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1.
Front Psychiatry ; 13: 944973, 2022.
Article in English | MEDLINE | ID: mdl-36213913

ABSTRACT

Introduction: Anxiety and depression have increased dramatically 2-3-fold with the COVID-19 pandemic. There is an urgent need for safe, cost-effective, and scalable approaches to alleviate this parallel mental health pandemic. Meditation has previously been shown to reduce stress, anxiety, and depression symptoms. Furthermore, online delivery of mind-body interventions will be impactful in addressing disparities in access to mental healthcare. In this observational pilot study, we investigate the impact of a digitally delivered guided meditation followed by daily practice on symptoms of anxiety and depression. Methods: Initially, 57 male and 202 female subjects enrolled in this study. Participants attended a webinar where they learned the Isha Kriya meditation practice. They were subsequently requested to perform the intervention daily for 6 weeks. Subjects were given scales to assess anxiety and depression at baseline, 2, 4, and 6 weeks following the training. The changes in the self-reported anxiety and depression scores were examined by the linear mixed effect models. Results: Participants completed survey responses for the following time points: baseline (n = 82), week 2 (n = 58), week 4 (n = 37), and week 6 (n = 28). During the 6 weeks of the study over 68% of subjects were compliant with their daily practice. When comparing baseline with week 2, the mean anxiety scores decreased from 25.4 to 16.8 (p < 0.01, d = 1.31). Similarly, mean depression scores decreased from 15 to 8.81 (p < 0.01, d = 0.9). The reduced scores for both anxiety and depression were maintained at weeks 4 and 6. Conclusion: This preliminary study assesses the effectiveness of online meditation training on self-reported symptoms of anxiety and depression. After 2 weeks of practice, those with baseline anxiety and depression showed significant improvement with a large effect size. The results from weeks 4 and 6 show sustained reduced anxiety and depression symptoms. These findings suggest that daily Isha Kriya practice could alleviate symptoms of these conditions. Future studies utilizing randomized control trials should be conducted to rigorously evaluate the benefits of this meditation practice on anxiety and depression. Trials registration: ClinicalTrials.gov, identifier: NCT05065476.

2.
Front Psychol ; 13: 814224, 2022.
Article in English | MEDLINE | ID: mdl-35572309

ABSTRACT

Introduction: The Covid-19 pandemic has been a major disruptor of routine life, resulting in increased stress and predisposing people to negative outcomes, such as insomnia, anxiety and hopelessness. Mind-body interventions have improved concentration, emotional balance, and positive emotions, with an enhanced sense of productivity, and self-confidence. We therefore hypothesized that exposure to an online mind-body intervention, "Inner Engineering Completion Online (IECO)," would reduce stress and promote well-being. Methods: This prospective cohort study enrolled participants registered for the IECO courses, which for the first time were delivered remotely, online. Participants learned a 21-min meditation practice called Shambhavi Mahamudra Kriya during the course, which incorporates controlled breathing and mediation techniques. Each enrolled participant was asked to complete self-reported electronic surveys at three key time points: at the time of consent, immediately after completing IECO, and 6 weeks after IECO completion. Effects of IECO practice were assessed using four well-validated neuropsychological scales: Perceived Stress Scale (PSS), Positive Emotion/Relationship/Engagement Scale (PERMA) Profiler, Pittsburgh Sleep Quality Index (PSQI), and Mindful Attention Awareness Scale (MAAS). A Signed Rank test was used to analyze the survey data and P-values of < 0.05 were considered statistically significant. Results: Of the 375 participants interested in participation, 164 participants were eligible. Sixty-eight participants completed surveys at all time points and were identified as compliant participants. The baseline median score for PSS in compliant participants (n = 95) was 13.5 (IQR 9, 18); immediate post-IECO median PSS score was 12 (IQR 8, 16) demonstrating a 1.5 unit decrease in PSS scores (p-value = 0.0023). Similarly, comparing PSS scores in compliant participants (n = 68) for immediate Post IECO [11.5 (IQR 8, 15.5)] to PSS scores at six weeks [8 (IQR 4.5, 12.5)] showed a statistically significant 3.5-unit decrease, indicating a reduction in stress upon routine practice of the intervention (p < 0.0001). Conclusion: Incorporating the remotely delivered mind-body intervention Shambhavi Mahamudra Kriya into daily life via the IECO program over as few as 6 weeks produced a significant stress reduction, improvement in sleep quality and mindfulness. Clinical Trial Registration: [ClinicalTrials.gov], identifier [NCT04189146].

