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PubMedDate not supplied

Optical coherence tomography study of optic disc melanocytoma.

Optic disc melanocytoma is a well-known clinical entity occurring as a deeply pigmented lesion on the optic nerve head. A 40-year-old man with a pigmented lesion overlying the left optic disc was evaluated with optical coherence tomography. The single high reflectance band from the anterior edge of the disc lesion with optical back shadowing behind on optical coherence tomography helped to pinpoint the diagnosis of the lesion as optic disc melanocytoma. Quantitative assessment of the mass with optical coherence tomography for its growth did not show any increase in size horizontally or vertically after 6 months. Optical coherence tomography is useful for obtaining the exact measurements of the mass lesion and may be used as a tool to follow the progress and growth pattern of the lesion.

Adult↗
PubMed2006

Stratus optical coherence tomography for evaluating optic disc pits associated with maculopathy before and after vitrectomy: two case reports.

Optic disc pit (ODP) can be either congenital or acquired. Congenital ODP is typically unilateral, and the visual acuity and visual field are normal unless associated with macular serous detachment, which occurs in about 25-75% of cases. Acquired ODP is known as an important risk factor for progressive visual field loss in glaucoma. The fundus finding of congenital ODP includes oval depression involving the optic disc, with or without macular serous detachment. We used third-generation Stratus optical coherence tomography (Straus OCT) to investigate the possible pathogenesis of ODP associated with maculopathy and to monitor the anatomic changes before and after treatment.

Adolescent↗
PubMedDate not supplied

Optical coherence tomography disc assessment in optic nerves with peripapillary atrophy.

BACKGROUND AND OBJECTIVE: Optical coherence tomography (OCT) is able to determine the optic disc margin automatically. The aim of this study was to investigate the accuracy of the automatic OCT optic nerve head measurements in the presence of peripapillary atrophy. PATIENTS AND METHODS: This was a cross-sectional, retrospective study. Thirty-one subjects with peripapillary atrophy underwent optic nerve head scanning with OCT version 3. Nineteen of the eyes were classified clinically as having glaucoma, nine had suspected glaucoma, and three were normal. Automatic OCT results were compared with manual tracing results. RESULTS: Significant differences were found between most OCT optic nerve head automated and manual disc assessment parameters; however, good agreement was found between the two methods for all parameters (intraclass correlation, 0.71 to 0.94). Areas under receiver operator characteristics curves for clinical status were similar for all parameters with both methods. CONCLUSION: Automated OCT optic nerve head analysis may be used in the clinical setting in the presence of peripapillary atrophy; however, caution should be used when comparing individual results with population-derived optic nerve head results.

Cross-Sectional Studies↗
PubMed2005

Dispersion compensation in high-speed optical coherence tomography by acousto-optic modulation.

We report studies of the analyses of and compensation for group dispersion to improve the axial resolution of high-speed optical coherence tomography (OCT) by acousto-optic modulation (AOM). Theoretical modeling and experiments reveal that the high-order group dispersion induced by acousto-optic crystals broadens the measured coherence length (Lc) and thus degrades the axial resolution of OCT imaging. Based on our experimental studies, we can compensate for the dispersion to less than 50% broadening of the source Lc by adjusting the grating-lens-based optical delay in the reference arm and can further eliminate it by inserting like acousto-optic crystals in the sample arm of the OCT system. The results demonstrate that this AOM-mediated OCT system permits high-performance OCT imaging at A-scan rates of as much as 4 kHz by use of a resonant scanner. Because of its ultrastable direct frequency modulation, this AOM-mediated OCT system can potentially improve the performance of high-speed Doppler OCT techniques.

Acoustics↗
PubMed2005

[Optical coherence tomography in choroidal osteoma: case report].

The authors present a case of choroidal osteoma diagnosed in a 62-year-old male patient. A well-defined and slightly elevated lesion located in the posterior pole of the right eye associated with internal vasculature and choroidal neovascularization at its superior and inferior temporal edge were suspicious of the tumor. Confirmation of diagnosis was obtained with A and B ecography and computed tomography. Optical coherence tomography showed high reflectivity through its thickness as well as elevation of the RPE-choriocapillaris complex at the choroidal neovascularization site. Although the literature and the present case show several different tomographical findings, optical coherence tomography can help establishing the diagnosis of choroidal osteoma.

Choroid Neoplasms↗
PubMed1998

Optical coherence tomography.

