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AIM: To explore the value of corneal epithelial thickness parameters in the diagnosis of early keratoconus by Fourier domain optical coherence tomography(FD-OCT).METHODS: Retrospective control study. Patients with early keratoconus who were admitted to the Department of Ophthalmology of the First Affiliated Hospital of Soochow University from January 2015 to October 2020 and patients who received laser refractive surgery for myopia during the same period were included in this study. Using FD-OCT to measure the cornea in circle centralized by the pupil and with diameter of 9mm in the early-keratoconus group and the control group. This was to obtain the thickness parameter of corneal epithelium with diameter of 7mm, the respective averaged thickness value of corneal epithelium and the respective averaged thickness value of the full corneal layer on each of the 25 divisions. The parameter value differences between the early-keratoconus group and the control group were compared, and the diagnosis value of parameters that hold difference was analyzed. RESULTS: The Min-e value in early-keratoconus group was significantly lower than that of the control group. On contrary, the value of Std.Dev, Max-Min-e, and Max-e were significantly higher in early-keratoconus group than that in latter one(all P

PurposeTo evaluate serially long-term macular morphologic changes after successful macula-involving rhegmatogenous retinal detachment repair and correlate changes with macular function.MethodsRepeat Fourier domain optical coherence tomography (FD OCT) imaging and microperimetry (MP-1) testing of 8 of the initial cohort of 17 eyes studied 5 years earlier.ResultsThe mean follow-up after rhegmatogenous retinal detachment repair was 3.4 months (range, 1-8.5 months) for the first FD OCT and 5 years (range, 3.75-5.75 years) for the follow-up FD OCT. The final postoperative best-corrected visual acuity mean was 20/201 (range, 20/20 to counting fingers). Six eyes with final best-corrected visual acuity >20/40 had an intact external limiting membrane and progressive resolution of photoreceptor inner segment-outer segment junction disruption and/or subretinal fluid on serial FD OCT, which correlated with improvement in macular function on MP-1. Two eyes with poor or worsening best-corrected visual acuity on follow-up had persistent or worsening inner segment-outer segment disruption on serial FD OCT. External limiting membrane was intact in one eye and persistently disrupted in the other.ConclusionMacular function may progressively improve or worsen long-term after successful rhegmatogenous retinal detachment repair. Progressive resolution of subretinal fluid and/or inner segment-outer segment disruption on FD OCT correlated with improvement in macular function, whereas worsening or persistent inner segment-outer segment disruption correlates with worsening or persistently poor visual outcome.

PurposeTo determine the macular morphologic features that correlate best with visual outcome in eyes with surgically closed idiopathic macular hole.MethodsTransversal observational case series of 24 eyes (22 subjects) imaged postoperatively using high-resolution Fourier domain optical coherence tomography (FD-OCT). Total and inner macular volume for central 3 mm area, central foveal thickness, and size of foveal inner segment-outer segment junction abnormality were correlated with best-corrected visual acuity. Microperimetry (MP-1) test was performed in a subset of 18 eyes.ResultsMean postoperative best-corrected visual acuity was 20/36 (range, 20/25-20/70). Postoperative follow-up mean was 32.97 ± 24.68 months (range, 5-96 months). Eighteen eyes underwent internal limiting membrane (ILM) peeling. Among FD-OCT parameters, logarithm of the minimum angle of resolution best-corrected visual acuity and mean total microperimetry-1 sensitivity correlated best with inner macular volume in all eyes and ILM-peeled eyes (P < 0.05). Macular surface irregularities were noted in 12 eyes (66.7%) with ILM peeling but in none of the non-ILM-peeled eyes (P = 0.02). No significant correlation was found between microperimetry-1 sensitivity and other FD-OCT parameters.ConclusionBecause inner macular volume strongly correlated with visual outcome in eyes with surgically closed macular hole, the possible effect of ILM peeling on visual outcome needs to be further investigated.

