Abstract
Most reported photoacoustic ocular imaging work to date uses small animals, such as mice and rats, the eyeball sizes of which are less than one-third of those of humans, posing challenges for clinical translation. Here we developed a novel integrated photoacoustic microscopy (PAM) and optical coherence tomography (OCT) system for dual-modality chorioretinal imaging of larger animals, such as rabbits. The system has quantified lateral resolutions of 4.1 µm (PAM) and 3.8 µm (OCT), and axial resolutions of 37.0 µm (PAM) and 4.0 µm (OCT) at the focal plane of the objective. Experimental results in living rabbits demonstrate that the PAM can noninvasively visualize individual depth-resolved retinal and choroidal vessels using a laser exposure dose of ~80 nJ below the American National Standards Institute (ANSI) safety limit 160 nJ at 570 nm; and the OCT can finely distinguish different retinal layers, the choroid, and the sclera. This reported work may be a major step forward in clinical translation of the technology.
Highlights
Visual impairment and blindness are prevalent worldwide and are increasing in the coming decades due to aging of the population
Retinal imaging techniques currently used in the clinic mainly include fundus photography, fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT) [2]
A coverslip sample with coated chromium gratings [linewidth: 10 μm, pitch: 40 μm, inset of Fig. 2(a)] providing excellent optical absorption and reflection contrasts as well as sharp edges was used as the target for lateral and axial resolution calibration of photoacoustic microscopy (PAM) and OCT
Summary
Visual impairment and blindness are prevalent worldwide and are increasing in the coming decades due to aging of the population. Retinal imaging techniques currently used in the clinic mainly include fundus photography, fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT) [2]. Using a larger fluorescence molecule with 98% bound to plasma, ICGA can reveal choroidal circulation but the images are often difficult to interpret. Both FA and ICGA are invasive and require intravenous injection of exogenous dyes that may cause complications such as emesis and anaphylactic reactions [3]. Without the need of dye injection, OCT and OCT angiography can provide structural and functional information of retina, but they often have limited visualization of the choroid and molecular imaging capabilities remain rudimentary [4, 5]. A large clinical need remains developing improved chorioretinal imaging techniques
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