3.
J Integr Complement Med ; 28(8): 674-682, 2022 Aug.
Article in English | MEDLINE | ID: mdl-35532984

ABSTRACT

Introduction: Samyama is an Isha Yoga 8-day residential meditation/yoga retreat combined with 60 days of preparation with vegan diet. We showed earlier Samyama retreat was associated with lower systemic inflammation and favorable lipid profiles along with other physical and mental health benefits. There is no mechanistic study on the impact of an advanced meditative process on multiple blood lipids and their implications on meditation-related improved physical and mental wellbeing. Methods: Sixty-four Samyama participants on vegan diet had blood sampled immediately before and immediately after the 8-day retreat for lipidomic analysis. The complex plasma lipidome was characterized using high-resolution mass spectrometric analysis and tandem mass spectrometry. Results: Pre- and post-Samyama blood samples of 64 Samyama participants were analyzed. Acylglycines (acetyl, propionyl, butyryl, and valeryl) were increased in the plasma post-Samyama compared with pre-Samyama (p < 0.001). Levels of glycerophosphocholines, glycerophosphoethanolamines, di-unsaturated ethanolamine plasmalogens, cholesterol esters, acylcarnitines, and acylgylcerines (triacylglycerols and diacylglycerols) decreased after the Samyama meditation. Plasma levels of glycerophosphoserines or glycerophosphoinositols were unchanged. Conclusion: An 8-day advanced meditation retreat resulted in increased acylglycines, an endocannabinoid-like fatty acid amide associated with increased cellular anandamide levels, anti-inflammation, analgesia, and vascular relaxation. Other serum lipid levels, including some that are associated with increased risk of atherosclerosis, were reduced following the Samyama program. ClinicalTrials.gov Registration: Identifier: NCT04366544.


Subject(s)
Meditation , Diet, Vegan , Humans , Lipids , Longitudinal Studies , Meditation/methods , Prospective Studies
4.
Appl Psychol Health Well Being ; 14(4): 1408-1428, 2022 11.
Article in English | MEDLINE | ID: mdl-35064741

ABSTRACT

College students experienced increased stress and anxiety during the COVID-19 pandemic. This study evaluated the effect of brief online Isha Upa Yoga modules on undergraduates' mental health and well-being. Randomized control trial (RCT) with waitlist control crossover (N = 679). The intervention group was instructed to learn and practice the modules daily for 12 weeks. At the end of the 4-week RCT, the control group was instructed to learn and practice the modules for the remaining 8 weeks. Primary outcomes included stress and well-being. Secondary outcomes included anxiety, depression, resilience, positive affect and negative affect. Linear mixed-effects models were used for analyses. Isha Upa Yoga significantly reduced stress (Group [intervention, control] × Time [baseline, Week 4] interaction, p = .009, d = .27) and increased well-being (Group × Time interaction p = .002, d = .32). By the study's end, the intervention and control groups experienced significant improvements in well-being (p < .001, p < .001), stress (p < .001, p < .001), anxiety (p < .001, p < .001), depression (p < .001, p = .004), positive affect (p = .04, p < .001), and negative affect (p < .001, p < .001). Online Isha Upa Yoga shows promise for mitigating the pandemic's negative impact on undergraduates' mental health and improving their well-being.


