Changes in Retinal Optical Coherence Tomography Angiography Indexes Over 24 Hours

Area of Science:

• Ophthalmology
• Medical Imaging
• Physiology

Background:

• The retinal microvasculature's diurnal changes are not well understood.
• Optical coherence tomography angiography (OCT-A) offers a non-invasive method to assess retinal vasculature.

Purpose of the Study:

• To investigate diurnal variations in macular retinal microvasculature using OCT-A in young adults.
• To explore correlations between these vascular changes and ocular/systemic parameters.

Main Methods:

• 44 young adults underwent serial OCT-A and OCT scans, blood pressure, intraocular pressure (IOP), and biometry measurements every 4 hours for 24 hours.
• Macular en face images of superficial and deep retinal layers were analyzed for vessel density, perfusion density, and foveal avascular zone metrics.
• Magnification-corrected vascular indexes were extracted.

Main Results:

• Significant diurnal variations were found in superficial retinal layer vessel and perfusion density (acrophase 4:30 PM–8:30 PM).
• Deep retinal layer showed diurnal variations only in foveal and parafoveal regions (acrophase 9 AM–3 PM).
• Myopes and nonmyopes exhibited different timing (acrophase) but not amplitude in superficial parafoveal perfusion density.

Conclusions:

• Significant diurnal variations exist in OCT-A derived macular vascular indexes over 24 hours.
• These variations correlate with systemic and ocular measurements like blood pressure, IOP, and axial length.
• Timing of superficial retinal layer perfusion density variations differs between myopes and nonmyopes.