The optical coherence tomograph is a new, noninvasive technical device that can obtain cross-sectional, high-resolution images-optical coherence tomographs (OCT)-of the retina. This instrument permits an accurate evaluation of various macular and chorioretinal pathologies and the early detection of glaucomatous damage. Images of the retina are obtained similar to ultrasound B-scan, with 10-microm longitudinal resolution. Because the OCT operates with a near-infrared wavelength (about 840 nm), the examination is of minimal discomfort for the patient. OCT examination is indicated in cases of macular pathologies such as vitreoretinal interface syndrome, in the early detection and quantitative assessment of macular edema, and in the evaluation of a glaucomatous damage by measuring the retinal nerve fiber layer thickness. The future role of this instrument and its applications for clinical diagnosis depend on the future improvement and updating of the software.

Humans↗
PubMed2007

Usefulness of optical coherence tomography parameters of the optic disc and the retinal nerve fiber layer to differentiate glaucomatous, ocular hypertensive, and normal eyes.

PURPOSE: To assess Stratus optical coherence tomography (OCT) original parameters for identifying glaucomatous damage and to evaluate differences among glaucomatous, ocular hypertensive, and normal eyes. DESIGN: Cross-sectional prospective study. SUBJECTS AND METHODS: The study was conducted at 2 centers. The study population consisted of 55 normal individuals, 95 patients with ocular hypertension (OHT), and 79 patients with glaucoma. Retinal nerve fiber layer (RNFL) and optic nerve head OCT protocols were used to evaluate all study participants. Measurements taken were RNFL thickness, several ratios, RNFL asymmetry between both eyes, rim volume, rim width, disc area, cup area, rim area, cup/disc (C/D) area ratio, and horizontal and vertical C/D ratios. The main outcome measures were the differences in OCT parameters among groups and the areas under the receiver operating characteristic curves (AROC). RESULTS: Mean RNFL thickness around the disc, and superior and inferior RNFL thickness, were significantly thinner in glaucomatous eyes than in OHT or normal eyes (P<0.001). Rim parameters were significantly smaller in glaucomatous eyes than in normal (P<0.001) and OHT eyes (P=0.01). C/D ratios were significantly greater in glaucomatous eyes than in OHT (P<0.001) and normal (P<0.001) eyes. Significant differences were found between normal and OHT eyes in 7 disc parameters. No difference was found among groups in parameters describing RNFL asymmetry between both eyes. The AROC curves of the other RNFL and disk parameters ranged from 0.741 to 0.85. CONCLUSIONS: Almost all RNFL and disc parameters showed significant differences and discriminated between glaucomatous and normal eyes. There were significant differences in some optic nerve parameters, but no RNFL parameters, between normal and OHT eyes.

Aged↗
PubMed2006

Retinal nerve fiber layer assessment using optical coherence tomography with active optic nerve head tracking.

PURPOSE: To develop an eye-motion-tracking optical coherence tomographic (OCT) method and assess its effect on image registration and nerve fiber layer (NFL) thickness measurement reproducibility. METHODS: A system capable of tracking common fundus features based on reflectance changes was integrated into a commercial OCT unit (OCT II; Carl Zeiss Meditec, Inc., Dublin, CA) and tested on healthy subjects and patients with glaucoma. Twenty successive peripapillary NFL scans were obtained with tracking and 20 without tracking, for 40 images in each session for each eye. Subjects participated in one session on three different days. Composite OCT scans and composite fundus images were generated for assessment of eye tracking. NFL thickness measurement reproducibility was also assessed. RESULTS: Seven healthy and nine glaucomatous eyes of 16 subjects were recruited. A qualitative assessment of composite OCT scans and composite fundus images showed little motion artifact or blurring along edges and blood vessels during tracking; however, those structures were less clearly defined when tracking was disengaged. There was no significant reproducibility difference with and without tracking in both intra- and intersession NFL measurement SD calculations in any location. The mean retinal pixel SD was significantly smaller with tracking than without (490.9 +/- 19.3 microm vs. 506.4 +/- 31.8 microm, P = 0.005, paired t-test). CONCLUSIONS: A retinal-tracking system was successfully developed and integrated into a commercial OCT unit. Tracking OCT improved the consistency of scan registration, but did not influence NFL thickness measurement reproducibility in this small sample study.

Adult↗
PubMed2002

Real-time in vivo color Doppler optical coherence tomography.