Subject(s)
COVID-19 , Yoga , Humans , Yoga/psychology , Mental Health , Anxiety/therapy , Students
5.
Front Psychol ; 12: 659667, 2021.
Article in English | MEDLINE | ID: mdl-34093351

ABSTRACT

Background: Meditation is gaining recognition as a tool to impact health and well-being. Samyama is an 8-day intensive residential meditation experience conducted by Isha Foundation requiring several months of extensive preparation and vegan diet. The health effects of Samyama have not been previously studied. The objective was to assess physical and emotional well-being before and after Samyama participation by evaluating psychological surveys and objective health biomarkers. Methods: This was an observational study of 632 adults before and after the Isha Samyama retreat. All participants were invited to complete surveys. Controls included household significant others. Surveys were completed at baseline (T1), just before Samyama (T2), immediately after Samyama (T3), and 3 months later (T4) to assess anxiety, depression, mindfulness, joy, vitality, and resilience through validated psychometric scales. Voluntary blood sampling for biomarker analysis was done to assess hemoglobin (Hb), HbA1c, lipid profile, and C-reactive protein (CRP). Primary outcomes were changes in psychometric scores, body weight, and blood biomarkers. Results: Depression and anxiety scores decreased from T1 to T3, with the effect most pronounced in participants with baseline depression or anxiety. Scores at T4 remained below baseline for those with pre-existing depression or anxiety. Vitality, resilience, joy, and mindfulness increased from T1 to T3 (sustained at T4). Body weight decreased by 3% from T1 to T3. Triglycerides (TG) were lower from T2 to T3. Participants had lower HbA1c and HDL at T2, and lower CRP at all timepoints compared with controls. Conclusions: Participation in the Isha Samyama program led to multiple benefits. The 2-month preparation reduced anxiety, and participants maintained lower anxiety levels at 3 months post-retreat. Physical health improved over the course of the program as evidenced by weight loss and improved HbA1C and lipid profile. Practices associated with the Samyama preparation phase and the retreat may serve as an effective way to improve physical and mental health. Future studies may examine their use as an alternative therapy in patients with depression and/or anxiety. Clinical Trial Registration: www.ClinicalTrials.gov, Identifier: 1801728792. Registered retrospectively on 4/17/2020.

6.
Article in English | MEDLINE | ID: mdl-32595741

ABSTRACT

BACKGROUND: Anxiety and depression are common in the modern world, and there is growing demand for alternative therapies such as meditation. Meditation can decrease perceived stress and increase general well-being, although the physiological mechanism is not well-characterized. Endocannabinoids (eCBs), lipid mediators associated with enhanced mood and reduced anxiety/depression, have not been previously studied as biomarkers of meditation effects. Our aim was to assess biomarkers (eCBs and brain-derived neurotrophic factor [BDNF]) and psychological parameters after a meditation retreat. METHODS: This was an observational pilot study of adults before and after the 4-day Isha Yoga Bhava Spandana Program retreat. Participants completed online surveys (before and after retreat, and 1 month later) to assess anxiety, depression, focus, well-being, and happiness through validated psychological scales. Voluntary blood sampling for biomarker studies was done before and within a day after the retreat. The biomarkers anandamide, 2-arachidonoylglycerol (2-AG), 1-arachidonoylglycerol (1-AG), docosatetraenoylethanolamide (DEA), oleoylethanolamide (OLA), and BDNF were evaluated. Primary outcomes were changes in psychological scales, as well as changes in eCBs and BDNF. RESULTS: Depression and anxiety scores decreased while focus, happiness, and positive well-being scores increased immediately after retreat from their baseline values (P < 0.001). All improvements were sustained 1 month after BSP. All major eCBs including anandamide, 2-AG, 1-AG, DEA, and BDNF increased after meditation by > 70% (P < 0.001). Increases of ≥20% in anandamide, 2-AG, 1-AG, and total AG levels after meditation from the baseline had weak correlations with changes in happiness and well-being. CONCLUSIONS: A short meditation experience improved focus, happiness, and positive well-being and reduced depression and anxiety in participants for at least 1 month. Participants had increased blood eCBs and BDNF, suggesting a role for these biomarkers in the underlying mechanism of meditation. Meditation is a simple, organic, and effective way to improve well-being and reduce depression and anxiety.

