The fovea is a depression in the center of the macula and is the site of the highest visual acuity. Optical coherence tomography (OCT) has contributed considerably in elucidating the pathologic changes in the fovea and is now being considered as an accompanying imaging method in drug development, such as antivascular endothelial growth factor and its safety profiling. Because animal numbers are limited in preclinical studies and automatized image evaluation tools have not yet been routinely employed, essential reference data describing the morphologic variations in macular thickness in laboratory cynomolgus monkeys are sparse to nonexistent. A hybrid machine learning algorithm was applied for automated OCT image processing and measurements of central retina thickness and surface area values. Morphological variations and the effects of sex and geographical origin were determined. Based on our findings, the fovea parameters are specific to the geographic origin. Despite morphological similarities among cynomolgus monkeys, considerable variations in the foveolar contour, even within the same species but from different geographic origins, were found. The results of the reference database show that not only the entire retinal thickness, but also the macular subfields, should be considered when designing preclinical studies and in the interpretation of foveal data.

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Diffusion models have shown impressive performance for generative modelling of images. In this paper, we present a novel semantic segmentation method based on diffusion models. By modifying the training and sampling scheme, we show that diffusion models can perform lesion segmentation of medical images. To generate an image specific segmentation, we train the model on the ground truth segmentation, and use the image as a prior during training and in every step during the sampling process. With the given stochastic sampling process, we can generate a distribution of segmentation masks. This property allows us to compute pixel-wise uncertainty maps of the segmentation, and allows an implicit ensemble of segmentations that increases the segmentation performance. We evaluate our method on the BRATS2020 dataset for brain tumor segmentation. Compared to state-of-the-art segmentation models, our approach yields good segmentation results and, additionally, detailed uncertainty maps.

To assess intrapupillary space (IPS) changes in healthy subjects with regard to decreased iris motility in patients with pseudoexfoliation glaucoma (PEXG) or non-arteritic anterior ischaemic optic neuropathy (NAION) in a feasibility study in a clinical environment.Methods: Scotopic and photopic IPS measurements using three-dimensionally rendered swept-source optical coherence tomography (SS-OCT) data were obtained and compared for all subjects. Intrapupillary space (IPS) parameters were evaluated such as absolute volumetric differences, relative light response for volumetric ratios and pupillary ejection fraction (PEF) for functional contraction measurements.Results: From a total of 122 IPS from 66 subjects, 106 IPS were eligible for comparison providing values for 72 normal, 30 PEXG and 4 NAION eyes. In healthy, PEXG and NAION subjects, scotopic overall mean IPS was 8.90, 3.45 and 4.16 mm 3 , and photopic overall mean IPS was 0.87, 0.74 and 1.13 mm 3 , respectively. Three-dimensional contractility showed a mean absolute difference of 8.03 mm 3 for normals (defined as 100% contractility), 2.72 mm 3 for PEXG (33.88% of normal) and 3.03 mm 3 for NAION (38.50% of normal) with a relative light response ratio between scotopic and photopic volumes of 10.26 (100%), 4.69 (45.70%) and 3.67 (35.78%), respectively. Pupillary ejection fraction (PEF) showed a contractile pupillary emptying of 88.11% for normals, 76.92% for PEXG and 70.91% for NAION patients. Conclusion:This 3D pupillometry OCT assessment allows for quantitative measurements of pupil function, contractility and response to light. More specifically, PEF is presented as a potential (neuro)-pupillary outcome measure that could be useful in the monitoring of ophthalmic disorders that affect pupillary function.

