stop squeezing after the two OCTA scans are acquired, or if they physically cannot squeeze any longer. *For sequence B), the same protocol as outlined for sequence A) will be performed although with the two OCTA scans with Isometric Hand Grip Test first, then the two OCTA scans without Isometric Hand Grip Test second. *Each sequence (A/B) takes approximately 10 minutes. *The research assistant will be monitoring the protocol continuously, and advise the study patient if any alterations are required, e.g., sit upright, squeeze harder. This will ensure study participant adherence to the protocol. Non-adherence will be noted by the research assistant.