Role of Optical Coherence Tomography on Corneal Surface Laser Ablation

This paper focuses on reviewing the roles of optical coherence tomography (OCT) on corneal surface laser ablation procedures. OCT is an optical imaging modality that uses low-coherence interferometry to provide noninvasive cross-sectional imaging of tissue microstructurein vivo.There are two types of OCTs, each with transverse and axial spatial resolutions of a few micrometers: the time-domain and the fourier-domain OCTs. Both have been increasingly used by refractive surgeons and have specific advantages. Which of the current imaging instruments is a better choice depends on the specific application. In laserin situkeratomileusis (LASIK) and in excimer laser phototherapeutic keratectomy (PTK), OCT can be used to assess corneal characteristics and guide treatment decisions. OCT accurately measures central corneal thickness, evaluates the regularity of LASIK flaps, and quantifies flap and residual stromal bed thickness. When evaluating the ablation depth accuracy by subtracting preoperative from postoperative measurements, OCT pachymetry correlates well with laser ablation settings. In addition, OCT can be used to provide precise information on the morphology and depth of corneal pathologic abnormalities, such as corneal degenerations, dystrophies, and opacities, correlating with histopathologic findings.

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Modern Trends in Imaging V: Optical Coherence Tomography for Rapid Tissue Screening and Directed Histological Sectioning

Analytical Cellular Pathology ◽

10.1155/2012/757236 ◽

2012 ◽

Vol 35 (3) ◽

pp. 129-143 ◽

Cited By ~ 11

Author(s):

Woonggyu Jung ◽

Stephen A. Boppart

Keyword(s):

Optical Coherence Tomography ◽

Real Time ◽

Image Guidance ◽

Diagnostic Yield ◽

Imaging Modality ◽

Imaging Techniques ◽

Optical Coherence ◽

Sampling Errors ◽

Cross Sectional

In pathology, histological examination of the “gold standard” to diagnose various diseases. It has contributed significantly toward identifying the abnormalities in tissues and cells, but has inherent drawbacks when used for fast and accurate diagnosis. These limitations include the lack ofin vivoobservation in real time and sampling errors due to limited number and area coverage of tissue sections. Its diagnostic yield also varies depending on the ability of the physician and the effectiveness of any image guidance technique that may be used for tissue screening during excisional biopsy. In order to overcome these current limitations of histology-based diagnostics, there are significant needs for either complementary or alternative imaging techniques which perform non-destructive, high resolution, and rapid tissue screening. Optical coherence tomography (OCT) is an emerging imaging modality which allows real-time cross-sectional imaging with high resolutions that approach those of histology. OCT could be a very promising technique which has the potential to be used as an adjunct to histological tissue observation when it is not practical to take specimens for histological processing, when large areas of tissue need investigating, or when rapid microscopic imaging is needed. This review will describe the use of OCT as an image guidance tool for fast tissue screening and directed histological tissue sectioning in pathology.

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The Value of Anterior Segment Optical Coherence Tomography in Different Types of Corneal Infections: An Update

Journal of Clinical Medicine ◽

10.3390/jcm10132841 ◽

2021 ◽

Vol 10 (13) ◽

pp. 2841

Author(s):

Ahmed A. Abdelghany ◽

Francesco D’Oria ◽

Jorge Alio Del Barrio ◽

Jorge L. Alio

Keyword(s):

Optical Coherence Tomography ◽

Imaging Modality ◽

Wide Spectrum ◽

Anterior Segment ◽

Corneal Edema ◽

Response To Treatment ◽

Optical Coherence ◽

Slit Lamp ◽

Cross Sectional

Anterior segment optical coherence tomography (AS-OCT) is a modality that uses low-coherence interferometry to visualize and assess anterior segment ocular features, offering several advantages of being a sterile and noncontact modality that generates high-resolution cross-sectional images of the tissues. The qualitative and quantitative information provided by AS-OCT may be extremely useful for the clinician in the assessment of a wide spectrum of corneal infections, guiding in the management and follow-up of these patients. In clinical practice, infections are routinely evaluated with slit-lamp biomicroscopy, an examination and imaging modality that is limited by the physical characteristics of light. As a consequence, the depth of pathology and the eventually associated corneal edema cannot be accurately measured with the slit-lamp. Therefore, it represents a limit for the clinician, as in vivo information about corneal diseases and the response to treatment is limited. Resolution of corneal infection is characterized by an early reduction in corneal edema, followed by a later reduction in infiltration: both parameters can be routinely measured with standardized serial images by AS-OCT.

