Many eye diseases, such as diabetic retinopathy (DR) and retinopathy of prematurity (ROP), can cause abnormalities at both central and peripheral regions of the fundus. Therefore, a wide field fundus imaging is desirable for screening, diagnosis, and treatment evaluation of eye diseases. The traditional fundus imaging device which uses trans-pupillary illumination has 30° to 60° field of view. In the trans-pupillary illumination, illumination path and observing path are typically separated by using different portions of the pupil to minimize the effect of reflectance artifact. Therefore, transpupillary illumination limits the field of view because only the central part can be used for imaging purpose. Transpalpebral illumination has been explored as an alternative approach to deliver light to the interior of the eye through the pars-plana, which enables capturing a wide portion of the fundus. Without the need of pharmacologic pupil dilation, a 150° visual angle fundus image was achieved. Previous studies implemented trans-palpebral illumination using a broadband LED. As it is well known that the transmission of long wavelength light is much higher than the short wavelength. Therefore, trans-palpebral illumination based fundus images are red oriented, with compromised image quality for visualizing retinal vasculatures. We have demonstrated the trans-palpebral illumination for the ultra-wide field fundus imaging. We report here the feasibility of using independent green and red illumination power controls to compensate for the difference of spectral efficiency. The color balanced trans-pars-planar illumination significantly increased dynamic range of the fundus camera.
Physiological dysfunction of diseased cells might occur prior to detectable morphological abnormalities such as retinal cell damage and thickness change. Functional assessment of photoreceptor physiology is essential for the early detection of eye diseases. It is desirable to develop a high-resolution method for objective assessment of photoreceptor physiology. Functional intrinsic optical signal (IOS) imaging, also known as optoretinography (ORG) or optophysiology, measures transient light changes correlated with retinal neural activities. The photoreceptor-IOS arises promptly after the beginning of stimulation, which ensures a unique biomarker for objective ORG measurement of physiological conditions of retinal photoreceptors. In this study, the feasibility of functional optical coherence tomography (OCT) imaging of fast photoreceptor-IOS in human photoreceptors has been demonstrated. The fast photoreceptor-IOS occurred before stimulus-evoked pupillary response and thus allows nonmydriatic ORG of human photoreceptors. The outer segment (OS) was confirmed as the source of fast photoreceptor-IOS by depth-resolved OCT. The active IOS changes were found at both OS boundaries, which connected to the inner segment and retinal pigment epithelium. This supports that the mechanism of the fast photoreceptor-IOS can be explained by transient OS shrinkage due to phototransduction.
This study is to validate the trans-pars-planar illumination for ultra-widefield multispectral imaging (MSI) of the retina and choroid. By freeing the available pupil for collecting imaging light only, the trans-pars-planar illumination enables a portable, nonmydriatic fundus camera, with 200o FOV in a single-shot image. The trans-pars-planar illumination, delivering illumination light from one side of the eye, naturally enables oblique illumination ophthalmoscopy to enhance the contrast of fundus imaging. Four wavelength LEDs, including 530 nm, 625 nm, 780 nm, and 970 nm, are illuminated for MSI of the retina and choroid.
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