Presbyopia, a decline in near vision due to aging, is primarily linked to changes in the crystalline lens. However, the ciliary muscle also contributes to this condition. Previous OCT studies focused on measuring ciliary muscle thickness at static accommodative states to understand its age-related functional response. Yet, this approach falls short in capturing the centripetal movement of the ciliary muscle towards the lens, which anatomically represents its functional response better than thickness changes. In this study, we introduce a novel method using statistical shape analysis, enabling dynamic assessment of the ciliary muscle's centripetal movement during accommodation through transscleral OCT images. This approach serves as a novel tool to explore the ciliary muscle's role in presbyopia development and optimize accommodating implant design.
This research uses Brillouin Microscopy and Optical Coherence Tomography (OCT) to improve our understanding of presbyopia, an age-related condition that affects near vision. Lens thickness change during accommodation and depth-dependent Brillouin shift profile were measured in vivo in 6 subjects in the age range from 21 to 54 years. We observed an age-dependent increase in lens thickness, decrease in lens thickness change and an increase in the central plateau in the Brillouin shift, consistent with previous research. We also found that the increase in the width of the plateau is associated with a decrease in the accommodative response.
KEYWORDS: In vivo imaging, Elastography, Mechanics, Visual process modeling, Microscopy, Eye, Data modeling, Visualization, Visual system, Therapeutics
Presbyopia is a loss of the dynamic accommodation response of our vision and affects everybody as they age. Despite many static corrections available, we still do not address the underlying biomechanical cause of lens stiffness. Novel lens softening therapies are limited by no ability to assess biomechanics in vivo. To address this, we developed a multimodal OCE/Brillouin system that maps spatial-varying modulus of a lens. The lens mechanical signature was measured, and a forward model was used to demonstrate the structure-function relationship of lens stiffness on clinical accommodation. This technique has the potential for patient-specific presbyopia models and therapeutic planning.
This study demonstrates the feasibility of using OCT to quantify microfluctuations in ocular biometry at steady-state accommodation. The preliminary results confirm the presence of two main frequency components in mechanical fluctuations of the lens consistent with prior studies on microfluctuations of optical accommodation (LFC: ≤ 0.6Hz and HFC: 1.0Hz – 2.5Hz). Both frequency components increased with accommodation. This study also measured axial eye length (AEL) fluctuations and found a peak around 2.5-3 Hz. The fluctuations in AEL may be caused by eye movements such as saccades.
In an effort to meet the need of imaging technology that reliably measure the dynamics of accommodation, we developed a swept source OCT system for imaging and biometry of the crystalline lens dynamics at high sampling rates (~100 Hz). Preliminary data suggests that high sampling rates improve detection of lens micro-fluctuations during accommodation and that sampling rates higher than 40 Hz might be needed to fully capture crystalline lens dynamics. Long term, the information acquired with the system will improve our understanding of the mechanism of accommodation and enable to design and evaluate new procedures to restore accommodation.
Anatomical changes of the growing crystalline lens influence its refractive development, including power and spherical aberration. We have recently developed a new instrument that characterizes both the optical and biometric properties of the lens in-vitro by merging Ray-Tracing Aberrometry (RTA) with three-dimensional OCT imaging. In this abstract, we describe the application of the RTA to the measurement of lens spherical aberration.
Experiments were performed on 54 isolated human lenses (age: 0.25 to 56 years). The system was programmed to sequentially deliver the probing beam through the lens using a raster scan pattern of 13 × 13 transversal positions spaced 0.5 mm apart. Exit rays were imaged after exiting the tissue chamber at 9 different axial positions (ΔZ = 0 mm to 8 mm) in 1 mm intervals. A total of 1,521 spot images were acquired per lens. All data was automatically analyzed using custom software we developed in MATLAB. Exit ray slopes over a 6 mm pupil were used to determine Zernike wavefront coefficients up to the sixth order. The 4th order Zernike coefficient Z[4,0] was used to measure primary spherical aberration (SA). The results suggest that spherical aberration of the growing lens becomes more negative before adulthood and less negative after around age 30. The data is consistent with results from in-vivo studies that suggest the lens spherical aberration becomes less negative in older lenses (>30 years).
Purpose: To objectively quantify dynamic changes in lens shape during accommodation using two-dimensional OCT images
Methods: In-vivo responses to an accommodative step stimulus of three subjects (aged 22, 39, and 45) were captured using a custom-made extended-depth SD-OCT system operating at 840 nm following an IRB-approved protocol (Ruggeri et al. 2012). Subjects focused on a visual accommodation target designed to produce an adjustable step stimulus of accommodation. Accommodative responses to 2-D and 4-D stimuli were captured ~1.5s before and ~4.5s after stimulation. Lens thickness, anterior curvature, and posterior curvature were measured using a newly-developed algorithm (validated using a calibration sphere). Dynamic changes in lens thickness and curvature were then fitted with an exponential model to produce time dependent constants.