Purpose: To examine the changes of non-arteritic anterior ischemic optic neuropathy (NAION) by serial morphometry using Fourier domain optical coherence tomography (FD-OCT). Materials and methods: Retrospective study in patients with newly diagnosed NAION (n=33, all unilateral) and controls (n=75 unilateral NAION patients with full contralateral eye vision) who underwent FD-OCT of the optic disk, optic nerve head (ONH), and macula within 1 week of onset and again 1, 3, 6, and 12 months later. The patients showed no improvement in vision during follow-up. Results: Within 1 week of onset, all NAION eyes exhibited severe ONH fiber crowding and peripapillary retinal nerve fiber layer (RNFL) edema. Four had subretinal fluid accumulation and 12 had posterior vitreous detachment (PVD) at the optic disc surface. Ganglion cell complex (GCC) and RNFL thicknesses were reduced at 1 and 3 months (p< 0.05), with no deterioration thereafter. Initial RNFL/GCC contraction magnitude in the superior hemisphere correlated with the severity of inferior visual field deficits. Conclusions: NAION progression is characterized by an initial phase of accelerated RNFL and GCC deterioration. These results reveal that the kinetic change of neural retina in NAION and may have implication on the time window for treatment of NAION. FD-OCT is useful in the evaluation of NAION. [ABSTRACT FROM AUTHOR]

Objective: To investigate the difference of structural retinal nave fiber layer (RNFL) thickness and ganglion cell layer thickness via using Fourier domain optical coherence tomography device (FD-OCT) in healthy individuals with family history of primary open angle glaucoma (POAG) disease. Material and Method: In this case-control observational study, average and the four quadrant RNFL thickness parameters; average, upper and lower halves of the ganglion cell layer thickness parameters were measured in healthy 30 individuals with family history of POAG disease and in agesex matched healthy individuals without family history of POAG disease via using Topcon 3D FD-OCT device. Wi thin each parameter the statistical difference between two groups was investigated with using Mann-Whitney U test. Results: In each individual group there were 12 men and 18 women with a mean age of 41.40±2.28 year. Average ganglion cell layer thickness was measured as 97.60±0.96 pm in individuals with family history of POAG disease and determined as 104.73±1.55 pm in individuals without family history of POAG disease. Tltis difference was statistically significant (p<0.001). The average RNFL thickness in individuals with family history of POAG disease was 98.13±1.69 pm, while the other group identified as 107.67±1.09 pm and the difference between two groups was also statistically significant (p<0.001). Conclusion: In individuals with family history of glaucoma, structurally thinner retinal nerve fiber layer and the ganglion cell layer were observed. Therefore, in individuals with a family history of glaucoma, glaucoma screening is of crucial importance for the early detection of glaucomatous damage. [ABSTRACT FROM AUTHOR]

Optical coherence tomography (OCT) is a very high-resolution imaging technique whose resolution depends on source bandwidth. Improving resolution is an important topic of research in OCT. Thus, to improve resolution, the bandwidth of the source must be increased. Practical sources have finite bandwidth. Therefore, it is suggested to use more sources. Previous work expected that resolution will be inevitably improved without mentioning to what extent it will be improved and without any referencing to the effect of spectral separation between the sources. We study the resolution of a Fourier-domain OCT (FD-OCT) system based on two sources. First, we show to what extent resolution is improved and we show that this improvement not only depends on the spectral widths of the sources but also on spectral separation of the sources. Second, we show that in most cases resolution will become poorer and discuss mathematically the origin of resolution worsening and reveal the problems encountered in such a system. Third, we propose two techniques to overcome these problems. One of them is by shifting spectral interferograms and the other is by multiplying the spatial interferogram. Then, we clarify their advantages, disadvantages, major drawbacks, and limitations. [ABSTRACT FROM AUTHOR]

