36,536 research outputs found
Neuronal processing of translational optic flow in the visual system of the shore crab Carcinus maenas
This paper describes a search for neurones sensitive to optic flow in the visual system of the shore crab Carcinus maenas using a procedure developed from that of Krapp and Hengstenberg. This involved determining local motion sensitivity and its directional selectivity at many points within the neurone's receptive field and plotting the results on a map. Our results showed that local preferred directions of motion are independent of velocity, stimulus shape and type of motion (circular or linear). Global response maps thus clearly represent real properties of the neurones' receptive fields. Using this method, we have discovered two families of interneurones sensitive to translational optic flow. The first family has its terminal arborisations in the lobula of the optic lobe, the second family in the medulla. The response maps of the lobula neurones (which appear to be monostratified lobular giant neurones) show a clear focus of expansion centred on or just above the horizon, but at significantly different azimuth angles. Response maps such as these, consisting of patterns of movement vectors radiating from a pole, would be expected of neurones responding to self-motion in a particular direction. They would be stimulated when the crab moves towards the pole of the neurone's receptive field. The response maps of the medulla neurones show a focus of contraction, approximately centred on the horizon, but at significantly different azimuth angles. Such neurones would be stimulated when the crab walked away from the pole of the neurone's receptive field. We hypothesise that both the lobula and the medulla interneurones are representatives of arrays of cells, each of which would be optimally activated by self-motion in a different direction. The lobula neurones would be stimulated by the approaching scene and the medulla neurones by the receding scene. Neurones tuned to translational optic flow provide information on the three-dimensional layout of the environment and are thought to play a role in the judgment of heading
Mobile Glaucoma Detection Application
Glaucoma is a debilitating optical degeneration disease that can lead to vision loss and eventually blindness. Given its asymptomatic nature, most people with Glaucoma aren’t even aware that they have the disease. As a result, the disease is often left untreated until it is too late. Detecting the presence of Glaucoma is one of the most important steps in treating Glaucoma, but is unfortunately also the most difficult to enforce. The Mobile Glaucoma Detection application aims to reduce the growing number of individuals who are unaware that they have Glaucoma by providing a simple detection mechanism to notify users if they are at risk. The system does this by enabling its users to independently conduct Tonometry exams through the application. Tonometry examinations allow doctors to determine if the intra-ocular pressure levels in a person’s eyes put them at risk for Glaucoma. The M.G.D.A(Mobile Glaucoma Detection Application) allows users to determine their intra-ocular pressure levels from the comfort of their own home via a special contact lens paired with a smartphone application. The system also offers users the opportunity to monitor, regulate, and track their use and progress through the system
Investigation of adaptive optics imaging biomarkers for detecting pathological changes of the cone mosaic in patients with type 1 diabetes mellitus
Purpose
To investigate a set of adaptive optics (AO) imaging biomarkers for the assessment of
changes of the cone mosaic spatial arrangement in patients with type 1 diabetes mellitus
(DM1).
Methods
16 patients with 20/20 visual acuity and a diagnosis of DM1 in the past 8 years to 37 years
and 20 age-matched healthy volunteers were recruited in this study. Cone density, cone
spacing and Voronoi diagrams were calculated on 160x160 μm images of the cone mosaic
acquired with an AO flood illumination retinal camera at 1.5 degrees eccentricity from the
fovea along all retinal meridians. From the cone spacing measures and Voronoi diagrams,
the linear dispersion index (LDi) and the heterogeneity packing index (HPi) were computed
respectively. Logistic regression analysis was conducted to discriminate DM1 patients without
diabetic retinopathy from controls using the cone metrics as predictors.
Results
Of the 16 DM1 patients, eight had no signs of diabetic retinopathy (noDR) and eight had
mild nonproliferative diabetic retinopathy (NPDR) on fundoscopy. On average, cone density,
LDi and HPi values were significantly different (P<0.05) between noDR or NPDR eyes
and controls, with these differences increasing with duration of diabetes. However, each
cone metric alone was not sufficiently sensitive to discriminate entirely between membership
of noDR cases and controls. The complementary use of all the three cone metrics in
the logistic regression model gained 100% accuracy to identify noDR cases with respect to
controls.
