Andoptical Coherence Tomography Research Articles

Long-term Outcomes of Submacular Perfluorocarbon Liquid Removal with Internal Limiting Membrane Peeling and Transretinal Aspiration.

An important complication associated with perfluorocarbon liquid (PFCL) use during pars plana vitrectomy (PPV) is its retention in the submacular area. The aim of this study was to present the long-term outcomes of the surgical method used in this study to remove submacular PFCL and to shed light on the advantages and disadvantages compared to other methods. This is a retrospective, single-center, observational study. Patients who underwent surgical intervention due to submacular PFCL were included in this study. The surgical procedural includes internal limiting membrane (ILM) peeling, transretinal aspiration of submacular PCFL with a 25/27-gauge soft-tipped cannula, then perfluoropropane (C3F8) gas tamponade, and facedown positioning for 5 days. The long-term anatomical and functional outcomes were evaluated with an ophthalmological examination and optical coherence tomography (OCT). A total of 15 patients with submacular PFCL were included in this study, and the mean age of the patients was 64.33 ± 10.36 years (47 - 83). The localization of submacular PFCL was subfoveal in nine patients (60.00%), non-subfoveal in four patients (26.67%), and both subfoveal and non-subfoveal in two patients (13.33%). The mean time of submacular PFCL diagnosis was 4.86 ± 1.02 weeks (2 - 8) and the mean time of the surgery was 9.80 ± 1.17 weeks (8 - 14). Complete removal of submacular PFCL was achieved in all cases (100%) and no significant treatment-associated complications were observed. The mean follow-up time was 37.60 ± 14.00 months (18 - 60) and the best-corrected visual acuity was significantly improved (p = 0.001). At the end of the follow-up time, prominent ellipsoid zone disruption was observed in six patients (40.00%), while in nine patients (60.00%), there was no prominent ellipsoid zone disruption. The surgical procedural for submacular PFCL removal is a reasonable option and improves visual acuity in the long term without any significant treatment-associated complications.

Optical Biopsy of Melanoma and Basal Cell Carcinoma Progression by Noncontact Photoacoustic and Optical Coherence Tomography: In Vivo Multi-Parametric Characterizing Tumor Microenvironment.

Measuring the structural and functional status of tumor microenvironment for malignant melanoma (MM) and basal cell carcinoma (BCC) is of profound significance in understanding dermatological condition for biopsy. However, conventional optical imaging techniques are limited to visualize superficial skin features and parameter information is deficient to depict pathophysiology correlations of skin diseases. Here, we demonstrate a preclinical device, all-optically integrated photoacoustic and optical coherence tomography (AOPA/OCT), that, for the first time, can simultaneously provide label-free biomarkers of vascular patterns, temporal and spatial heterogeneity of blood flow, and tissue micro-structure changes during tumor growth with pathophysiological correlations in mice models. We found that tumor microenvironment of MM and BCC led to the alternation in spatial-temporal heterogeneity that affected morphological and functional parameters, performing the AOPA/OCT quantitative metrics. A robust correlation between imaging biomarkers derived from this in vivo technique and histopathology validation ex vivo in distinguishing benign from malignant is also presented. In receiver operating characteristics (ROC) analysis, multi-parametric AOPA/OCT yields improved diagnostic accuracy of 98.4% and 95.8% for MM and BCC respectively, which indicate that AOPA/OCT represents a high-performance and clinically translatable technique for accurate diagnosis and therapy monitoring in dermatology.

Light reflectivity and interference in cone photoreceptors.

In several modes of retinal imaging, the primary means of visualizing cone photoreceptors is from reflected light. Understanding how such images are formed, particularly when adaptive optics techniques are used, will help to guide their interpretation. Toward this end, we used finite difference beam propagation to model reflections from cone photoreceptors. We investigated the formation of cone images in adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography (AOOCT). Three cone models were tested, one made up of three segments of varying refractive index, the other two having additional boundaries at the inner/outer segment junction and outer segment tip. Images formed by the first model did not correspond to AOOCT observations in the literature, while the latter two did. The predicted distributions of reflected light intensity from the latter cone models were compared to the distribution from AOSLO images, both studied with light sources of varied coherence length. The cone model with the most reflections at the inner/outer segment junction best fit the data measured in vivo. These results show that variance in cone reflection can originate from light interfering from reflectors much more closely spaced than the outer segment length. We also show that subtracting images taken with different coherence length sources highlights these changes in interference. Differential coherence images of cones occasionally revealed an annular reflection profile, which modeling showed to be very sensitive to cone size and the gaps bracketing the outer segment, suggesting that such imaging may be useful for probing photoreceptor morphology.