Longitudinal measurement using intravascular ultrasound is limited because the motorized pullback device assumes no cardiac motion. A newly developed intracoronary imaging modality, optical frequency domain imaging (OFDI), has higher resolution and an increased auto-pullback speed with presumably lesser susceptibility to cardiac motion artifacts during pullback for longitudinal measurement; however, it has not been fully investigated. We aimed to clarify the influence of cardiac motion on the accuracy and reproducibility of longitudinal measurements obtained using OFDI and to determine the optimal pullback speed. This ex vivo study included 31 stents deployed in the mid left anterior descending artery under phantom heartbeat and coronary flow simulation. Longitudinal stent lengths were measured twice using OFDI at three pullback speeds. Differences in stent lengths between OFDI and microscopy and between two repetitive pullbacks were assessed to determine accuracy and reproducibility. Furthermore, three-dimensional (3D) reconstruction was used for evaluating image quality. With regard to differences in stent length between OFDI and microscopy, the intraclass correlation coefficient values were 0.985, 0.994, and 0.995 at 10, 20, and 40 mm/s, respectively. With regard to reproducibility, the values were 0.995, 0.996, and 0.996 at 10, 20, and 40 mm/s, respectively. 3D reconstruction showed a superior image quality at 10 and 20 mm/s compared with that at 40 mm/s. OFDI demonstrated high accuracy and reproducibility for longitudinal stent measurements. Moreover, its accuracy and reproducibility were remarkable at a higher pullback speed. A 20-mm/s pullback speed may be optimal for clinical and research purposes. [ABSTRACT FROM AUTHOR]

Purpose To assess the repeatability, reproducibility, and agreement of central corneal thickness (CCT) measured by non-contact Fourier domain optical coherence tomography (FD-OCT; OptoVue) with the other two contact devices, ocular response analyzer (ORA; Reichert Ophthalmic Instruments) and Ultrasound Pachymetry (USP; DGH Technologies). Methods This observational cross-sectional study measured CCT sequentially using FD-OCT, ORA and USP. The first 16 volunteers (32 eyes) received three measurements by two independent examiners in a single session to determine intra-observer repeatability and inter-observer reproducibility. An additional 27 volunteers (54 eyes) received one measurement by the same examiner. The measurements of all 86 eyes were analyzed for the difference, correlation, and agreement among the three devices. Results FD-OCT measured the thinnest while USP measured the thickest CCT (548.6 ± 28.3 μm, 556.9 ± 28.8 μm, and 560.0 ± 28.8 μm by FD-OCT, ORA, and USP, respectively, p < 0.001). The mean differences (lower/upper limit of agreement) for CCT measurements were 8.4 ± 7.6 μm (−6.5/23.2) between ORA and FD-OCT, 11.4 ± 7.3 μm (−2.8/25.7) between USP and FD-OCT, and 3.1 ± 5.1 μm (−6.9/13.1) between ORA and USP. The intra-class correlation coefficients were above 0.98 for all tested groups. FD-OCT had the lowest intra-examiner variability (coefficient of repeatability of 0.64%) and lowest inter-examiner variability (coefficient of reproducibility of 1.16%). Conclusion FD-OCT, ORA, and USP demonstrated good inter-observer reproducibility and intra-observer repeatability. The three measurements were highly correlated; however, systematic differences between the three tested devices did exist. FD-OCT was a reliable and examiner-independent method in CCT measurement. [ABSTRACT FROM AUTHOR]

We assessed the reproducibility of lateral and axial measurements performed with spectral-domain optical coherence tomography (SDOCT) instruments from a single manufacturer and across several manufacturers. One human retina phantom was imaged on two instruments each from four SDOCT platforms: Zeiss Cirrus, Heidelberg Spectralis, Bioptigen SDOIS, and hand-held Bioptigen Envisu. Built-in software calipers were used to perform manual measurements of a fixed lateral width (LW), central foveal thickness (CFT), and parafoveal thickness (PFT) 1 mm from foveal center. Inter- and intraplatform reproducibilities were assessed with analysis of variance and Tukey-Kramer tests. The range of measurements between platforms was 5171 to 5290 µm for mean LW (p < 0.001), 162 to 196 µm for mean CFT (p < 0.001), and 267 to 316 µm for mean PFT (p < 0.001). All SDOCT platforms had significant differences between each other for all measurements, except LW between Bioptigen SDOIS and Envisu (p = 0.27). Intraplatform differences were significantly smaller than interplatform differences for LW (p = 0.020), CFT (p = 0.045), and PFT (p = 0.004). Conversion factors were generated for lateral and axial scaling between SDOCT platforms. Lateral and axial manual measurements have greater variance across different SDOCT platforms than between instruments from the same platform. Conversion factors for measurements from different platforms can produce normalized values for patient care and clinical studies. [ABSTRACT FROM AUTHOR]

