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The purpose of this study was to use a portable optical coherence tomography (OCT) for characterization of corneal stromal striae (CSS) in an ovine animal model and human corneas with histological correlation, in order to evaluate their architectural pattern by image analysis. Forty-six eyes from female adult sheep (older than 2 years), and 12 human corneas, were included in our study. The eyes were examined in situ by a portable OCT, without enucleation. All OCT scans were performed immediately after death, and then the eyes were delivered to a qualified histology laboratory. In the ovine animal model, CSS were detected with OCT in 89.1% (41/46) of individual scans and in 93.4% (43/46) of histological slices. In human corneas, CSS were found in 58.3% (7/12) of cases. In both corneal types, CSS appeared as "V"- or "X"-shaped structures, with very similar angle values of 70.8° ± 4° on OCT images and 71° ± 4° on histological slices (p ≤ 0.01). Data analysis demonstrated an excellent degree of reproducibility and inter-rater reliability of measurements (p < 0.001). The present study demonstrated that by using a portable OCT device, CSS can be visualized in ovine and human corneas. This finding suggests their generalized presence in various mammals. The frequent observation, close to 60%, of such collagen texture in the corneal stroma, similar to a 'truss bridge' design, permits to presume that it plays an important structural role, aimed to distribute tensile and compressive forces in various directions, conferring resilience properties to the cornea.

To assess the repeatability and reproducibility of post-mortem central corneal thickness (CCT) measurements made by the portable iVue spectra-domain (SD) optical coherence tomography OCT (Optovue Inc, Fremont, CA) system in humans, and to prospectively establish the time-course of CCT after death. In a prospective multicenter setting, CCT measurements were obtained from 58 human eyes at the following 16 time-points after death: immediately (within 2 h), and at each hour by the next 17 h. The range of CCT values for each subject was determined and longitudinal data were used to illustrate the variation in open and close eye mode. All measurements were made by two independent and well-trained examiners for session. Main outcome measures were intraclass correlation coefficients (ICC), repeatability and reproducibility coefficients, and coefficients of variation of the average central (0-2 mm). Overall, a total of 5,568 OCT measurements were performed by examiners. The repeatability coefficient varied from 0.3 to 1.7% and the reproducibility coefficient varied from 0.3 to 1.6% throughout the entire experimental time frame. Furthermore, the values of the different ICCs were also high during the different postmortem intervals, thus demonstrating the excellent repeatability and reproducibility of the present OCT approach. When CCT measurements were analyzed longitudinally, corneal thickness showed different behavior based on the open or close eye mode. The present study demonstrates that portable OCT imaging can be reliably used for corneal pachymetric measurements in supine subjects and during the post mortem period, i.e. without visual fixation and normal physiology/architecture of examined tissues.

Objectives: To evaluate retinal axonal density and retinal capillary flow density (CFD) variations in patients affected by multiple sclerosis (MS) as documented by Optical Coherence Tomography Angiography (OCT-A)., Material and Methods: A cross-sectional study was performed in a tertiary university eye hospital on 94 eyes from 48 MS patients compared to 37 eyes from 23 matched controls. MS patients were divided in two groups: those with previous episodes of optic neuritis (MS ON+, 71.4%) and those without any previous visual complaint (no optic neuritis group, MS ON, 28.6%). Patients underwent macular and optic nerve head OCT-A with Optovue XR Avanti (Optovue, Freemont, California) after that preliminary evaluation of the ganglion cell complex (GCC) and of the retinal nerve fiber layer (RNFL) was achieved for each single eye by SD-OCT. CFD was evaluated in three different retinal layers of MS patients and controls: superficial capillary plexus (SCP), deep capillary plexus (DCP) and the choriocapillaris layer (CL). Each layer was analyzed in 18 preset subregions automatically detected by the system. CFD values were then correlated to the RNFL thickness and GCC thickness in the groups: p values were computed by t-tests between each group of MS patients and controls. A p-value of <0.05 was considered significant., Results: A significant difference in the overall CFD values was found between ON+ and ON- patients when compared to controls in 18 subregions of SCP. Furthermore, a significant difference was found between MS patients and controls in 16 subregions analyzed corresponding to the CL layer without difference between the two MS subgroups (ON+ and ON-)., Conclusions: OCT-A when performed at the optic nerve head level and at the macular region is characterized by a reduction of retinal perfusion in a significant portion of MS patients independently if they had a previous history of optic nerve inflammation or not., Competing Interests: The authors have declared that no competing interests exist.