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Longitudinal Monitoring of Flow-Diverting Stent Tissue Coverage After Implant in a Bifurcation Model Using Neurovascular High-Frequency Optical Coherence Tomography

Neurosurgery ◽

10.1093/neuros/nyaa208 ◽

2020 ◽

Author(s):

Jildaz Caroff ◽

Robert M King ◽

Giovanni J Ughi ◽

Miklos Marosfoi ◽

Erin T Langan ◽

...

Keyword(s):

Optical Coherence Tomography ◽

High Frequency ◽

Imaging Modality ◽

Rabbit Model ◽

Flow Diverter ◽

Tissue Growth ◽

Data Sets ◽

Optical Coherence ◽

Cross Sectional

Abstract BACKGROUND Tissue growth over covered branches is a leading cause of delayed thrombotic complications after flow-diverter stenting (FDS). Due to insufficient resolution, no imaging modality is clinically available to monitor this phenomenon. OBJECTIVE To evaluate high-frequency optical coherence tomography (HF-OCT), a novel intravascular imaging modality designed for the cerebrovascular anatomy with a resolution approaching 10 microns, to monitor tissue growth over FDS in an arterial bifurcation model. METHODS FDS were deployed in a rabbit model (n = 6), covering the aortic bifurcation. The animals were divided in different groups, receiving dual antiplatelet therapy (DAPT) (n = 4), aspirin only (n = 1), and no treatment (n = 1). HF-OCT data were obtained in vivo at 3 different time points in each animal. For each cross-sectional image, metal and tissue coverage of the jailed ostium was quantified. Scanning electron microscopy images of harvested arteries were subsequently obtained. RESULTS Good quality HF-OCT data sets were successfully acquired at implant and follow-up. A median value of 41 (range 21-55) cross-sectional images were analyzed per ostium for each time point. Between 0 and 30 d after implant, HF-OCT analysis showed a significantly higher ostium coverage when DAPT was not given. After 30 d, similar growth rates were found in the DAPT and in the aspirin group. At 60 d, a coverage of 90% was reached in all groups. CONCLUSION HF-OCT enables an accurate visualization of tissue growth over time on FDS struts. The use of FDS in bifurcation locations may induce a drastic reduction of the jailed-branch ostium area.

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Optical coherence tomography of the oval window niche

The Journal of Laryngology & Otology ◽

10.1017/s0022215109004381 ◽

2009 ◽

Vol 123 (6) ◽

pp. 603-608 ◽

Cited By ~ 14

Author(s):

T Just ◽

E Lankenau ◽

G Hüttmann ◽

H W Pau

Keyword(s):

Optical Coherence Tomography ◽

Middle Ear ◽

Imaging Modality ◽

Oval Window ◽

Annular Ligament ◽

Middle Ear Surgery ◽

Optical Coherence ◽

Ear Surgery ◽

Temporal Bones

AbstractObjective:Optical coherence tomography was used to study the stapes footplate, both in cadaveric temporal bones and during middle-ear surgery.Materials and methods:Optical coherence tomography was conducted on five temporal bone preparations (from two children and three adults) and in eight patients during middle-ear surgery. A specially equipped operating microscope with integrated spectral domain optical coherence tomography apparatus was used for standard middle-ear surgical procedures.Results:This optical coherence tomography investigation enabled in vivo visualisation and documentation of the annular ligament, the different layers of the footplate and the inner-ear structures, both in non-fixed and fixed stapes footplates. In cases of otosclerosis and tympanosclerosis, an inhomogeneous and irregularly thickened footplate was found, in contrast to the appearance of non-fixed footplates. In both fixed and non-fixed footplates, there was a lack of visualisation of the border between the footplate and the otic capsule.Conclusions:Investigation of the relatively new technology of optical coherence tomography indicated that this imaging modality may assist the ear surgeon to assess the oval window niche intra-operatively.

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Optical coherence tomography of the pancreatic and bile ducts: are we ready for prime time?

