Modification of the Heidelberg retinal flowmeter to record pattern and flicker induced blood flow changes

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Retinal Imaging

Background:

• The Heidelberg Retina Flowmeter (HRF) measures retinal capillary perfusion.
• Assessing dynamic changes in retinal perfusion is crucial for understanding ocular health.
• Novel methods for retinal stimulation are needed to probe physiological responses.

Purpose of the Study:

• To evaluate a prototype retinal stimulator interfaced with the HRF.
• To determine if flicker and pattern stimulation can evoke measurable changes in retinal perfusion.
• To assess the efficacy of superimposed visual stimuli for retinal studies.

Main Methods:

• A prototype stimulator was developed to optically superimpose monitor displays onto the retina.
• The stimulator projected flicker and pattern stimuli (checkerboard, m-sequence) within a 55-degree visual angle.
• Retinal perfusion was measured using the HRF in 10 human subjects during stimulation.

Main Results:

• HRF images were successfully acquired and processed.
• No significant differences in retinal perfusion values were observed during flicker or pattern stimulation compared to control.
• The prototype device allowed for image acquisition during stimulation.

Conclusions:

• The study's findings contradict previous research suggesting flicker-induced increases in HRF perfusion.
• Retinal perfusion, as measured by the HRF, was not affected by the prototype's flicker and pattern stimulation.
• Discrepancies may stem from stimulation techniques, image acquisition parameters, or differences in experimental setups.