7.
Quant Imaging Med Surg ; 5(1): 163-70, 2015 Feb.
Article in English | MEDLINE | ID: mdl-25694966

ABSTRACT

To explore ocular graft-versus-host disease (GVHD), anterior segment optical coherence tomography (AS-OCT) imaging of eyelids, tear meniscus, cornea and conjunctiva is performed in subsequent sessions on a patient who has ocular GVHD after allogeneic related donor stem cell transplant. The OCT results are presented together with those from a normal subject. OCT imaging is promising in visualizing several ocular GVHD manifestations, such as abnormal meibomian gland orifice (MGO), conjunctival keratinization, conjunctival hyperemia and chemosis, corneal epithelium opacification, thinning and sloughing. This case study demonstrates the capability of AS-OCT in the imaging and monitoring of ocular GVHD, which may be useful in the development of current ocular GVHD staging system and the clinical management for GVHD treatment.

8.
J Biomed Opt ; 19(10): 106013, 2014.
Article in English | MEDLINE | ID: mdl-25349094

ABSTRACT

The aqueous outflow system (AOS) is responsible for maintaining normal intraocular pressure (IOP) in the eye. Structures of the AOS have an active role in regulating IOP in healthy eyes and these structures become abnormal in the eyes with glaucoma. We describe a newly developed system platform to obtain high-resolution images of the AOS structures. By incorporating spectral domain optical coherence tomography (SD-OCT), the platform allows us to systematically control, image, and quantitate the responses of AOS tissue to pressure with a millisecond resolution of pulsed flow. We use SD-OCT to image radial limbal segments from the surface of the trabecular meshwork (TM) with a spatial resolution of ∼5 µm in ex vivo nonhuman primate eyes. We carefully insert a cannula into Schlemm's canal (SC) to control both pressures and flow rates. The experimental results demonstrate the capability of the platform to visualize the unprecedented details of AOS tissue components comparable to that delivered by scanning electron microscopy, as well as to delineate the complex pressure-dependent relationships among the TM, structures within the SC, and collector channel ostia. The described technique provides a new means to characterize the anatomic and pressure-dependent relationships of SC structures, particularly the active motion of collagenous elements at collector channel ostia; such relationships have not previously been amenable to study. Experimental findings suggest that continuing improvements in the OCT imaging of the AOS may provide both insights into the glaucoma enigma and improvements in its management.


Subject(s)
Anterior Chamber/anatomy & histology , Image Processing, Computer-Assisted/methods , Tomography, Optical Coherence/methods , Trabecular Meshwork/anatomy & histology , Animals , Anterior Chamber/physiology , Intraocular Pressure , Macaca , Trabecular Meshwork/physiology
9.
J Biomed Opt ; 18(2): 26017, 2013 Feb.
Article in English | MEDLINE | ID: mdl-23396538

ABSTRACT

An ultrahigh resolution spectral domain optical coherence tomography (SD-OCT) system is used to observe for the first time in vivo the early effect of sodium iodate (NaIO3) toxicity on retinal morphology. Retinal degeneration is induced in rats via tail vein injection of NaIO3 and structural changes in the outer retina are assessed longitudinally at baseline and 1, 2, 3, 6, 8, and 10 h, and 12 post drug administration with OCT, H&E histology, and IgG immunochemistry. Disruption of the structural integrity and changes in the optical reflectivity of the photoreceptor inner (IS) and outer segment (OS) layers are observed as early as 1 h post NaIO3 injection. A new layer is observed in the OCT tomograms to form between the retinal pigmented epithelium and the photoreceptors OS a few hours post NaIO3 injection. The dynamics and the low optical reflectivity of this layer, as well as cell swelling and disruption of the blood-retina barrier observed in the histological and immunohistochemistry cross-sections suggest that the layer corresponds to temporary fluid accumulation in the retina. Results from this study demonstrate the effectiveness of OCT technology for monitoring dynamic changes in the retinal morphology and provide better understanding of the early stages of outer retina degeneration induced by NaIO3 toxicity.