Optical coherence tomography (OCT) is an interferometric imaging technique that has revolutionized clinical ophthalmology since the first half of the 1990's. Despite this approach being successfully employed in ophthalmology and having great potential in forensic cases, its use in different forensic fields appears to be quite limited. In this review we reviewed the scientific literature regarding the application of OCT in forensic science and legal medicine from 1995 to 2019. Our research showed the usefulness of this approach for the study of coronary injuries, postmortem ocular changes, forensic entomology, and several other applications of specific forensic interest (the study of blood stains, fingerprints, and hair bulbs for personal identification, as well as the study of materials found in the crime scene for comparation, or anti-fraud investigation). The creation of specific 'ad hoc' devices and a better knowledge of this type of technology by pathologists will be a fundamental step to continue to develop the use of OCT forensic fields.

The aim of the study was to define and characterize the optical behavior of the tear film during visual fixation in humans on en-face optical coherence tomography (OCT). We included 20 healthy participants, 60% female, aged from 25 to 42 years (33.05 ± 4.97 [mean ± SD]) and ten patients with severe dry eye, 50% female, aged from 26 to 42 years (33.7 ± 5.31). To perform high-resolution tear film imaging, participants were asked to gaze at the internal fixation point in the spectral-domain anterior segment OCT device, and meanwhile scanning session was executed at the following time-points after blinking: at the 2 nd , 3 rd , 4 th , 5 th , and 6 th second. After one hour, OCT imaging was repeated (second session) by a different operator masked to the study to verify the reliability of results. During each measuring session, a pulse oximetry was used for continuously measuring the heart rate and oxygen saturation (SpO 2 %). A preliminary experiment was also performed to test the absence of geometric patterns from the anterior surface of a motionless artificial eye. OCT imaging showed a motionless, stable anterior surface of the artificial eye and in dry eye patients. Conversely, in the healthy participants of the study, a bull's eye pattern of the tear film was detected by OCT at the 2 nd , 3 rd , 4 th , 5 th , and 6 th second after blinking, respectively, in 45%, 60%, 45%, 60%, and 40% of OCT scans during the first session, and in 35%, 65%, 65%, 60%, and 35% of cases in the second session. Overall, a total of 200 OCT scans were performed in normal human population. A significant correlation was found between the novel tear film pattern and heart rate during the first and the second session (p < 0.01) in healthy eyes. Conversely, no correlation was revealed with SpO2%. Intraclass correlation (ICC) analysis for OCT imaging of the tear film revealed a statistically significant reproducibility of the results (ICC = 0.838; p < 0.01), indicating the high level of reliability of the method, independently of heart rate and SpO2% variables. There exists a novel, geometric pattern of the tear film during visual fixation detectable by en-face OCT, which is mainly evident as heart rate increases. Its discovery implies in turn the presence of a specific vibration (or imperceptible motion) of the tear film that, at present, is not recognized and corrected by the OCT software (in image postprocessing) unlike other eyeball movements.

