High-resolution Spectral-domain Optical Coherence Research Articles

Macular Morphology in Patients with Retinopathy of Prematurity

Purpose: To investigate macular morphology by spectral domain optical coherence tomography (SDOCT) in children with history of the retinopathy of prematurity (ROP). Materials and methods: In this cross-sectional study we included 35 eyes of 18 patients, aged 4 to 8 years, with history of ROP. Twenty-one eyes had received treatment for type 1 pre-threshold ROP. The others showed spontaneous regression of the disease. A 7 × 7-mm retinal area was sampled using a 3-dimensional scanning protocol with high-resolution spectral domain optical coherence tomography (SOCT Copernicus REVO). The central foveal thickness, mean macular thickness, macular volume and foveal depression were measured. The macular anatomy and the foveal contour were examined. Results: The mean birth weight was 1338.29 ± 324.05 grams. Mean gestational age at birth was 29.37 ± 2.07 weeks. Twenty-one eyes were treated with laser or cryotherapy. All of them showed regression of the disease. The mean best corrected visual acuity was 20/28. The average central foveal thickness was 262.26 ± 37.39, with 68.57% of preterm > 240 μm and 22.86% > 220 μm. In all eyes, the foveal contour is abnormal. A foveal depression was absent in 25 eyes (71%). Conclusion: In the majority of children with a history of ROP, we found changes in macular morphology, including retention of inner retinal layers and absent foveal depression. In our study foveal hypoplasia was associated with good functional outcome.

High-spatial-resolution deep tissue imaging with spectral-domain optical coherence microscopy in the 1700-nm spectral band.

.We present three-dimensional (3-D) high-resolution spectral-domain optical coherence microscopy (SD-OCM) by using a supercontinuum (SC) fiber laser source with 300-nm spectral bandwidth (full-width at half-maximum) in the 1700-nm spectral band. By using low-coherence interferometry with SC light and a confocal detection scheme, we realized lateral and axial resolutions of 3.4 and in tissue (), respectively. This is, to the best of our knowledge, the highest 3-D spatial resolution reported among those of Fourier-domain optical coherence imaging techniques in the 1700-nm spectral band. In our SD-OCM, to enhance the imaging depth, a full-range method was implemented, which suppressed the formation of a coherent ghost image and allowed us to set the zero-delay position inside the samples. We demonstrated the 3-D high-resolution imaging capability of 1700-nm SD-OCM through the measurement of an interference signal from a mirror surface and imaging of a single 200-nm polystyrene bead and a pig thyroid gland. Deep tissue imaging at a depth of up to 1.8 mm was also demonstrated. This is the first demonstration of 3-D high-resolution SD-OCM in the 1700-nm spectral band.

Immediate effects of smoking on optic nerve and macular perfusion measured by optical coherence tomography angiography

The aim of this study was the assessment of the relationship between cigarette smoking and optic nerve and macular vessel density measured by optical coherence tomography angiography. We examined 30 eyes from 30 healthy habitual smokers. The examination was performed using a high-speed and high-resolution spectral-domain optical coherence tomography RTVue XR Avanti with AngioVue (Optovue, Fremont, CA, USA) with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, vascular density in the area of the optic nerve head (4.5*4.5 mm) and vascular density with the foveal avascular zone in the central macula (3.0*3.0 mm) were measured and analyzed before, immediately after and 30 minutes after cigarette smoking. Quantitative measurements were carried out by AngioAnalytics Phase 7 software. Immediately after smoking both heart rate and blood pressure increased significantly (p < 0.001) compared to values before smoking and then significantly decreased after 30 minutes comparing to values obtained right after smoking (p < 0.001). The mean area of the foveal avascular zone, parafoveal vessel density, and peripapillary vessel density did not change significantly. Our results show no immediate influence of smoking on vessel density parameters measured by specific OCTA machine in healthy habitual smokers.