Subject(s)
Iodates/toxicity , Retinal Degeneration/chemically induced , Retinal Degeneration/pathology , Tomography, Optical Coherence/methods , Animals , Disease Models, Animal , Female , Imaging, Three-Dimensional , Optical Phenomena , Rats , Rats, Long-Evans , Retinal Photoreceptor Cell Outer Segment/drug effects , Retinal Photoreceptor Cell Outer Segment/pathology , Retinal Pigment Epithelium/drug effects , Retinal Pigment Epithelium/pathology , Time Factors
10.
Invest Ophthalmol Vis Sci ; 53(11): 6863-9, 2012 Oct 03.
Article in English | MEDLINE | ID: mdl-22930724

ABSTRACT

PURPOSE: To demonstrate the ability of high speed, ultrahigh-resolution optical coherence tomography (UHR-OCT) to measure and characterize in vivo visual stimulus-specific pupil dynamics in birds. METHODS: Ten two-week old White Leghorn (Gallus gallus domesticus) chickens were imaged in this study. The chickens were dark-adapted for 1 hour and anesthetized with 2% isoflurane prior to the imaging procedure. Blue, green, and red single flash visual stimuli of 7 ms duration were used to evoke pupillary responses. UHR-OCT cross-sectional images of the pupil were acquired prior, during, and for several seconds after the visual stimuli onset. Images were processed with a novel custom automatic algorithm, designed to determine the pupil diameter changes over time. RESULTS: Results from this study show that the pupillary constriction begins with the onset of the visual stimuli; however, maximum pupil constriction occurs ∼150 ms later. No statistically significant variation in the timing of the maximum pupillary constriction was observed for stimuli of different colors. However, significant variation was observed in the maximum pupil constriction amplitudes, between red-green and red-blue stimuli, but not between blue-green stimuli. Furthermore, the magnitude of the maximum pupil constriction decreased monotonically with time under isoflurane anesthesia. CONCLUSIONS: We demonstrated, for the first time, measurements of visually evoked pupillary dynamics in animals using high speed UHR-OCT. The results suggest dependence of the pupillary dynamics on the color of the visual stimulus, and adverse effects of isoflurane anesthesia on the visually evoked pupillary responses in chickens.


Subject(s)
Chickens/physiology , Image Enhancement/methods , Pupil/physiology , Tomography, Optical Coherence/methods , Animals , Photic Stimulation , Reaction Time
11.
Invest Ophthalmol Vis Sci ; 53(4): 1982-9, 2012 Apr 18.
Article in English | MEDLINE | ID: mdl-22395894

ABSTRACT

PURPOSE: To provide in vivo quantitative assessment of sodium iodate-induced retinal damage in a rat model of outer retinal degeneration using ultrahigh resolution optical coherence tomography (UHR-OCT). METHODS: Outer retinal degeneration was induced in four female Long Evans rats via tail vein injection of sodium iodate (40 mg/kg). Changes in the thickness and optical reflectivity of individual retinal layers were extracted using a semi-automatic segmentation algorithm and were assessed in vivo at 6 hours, days 1, 3, and 7, and up to 3 months post injection with UHR-OCT. Hematoxylin and eosin (H&E) histology was used to confirm the morphologic changes observed in the UHR-OCT images. RESULTS: UHR-OCT tomograms showed progressive structural damage in the rat retina over time, such as swelling, thinning, complete disintegration of individual retinal layers, and clustering of highly reflective cellular debris. Photoreceptor swelling was observed 6 hours after injection of sodium iodate, followed by progressive structural decomposition of the outer retina. At 3 months post injection, the outer retina was completely disintegrated, and the inner nuclear layer (INL) was in direct contact with the choroid. Changes in the reflectivity of individual retinal layers were observed over time and correlated well with the morphologic changes. CONCLUSIONS: UHR-OCT permits in vivo, noninvasive, longitudinal, quantitative assessment of the progressive changes in retinal morphology and optical reflectivity in a sodium iodate rodent model of outer retinal degeneration.


Subject(s)
Image Enhancement , Retinal Degeneration/diagnosis , Retinal Photoreceptor Cell Outer Segment/pathology , Tomography, Optical Coherence/methods , Animals , Disease Models, Animal , Disease Progression , Female , Follow-Up Studies , Hypertrophy , Photic Stimulation , Rats , Rats, Long-Evans , Retinal Degeneration/chemically induced
12.
J Biomed Opt ; 17(1): 016011, 2012 Jan.
Article in English | MEDLINE | ID: mdl-22352661

ABSTRACT

Visually evoked fast intrinsic optical signals (IOSs) were recorded for the first time in vivo from all layers of healthy chicken retina by using a combined functional optical coherence tomography (fOCT) and electroretinography (ERG) system. The fast IOSs were observed to develop within ∼5 ms from the on-set of the visual stimulus, whereas slow IOSs were measured up to 1 s later. The visually evoked IOSs and ERG traces were recorded simultaneously, and a clear correlation was observed between them. The ability to measure visually evoked fast IOSs non-invasively and in vivo from individual retinal layers could significantly improve the understanding of the complex communication between different retinal cell types in healthy and diseased retinas.