Results: All calibration OCT images were automatically analyzed in under 2 seconds. A radius of 7.793mm ± 0.051mm was calculated resulting in a difference of 2.4μm from the reported nominal value of the calibration sphere. Anterior lens radius decreased over time in all subjects. Radius of the posterior lens experienced a slight increase for all subjects.
Conclusion: This study demonstrates the feasibility of quantifying the dynamic changes in lens curvature and thickness during accommodation using extended-depth OCT combined with a step accommodation stimulus and an automated segmentation algorithm.
Age-related changes in the crystalline lens shape and refractive index gradient produce changes in dioptric power and high-order aberrations that influence the optics of the whole eye and contribute to a decrease in overall visual quality. Despite their key role, the changes in lens shape and refractive index gradient with age and accommodation and their effects on high-order aberrations are still not well understood. The goal of this project was to develop a combined laser ray tracing (LRT) and optical coherence tomography (OCT) system to measure high-order aberrations, shape and refractive index gradient in non-human primate and human lenses. A miniature motorized lens stretching system was built to enable imaging and aberrometry of the lens during simulated accommodation. A positioning system was also built to enable on- and off-axis OCT imaging and aberrometry for characterization of the peripheral defocus of the lens. We demonstrated the capability of the LRT-OCT system to produce OCT images and aberration measurements of crystalline lens with age and accommodation in vitro. In future work, the information acquired with the LRT-OCT system will be used to develop an accurate age-dependent lens model to predict the role of the lens in the development of refractive error and aberrations of the whole eye.
Purpose: To determine the dynamic interaction between ciliary muscle and lens during accommodation and disaccommodation through synchronous imaging of ciliary muscle and lens response to pulse stimulus
Methods: The ciliary muscle and lens were imaged simultaneously in a 33 year old subject responding to a 4D pulse stimulus (accommodative stimulus at 1.7 s, disaccommodative stimulus at 7.7 s) using an existing imaging system (Ruggeri et al, 2016) consisting of an Anterior Segment Optical Coherence Tomography system, Ciliary Muscle Optical Coherence Tomography system, and custom-built accommodation module. OCT images were recorded at an effective frame rate of 13.0 frames per second for a total scan time of 11.5 s.
An automated segmentation algorithm was applied to images of the anterior segment to detect the boundaries of the cornea and lens, from which lens thickness was extracted. Segmentation of the ciliary muscle was performed manually and then corrected for distortion due to refraction of the beam to obtain measurements of thicknesses at the apex and fixed distances from the scleral spur.
Results: The dynamic biometric response to a pulse stimulus at 4D was determined for both the ciliary muscle and lens, suggesting the ciliary muscle and lens interact differently in accommodation and disaccommodation.
Conclusions: The study introduces new data and analyses of the ciliary muscle and lens interaction during a complete accommodative response from the relaxed to the accommodated state and back, providing insight into the interplay between individual elements in the accommodative system and how their relationships may change with age.
Hand-held wide-field contact color fundus photography is currently the standard method to acquire diagnostic images of children during examination under anesthesia and in the neonatal intensive care unit. The recent development of portable non-contact hand-held OCT retinal imaging systems has proved that OCT is of tremendous help to complement fundus photography in the management of pediatric patients. Currently, there is no commercial or research system that combines color wide-field digital fundus and OCT imaging in a contact-fashion. The contact of the probe with the cornea has the advantages of reducing motion experienced by the photographer during the imaging and providing fundus and OCT images with wider field of view that includes the periphery of the retina. In this study we produce proof of concept for a contact-type hand-held unit for simultaneous color fundus and OCT live view of the retina of pediatric patients. The front piece of the hand-held unit consists of a contact ophthalmoscopy lens integrating a circular light guide that was recovered from a digital fundus camera for pediatric imaging. The custom-made rear piece consists of the optics to: 1) fold the visible aerial image of the fundus generated by the ophthalmoscopy lens on a miniaturized level board digital color camera; 2) conjugate the eye pupil to the galvanometric scanning mirrors of an OCT delivery system. Wide-field color fundus and OCT images were simultaneously obtained in an eye model and sequentially obtained on the eye of a conscious 25 year-old human subject with healthy retina.