Purpose: To evaluate the feasibility of 3D anterior segment optical coherence tomography (AS-OCT) for the detection of corneal endothelial features in patients with Fuchs' Endothelial Corneal Dystrophy (FECD)., Methods: Twenty patients with clinical diagnosis of FECD (group A), and 20 control subjects (group B) were enrolled. In all patients a complete ophthalmological examination was performed, including best corrected visual acuity (BCVA), slit lamp examination for subjective grading of FECD and corneal endothelial specular microscopy. A 512x128 AS-OCT cube centered on the corneal apex was performed, and then the inner surface of the cornea was visualized and analyzed individually., Results: Overall, the study participants were adults (mean age was 57.35 ± 8.45 years [mean ± SD] 80% female) with a BCVA ranged from 1.3 to 0 LogMAR. The OCT analysis disclosed three different patterns of the corneal endothelium (1, 2, 3) according to the signal distribution and the level of reflectivity: a homogenous, hypo-reflective surface (pattern 1); the presence of hyper-reflective orange-yellowish points (pattern 2); and a mottled appearance with a variable number of hyper-reflective areas (pattern 3). The distributions of these morphological models in the two populations were as follows: patterns 1, 2 and 3 were observed respectively in 0%, 80%, and 20% of patients in group A, and in 80%, 20% and 0% of subjects in group B. Correlation analysis unveiled a positive relationship between OCT corneal endothelium reflectivity and the clinical severity score (assessed with biomicroscopy), as well as an inverse relationship between the OCT pattern and the integrity of corneal endothelium., Conclusion: 3D AS-OCT is a useful tool in investigation of endothelial features and therefore may represent a valuable support in the setting of FECD diagnosis and staging., Competing Interests: The authors have declared that no competing interests exist.

Purpose: To assess the usefulness of spectral-domain optical coherence tomography (SD-OCT) peripapillary retinal nerve fiber layer (RNFL) thickness measurement in discriminating early phase optic disc edema (ODE) from pseudoedema (PODE)., Methods: Hospital-based, multicenter, cross-sectional study involving external patients referred for recent identification of "presumed ODE". Patients underwent SD-OCT optic nerve head (ONH) RNFL thickness measurement at their first evaluation. In 155 of these, the causative etiology was subsequently ascertained and the respective eyes (one per patient) were assigned to the ODE (95 eyes) or PODE (60 eyes) group. Admission SD-OCT data were retrieved and used for the analysis. ROC curve analysis was used to calculate specificity, sensitivity and predictive value (PV) of the RNFL values., Results: The PODE group was significantly younger than the ODE group (p = 0.007). The average and any single-quadrant RNFL thickness was significantly higher in the ODE group compared with the PODE and control groups. The average and the inferior quadrant thicknesses tested the most powerful parameters to differentiate ODE from PODE. A cutoff value of ≥ 110 μm for the average area, or of ≥ 150 μm for the inferior quadrant was associated with maximal sensitivity and specificity with positive PV greater than 80%., Conclusions: The SD-OCT evaluation of the peripapillary RNFL achieved good specificity, sensitivity and positive PV in discriminating between ODE and PODE. Despite the correct differential diagnosis between these categories still relies on a careful medical history taking and other ancillary testing, we proved the usefulness of SD-OCT RNFL measurement in supporting the diagnostic process., Competing Interests: The authors have declared that no competing interests exist.

The aim of this work was to describe, for the first time, the morphological modifications, in a three-dimensional mode, of the central cornea at different intervals since death. The study design involved the analysis of 30 eyes (15 heads) of female, adult sheep (>2 years) sacrificed at a local slaughterhouse. The eyes, after animal decapitation, were examined in situ, without enucleation. Ocular globes were stored at well-known temperature (within a range of 12-22 °C) and humidity (within a range of 50-60%). The instrumental analysis was executed using a portable spectral-domain OCT (SD-OCT) system (iVue SD-OCT, Optovue Inc, Fremont, CA) calibrated to the corneal mode. OCT imaging was performed at different time-points since death. Pachymetric map, morphological and ultrastructural analysis (epithelium, stroma, and endothelium), were performed for each time-point. After an initial thinning of tissues and an enhancement of epithelial reflectivity, stromal thickness increased from the 2nd up to the 6th hour. Subsequently, a new trend incorneal thinning was observed in association with the appearance ofone or more demarcation lines between the anterior andposterior stroma. After the 12th hour, a recurrence of corneal swelling was detected in association with thedelamination of stromal tissue. Since the 24th hour, the epithelium disappeared in 50% of cases and the anterior chamberdepth progressively decreased. At the 48th hour, various ocular structures showed the onset of putrefaction processes, such as theappearance of hyper-reflective dots in anterior chamber, iridocorneal contact, and the massive vacuolization of theposterior stroma until the total delamination. The portable OCT system is a useful approach for in situ postmortem corneal examination, and it may be potentially applied for the selection of donor cornea in transplantology and for the determination of post-mortem intervals in forensic medicine., (Copyright © 2018. Published by Elsevier Ltd.)