Subject(s)
Electroretinography/methods , Evoked Potentials, Visual/physiology , Retina/physiology , Signal Processing, Computer-Assisted , Tomography, Optical Coherence/methods , Animals , Chickens
13.
Biomed Opt Express ; 3(1): 160-9, 2012 Jan 01.
Article in English | MEDLINE | ID: mdl-22254176

ABSTRACT

A novel optical coherence tomography (OCT) reconstruction approach is introduced for improved visualization of inner-retina capillaries in retinal OCT tomograms. The proposed method utilizes a minimization framework based on a tensor total variation (TTV) energy functional, to enforce capillary structural characteristics in the spatial domain. By accounting for structure tensor characteristics, the TTV reconstruction method allows for contrast enhancement of capillary structural characteristics. The novel TTV method was tested on high resolution OCT images acquired in-vivo from the foveal region of the retina of a healthy human subject. Experimental results demonstrate significant contrast and visibility enhancement of the inner retina capillaries in the retinal OCT tomograms, achieved by use of the TTV reconstruction method. Therefore, the TTV method has a strong potential for improved disease progression analysis based on the study of disease-induced changes in the inner retina vasculature.

14.
Opt Lett ; 36(23): 4575-7, 2011 Dec 01.
Article in English | MEDLINE | ID: mdl-22139247

ABSTRACT

Visually evoked intrinsic optical signals (IOSs) were measured in vivo for the first time to our knowledge from all retina layers of the chicken retina with a combined functional optical coherence tomography and electroretinography (ERG) system. IOS traces were recorded from a small volume in the retina with 3.5 µm axial resolution and 7 ms time resolution. Comparison of the IOS and ERG traces shows a correlation between the positive and negative IOS measured from different retinal layers and the timing of the a and b waves in the ERG recording.


Subject(s)
Evoked Potentials, Visual/physiology , Retina/physiology , Tomography, Optical Coherence/methods , Animals , Chickens , Electroretinography/instrumentation , Electroretinography/methods , Optical Phenomena , Photic Stimulation , Retina/anatomy & histology , Tomography, Optical Coherence/instrumentation
15.
Biomed Opt Express ; 2(5): 1268-74, 2011 Apr 19.
Article in English | MEDLINE | ID: mdl-21559138

ABSTRACT

The chicken retina is an established animal model for myopia and light-associated growth studies. It has a unique morphology: it is afoveate and avascular; oxygen and nutrition to the inner retina is delivered by a vascular tissue (pecten) that protrudes into the vitreous. Here we present, to the best of our knowledge, the first in vivo, volumetric high-resolution images of the chicken retina. Images were acquired with an ultrahigh-resolution optical coherence tomography (UHROCT) system with 3.5 µm axial resolution in the retina, at the rate of 47,000 A-scans/s. Spatial variations in the thickness of the nerve fiber and ganglion cell layers were mapped by segmenting and measuring the layer thickness with a semi-automatic segmentation algorithm. Volumetric visualization of the morphology and morphometric analysis of the chicken retina could aid significantly studies with chicken retinal models of ophthalmic diseases.

16.
J Biomed Opt ; 15(4): 040506, 2010.
Article in English | MEDLINE | ID: mdl-20799773

ABSTRACT

A combined ultrahigh resolution optical coherence tomography (UHROCT) and a electroretinography (ERG) system is presented for simultaneous imaging of the retinal structure and physiological response to light stimulation in the rodent eye. The 1060-nm UHROCT system provides approximately 3x5 microm (axialxlateral) resolution in the rat retina and time resolution of 22 micros. A custom-designed light stimulator integrated into the UHROCT imaging probe provides light stimuli with user-selected color, duration, and intensity. The performance of the combined system is demonstrated in vivo in healthy rats, and in a rat model of drug-induced outer retinal degeneration. Experimental results show correlation between the observed structural and physiological changes in the healthy and degenerated retina.