Endoscopy International Open ◽

10.1055/a-1119-6248 ◽

2020 ◽

Vol 08 (05) ◽

pp. E644-E649

Author(s):

Amy Tyberg ◽

Isaac Raijman ◽

Aleksey A. Novikov ◽

Divyesh V. Sejpal ◽

Petros C. Benias ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Pancreatic Duct ◽

Imaging System ◽

Biliary Duct ◽

Optical Coherence ◽

Cross Sectional ◽

Reflective Surface ◽

Cross Sectional Imaging ◽

Sectional Imaging

Abstract Background and study aims First-generation optical coherence tomography (OCT) has been shown to increase diagnostic sensitivity for malignant biliary and pancreatic-duct strictures. A newer OCT imaging system, NVision Volumetric Laser Endomicroscopy (VLE), allows for in vivo cross-sectional imaging of the ductal wall at the microstructure level during endoscopic retrograde cholangiopancreatography (ERCP). The aim of this study was to identify and evaluate characteristics on OCT that are predictive of benign and malignant strictures. Patients and methods Consecutive patients from six centers who underwent OCT between September 2016 and September 2017 were included in a dedicated registry. OCT images were analyzed, and nine recurring characteristics were further assessed. Final diagnosis was based on histology and/or surgical pathology. Results 86 patients were included (49 % male, mean age 64.7). OCT was performed in the bile duct in 79 patients and the pancreatic duct in seven. Nine OCT characteristics were identified: dilated hypo-reflective structures (n = 7), onion-skin layering (n = 8), intact layering (n = 17), layering effacement (n = 25), scalloping (n = 20), thickened epithelium (n = 42), hyper-glandular mucosa (n = 13), prominent blood vessels (n = 6), and a hyper-reflective surface (n = 20). Presence of hyper-glandular mucosa, hyper-reflective surface and scalloping significantly increased the odds of malignancy diagnosis by 6 times more (P = 0.0203; 95 % CI 1.3 to 26.5), 4.7 times more (P = 0.0255; 95 % CI 1.2 to 18.0) and 7.9 times more (P = 0.0035; 95 % CI 1.97 to 31.8) respectively. Conclusion By providing in-vivo cross-sectional imaging of the pancreatic and biliary duct wall, OCT technology may improve sensitivity in diagnosing malignant strictures and provide standardizable criteria predictive of malignancy.

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Measurement of Vibrating Tympanic Membrane in an In Vivo Mouse Model Using Doppler Optical Coherence Tomography

Journal of Imaging ◽

10.3390/jimaging5090074 ◽

2019 ◽

Vol 5 (9) ◽

pp. 74

Author(s):

Jeon ◽

Kim ◽

Jeon ◽

Kim

Keyword(s):

Optical Coherence Tomography ◽

Phase Shift ◽

Tympanic Membrane ◽

Middle Ear ◽

Acoustic Stimulus ◽

Optical Coherence ◽

Cross Sectional ◽

Vibratory Motion ◽

Doppler Optical Coherence Tomography

Optical coherence tomography (OCT) has a micro-resolution with a penetration depth of about 2 mm and field of view of about 10 mm. This makes OCT well suited for analyzing the anatomical and internal structural assessment of the middle ear. To study the vibratory motion of the tympanic membrane (TM) and its internal structure, we developed a phase-resolved Doppler OCT system using Kasai’s autocorrelation algorithm. Doppler optical coherence tomography is a powerful imaging tool which can offer the micro-vibratory measurement of the tympanic membrane and obtain the micrometer-resolved cross-sectional images of the sample in real-time. To observe the relative vibratory motion of individual sections (malleus, thick regions, and the thin regions of the tympanic membrane) of the tympanic membrane in respect to auditory signals, we designed an experimental study for measuring the difference in Doppler phase shift for frequencies varying from 1 to 8 kHz which were given as external stimuli to the middle ear of a small animal model. Malleus is the very first interconnecting region between the TM and cochlea. In our proposed study, we observed that the maximum change in Doppler phase shift was seen for the 4 kHz acoustic stimulus in the malleus, the thick regions, and in the thin regions of the tympanic membrane. In particular, the vibration signals were higher in the malleus in comparison to the tympanic membrane.