The purpose of this project is to design and evaluate a system that will enable objective assessment of the optical accommodative response in real-time while acquiring axial biometric information. The system combines three sub-systems which were integrated and mounted on a joystick x-y-z adjustable modified slit-lamp base to facilitate alignment and data acquisition: (1) a Shack-Hartmann wavefront sensor for dynamic refraction measurement, provided software calculates sphere, cylinder and axis values, (2) an extended-depth Optical Coherence Tomography (OCT) system using an optical switch records high-resolution cross-sectional images across the length of the eye, from which, dynamic axial biometry (corneal thickness, anterior chamber depth, crystalline lens thickness and vitreous depth) can be extracted, and (3) a modified dual-channel accommodation stimulus unit based on the Badal optometer for providing a step change in accommodative stimulus. The prototypal system is capable of taking simultaneous measurements of both the optical and the mechanical response of lens accommodation. These measurements can provide insight into correlating changes in lens shape with changes in lens power and ocular refraction and ultimately provide a more comprehensive understanding of accommodation, presbyopia and an objective assessment of presbyopia correction techniques.
Little is known about the structural changes of the ciliary muscle with age and how it may contribute to presbyopia.
Optical coherence tomography (OCT) has been used to perform ciliary muscle biometry at different age and
accommodative states with low resolution and speed. Dynamic imaging and accurate biometry of the ciliary muscle
requires high-speed, high-resolution and correction of the OCT image distortions. We integrate an existing custom-made
Spectral Domain OCT (SD-OCT) platform working at 840nm for biometry of the human eye with a SD-OCT system
working at 1325nm that enables high-speed and high-resolution transscleral imaging of the ciliary muscle dynamically
during accommodation and we developed an algorithm to provide corrected thickness measurements of the ciliary
muscle.
A custom-built OCT system was used to obtain images of the whole mouse eye. We developed a semi-automated segmentation method to detect the boundaries of the anterior and posterior corneal, lens and retinal surfaces as well as the anterior surface of the iris. The radii of curvature of the surfaces were calculated using a conic section fit of each boundary. Image distortions due to refraction of the OCT beam at the successive boundaries were corrected
using a ray-tracing algorithm. Corrected ocular distances, radii of curvature of the cornea and lens surfaces, and anterior chamber angle were obtained on 3 C57BL/6J mice. In vivo imaging of the whole eye, segmentation, conic function fits and correction were successful in all three animals. The posterior lens surface of one mouse could not be fit accurately with a conic section. Biometric parameters of C57BL/6J mice compared well with previous published data obtained from histological sections. The study demonstrates the feasibility of quantitative in vivo biometry of mouse models.
We find for the first time that polarization mismatch of the sample and reference arms in optical-fiber-based optical coherence tomography (OCT) has critical effect on its depth resolution when the light source is partially polarized. When the polarization states of the two arms are matched, the measured point spread function (PSF) is almost identical to the theoretical prediction. When their polarization states are mismatched, the PSF can be so distorted that the depth resolution is degraded to several times the theoretical value. When we polarize the source light with a polarizer, then the degree of polarization (DOP) is unity, and the depth resolution becomes independent of the polarization mismatch. This discovery has fundamental importance for high-resolution OCT imaging of biological tissues. With DOP<1, the depth resolution can be quickly degraded by either birefringence or scattering in the sample. Adjusting polarization controllers can only improve the depth resolution at a certain depth in a sample if the polarization state of light changes along the depth. When DOP=1, uniform resolution along the depth of a sample can be achieved.
Optical Doppler tomography (ODT) is a branch of optical coherence tomography (OCT) that can measure the speed of a
blood flow by measuring the Doppler shift impinged on the probing sample light by the moving blood cells. However,
the measured speed of blood flow is a function of the Doppler angle, which needs to be determined in order to calculate
the absolute velocity of the blood flow inside a vessel. We developed a technique that can extract the Doppler angle from
the 3D data measured with spectral-domain OCT, which needs to extract the lateral and depth coordinates of a vessel in
each measured ODT and OCT image. The lateral coordinates and the diameter of a blood vessel were first extracted in
each OCT structural image by using the technique of blood vessel shadowgram, a technique first developed by us for
enhancing the retinal blood vessel contrast in the en face view of the 3D OCT. The depth coordinate of a vessel was then
determined by using a circular averaging filter moving in the depth direction along the axis passing through the vessel
center in the ODT image. The Doppler angle was then calculated from the extracted coordinates of the blood vessel. The
technique was applied in blood flow measurements in retinal blood vessels, which has potential impact on the study and
diagnosis of blinding diseases like glaucoma and diabetic retinopathy.