Color Doppler optical coherence tomography (CDOCT) is a functional extension of optical coherence tomography (OCT) that can image flow in turbid media. We have developed a CDOCT system capable of imaging flow in real time. Doppler processing of the analog signal is accomplished in hardware in the time domain using a novel autocorrelation technique. This Doppler processing method is compatible with a high speed OCT system capable of imaging in real time. Using this system, we demonstrate cross-sectional imaging of bidirectional flow with CDOCT at four frames per second in a tissue-simulating phantom consisting of intralipid solution flowing in glass capillaries. As a demonstration of real-time imaging of blood flow in vivo we imaged pulsatible blood flow in a rat femoral artery at eight frames per second. Issues of velocity sensitivity, imaging speed, and range of velocity measurement are discussed, as well as potential applications of real-time CDOCT.

Animals↗
PubMed2005

Measurement of the scleral canal using optical coherence tomography in patients with optic nerve drusen.

PURPOSE: The etiology of optic nerve drusen (OND) is unknown. A leading hypothesis is that eyes with OND have a small scleral canal. The small scleral canal presumably leads to optic nerve fiber compression, ganglion cell degeneration, extrusion of axonal mitochondria, and calcification of the extruded mitochondria. To determine if subjects with OND have scleral canals that are smaller than subjects without OND, we used optical coherence tomography (OCT) to measure the scleral canal in subjects with and without OND. DESIGN: Prospective, observational case control study. METHODS: The study was conducted with subjects recruited from the clinics of the John A. Moran Eye Center, University of Utah Department of Ophthalmology and Visual Sciences. The study population included 25 subjects with OND, 13 unaffected first-degree relatives of OND subjects, and 17 control subjects. All subjects underwent measurement of the scleral canal with OCT. The main outcome measure was the scleral canal area calculated by OCT. RESULTS: The average areas of the scleral canals were as follows: control eyes: 1.832 mm(2), unaffected eyes of subjects with unilateral OND: 1.836 mm(2), eyes of unaffected first-degree relatives: 2.067 mm(2), and eyes with OND: 2.520 mm(2). The scleral canal area of unaffected eyes of subjects with unilateral drusen was not significantly different from the control. The eyes of first-degree relatives and eyes with OND both had scleral canal areas significantly larger than the control. CONCLUSIONS: Scleral canal size is probably not an etiologic factor in the pathogenesis of OND.

Adolescent↗
PubMedDate not supplied

Measurement of optical path length change following pulsed laser irradiation using differential phase optical coherence tomography.

Differential phase optical coherence tomography (DPOCT) is introduced to measure optical path length changes in response to pulsed laser irradiation (585 nm). An analytical equation that includes thermoelastic surface displacement and thermorefractive index change is derived to predict optical path length change in response to pulsed laser irradiation for both "confined surface" and "free surface" model systems. The derived equation is tested by comparing predicted values with data recorded from experiments using two model systems. Thermorefractive index change and the thermal expansion coefficient are deduced from differential phase change (dDeltaphi) and temperature increase (DeltaT0) measurements. The measured n(T0)beta(T0)+dndT[=1.7410(-4)+/-1.710(-6) (1K)] in the free surface experiment matches with the National Institute of Standards and Technology (NIST) data value [=1.7710(-4) (1K)]. Exclusion of lateral thermal expansion in the analytical model for the confined surface experiment causes difference between the measured dndT[=-2.310(-4)+/-7.310(-6)(1K)] and the NIST value [=-9.4510(-5) (1K)]. In spite of the difference in the confined surface experiment, results of our studies indicate DPOCT can detect dynamic optical path length change in response to pulsed laser irradiation with high sensitivity, and applications to tissue diagnostics may be possible.

Body Temperature↗
PubMed2005

Fiber-optic-bundle-based optical coherence tomography.

A fiber-optic-bundle-based optical coherence tomography (OCT) probe method is presented. The experimental results demonstrate this multimode optical fiber-bundle-based OCT system can achieve a lateral resolution of 12 microm and an axial resolution of 10 microm with a superluminescent diode source. This novel OCT imaging approach eliminates any moving parts in the probe and has a primary advantage for use in extremely compact and safe OCT endoscopes for imaging internal organs and great potential to be combined with confocal endoscopic microscopy.

Animals↗
PubMed2006

[Principals and clinical applications of optical coherence tomography in glaucoma].

Optical coherence tomography (OCT) supplies morphological information from different retinal layers. In glaucoma, analysis of the nerve fiber layer is gaining more and more significance: Losses in this layer often precede by years functional losses in the visual field and end up in optical nerve head changes. OCT offers a means for imaging and for measurement of the nerve fiber layer besides morphological analysis of ONH as one of the earliest sensitive parameters in modern glaucoma diagnostics. However, because of the lack of extensive comparative data, the priority use of optical coherence morphometry is to be seen mainly in intraindividual follow-up.