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Accuracy of the indices of MS-39 anterior segment optical coherence tomography in the diagnosis of keratoconic corneas

European Journal of Ophthalmology ◽

10.1177/11206721211063720 ◽

2021 ◽

pp. 112067212110637

Author(s):

Rania S Elkitkat ◽

Yasser Rifay ◽

Hesham M Gharieb ◽

Hossam Eldin A Ziada

Keyword(s):

Optical Coherence Tomography ◽

Anterior Segment ◽

Front Surface ◽

Receiver Operating Curve ◽

P Value ◽

Optical Coherence ◽

Corneal Surface ◽

Cross Sectional ◽

The Mean ◽

Group 2

Purpose To determine the normative and the cut-off values of various indices available in the MS 39 Anterior Segment Optical Coherence Tomography (MS-39 AS-OCT) for keratoconus (KC) diagnosis, and to detect the accuracy of the variable available parameters. Methods This cross sectional observational study was conducted at Dr Rifay Ophthalmology Center, Rabat, Morocco, on 172 eyes with KC (group 1) and 248 eyes of healthy controls (group 2). Participants were screened using MS-39 AS-OCT (CSO, Firenze, Italy). The investigated indices included: keratometric indices, pachymetric indices, elevation indices, Keratoconus Summary Indices (KSI), aberration indices, and epithelial mapping evaluation. Results Most of the studied indices were significantly different between both groups (P value <0.001). Twenty two indices had Area Under the Receiver Operating Curve (AUROC) values >0.950, eight of which were from the KSI. The indices with the highest AUROC values were: Root Mean Square (RMS) for the front corneal surface at 6 mm circle (AUROC = 0.996, and best cut-off >1.69 with sensitivity of 97.67% and specificity of 97.98%) and RMS per unit of area for the front surface at 6 mm circle (AUROC = 0.996, and best cut-off >0.06 with sensitivity of 97.67% and specificity of 97.98%). Epithelial thickness-derived metrics were not among the parameters with the highest accuracy. Conclusions This study presented the mean and the cut-off values for a plethora of parameters available in the MS-39 AS-OCT. The results of this study show that MS-39 AS-OCT is a valuable equipment for diagnosing keratoconic corneas, with a high accuracy detected for many parameters.

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In vivo three dimensional optical coherence tomography. A novel imaging modality to visualize the edge vascular response

International Journal of Cardiology ◽

10.1016/j.ijcard.2012.09.161 ◽

2013 ◽

Vol 164 (3) ◽

pp. e35-e37 ◽

Cited By ~ 5

Author(s):

Bill D. Gogas ◽

Takashi Muramatsu ◽

Hector M. Garcia-Garcia ◽

Christos V. Bourantas ◽

Niels R. Holm ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Imaging Modality ◽

Three Dimensional ◽

Optical Coherence ◽

Vascular Response

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Quantification of Trabecular-Iris Contact and its Prevalence by Optical Coherence Tomography in a Healthy Caucasian Population

European Journal of Ophthalmology ◽

10.5301/ejo.5000919 ◽

2016 ◽

Vol 27 (4) ◽

pp. 417-422 ◽

Cited By ~ 4

Author(s):

José Ignacio Fernández-Vigo ◽

Lucía De-Pablo-Gómez-De-Liaño ◽

Cristina Fernández-Vigo ◽

Inés Sánchez-Guillén ◽

Enrique Santos-Bueso ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Anterior Chamber ◽

Refractive Error ◽

Axial Length ◽

Corneal Thickness ◽

Anterior Segment ◽

Anterior Chamber Depth ◽

Fourier Domain ◽

Optical Coherence ◽

Cross Sectional

Purpose To determine the prevalence of trabecular-iris contact (TIC) and quantify this contact in healthy Caucasian individuals using Fourier-domain optical coherence tomography (FD-OCT). Methods For this cross-sectional study, 2,012 eyes of 1,006 healthy subjects were recruited among individuals undergoing a routine ophthalmologic checkup. In each participant, age, sex, intraocular pressure, and spherical refractive error were first recorded along with anterior chamber depth and volume, central corneal thickness measured with the Pentacam, and axial length with the IOLMaster. Anterior chamber angle variables and the presence of TIC in the horizontal quadrants were determined by anterior segment FD-OCT (RTVue 100®). When TIC was observed, TIC length (TICL) and its percentage in relation to the length of the trabecular meshwork (TICL percentage) were also measured. Results Trabecular-iris contact in the horizontal quadrants was observed in 34 eyes of 25 patients, representing 1.6% of the total number of eyes examined. In this subgroup of individuals, mean age was 55.8 years, 84% were women, and spherical refractive error ranged from -0.25 to 8.25 D. Eyes with TIC showed an angle width of less than 23.2 degrees and axial length shorter than 23.7 mm. Mean TICL was 239 ± 79 μm (103-495 μm) and mean TICL percentage was 46.9% ± 13.9% (17.2%-76.3%). Conclusions The prevalence of TIC was low in this population. Fourier-domain optical coherence tomography emerged as useful to assess its prevalence and quantify the extent of TIC.

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