PLOS ONE | DOI:10.1371/journal.pone.0151380 March 10, 2016 1 / 14
OPEN ACCESS
Citation: Lombardo M, Parravano M, Serrao S,
Ziccardi L, Giannini D, Lombardo G (2016)
Investigation of Adaptive Optics Imaging Biomarkers
for Detecting Pathological Changes of the Cone
Mosaic in Patients with Type 1 Diabetes Mellitus.
PLoS ONE 11(3): e0151380. doi:10.1371/journal.
pone.0151380
Editor: Knut Stieger, Justus-Liebig-University
Giessen, GERMANY
Received: December 17, 2015
Accepted: February 27, 2016
Published: March 10, 2016
Copyright: © 2016 Lombardo et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are
credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Funding: Research for this work was supported by
the Italian Ministry of Health (5x1000 funding), by the
National Framework Program for Research and
Innovation PON (grant n. 01_00110) and by
Fondazione Roma. The funders had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript. Vision
Engineering Italy srl funder provided support in the
form of salaries for author GL, but did not have any
Conclusion
The present set of AO imaging biomarkers identified reliably abnormalities in the spatial
arrangement of the parafoveal cones in DM1 patients, even when no signs of diabetic retinopathy
were seen on fundoscopy
Digital Color Imaging
This paper surveys current technology and research in the area of digital
color imaging. In order to establish the background and lay down terminology,
fundamental concepts of color perception and measurement are first presented
us-ing vector-space notation and terminology. Present-day color recording and
reproduction systems are reviewed along with the common mathematical models
used for representing these devices. Algorithms for processing color images for
display and communication are surveyed, and a forecast of research trends is
attempted. An extensive bibliography is provided
Effects of Intraframe Distortion on Measures of Cone Mosaic Geometry from Adaptive Optics Scanning Light Ophthalmoscopy
Purpose: To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images.
Methods: We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.08 temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images (n ¼ 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions.
Results: We observed substantial variation across subjects in the repeatability of density (1.2%–8.7%), inter-cell distance (0.8%–4.6%), percentage of six-sided Voronoi cells (0.8%–10.6%), and Voronoi cell area regularity (VCAR) (1.2%–13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images.
Conclusions: Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a ‘‘distortionless’’ image, though more work is needed to evaluate the feasibility of this approach.
Translational Relevance: Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments
The open cluster Berkeley 53
We present a photometric study of the neglected open cluster Berkeley 53. We
derived its fundamental parameters, such as the age, the interstellar
reddening, and the distance from the Sun, based on BV photometry combined with
near-infrared JHK data. The structure and the mass function of the cluster were
also studied and the total number of members and the total mass were estimated.
The cluster was found to be a rich and massive stellar system, located in the
Perseus Arm of the Milky Way, 3.1+/-0.1 kpc from the Sun. Its age exceeds 1 Gy
but it seems to be very young in the context of its dynamical evolution. The
analysis of the two-color diagrams and color-magnitude diagrams indicates that
the cluster is significantly reddened. However, both methods resulted in
different values of E(B-V), i.e. 1.21+/-0.04 and 1.52+/-0.01, respectively.
This discrepancy suggests the presence of an abnormal interstellar extinction
law toward the cluster
Compact multi-aperture imaging with high-angular-resolution
Previous reports have demonstrated that it is possible to emulate the imaging function of a single conventional
lens with an NxN array of identical lenslets to provide an N-fold reduction in imaging-system track length. This
approach limits the application to low-resolution imaging. We highlight how using an array of dissimilar lenslets,
with an array width that can be much wider than the detector array, high-resolution super-resolved imaging is
possible. We illustrate this approach with a ray-traced design and optimization of a long-wave infrared system
employing a 3x3 array of free-form lenslets to provide a four-fold reduction in track length compared to a baseline
system. Simulations of image recovery show that recovered image quality is comparable to that of the baseline
system
- …