Subject(s)
Electroretinography/instrumentation , Electroretinography/veterinary , Retina/cytology , Retina/physiology , Retinoscopes/veterinary , Tomography, Optical Coherence/instrumentation , Tomography, Optical Coherence/veterinary , Animals , Equipment Design , Equipment Failure Analysis , Female , Rats , Rats, Long-Evans , Systems Integration
17.
Invest Ophthalmol Vis Sci ; 51(9): 4579-84, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20435597

ABSTRACT

PURPOSE: To evaluate the change in thickness of the anterior, stromal, and posterior corneal laminae in response to hypoxia-induced corneal swelling, by means of ultrahigh-resolution optical coherence tomography (UHR-OCT). METHODS: A UHR-OCT system, operating in the 1060-nm range, was used to acquire in vivo cross-sectional images of human cornea with a 3.2x10-microm (axial x lateral) resolution in corneal tissue. Corneal edema was induced by inserting a thick, positive-powered, soft contact lens, over which the eye was closed and patched for 3 hours. Tomograms were acquired from eight non-contact-lens wearers. Baseline images were obtained before inducing corneal edema, immediately after removal of the patch and the lens, and then every 15 minutes for approximately 2 hours. All images were postprocessed with a segmentation algorithm to identify the laminae visible in the image. The apical thickness of the laminae (epithelium [EPI], epithelial-Bowman's membrane [Ep-BM] complex, stroma, and endothelial-Descemet's membrane [En-DM] complex) were determined at each time interval. RESULTS: There was an interaction between time after removal of the hypoxic stimulus and deswelling of the layers (RM-ANOVA; P<0.001). The epithelial and stromal thickness reduced significantly with time (P=0.001; P<0.001, respectively), whereas the Ep-BM and En-DM complexes did not (P>0.50). All layers except the En-DM complex exhibited a biphasic pattern of recovery. CONCLUSIONS: UHR-OCT showed regional differences in swelling due to hypoxic provocation. On removal of the hypoxic stimulus, the rate of recovery varied between layers, and all layers except the En-DM complex exhibited a biphasic recovery.


Subject(s)
Corneal Edema/pathology , Descemet Membrane/pathology , Hypoxia/pathology , Tomography, Optical Coherence/instrumentation , Tomography, Optical Coherence/methods , Adult , Algorithms , Anthracenes , Contact Lenses, Hydrophilic/adverse effects , Corneal Edema/etiology , Corneal Edema/metabolism , Descemet Membrane/metabolism , Female , Humans , Hypoxia/complications , Hypoxia/metabolism , Male , Middle Aged , Recovery of Function , Young Adult
18.
Opt Express ; 17(26): 24304-16, 2009 Dec 21.
Article in English | MEDLINE | ID: mdl-20052141

ABSTRACT

A computational model was developed to evaluate the limitations to the highest axial resolution, achievable with ultrahigh resolution optical coherence tomography (UHROCT) in the 1060 nm wavelength region for in-vivo imaging of the human and rodent retina. The model considers parameters such as the wavelength dependent water absorption, the average length of the human and rodent eyes, and the power limitations for the imaging beam as defined in the ANSI standard. A custom-built light source with re-shaped spectrum was used to verify experimentally the results from the computational model. Axial OCT resolution of 4.2 microm and 7.7 microm was measured from a mirror reflection with the custom light source by propagating the imaging beam through water cells with 5 mm and 25 mm thickness, corresponding to the average axial length of the rodent and human eye respectively. Assuming an average refractive index of 1.38 for retinal tissue, the expected axial OCT resolution in the rodent and human retina is 3 microm and 5.7 microm respectively. Retinal tomograms acquired in-vivo from the rat eye with the modified light source show clear visualization of all intraretinal layers, as well as a network of capillaries (approximately 10 microm in diameter) in the inner- and outer plexiform layers of the retina.


Subject(s)
Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Retinoscopy/methods , Tomography, Optical Coherence/methods , Animals , Humans , Rats , Reproducibility of Results , Sensitivity and Specificity
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