Among birds, raptors are well known for their exceptional eyesight, which is partly due to the unique structure of
their retina. Because the raptor retina is the most advanced of any animal species, in vivo examination of its structure
would be remarkable. Furthermore, a noticeable percentage of traumatic ocular injuries are identified in birds of
prey presented to rehabilitation facilities. Injuries affecting the posterior segment have been considered as a major
impact on raptor vision. Hence, in vivo examination of the structure of the posterior segment of the raptors would be
helpful for the diagnosis of traumatized birds. The purpose of this study is to demonstrate the application of
ultrahigh-resolution Spectral Domain Optical Coherence Tomography (SD-OCT) for non contact in vivo imaging of
the retina of birds of prey, which to the best of our knowledge has never been attempted. For the first time we
present high quality OCT images of the retina of two species of bird of prey, one diurnal hawk and one nocturnal
owl.
The integrity of the tear film on the surface of contact lenses is essential to maintaining visual clarity and the overall
health of the superficial structures of the eye (cornea and conjunctiva) for contact lens wearers. It is very critical to
evaluate pre- and post-lens tear films in contact lens practice to make sure the lens is properly fitted. Improper lens
fitting may cause ocular discomfort, visual distortion and ocular infection. It is very often for soft contact lens wearers to
experience dry eye, especially in the afternoon after wearing the lens for a period of time. Dry eye has been a common
cause of contact lens drop-off. There is currently no method available to directly visualize the tears on and underneath
the contact lens in situ on human eye, mainly due to the extremely difficulty in imaging the micrometer-thin tear layer.
An ultra-high resolution spectral domain optical coherence tomography has been developed with a telecentric light
delivery system mounted with a slit-lamp. The system has a 3 micrometer depth resolution with a scan width up to 15
mm. The system was used to image soft contact lenses on the human eye. For the first time to our knowledge, tear films
on the center and edge of the soft contact lens were directly visualized in vivo.
Noninvasive in vivo examination of the rodent retina without sacrificing the animal is the key to being able to perform
longitudinal studies. This allows the monitoring of disease progression and the response to therapies through its entire
course in individual animal. A high-speed high resolution three-dimensional spectral-domain OCT is built for non-contact in vivo imaging of rodent retina. The system is able to acquire high quality 3D images of the rodent retina in 2.7
seconds (total imaging time is ~5 minutes). The system was tested on mice with normal retina (B6/SJLF2), mouse model
for photoreceptor degeneration (Rho-/-), and mouse model for retinoblastoma (LHBETATAG). For the first time to our
knowledge, 3D image of the tumor in retinoblastoma mouse model was successfully imaged in vivo. By segmenting the
tumor boundaries in each frame of the OCT image the volume of the tumor was successfully calculated.
The purpose of this study is to demonstrate the application of ultrahigh-resolution Spectral Domain Optical Coherence Tomography (SD-OCT) for non contact in vivo imaging of the retina of small animals and quantitative retinal information extraction using 3D segmentation of the OCT images. An ultrahigh-resolution SD-OCT system was specifically designed for in vivo retinal imaging of small animal. En face fundus image was constructed from the measured OCT data, which enables precise registration of the OCT images on the fundus. 3D segmentation algorithms were developed for the calculation of retinal thickness map. High quality OCT images of the retina of mice (B6/SJLF2 for normal retina, Rho-/- for photoreceptor degeneration and LHBETATAG for retinoblastoma) and rats (Wistar for normal retina) were acquired, where all the retinal layers can be clearly recognized. The calculated retinal thickness map makes successful quantitative comparison of the retinal thickness distribution between normal and degenerative mouse retina. The capabilities of the OCT system provide a valuable tool for longitudinal studies of small animal models of ocular diseases.
Measurement of retinal blood vessel parameters like the blood blow in the vessels may have significant impact on the
study and diagnosis of glaucoma, a leading blinding disease worldwide. Optical coherence tomography (OCT) is a noninvasive
imaging technique that can provide not only microscopic structural imaging of the retina but also functional
information like the blood flow velocity in the retina. The aim of this study is to automatically extract the parameters of
retinal blood vessels like the 3D orientation, the vessel diameters, as well as the corresponding absolute blood flow
velocity in the vessel. The parameters were extracted from circular OCT scans around the optic disc. By removing the
surface reflection through simple segmentation of the circular OCT scans a blood vessel shadowgram can be generated.
The lateral coordinates and the diameter of each blood vessel are extracted from the shadowgram through a series of
signal processing. Upon determination of the lateral position and the vessel diameter, the coordinate in the depth
direction of each blood vessel is calculated in combination with the Doppler information for the vessel. The extraction of
the vessel coordinates and diameter makes it possible to calculate the orientation of the vessel in reference to the
direction of the incident sample light, which in turn can be used to calculate the absolute blood flow velocity and the
flow rate.
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.