Design and optimization of a spectrometer for high-resolution SD-OCT

We report the design of a high-efficiency spectrometer for high-resolution spectral-domain optical coherence tomography (SD-OCT). The advantages of the proposed spectrometer are two-fold: first, we use a concave mirror instead of a camera lens (as typically used) as the focusing optics to both improve the transmission efficiency and eliminate chromatic aberrations; second, the efficiency of the proposed spectrometer is approximately 1.23 times that of a refractive optics-based spectrometer for an SD-OCT system, with comparable ranging depth and axial resolution. Both theoretical analyses and imaging experiments were conducted to characterize and validate the performance of the proposed spectrometer.

Evaluation of outer retinal tubulations in diabetic macular edema underwent anti-VEGF treatment.

To investigate the incidence and subsequent changes of outer retinal tubulations (ORTs) in diabetic macular edema (DME) underwent anti-vascular endothelial growth factor (VEGF) therapy, and to assess the possibility of ORT as a biomarker of DME severity or response to anti-VEGF therapy. This retrospective and descriptive study included a total of 228 patients (435 eyes) with DME and treated with intravitreal anti-VEGF agents between March 2016 and January 2018. Patients were divided into 2 groups according to the presence of ORTs. High-resolution spectral-domain optical coherence tomography (SD-OCT) images acquired by vertical and horizontal scans and over consecutive visits were analyzed. The evolution of ORT over time, type of fluid and subfoveal photoreceptor integrity on OCT imaging was also assessed. ORTs were identified in 108 eyes of 435 eyes with an overall incidence rate of 24.83% at baseline. ORTs were prone to locate adjacent to the lesions of exudation and/or cystoid edema and possibly situated in outer nuclear layer (ONL), outer plexiform layer (OPL) and/or inner nuclear layer (INL) in eyes with DME. The formation process of ORT led to focal downward displacement of OPL and INL toward RPE near the lesion. During the follow up, 45 eyes had steady ORTs and 63 eyes had dynamic variants in ORTs, including disappearance, reappearance, collapse, diminution, and enlargement. There were higher proportion of closed ORTs and fewer proportion of forming ORTs in eyes with steady ORTs, which showed a statistically significance when compared with eyes with variant ORTs (P=0.006, P=0.017, respectively). The eyes without ORTs had significantly better final best corrected visual acuity (BCVA) and more BCVA change than those eyes with ORTs in DME patients after anti-VEGF therapy (P=0.023, P=0.009, respectively). The disruption of subfoveal photoreceptor integrity in eyes with ORTs was more serious than that in eyes without ORTs (P=0.013). The proportion of stable vision in eyes with ORTs was significantly higher than that in eyes without ORTs, showing statistical significance (P=0.016). ORTs were associated with worse visual prognosis due to damage of the subfoveal photoreceptor integrity. ORTs have a high incidence and changes over time in DME with anti-VEGF treatment and may be located at various retinal layers. Persistent ORT can be as a negative biomarker of outcome of DME.

Spectral-domain optical coherence tomography foveal morphology as a prognostic factor for vision performance in congenital aniridia.

Patients with congenital aniridia usually have some degree of foveal hypoplasia, thus representing a limiting factor in the final visual acuity achieved by these patients. The purpose of this study was to analyze whether the foveal morphology assessed by spectral-domain optical coherence tomography may serve as a prognostic indicator for best-corrected visual acuity in congenital aniridia patients. Observational two-center study performed between January 2012 and March 2017 in the pediatric ophthalmology department at Vissum Alicante and Vissum Madrid, Spain. A total of 31 eyes from 19 patients with congenital aniridia were included. After a complete ophthalmological examination, a high-resolution spectral-domain optical coherence tomography with a three-dimensional scan program macular protocol was used. A morphological grading system of foveal hypoplasia was used varying from grade 1 in which there is a presence of a shallow foveal pit, extrusion of inner retinal layers, outer nuclear layer widening, and a presence of outer segment lengthening to grade 4 in which none of these processes occur. No correlation between central, mid-peripheral, and peripheral macular thickness and logMAR best-corrected visual acuity was found. The presence of outer segment lengthening was associated with better best-corrected visual acuity with a median best-corrected visual acuity, 0.30 logMAR, whereas the absence of this morphologic feature was associated with poorer VA with a median best-corrected visual acuity of 0.61 logMAR (p < 0.001). Foveal hypoplasia morphology can predict the best-corrected visual acuity. Specifically, the morphologic optical coherence tomography feature that is related to a better best-corrected visual acuity in congenital aniridia patients is the presence of outer segment lengthening.

