Abstract
We describe a low-cost, easy to use binocular instrument to acquire retinal video sequences of both eyes simultaneously. After image registration, cardiac cycle-induced pulsatile light attenuation changes can be measured quantitatively with high spatial and temporal resolution. Parameters such as amplitude, pulse form, and time shift between light attenuation changes can be calculated and compared between eye sides. Deviation from inter-eye symmetry can be not only an early sign of beginning eye diseases such as glaucoma but also a sign of pathological changes in the carotid arteries; hence, this method can improve the early detection of pathological changes. Important features compared to existing monocular instruments are a narrow band light source with the wavelength close to the peak of the blood extinction, and a proportional relationship of image intensity and light intensity, which are the main requirements for quantitative evaluation.
Highlights
The accessible retinal blood vessels, capillaries, and tissue offer possibilities for direct observation and a unique possibility to study vascular, neural, and ophthalmic disorders
We describe an instrument for the acquisition of retinal video sequences of both eyes simultaneously with exact synchronization, a method to quantitatively calculate pulsatile attenuation changes from intensity values with high temporal and spatial resolution, and different examples demonstrating the characteristics of the presented method and possible clinical application
This section describes the evaluation of a typical measurement and includes specific cases that demonstrate the potential of the proposed instrument
Summary
The accessible retinal blood vessels, capillaries, and tissue offer possibilities for direct observation and a unique possibility to study vascular, neural, and ophthalmic disorders. Different parameters of the human eye change according to the cardiac cycle, e.g., the intraocular pressure (IOP), eye length, and retinal reflection. The pulsatile changing light reflection is due to the pulsatile changing amount of blood in the retinal tissue and vessels [1,2,3,4,5,6,7,8]. Retinal video recording and image processing methods have been employed to assess different parameters of the eye, e.g., the reaction of the vessel caliber to flickering light stimulation [10,11], to assess spontaneous venous pulsation [8,12,13,14,15], and to measure flickering light-induced reflectance changes of the human papilla and peripapillary region [16]
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