Abstract
Purpose: :
To develop a novel ophthalmic imaging technology named photoacoustic ophthalmoscopy (PAOM) for both anatomical and functional imaging of the retina. To demonstrate the applicability of PAOM to in vivo imaging of the retinal vessels and the retinal pigment epithelium (RPE) in small animals, which is critical for the diagnoses of several major blinding diseases such as diabetic retinopathy and age-related macular degeneration.
Methods: :
Photoacoustic imaging has the potential to quantitatively measure the physiological-specific optical absorption contrast in the eye, which is not available with existing retinal imaging technologies. We developed a PAOM technique by integrating a laser-scanning optical-resolution photoacoustic microscopy with a spectral-domain OCT. The wavelengths of the illumination laser for photoacoustic imaging and the light source of OCT were 532 nm and 840 nm, respectively. Both PAOM and OCT share the same optical delivering and scanning system so that the two imaging modalities were integrated seamlessly and the images acquired from them are intrinsically registered. To facilitate in vivo retinal imaging the two imaging sub-systems were built on a slit lamp. At the beginning of an imaging cycle, OCT was first used to locate the region of interest in the retina. OCT guidance was used for two reasons: (1) OCT and PAOM can provide complementary contrast and (2) OCT used invisible light, which is safer for alignment purpose. Once the region of interest is identified, PAOM was turned on for imaging. Only a single 2D scanning is required to acquire two volumetric images as the acquisitions were performed simultaneously.
Results: :
Both OCT and PAOM in vivo imaging of mouse ear (Swiss Webster) and rat retina (Long Evans) were accomplished successfully. In the PAOM images of the retina, retinal vessels and the RPE layer were both clearly imaged with high contract to noise ratio and were well resolved along both depth and lateral directions. The OCT and PAOM images demonstrated complementary contrasts and together can potentially provide comprehensive anatomical and functional information of the retina, especially the retinal vessels and the RPE.
Conclusions: :
We have successfully developed an OCT guided PAOM technology. The test results have shown that PAOM is a promising powerful tool for the diagnosis and study of retinal diseases related to vascular and RPE malfunction.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • diabetic retinopathy