Tear dynamics under scleral lenses.

To evaluate post-lens tear dynamics at two different time points during scleral lens wear in two cohorts with 10 neophytes each. All subjects wore bilaterally scleral lenses for 5 h on 3 separate visits. Post-lens tear exchange was measured using Out-in method, which required 5 μL of 2% FITC-Dextran instilled on the bulbar conjunctiva during lens wear. Time taken to observe the first sign of fluorescence in post-lens tear reservoir was recorded with a stopwatch. Out-in measurements were collected at 5-hour post-lens insertion in Group 1 and compared with those obtained at 20 min of lens wear in Group 2. Tear dynamics under the lens was observed in Group 2 with fluorogram using a modified slit-lamp technique (Tan et al., 2018) to monitor post-lens fluorescence intensity and with high-resolution spectral domain optical coherence tomography (ENVISU 2300; Bioptigen Inc.) to measure post-lens tear thickness (PoLTT) over 5 h of lens wear. 60% of subjects in Group 1 achieved Out-in times less than 5 min at 5-hour post-lens insertion, compared with 67% of subjects at 20-min lens wear (Tan et al., 2018). Using qualitative analysis on 60 series of data in Group 2 to compare the changes in fluorescence intensity and PoLTT with respect to lens-wearing time, 27% was due to lens settling, 13% was due to tear exchange and mixing while 60% indicated tear dynamics under scleral lenses was due to a combination of tear exchange, mixing, and lens settling. Tear flow into tear reservoir under a scleral lens on subjects with healthy cornea occurred at 20 min and 5 h after lens insertion. After 5 h of lens wear, roughly one third of the subjects had no tear flow into post-lens reservoir, as the observed decline in post-lens tear fluorescence was predominately due to lens settling.

QUANTITATIVE ANALYSIS OF THE INNER RETINAL LAYER THICKNESSES IN AGE-RELATED MACULAR DEGENERATION USING CORRECTED OPTICAL COHERENCE TOMOGRAPHY SEGMENTATION.

To characterize inner retinal damage in patients with dry age-related macular degeneration (AMD) using high-resolution spectral domain optical coherence tomography images. Sixty eyes of 60 patients with AMD were categorized using the Age-Related Eye Disease Study (AREDS) severity scale. Spectral domain optical coherence tomography images of these patients were quantified by manually correcting the segmentation of each retinal layer, including the retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer to ensure accurate delineation of layers. The mean ganglion cell complex thickness values (ganglion cell layer + inner plexiform layer + retinal nerve fiber layer) were compared with 30 eyes of 30 healthy subjects. Ninety percent of eyes (81 eyes) required manual correction of segmentation. Compared with healthy subjects, mean ganglion cell complex thicknesses significantly decreased in more advanced dry AMD eyes, and this decrease was predominantly related to a change in inner plexiform layer thickness. There was no significant difference in thickness-related measurements between milder dry AMD (AREDS-2) eyes and healthy eyes (P > 0.05). In patients with dry AMD, automatic optical coherence tomography segmentation algorithms may be erroneous. As the severity of dry AMD increases, the inner plexiform layer layer becomes thinned, suggesting that transsynaptic degeneration may be occurring, as the photoreceptor layer is affected by AMD.

