We thank the generous support from the National Science Foundation (CAREER CBET-1055379) and the National Institutes of Health (1RC4EY021357, 1R01EY019951). We also acknowledge the support from the China Scholarship Council to Wei Song.

1. System Configuration
<ol>
	<li>PAOM Subsystem
	<ol>
		<li>Illumination source: a Nd:YAG laser (SPOT-10-100, Elforlight Ltd, UK: 20 &mu;J/pulse; 2 nsec pulse duration; 30 kHz maximum pulse repetition rate).</li>
		<li>The output laser at 1064 nm is frequency-doubled to 532 nm by a beta-barium-borate (BBO) crystal (CasTech, San Jose, CA). After further split by a laser line mirror, 532 nm light is delivered through a single-mode optical fiber (P1-460A-FC-5, Thorlabs), and 1064 nm laser is recorded by a photod...

<ol>
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All experimental animal procedures were approved by the Institutional Animal Care and Use Committee of Northwestern University.

Here, we present a detailed instruction on simultaneous in vivo retinal imaging of rat eyes using PAOM combined with SD-OCT. Optical-scattering-based SD-OCT is, perhaps, the clinical "gold standard" for retinal imaging3; however, it is not sensitive to detect the optical absorption in the retina. The newly-developed PAOM is the only optical-absorption-based ophthalmic imaging modality that provides optical absorption properties of the retina6. Because hemoglobin and melanin are endogen...

integrated photoacoustic ophthalmoscopy and spectral-domain optical coherence tomography

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging technologies. Existing retinal imaging modalities, such as fundus photography1, confocal scanning laser ophthalmoscopy (cSLO)2, and optical coherence tomography (OCT)3, have significant contributions in monitoring disease onsets and progressions, and developing new therapeutic strategies. However, they predominantly rely on the back-reflected photons from the retina. As a consequence, the optical absorption properties of the retina, which are usually strongly associated with retinal pathophysiology status, are inaccessible by the traditional imaging technologies.
Photoacoustic ophthalmoscopy (PAOM) is an emerging retinal imaging modality that permits the detection of the optical absorption contrasts in the eye with a high sensitivity4-7 . In PAOM nanosecond laser pulses are delivered through the pupil and scanned across the posterior eye to induce photoacoustic (PA) signals, which are detected by an unfocused ultrasonic transducer attached to the eyelid. Because of the strong optical absorption of hemoglobin and melanin, PAOM is capable of non-invasively imaging the retinal and choroidal vasculatures, and the retinal pigment epithelium (RPE) melanin at high contrasts 6,7. More importantly, based on the well-developed spectroscopic photoacoustic imaging5,8 , PAOM has the potential to map the hemoglobin oxygen saturation in retinal vessels, which can be critical in studying the physiology and pathology of several blinding diseases 9 such as diabetic retinopathy and neovascular age-related macular degeneration.
Moreover, being the only existing optical-absorption-based ophthalmic imaging modality, PAOM can be integrated with well-established clinical ophthalmic imaging techniques to achieve more comprehensive anatomic and functional evaluations of the eye based on multiple optical contrasts6,10 . In this work, we integrate PAOM and spectral-domain OCT (SD-OCT) for simultaneously in vivo retinal imaging of rat, where both optical absorption and scattering properties of the retina are revealed. The system configuration, system alignment and imaging acquisition are presented.

Figure 2 shows the 2-D fundus images of SD-OCT and PAOM acquired simultaneously in an albino rat (A and B) and a pigmented rat (C and D), respectively. In the SD-OCT fundus images (Figures 2A and 2C), retinal vessels have dark appearance due to the hemoglobin absorption of probing light. In addition to retinal vessels (RV in Figure 2B), PAOM visualizes the choroidal vasculatures (CV in Figure 2B) in albino eye because of...

Watch this Scientific Journal Video about Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography at JoVE.com

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

Photoacoustic ophthalmology (PAOM), an optical-absorption-based imaging modality, provides the complementary evaluation of the retina to the currently available ophthalmic imaging technologies. We report the using of PAOM integrated with spectral-domain optical coherence tomography (SD-OCT) for simultaneous multimodal retinal imaging in rats.

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging ...

integrated-photoacoustic-ophthalmoscopy-spectral-domain-optical

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11.4K Views.  Northwestern University. Photoacoustic ophthalmology (PAOM), an optical-absorption-based imaging modality, provides the complementary evaluation of the retina to the currently available ophthalmic imaging technologies. We report the using of PAOM integrated with spectral-domain optical coherence tomography (SD-OCT) for simultaneous multimodal retinal imaging in rats.