Analysis of Blood Flow in the Macula and Optic Nerve Head in Healthy Young Volunteers Using Laser Speckle Flowgraphy

Purpose To assess optic nerve head (ONH) and macular blood flow in young healthy volunteers using laser speckle flowgraphy (LSFG). Methods This is a prospective single-center study conducted at the Department of Ophthalmology, University Hospital Zurich from May to November 2021. Young, healthy men aged >= 18 years without ocular or systemic diseases were included. A corrected visual acuity (VA) of 0.0 logMAR or better in both eyes and an intraocular pressure (IOP) of 21 mmHg or lower were required for inclusion. Subjects exceeding a spherical equivalent (SE) of +/- 6 diopters (dpt) were excluded. Blood flow in the macula and the ONH was recorded using the Nidek LSFG RetFlow device (Nidek Company, Ltd., Hirioshicho, Japan). Laser power was set to 0.5 Millivolts (mV). Mean blur rate (MBR) was recorded as a parameter for blood flow. MBR is a calculated parameter that represents relative blood flow velocity correlated with the real anatomical blood flow rate. Colored heat maps of the recorded retinal area were generated automatically by the RetFlow device. Results Final analyses included 83 eyes of 43 male volunteers. Mean age was 21.9 years (SD +/- 1.5, range: 20 to 29). Mean corrected VA was - 0.1 logMAR (SD +/- 0.05, range: - 0.2 to 0.0), mean IOP was 15.4 mmHg (SD +/- 2.5, range: 8.5 to 18.5), and mean SE was - 0.3 dpt (SD +/- 1.2, range: - 5.0 to 1.2). Mean ONH MBR was 37.44 (SD +/- 7.9, range: 22.5 to 53.5) and mean macular MBR was 27.8 (SD +/- 9.7, range: 6.4 to 57.7). Pearson's Test showed a strong correlation between macular and papillary blood flow (p < 0.05, coefficient: 0.647). Conclusion This study provides both ONH and macular blood flow data in a healthy young male population, showing a strong correlation between ONH and macular blood flow in the examined eyes. Further investigations are required to assess the validity of MBR as a parameter for the combined evaluation of retinal blood flow at the macula and ONH in healthy volunteers and patients with various diseases.