Glaucoma↗
PubMed2004

Jones matrix analysis for a polarization-sensitive optical coherence tomography system using fiber-optic components.

We present an analysis for polarization-sensitive optical coherence tomography that facilitates the unrestricted use of fiber and fiber-optic components throughout an interferometer and yields sample birefringence, diattenuation, and relative optic axis orientation. We use a novel Jones matrix approach that compares the polarization states of light reflected from the sample surface with those reflected from within a biological sample for pairs of depth scans. The incident polarization alternated between two states that are perpendicular in a Poincaré sphere representation to ensure proper detection of tissue birefringence regardless of optical fiber contributions. The method was validated by comparing the calculated diattenuation of a polarizing sheet, chicken tendon, and muscle with that obtained by independent measurement. The relative importance of diattenuation versus birefringence to angular displacement of Stokes vectors on a Poincaré sphere was quantified.

Algorithms↗
PubMed2005

Retinal nerve fiber layer evaluation by optical coherence tomography in Leber's hereditary optic neuropathy.

PURPOSE: To study retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (StratusOCT) in patients with Leber's hereditary optic neuropathy (LHON). DESIGN: Cross-sectional study. PARTICIPANTS AND/OR CONTROLS: Thirty-eight patients with LHON were analyzed and compared with an age-matched control group of 75 patients. Patients with LHON were classified as having early LHON (E-LHON, n = 8) when the duration of the disease was shorter than 6 months and atrophic LHON (A-LHON, n = 30) when the duration was longer than 6 months. METHODS: The fast RNFL thickness (3.4) scan acquisition protocol was used. MAIN OUTCOME MEASURE: Retinal nerve fiber layer thickness as measured by StratusOCT. RESULTS: Compared with the control group, eyes with E-LHON showed a thicker RNFL in the 360 degrees average measurement (P<0.01) and in the superior (P<0.01), nasal (P<0.05), and inferior quadrants (P<0.05); no significant changes were detected in the temporal quadrant. Eyes with A-LHON revealed a thinner RNFL in all measurements (P<0.001); the fibers of the nasal quadrant showed the lowest amount of reduction (38% vs. 42%-49.8% in the other quadrants). In cases with A-LHON and visual recovery, RNFL was significantly thicker in all measurements (P<0.001), except the temporal quadrant, with respect to A-LHON without visual recovery. CONCLUSIONS: On the basis of OCT data, the RNFL is thickened in E-LHON and severely thinned in A-LHON. RNFL is likely to be partially preserved in A-LHON with visual recovery. The temporal fibers (papillomacular bundle) are the first and most severely affected; the nasal fibers seem to be partially spared in the late stage of the disease.

Acute Disease↗
PubMed2006

Assessment of coronary arterial thrombus by optical coherence tomography.

We analyzed optical coherence tomographic (OCT) characteristics of different types of coronary thrombi that had been confirmed at postmortem histologic examination. We examined 108 coronary arterial segments of 40 consecutive human cadavers. OCT images of red and white thrombi were obtained and the intensity property of these thrombi was analyzed. Red and white thrombi were found in 16 (17%) and 19 (18%) of the 108 arterial segments, respectively. Red thrombi were identified as high-backscattering protrusions inside the lumen of the artery, with signal-free shadowing in the OCT image. White thrombi were identified as low-backscattering projections in the OCT image. There were no significant differences in peak intensity of OCT signal between red and white thrombi (130+/-18 vs 145+/-34, p=0.12). However, the 1/2 attenuation width of the signal intensity curve, which was defined as the distance from peak intensity to its 1/2 intensity, was significantly different between red and white thrombi (324+/-50 vs 183+/- 42 microm, p<0.0001). A cut-off value of 250 microm in the 1/2 width of signal intensity attenuation can differentiate white from red thrombi with a sensitivity of 90% and specificity of 88%. We present the first detailed description of the characteristics of different types of coronary thrombi in OCT images. Optical coherence tomography may allow us not only to estimate plaque morphology but also to distinguish red from white thrombi.

Aged↗
PubMed2004

Second-harmonic optical coherence tomography.

Second-harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical responses of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second-harmonic waves from collagen harvested from rat tail tendon and a reference non-linear crystal. Second-harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of second-harmonic generation on molecular and tissue structures, this technique imparts contrast and resolution enhancement to conventional optical coherence tomography.

Animals↗