Purpose: To compare a novel spectral-domain optical coherence tomography (SD-OCT) technique with traditional lid transillumination for evaluation of meibomian glands (MGs) and to assess the relation of MG morphologic changes to the glandular atrophy., Design: Evaluation of diagnostic technology., Participants: Sixty-one patients with obstructive MGD (30 men, 31 women; age [mean ± standard deviation] 45.1 ± 12.1 years), and 75 control subjects (32 men, 43 women; 44.1 ± 12.5 years) were recruited in order to have a balanced distribution of glandular features., Methods: Agreement between SD-OCT and lid transillumination examination for the detection of drop-out (partial or complete loss of MGs) and microscopic changes (i.e. shortening, distortion, segmentation and entanglement), as well as the relationship between morphological features and MG atrophy were evaluated., Main Outcome Measures: Agreement between the two meibographic techniques, bias in symmetry of classification, and association analysis between microscopic changes and MG dropout., Results: Overall agreement for all morphological features was substantial (Cohen kappa coefficient = 0.77; p<0.001), even if, the majority of disagreement occurred for cases with segmentation, where agreement was present in only 108 (81.82%) of 132 eyes with adequate images for interpretation, and where SD-OCT tended to diagnose more cases not detected by traditional lid transillumination (McNemar test, p<0.001). Moreover, segmentation and distortion pattern negatively correlated with the degree of drop-out, whereas shortening and entanglement pattern demonstrated only a weak correlation (Spearman's ρ was -0.691, -0.491, -0.359, -0.385, respectively)., Conclusions: Each method has its advantages but in general there was close agreement between these meibographic techniques, particularly for MG dropout, which supports the reliability of our novel, simple and patient-friendly SD-OCT approach., Competing Interests: The authors have declared that no competing interests exist.

The purpose of this study was to determine the repeatability and reproducibility of post-mortem central corneal thickness (CCT) measurements by using a real-time, portable optical coherence tomography (OCT) system on an animal model, and to prospectively evaluate the time-course of post-mortem changes in CCT. Forty-six ocular globes of sheep (Ovis aries) were analyzed with a portable spectral-domain OCT device by two operators at different postmortem intervals (PMIs) as follows: immediately (i.e. within 10 minutes), at the 30(th) minute, at the 1(st), 6(th), 12(th), 24(th) and 48(th) hour, and later (up to the 96(th) hour). The coefficient of repeatability ranged from 0.3% to 3.5%, and coefficients of reproducibility ranged from 0.2% to 3.7% in the central region of the cornea. The intraclass correlation coefficients were particularly high at different PMIs, thus confirming good measurement reliability with the portable OCT. The average CCT decreased immediately and then increased thereafter, with two peaks at 6 and 24 hours after death. Our results suggest that portable OCT is a reliable tool for monitoring CCT variations after death and may be useful in characterizing corneas before explantation, detecting quantitative variations during post-mortem corneal degeneration or assessing changes in CCT for forensic implications.

Objective: The aim was to determine the influence of meibomian gland dysfunction (MGD) and aqueous tear deficiency dry eye (ADDE) on the adhesive properties of the central cornea by means of optical coherence tomography (OCT), and to investigate the relationship between corneal adhesiveness and classical tear tests, as well as the reliability of results, in these lacrimal functional unit disorders., Design: Prospective, case-control study., Methods: Twenty-eight patients with MGD and 27 patients with ADDE were studied. A group of 32 healthy subjects of similar age and gender distribution served as a control group. The adhesive properties of the anterior corneal surface were measured by OCT, based on the retention time of adhesion marker above it, in all participants., Results: An excellent (≥5 minutes), borderline (within 3-5 minutes), fair (within 1-3 minutes) and poor (<1 minute) values of corneal adhesiveness were found, respectively, in 0%, 7.1%, 64.3% and 28.6% of MGD, in 0%, 7.4%, 63% and 29.6% of ADDE, and in 31.3%, 65.6%, 3.1% and 0% of healthy patients. The differences in time of corneal adhesiveness between MGD and healthy patients, as well as between ADDE and healthy patients, were found to be statistically significant (p<0.001; p<0.001; respectively). Conversely, no statistical significant differences between MGD and ADDE were found (p = 0.952). Data analysis revealed a statistically significant correlation between corneal adhesiveness and clinical tests of dry eye, as well as an excellent degree of inter-rater reliability and reproducibility for OCT measurements (p<0.001)., Conclusion: ADDE and MGD share similar abnormalities on OCT imaging. Decreased adhesive properties of the anterior cornea were identified as a common feature of MGD and ADDE. This simple OCT approach may provide new clues into the mechanism and evaluation of dry eye syndrome.