Abstract: A scattering imaging method for skin tissue in Fourier domain optical coherence tomography is proposed. In this method, parameter F image is obtained from the intensity signal as a function of the depth. Since parameter F contains only the scattering coefficient and its first order derivative, the scattering coefficient image can be calculated from the parameter F image. Two-dimensional (2D) scattering coefficient images of palm skin are calculated after extracting the tissue interfaces in the 2D parameter F images. [Copyright &y& Elsevier]

Purpose: To investigate the relative involvement of chromatic and achromatic visual subsystems in central serous chorioretinopathy, and to correlate the function changes with the changes of the foveal photoreceptor layer using Fourier domain optical coherence tomography (FD-OCT). Methods: Central serous chorioretinopathy patients and control subjects were tested and compared. Equiluminant Chromatic sinusoidal gratings were presented in a pattern onset-offset mode. We measured the distance between the internal limiting membrane (ILM) and the external limiting membrane (ELM) on FD-OCT images. Results: Visual evoked potential mean latency was delayed significantly in central serous chorioretinopathy patients compared to controls. The visual evoked potential delay was greater for chromatic than for achromatic stimuli. Retinal thickness from ILM to ELM was associated significantly and selectively with short-wavelength-sensitive (S) cone visual evoked potential latency (r = )0.40, p = 0.032). Conclusions: These results are consistent with data that indicate the loss of photoreceptors in central serous chorioretinopathy resulting in a reduced thickness of the outer nuclear layer. Additionally, they are consistent with data which indicate that the photoreceptor loss is relatively greater in cones. The S-cone pathway was affected the most. [ABSTRACT FROM AUTHOR]

Abstract: We present a common path Fourier domain optical coherence tomography (FDOCT) setup where the reference signal arises from multiple reflections within the sample arm. Two configurations are demonstrated. The first is based on a reflective microscope objective while the second is based on a normal (refractive) microscope objective. The second configuration is effectively a Mireau interferometer. We present a sensitivity analysis of these setups and images of in vivo skin. Advantages of both common path arrangements include: 1) the reference surface is not close to the sample surface while keeping the optical path lengths matched (so the additional interferometer is not needed) and 2) the user can independently control reference and sample arm power. Additionally, the configuration using the refractive objective ensures that the coherence gate and focus gate always match. A disadvantage is that the reference arm power in certain circumstances is not optimal (i.e. close to saturating the CCD). However, this issue can be removed by a light source of sufficient output power. We believe the idea is scalable and therefore of interest to endoscopy applications. [Copyright &y& Elsevier]

PurposeWith a new Fourier domain optical coherence tomography (FD OCT) device, SL SCAN-1 (Topcon Europe Medical BV, Capelle a/d IJssel, The Netherlands), integrated into a slit-lamp OCT, scans can be obtained through a handheld lens. The necessary adjustment of the reference arm is possible by fast Z-alignment. This study was performed to prove the capability of SL SCAN-1 to scan through a three-mirror contact lens, scanning the peripheral retina and anterior chamber angle.MethodsDifferent representative pathologies of the peripheral retina and anterior chamber were simultaneously observed and scanned with the SL SCAN-1. The scans of peripheral retinal lesions were obtained both through a handheld lens and through a three-mirror contact lens. The anterior chamber angle was scanned directly with the SL SCAN-1 in anterior mode, and through the gonio-mirror of a three-mirror contact lens with the SL SCAN-1 in posterior mode.ResultsOCT scans could be obtained with the SL SCAN-1 of the peripheral retina through both, a common handheld lens and a three-mirror contact lens. The scans obtained through a three-mirror contact lens were of better quality, visualizing details of the different layers of the retina more clearly. The scans of the anterior chamber, obtained through the gonio-mirror of a three-mirror contact lens, visualized the open anterior chamber angle, with details of fine structures.ConclusionsThe SL SCAN-1 is a unique FD OCT system, which is able to scan not only the posterior pole and anterior segment but also the anterior chamber angle and the more peripheral retina. These four modalities combined into one device could make the SL SCAN-1 a very powerful aid in daily practice. [ABSTRACT FROM AUTHOR]