Purpose: To evaluate the degenerative findings including cistern formation in the premacular vitreous using optical coherence tomography.Methods: A novel enhanced vitreous imaging method by which four A-scans at each position were averaged before the Fourier transform increased the image quality per frame so that subsequent image registration for averaging could occur. Analysis of B-scans and volume-rendered images of eyes in subjects of various ages was performed.Results: There were 43 eyes of 23 subjects ranging in age from 23 to 68 years. The texture in the vitreous images suggests specific orientations of the vitreous fibers in the macular region; there were fibers circumferential to the retina immediately anterior to the premacular bursa. The pattern of the vitreous fibers seemed less well-defined internal to the zone of circumferential fibers. In younger eyes, there were striations oriented in a roughly inferior to superior direction in this zone. In older eyes, there were striations in the same orientation but actually were alternating zones of vitreous synchysis and syneresis. In these same eyes, numerous cisterns appeared at various levels in the vitreous gel. With extensive vitreous condensation and synchysis, definition of the premacular bursa was lost.Conclusion: With this novel method of enhanced vitreous imaging, the vitreous seemed to have stereotypic patterns of degeneration. The formation of vitreous syneresis and synchysis may be related to organization architecture of the vitreous, including the pattern of vitreous collagen deposition, and the effects of eye motion through decades of time.

Purpose: To evaluate the anatomic changes in the vitreous associated with evolving posterior vitreous detachment over the macula.Methods: A novel scanning method by which four A-scans at each position were averaged before the Fourier transform that boosted the image quality sufficiently such that frame averaging could occur. B-scans and volume rendered images of eyes with evidence of any partial separation of the vitreous in the macular regions were evaluated.Results: There were 43 eyes of 23 subjects with particular attention paid to the findings of seven eyes with various stages of posterior vitreous detachment occurring over the macula. In eyes from young subjects with no vitreous degeneration, the outer vitreous showed a diffuse, poorly defined increase in reflectivity in the region where the vitreous cortex was expected to be. In eyes with vitreous degeneration, there was a hyperreflective zone, called the cortical vitreous condensation, that coursed parallel to the curvature of the retina. The posterior vitreous face elevated from the retina with either a well-defined, smooth outer surface, consistent with the posterior vitreous membrane, or a poorly defined flocculent outer border. The cortical vitreous near the fovea was thin and in eyes in the process of posterior vitreous detachment had visible tears. In more advanced eyes, a circular dehiscence of the cortical vitreous in the central macula occurred with herniation of the vitreous gel through the hole. Conclusion:The methodology produced images of unprecedented clarity that highlighted several newly described details concerning the vitreous changes associated with posterior vitreous detachment over the macula.

Optical coherence tomography angiography (OCTA) enables three-dimensional, high-resolution, depth-resolved flow to be distinguished from non-vessel tissue signals in the retina. Thus, it enables the quantification of the 3D surface area of the retinal vessel signal. Despite the widespread use of OCTA, no representative spatially rendered reference vessel surface area data are published. In this study, the OCTA vessel surface areas in 203 eyes of 107 healthy participants were measured in the 3D domain. A Generalized Linear Model (GLM) model analysis was performed to investigate the effects of sex, age, spherical equivalent, axial length, and visual acuity on the OCTA vessel surface area. The mean overall vessel surface area was 54.53 mm2 (range from 27.03 to 88.7 mm2). OCTA vessel surface area was slightly negatively correlated with age. However, the GLM model analysis identified axial length as having the strongest effect on OCTA vessel surface area. No significant correlations were found for sex or between left and right eyes. This is the first study to characterize three-dimensional vascular parameters in a population based on OCTA with respect to the vessel surface area.

This study aimed to provide volumetric choroidal readings regarding sex, origin, and eye side from healthy cynomolgus monkey eyes as a reference database using optical coherence tomography (OCT) imaging. A machine learning (ML) algorithm was used to extract the choroid from the volumetric OCT data. Classical computer vision methods were then applied to automatically identify the deepest location in the foveolar depression. The choroidal thickness was determined from this reference point. A total of 374 eyes of 203 cynomolgus macaques from Asian and Mauritius origin were included in the analysis. The overall subfoveolar mean choroidal volume in zone 1, in the region of the central bouquet, was 0.156 mm3 (range, 0.131–0.193 mm3). For the central choroid volume, the coefficient of variation (CV) was found of 6.3%, indicating relatively little variation. Our results show, based on analyses of variance, that monkey origin (Asian or Mauritius) does not influence choroid volumes. Sex had a significant influence on choroidal volumes in the superior-inferior axis (p ≤ 0.01), but not in the fovea centralis. A homogeneous foveolar choroidal architecture was also observed.