Purpose: The purpose of this work was to gather preliminary data on tear film stability, and the adhesive properties of the corneal surface in dry eye patients and control group subjects, using a new, minimally invasive optical coherence tomography (OCT) imaging method., Methods: We screened 85 human subjects for dry eye and classified them in two groups, as dry eye or normal patients. Sodium carboxymethylcellulose (NaCMC) adhesiveness over the central cornea was measured using Fourier domain anterior segment OCT. The corneal adhesiveness for NaCMC was compared between the two groups, correlated with classical tests, and analyzed for diagnostic validity and repeatability., Results: The corneal adhesiveness for NaCMC median and mode values was fair (between 1 and 3 minutes) for dry eye subjects (n = 36) and borderline (between 3 and 5 minutes) for control group subjects (n = 49), and was significantly different between the two groups (P < 0.001). Significant correlations were observed between the corneal adhesiveness measures and dry eye patients' symptoms (P < 0.001), Schirmer I test (P < 0.001), ocular surface staining (P < 0.001), and, particularly, fluorescein break-up time (P < 0.001). The area under the receiver operating characteristic curve was 0.94 (P < 0.001), suggesting reliable sensitivity and specificity of OCT imaging. A statistically significant intraclass correlation (ICC) value of 0.99 was found for measurements of corneal adhesiveness on two subsequent days at the same time (P < 0.001)., Conclusions: This minimally invasive, novel technique of OCT imaging of the corneal surface following NaCMC drop instillation provides a measure of corneal adhesiveness. This technique may improve the clinician's ability in the understanding and diagnosis of the dry eye syndrome., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Objective: To provide a qualitative and quantitative analysis of filtering blebs with optical coherence tomography (OCT) in patients after primary trabeculectomy., Design: Evaluation of diagnostic technology., Participants: We retrospectively studied 20 eyes of 20 patients who had a fornix-based flap in primary trabeculectomy: 14 with mitomycin C (MMC) and 6 without MMC., Methods: Filtering blebs were examined using 2 types of OCTs working at a wavelength of 840 and 1310 nm. In this study, we analyzed both the OCT morphologic pattern and the internal structures of blebs, including bleb wall thickness, scleral flap thickness, and the route under the scleral flap, and quantified the reflectivity of the intrableb area., Results: Blebs were classified according to the Hirooka scheme in 3 OCT morphologic patterns: cystoid, diffuse, and layer type. The MMC was associated with the surgical success (100%). A significant association was found between good functionality and cystoid type with both devices: 840-nm OCT (p = 0.02) and 1310-nm OCT (p = 0.04). A significant difference in morphologic patterns was found using the 2 OCTs. There were no significant differences between successful and unsuccessful filtering surgery for intrableb structures. The reflectivity of filtering blebs correlated very well to the postoperative intraocular pressure (IOP; R(2) = 0.90; p < 0.001) and to the reduction of IOP (R(2) = 0.58; p = 0.001). Our method to quantify the reflectivity showed a significant degree of intergrader consensus (intraclass correlation coefficient = 0.99; p < 0.001)., Conclusions: Although 840-nm OCT was not developed to assess the anterior segment, it may be considered a useful tool to evaluate the functionality of blebs in the postoperative period., (© 2013 Canadian Ophthalmological Society Published by Canadian Ophthalmological Society All rights reserved.)