Enhanced Depth Imaging by High-Resolution Spectral Domain Optical Coherence Tomography in Tubercular Multifocal Serpiginoid Choroiditis

ABSTRACTPurpose: To report the choroidal changes by enhanced depth imaging optical coherence tomography (EDI-OCT) in tubercular multifocal serpiginoid choroiditis (MSC).Methods: Prospective study of 20 patients (23 eyes) with active MSC who underwent simultaneous fundus autofluorescence and EDI-OCT imaging at regular visits.Results: Eyes with acute lesions demonstrated diffuse choroidal thickening at presentation, which decreased significantly as the lesions healed. Additionally, the region of (thickened) choroid just beneath the active choroiditis lesion demonstrated a localized area of mixed reflectivity (a central hyperreflectivity surrounded by a zone of hyporeflectivity), suggesting choroidal involvement deeper to choriocapillaris. Once the lesions healed, the choroid under the scar showed a localized thinning, along with outer retinal layers loss.Conclusion: EDI-OCT highlighted diffuse and localized choroidal structural changes in MSC as the lesions evolved from acute to healed stage, providing an adjunct to clinical examination for monitoring response to therapy.

Sheets of human retinal progenitor transplants improve vision in rats with severe retinal degeneration

Loss of photoreceptors and other retinal cells is a common endpoint in retinal degenerate (RD) diseases that cause blindness. Retinal transplantation is a potential therapy to replace damaged retinal cells and improve vision. In this study, we examined the development of human fetal retinal sheets with or without their retinal pigment epithelium (RPE) transplanted to immunodeficient retinal degenerate rho S334ter-3 rats. Sheets were dissected from fetal human eyes (11–15.7 weeks gestation) and then transplanted to the subretinal space of 24–31 d old RD nude rats. Every month post surgery, eyes were imaged by high-resolution spectral-domain optical coherence tomography (SD-OCT). SD-OCT showed that transplants were placed into the subretinal space and developed laminated areas or rosettes, with clear development of plexiform layers first seen in OCT at 3 months post surgery. Several months later, as could be expected by the much slower development of human cells compared to rat cells, transplant photoreceptors developed inner and later outer segments. Retinal sections were analyzed by immunohistochemistry for human and retinal markers and confirmed the formation of several retinal subtypes within the retinal layers. Transplant cells extended processes and a lot of the cells could also be seen migrating into the host retina. At 5.8–8.6 months post surgery, selected rats were exposed to light flashes and recorded for visual responses in superior colliculus, (visual center in midbrain). Four of seven rats with transplants showed responses to flashes of light in a limited area of superior colliculus. No response with the same dim light intensity was found in age-matched RD controls (non-surgery or sham surgery). In summary, our data showed that human fetal retinal sheets transplanted to the severely disturbed subretinal space of RD nude rats develop mature photoreceptors and other retinal cells, integrate with the host and induce vision improvement.

Intraoperative optische Kohärenztomographie bei explorativer Vitrektomie an Patienten mit Glaskörperblutung – eine Fallserie

High-resolution spectral domain optical coherence tomography (SD-OCT) is agold standard technique for diagnosis, management and monitoring of patients with vitreoretinal diseases. Preoperative diagnostics for evaluation of intraocular and retinal status in patients with vitreous haemorrhage are limited, thus final therapeutic decisions can only be made during explorative vitrectomy. We evaluated the use of intraoperative SD-OCT (iSD-OCT) as areal-time additional diagnostic tool during explorative vitrectomy in patients with vitreous haemorrhage. We report on 9patients (11eyes) with vitreous haemorrhage. Preoperative ultrasound was performed to evaluate intraocular status. Subsequently, an explorative 23G pars plana vitrectomy was performed under visualisation with the OPMI Lumera700 surgical microscope (Carl Zeiss Meditec, Jena, Germany) equipped with afully integrated iSD-OCT device (Rescan 700, Carl Zeiss Meditec, Jena, Germany) as areal-time diagnostic tool. In all patients, intraoperative iSD-OCT allowed real-time evaluation of the preretinal, intraretinal and subretinal structures in addition to the intraoperative en face image. The further surgical strategy, i. e. necessity for peeling of epiretinal membranes (ERM) or of the inner limiting membrane (ILM), application of intravitreal medication and selection of the appropriate tamponade, was based on and optimised according to the iSD-OCT images. Intraoperative iSD-OCT is highly useful as an additional intraoperative diagnostic tool in patients with vitreous haemorrhage. In addition to the en face microscope image, it facilitates intraoperative real-time diagnosis and aids therapeutic decision-making during surgery.

