KEYWORDS: Depolarization, Signal to noise ratio, Eye, Retina, Tissues, Polarization, In vivo imaging, Optical calibration, Calibration, Image segmentation
SignificanceA data-based calibration method with enhanced depolarization contrast in polarization-sensitive optical coherence tomography (PS-OCT) was developed and demonstrated effective for detecting melanin content in the eye.AimWe aim to mitigate the dependence between the measured depolarization metric and the intensity signal-to-noise ratio (SNR) for improved visualization of depolarizing tissues, especially in low SNR regions, and to demonstrate the enhanced depolarization contrast to evaluate melanin presence.ApproachA function for calibrating the depolarization metric was experimentally derived from the young albino guinea pig, assuming depolarization free in the retina. A longitudinal study of guinea pigs (9 weeks) was conducted to assess the accumulation of melanin during early eye growth. Furthermore, the melanin content of the sub-macular choroid was compared in eyes with light and dark irides involving 14 human subjects in early middle adulthood.ResultsWe observed an increase in the improved depolarization contrast, which indicates potential melanin accumulation in the early eye development with age in the pigmented guinea pig eyes. We found a significant difference in melanin content between human eyes with light and dark colors.ConclusionsOur proposed calibration method enhanced the visualization of depolarizing structures in PS-OCT, which can be generalized to all kinds of polarization-sensitive imaging and can potentially monitor melanin in healthy and pathological eyes.
Ocular aberrometry with a wide dynamic range for assessing vision performance and anterior segment imaging that provides anatomical details of the eye are both essential for vision research and clinical applications. Defocus error is a major limitation of digital wavefront aberrometry (DWA) as the blurring of the detected point spread function (PSF) results in a significant reduction of SNR beyond ±3 D range. With the aid of Badal-like precompensation of defocus, the dynamic defocus range of the captured aberrated PSFs can be effectively extended. We demonstrate a dual-modality MHz VCSEL-based swept-source OCT (SS-OCT) system, with an easy switch between DWA and OCT imaging mode. The system is capable of measuring aberrations with defocus dynamic range of D as well as providing fast anatomical imaging of the anterior segment at an A-scan rate of 1.6 MHz. The dual-mode system stands out for its modular design wherein simple hardware additions to an SS-OCT system enable the aberration measurement in DWA mode. In DWA mode, a diffraction-limited stationary spot is formed at the retina by a narrow illumination beam. The reflected light passes then through the full pupil of the eye, thereby the single path optical aberrations are captured. The OCT detection leads to volumetric PSFs, which are post-processed using the digital lateral shearing-based digital adaptive optics technique (DLS-DAO) to reconstruct the wavefront error. Capturing both optical and anatomical information of the eye can be potentially helpful for improved diagnosis and targeted treatment of ocular diseases.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.