Abstract
Laser Doppler holography (LDH) is a full-field blood flow imaging technique able to reveal human retinal and choroidal blood flow with high temporal resolution. We here report on using LDH in the anterior segment of the eye without making changes to the instrument. Blood flow in the bulbar conjunctiva and episclera as well as in corneal neovascularization can be effectively imaged. We additionally demonstrate simultaneous holographic imaging of the anterior and posterior segments by simply adapting the numerical propagation distance to the plane of interest. We used this feature to track the movements of the retina and pupil with high temporal resolution. Finally, we show that the light backscattered by the retina can be used for retro-illumination of the anterior segment. Hence digital holography can reveal opacities caused by absorption or diffusion in the cornea and eye lens.
Highlights
Laser Doppler holography (LDH) is a digital holographic method where blood flow is measured from the interference between light backscattered by the eye and a reference beam [1]
We have explored the potential clinical uses of LDH in the anterior segment
We first showed that LDH can be used to image blood flow with a high temporal resolution and over a field of view that can be adapted in the conjunctiva and episclera as well as in corneal neovascularization
Summary
Laser Doppler holography (LDH) is a digital holographic method where blood flow is measured from the interference between light backscattered by the eye and a reference beam [1]. A technical difficulty to overcome is to separate the contributions of refraction errors from those due of diffusion and absorption, and to give a grade that correlates as much as possible with the subject vision Another recurrent issue in the anterior segment is corneal neovascularization, which is caused by a disruption in the balance of angiogenic and antiangiogenic factors, often secondary to inflammation or hypoxia [16]. The angiography of corneal neovascularization can be realized with fluorescent dyes, or with optical coherence tomography (OCT) [19,20,21] These methods do not offer a quantitative blood flow contrast, and provide mainly structural information about the neovessels. We explored the possibility to image blood flow in the surface vasculatures of the anterior segment, in the conjunctiva/episclera as well as in cases of corneal neovascularization. We imaged the eye of subjects affected by cataract or corneal scarring and showed that holographic reconstructions in the pupil plane of light backscattered by the retina can reveal the absorbing or diffusing features in the cornea and lens
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