Multi-Scale Segmentation and Surface Fitting for Measuring 3-D Macular Holes.

Macular holes are blinding conditions, where a hole develops in the central part of retina, resulting in reduced central vision. The prognosis and treatment options are related to a number of variables, including the macular hole size and shape. High-resolution spectral domain optical coherence tomography allows precise imaging of the macular hole geometry in three dimensions, but the measurement of these by human observers is time-consuming and prone to high inter- and intra-observer variability, being characteristically measured in 2-D rather than 3-D. We introduce several novel techniques to automatically retrieve accurate 3-D measurements of the macular hole, including: surface area, base area, base diameter, top area, top diameter, height, and minimum diameter. Specifically, we introduce a multi-scale 3-D level set segmentation approach based on a state-of-the-art level set method, and we introduce novel curvature-based cutting and 3-D measurement procedures. The algorithm is fully automatic, and we validate our extracted measurements both qualitatively and quantitatively, where our results show the method to be robust across a variety of scenarios. Our automated processes are considered a significant contribution for clinical applications.

Optimized linear wavenumber spectrometer based spectral-domain optical coherence tomography system

In spectraldomain optical coherence tomography the sample is illuminated by a broadband light source, and the spectrum of the interference light between the light returned from the sample and a reference mirror is detected by a grating spectrometer. Conventionally, the grating spectrometer is comprised of a diffraction grating, a focusing lens, and a line-scan camera. According to the grating equation the diffraction angle from the grating is approximately linearly related to the optical wavelength. Thus the distribution function of the light spectrum at the line-scan camera is nonlinearly dependent on wavenumber. For the high-quality image reconstruction, the numerical resampling of the spectral interference data from wavelength-space to wavenumber-space is commonly required prior to the Fourier Transformation. The nonlinear detection of the spectral interferograms in wavenumber space also degrades the depth-dependent signal sensitivity in conventional linear-wavelength spectrometer based spectraldomain optical coherence tomography. Recently reported spectraldomain optical coherence tomography based on a linearwavenumber spectrometer does not need the resampling or interpolating of the nonlinearwavenumber interference spectral data, which greatly reduces the cost of computation and improves the imaging sensitivity. Various methods based on the different evaluation protocols for optimizing the design of the linear-wavenumber spectrometer have been reported. Here we report an effective optimization method for linear-wavenumber spectrometer used in a high-resolution spectral domain optical coherence tomography system. We take the reciprocal of the fullwidthhalfmaximum of the simulated point spread function as an evaluating criterion to optimize the structure parameters of the linearwavenumber spectrometer, including the refractive index and the vertex angle of the dispersive prism and the rotation angle between the diffraction grating and the dispersive prism. According to the optimization, an F2 equilateral dispersive prism is used to construct the optimized linearwavenumber spectrometer with a rotation angle of 21.8°. We construct an optimized linearwavenumber spectrometer and implement the spectrometer in a developed spectraldomain optical coherence tomography system as a detection unit. We evaluate the performances of the linear-wavenumber spectrometer both theoretically and experimentally. The experimentally measured axial resolution of the spectraldomain optical coherence tomography system based on the linear-wavenumber spectrometer is 8.52 μm, and the sensitivity is measured to be 91 dB with -6 dB sensitivity roll-off within a depth range of 1.2 mm. The experimentally measured sensitivity roll-off curve accords well with the theoretical sensitivity roll-off curve. Utilizing the general parallel computing capability of a GPU card, the highquality spectraldomain optical coherence tomography images of the human finger skin can be reconstructed in real time without any resampling or interpolating process.