Long-Term Outcomes of Treat and Extend Regimen of Anti-Vascular Endothelial Growth Factor in Neovascular Age-Related Macular Degeneration

This retrospective cross-sectional cohort study describes the long-term visual and anatomic outcomes of anti-vascular endothelial growth factor (VEGF) treatment using a treat and extend (TAE) regimen. The cohort consisted of 224 treatment-naïve eyes with age related macular degeneration (NV-AMD) from 202 patients that were treated with anti-VEGF agents bevacizumab, ranibizumab, and aflibercept using a TAE regimen by four physician investigators in a large urban referral center from 2008-2015. Subjects were evaluated for visual acuity, injection frequency and optical coherence tomography (OCT). Over a seven-year follow-up period (mean 3.4 years), an average 20.2 ± 14.7 injections were administered per patient. Visual acuity was 0.70 logMAR (20/100 Snellen) at the first visit and 0.67 logMAR (20/93 Snellen) at the final visit, with 74% of eyes maintaining or gaining more than 2 lines of vision. Longterm, 45.1% of eyes achieved 20/50 or better, while 27.1% were 20/200 or worse. 61.2% received monotherapy with no difference in visual acuity outcomes or injection frequency between the agent used. OCT analysis showed decreased fluid from initial to final follow-up visit: 70.1% to 15.6% with sub-retinal fluid (SRF) and 47.3% to 18.8% with intraretinal fluid (IRF) with no difference between the agent used. This study demonstrates that most patients (74%) improve or maintain visual acuity gains long-term using a TAE model with a significant portion (45.1%) achieving 20/50 or better with sustained treatment.

Optical biopsy approach to basal cell carcinoma and melanoma based on all-optically integrated photoacoustic and optical coherence tomography.

Basal cell carcinoma (BCC) and melanoma (MM), with the highest morbidity and mortality, respectively, are considered as two skin cancers of concern in dermatology. Histological studies have demonstrated that vascular patterns and collagenous stroma serve as key parameters for BCC and MM classification. In this Letter, we sought to identify BCC and MM based on the dual parameters of vascular patterns and scattering structures provided by all-optically integrated photoacoustic and optical coherence tomography (AOPA/OCT). The imaging capability of the AOPA/OCT was verified by the mimic phantoms. Furthermore, in vivo characterization of vasculatures and tissue structures from BCC and MM mice were successfully achieved with high resolution. Results prove the feasibility of AOPA/OCT as a novel method to dedicate to the in vivo biopsy of skin cancers which shows new insights into the study of skin diseases in early stages.

Microstructure of subretinal drusenoid deposits revealed by adaptive optics imaging

Subretinal drusenoid deposits (SDD), a recently recognized lesion associated with progression of age-related macular degeneration, were imaged with adaptive optics scanning laser ophthalmoscopy (AO-SLO) and optical coherence tomography (AO-OCT). AO-SLO revealed a distinct en face structure of stage 3 SDD, showing a hyporeflective annulus surrounded reflective core packed with hyperreflective dots bearing a superficial similarity to the photoreceptors in the unaffected retina. However, AO-OCT suggested that the speckled appearance over the SDD rendered by AO-SLO was the lesion material itself, rather than photoreceptors. AO-OCT assists proper interpretation and understanding of the SDD structure and the lesions' impact on surrounding photoreceptors produced by AO-SLO and vice versa.

In vivo photoacoustic tomography of chemicals: high-resolution functional and molecular optical imaging at new depths.

High-resolution volumetric optical imaging modalities, such as confocal microscopy, two-photon microscopy, and optical coherence tomography, have become increasingly important in the biomedical imaging field. However, due to strong light scattering, the penetration depths of these imaging modalities are limited to the optical transport mean free path in biological tissues, for example, ∼1 mm in the skin. Photoacoustic tomography (PAT), an emerging hybrid imaging modality that can provide strong endogenous and exogenous optical absorption contrasts with high ultrasonic spatial resolution using the photoacoustic (PA) effect, has overcome the fundamental depth limitation. The image resolution is scalable with the ultrasonic frequency. The imaging depth is limited to the reach of photons and up to a few centimeters deep in biological tissues. This Review will focus on the following aspects of PAT described in works published from 2003 to 2009: (1) multiscale PAT systems, (2) morphological and functional PAT using intrinsic contrasts (hemoglobin or melanin), and (3) functional and molecular PAT using exogenous contrast agents (organic dyes, nanoparticles, reporter genes, or fluorescence proteins).