PurposeFourier Domain Optical Coherence Tomography (FD-OCT) provides high resolution cross-sectional images of the retina and the anterior segment. It has become an important tool in ophthalmology in the examination, diagnosis, and treatment of important and common diseases. Present OCT imaging systems are stand-alone devices. The aim of this paper is to show the quality of images made with a prototype of a Fourier Domain (FD-) OCT imaging system (SLSCAN-1) integrated into a slit lamp.MethodsDifferent representative pathologies of the posterior and anterior segment were observed with the slit lamp and simultaneously scanned with a prototype of the slit lamp-integrated FD-OCT system. The clinical interpretation of posterior segment images made with the prototype were compared to those obtained with a stand-alone FD-system (3D-OCT-1000 Mark II, Topcon).ResultsImages made with the slit lamp-integrated FD-OCT were of sufficient quality to allow for a correct interpretation of the observed pathological conditions. Conclusions based on the images of the posterior segment of the prototype were identical to the conclusions based on the images of a stand-alone FD-system (3D-OCT-1000 Mark II, Topcon). In addition to the images of the posterior segment, images could be made of the anterior segment. The OCT system did not interfere with the normal functionality of the slit lamp.ConclusionThe slit lamp-integrated FD-OCT system provided high quality images of both the anterior and the posterior segment. Scans made with the slit lamp-integrated FD-OCT system could be of use in clinical practice. [ABSTRACT FROM AUTHOR]

Corneal thickness measurement is important for assessing intraocular pressure in patients with glaucoma. This study investigated the changes in corneal epithelial thickness (CET) induced by antiglaucoma medications and explored the factors affecting CET measurement. CET was measured over a 9.0 mm diameter area by using Fourier domain optical coherence tomography in 125 patients with primary open-angle glaucoma and 125 age-matched controls without glaucoma. The influence of sex, age, benzalkonium chloride (BAK)-containing instillations, disease severity, and types and numbers of medications was analyzed using simple and multiple regression analyses. CET over 25 sectors was smaller in the glaucoma group than in the control group (mean difference of 4.2 µm in the central 2.0 mm zone; 52.8 ± 3.6 vs. 48.5 ± 3.9, p < 0.001). Simple regression analysis revealed age, use of β-blockers, prostaglandin, carbonic anhydrase inhibitors, total number of medications, and number of daily BAK-containing instillations were associated with a thinner epithelium. Multiple regression analysis revealed β-blockers, prostaglandin, and number of BAK-containing instillations were significant factors. Use of β-blockers and number of BAK-containing instillations were also associated with a thinner epithelium in the monotherapy subgroup analysis. CET was significantly smaller in patients with glaucoma receiving topical medications and was affected by the use of β-blockers, prostaglandin, and BAK. [ABSTRACT FROM AUTHOR]

The article discusses the case of a 24-year-old woman who was diagnosed with Camurati-Engelmann disease (CED) with papilledema using Fourier domain optical coherence tomography (FD-OCT), where a loss of retinal thickness in the ganglion cell complex was noted but not in the outer retinal layers. The findings showed that papilledema may have been the cause of the retinal nerve fiber layer (RNFL) thinning in the area corresponding to the right eye visual field defect.

A polarization-sensitive Fourier domain optical coherence tomography (PS-FD-OCT) system has been developed. By using a two-dimensional CCD camera, this PS-FD-OCT simultaneously obtains two spectral interferograms corresponding to orthogonal polarization components of a probing beam. FD-OCT avoids axial mechanical scanning, therefore, two OCT images are obtained by a single lateral scanning. This system requires only two one-dimensional scannings for determining the Müller matrix images of a sample. In the Müller matrix images, the birefringence properties of the inner surface of a porcine esophagus are revealed. [ABSTRACT FROM AUTHOR]

Several tissue pathologies are correlated with changes in the blood vessel morphology and microcirculation that supplies the tissue. Optical coherence tomography (OCT) is an imaging technique that enables acquiring non-invasive three-dimensional images of biological structures with micrometer resolution. Optical microangiography (OMAG) is a method of processing OCT data which enables visualizing the three-dimensional blood vessel morphology within biological tissues. OMAG has high spatial resolution which allows visualizing single capillary vessels, and does not require the use of contrast agents. The intrinsic optical signals backscattered by the moving blood cells inside blood vessels are used as the contrast for which OMAG images are based on. In this paper, we discuss a brief review of the OMAG theory, and present some examples of applications for this technique.