Optical coherence tomography characteristics of active and regressed retinal neovessels secondary to proliferative diabetic retinopathy before and after panretinal photocoagulation

Aim: To describe the changes in the appearance of diabetic neovascularization and vitreoretinal interface before and after panretinal photocoagulation (PRP) using high-resolution spectral-domain optical coherence tomography (SD-OCT). Design: A prospective noncomparative observational case series study was performed on 15 eyes with proliferative diabetic retinopathy (PDR). Patients and Methods: Patients with PDR were scanned using SD-OCT scans directly over the region of the neovessels before and after PRP treatment. Results: The study included 15 treatment-naive eyes with PDR of 11 patients, 8 females and 3 males with a mean age of 54.18 ± 10.9 years (range 29–65 years). The mean best-corrected logarithm of the minimum angle of resolution visual acuity was 0.68 ± 0.19 (range 0.4–1). One (9.1%) case had insulin-dependent diabetes mellitus (type 1) and 10 (9.1%) cases had noninsulin-dependent diabetes (type 2). Posterior hyaloid was detached and identifiable in pretreatment SD-OCT scans in 11 (73.33% of studied eyes) eyes and not identifiable in 4 (36.67%) eyes. Changes in SD-OCT scan appearance after PRP included progression of posterior hyaloid separation with possible progressive retinal traction and retinoschisis, consolidation of the neovessels, regression of neovessels, or occurrence of preretinal hemorrhage. One case showed no visible change at the vitreoretinal interface. Conclusion: There are changes in the appearance of the diabetic neovessels and the vitreoretinal interface after PRP treatment that could be detected by SD-OCT.

SHORT-TERM EFFECTS OF EXERCISE ON OPTIC NERVE AND MACULAR PERFUSION MEASURED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

To evaluate the effects of exercise on optic nerve and macular perfusion using optical coherence tomography angiography. Thirteen eyes of 13 healthy volunteers were examined using a high-speed and high-resolution spectral-domain optical coherence tomography XR Avanti with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, the mean area of the foveal avascular zone , and flow density on the optic nerve head and macula, before and after exercise were measured and analyzed. Mean patient age was 27.3 ± 3.5 years. Heart rate, systolic and diastolic blood pressure increased significantly after exercise (P < 0.001). The mean area of the foveal avascular zone did not change significantly after exercise (before: 0.27 ± 0.07 mm; after: 0.26 ± 0.07 mm; P = 0.10). The peripapillary and the parafoveal flow density decreased significantly after exercise (peripapillary: before: 65.1 ± 2.1; after: 62.3 ± 3.0; P < 0.001 and parafoveal: before: 56.7 ± 1.3; after: 55.6 ± 1.5; P = 0.007). Increased physical activity induced significant changes in optic nerve and macular perfusion, which were measured using split-spectrum amplitude-decorrelation angiography optical coherence tomography angiography. In studies that aim to evaluate optic nerve and macular perfusion using optical coherence tomography angiography, it should be strongly recommended that patients rest before imaging is performed and that data concerning systemic circulation including blood pressure and pulse is included within the evaluation.

Optimization of linear-wavenumber spectrometer for high-resolution spectral domain optical coherence tomography

Nonlinear detection of the spectral interferograms in wavenumber (k) space degrades the depth-dependent signal sensitivity in conventional linear-in-λ spectrometer based spectral domain optical coherence tomography (SDOCT). Linear-k spectrometer enables high sensitivity SDOCT imaging without the need of resampling the digitized non-linear-in-k data. Here we report an effective optimization method for linear-k spectrometer used in a high-resolution SDOCT system. The design parameters of the linear-k spectrometer, including the material of the dispersive prism, the prism vertex angle, and the rotation angle between the grating and prism, are optimized through the numerical simulation of the spectral interference signal. As guided by the optimization results, we constructed the linear-k spectrometer based SDOCT system and evaluated its imaging performances. The axial resolution of the system can be maintained to be higher than 9.1μm throughout the imaging depth range of 2.42 mm. The sensitivity was experimentally measured to be 91 dB with −6 dB roll-off within the depth range of 1.2 mm.

