1 - Complementary capabilities of photoacoustic imaging to existing optical ocular imaging techniques

Abstract

Since 1886, when the first picture of the human retina was taken, ocular imaging has played a crucial role in the diagnosis and management of ophthalmic diseases. One of the biggest contributors to the advancement of ocular imaging is the adoption of optical imaging techniques. Optical imaging is a method of looking into the body in a noninvasive way, like X-rays. However, unlike radiological imaging techniques that use ionizing radiation, optical imaging uses light and the properties of photons to produce detailed images ranging from structures as small as cells and molecules to structures as large as tissues and organs. There are plenty of advantages of using optical imaging compared to radiological imaging. For one, optical imaging is much safer for patients since it uses nonionizing radiation to excite electrons without causing damage. Additionally, since it is fast and safe, optical imaging can be used to monitor acute and chronic diseases, as well as treatment outcomes. Optical imaging is also useful for imaging soft tissue since different types of tissues absorb and scatter light differently. Finally, optical imaging can advantageously use varying colors of light to see and measure multiple properties of tissues at a time. Therefore, it is no surprise that the optical imaging modalities of fundus photography in the 1920s, scanning laser ophthalmoscope (SLO) imaging in 1981, and optical coherence tomography (OCT) in 1991 have touted a “golden age” in ophthalmic imaging applications. A new technology, photoacoustic imaging, has been shown to have promising features that could make it the next major imaging technique in ophthalmology. Additionally, photoacoustic imaging (PAI) can combine with preexisting optical microscopic imaging modalities to achieve multimodal imaging of the eye. In this chapter, we present a brief overview of fundus photography, SLO, and OCT while discussing the potential of PAI as the next major ocular imaging modality.