Structural Analysis of Polymer Composites Using Spectral Domain Optical Coherence Tomography.

The structural analysis of nylon/graphene oxide (NY/GO) and polyetherblockamide/ trisilinolphenyl-polyhederal oligomeric silsesquioxane (PEBA/t-POSS) composites were performed using high-resolution spectral domain optical coherence tomography (SD-OCT). This optical technology revealed both cross-sectional, as well as sub-layer depth information of sample. The non-destructive real-time imaging demonstrated the nature of defects in the composites. The thickness and location of each defect point in the composites were measured using A-scan analysis on the SD-OCT images. The cross-sectional and volumetric images clearly demonstrate the effectiveness of SD-OCT for composite research, as well as the for industrial quality assurance of polymer materials.

Single-camera full-range high-resolution spectral domain optical coherence tomography.

We developed spectral domain optical coherence tomography using a dual-channel spectrometer for complex conjugate artifacts (CCA) suppression. We used a three-line charge coupled device to simultaneously detect two interferometric spectra with 2π/3 phase difference. The complex interferometric signal was reconstructed by trigonometric manipulation of two real interferometric spectra, and then full-range images were obtained by use of inverse Fourier transform. Artifacts at direct current (DC) and the ghost remnant of the CCA are common issues with the previously reported two-spectrometer method because the slight mismatching between two spectral detection channels had strong negative effects on CCA suppression and appeared to be the limiting factor on system performance. This novel dual-channel spectrometer uses the same spectrometer optics for the two spectral detection channels and, therefore, achieves better matching between two spectral detection channels and consequently better performance in CCA suppression as compared with the dual spectrometer solution. Full-range imaging with CCA suppression up to ∼25 dB was demonstrated when imaging an attenuated reflector. The efficacy of both CCA and DC suppressions also was validated by imaging the anterior segment of a rat eye ex vivo. The quality of CCA-suppressed images was significantly improved with regard to those obtained with the dual-spectrometer design.

Prevalence and predictors of metamorphopsia after successful rhegmatogenous retinal detachment surgery: a cross-sectional, comparative study

AimsTo evaluate the prevalence of metamorphopsia after successful rhegmatogenous retinal detachment (RRD) surgery and determine the independent predictors of metamorphopsia.MethodsA cross-sectional, comparative study. The study included 380 eyes of 357...

Corneal Epithelial Remodeling Induced by Small Incision Lenticule Extraction (SMILE).

To assess the reactive changes of the corneal epithelial thickness (ET) profile induced by small incision lenticule extraction (SMILE) for treatment of myopia. This prospective observational study included 46 eyes of 23 patients that were scheduled for myopic SMILE. High-resolution spectral-domain optical coherence tomography (SD-OCT) and a custom image segmentation algorithm were applied to measure corneal ET at multiple time points within the central 5-mm zone. Postoperative ET alterations were correlated with treatment parameters and refractive outcomes. Mean age was 33 ± 6 years and mean spherical equivalent of surgical refractive correction was -4.78 ± 1.75 diopters. The average ET (averaged over the central 5-mm zone) increased from 52.3 ± 3.6 μm preoperatively to 57.7 ± 5.1 μm 6 months postoperatively (P < 0.01). Average ET was 101.9% of the preoperative thickness at 24 hours postoperatively, 103.2% at 1 week, 106.7% at 6 weeks, 109.3% at 3 months, and 110.4% at 6 months postoperatively. The epithelial thickening response could be modeled by an exponential recovery function and stabilized after 3 months. The extent of epithelial hyperplasia was highly dependent on the magnitude of the induced refractive correction (P = 0.002). In this initial study of corneal ET remodeling after myopic SMILE, significant epithelial thickening was detected as a function of the extent of surgical refractive correction. Moreover, the epithelial remodeling response to the corneal refractive change appeared to decrease with higher age. In our hands, the observed epithelial changes did not appear to affect the refractive outcome of SMILE. (ClinicalTrials.gov number, NCT02614625).