Quantifying frequency content in cross-sectional retinal scans of diabetics vs. controls

Purpose To examine subtle differences in the structure of diabetic vs. control retinas. Methods Spectral-domain optical coherence tomography (SD-OCT) images were compared for the retinas of 33 diabetic subjects who did not have clinical evidence of diabetic macular edema and age-matched controls, with central macular thicknesses of 275 and 276 microns, respectively. Cross-sectional retinal images through the fovea, called B-scans, were analyzed for spatial frequency content. The B-scans were processed to remove and smooth the portions of the retinal image not within regions of interest in the retina. The remaining retinal images were then quantified using a Fast Fourier Transform (FFT) approach that provided amplitude as a function of spatial frequency. Results The FFT analysis showed that diabetic retinas had spatial frequency content with significantly higher power compared to control retinas particularly for a deeper fundus layer at mid-range spatial frequencies, ranging from p = 0.0030 to 0.0497 at 16.8 to 18.2 microns/cycle. There was lower power at higher spatial frequencies, ranging from p = 0.0296 and 0.0482 at 27.4 and 29.0 microns/cycle. The range of mid-range frequencies corresponds to the sizes of small blood vessel abnormalities and hard exudates. Retinal thickness did not differ between the two groups. Conclusions Diabetic retinas, although not thicker than controls, had subtle but quantifiable pattern changes in SD-OCT images particularly in deeper fundus layers. The size range and distribution of this pattern in diabetic eyes were consistent with small blood vessel abnormalities and leakage of lipid and fluid. Feature-based biomarkers may augment retinal thickness criteria for management of diabetic eye complications, and may detect early changes.

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Association between central retinal thickness and low luminance visual acuity in early age-related macular degeneration

European Journal of Ophthalmology ◽

10.1177/1120672120968740 ◽

2020 ◽

pp. 112067212096874

Author(s):

María Cinta Puell ◽

Francisco Javier Hurtado-Ceña ◽

María Jesús Pérez-Carrasco ◽

Inés Contreras

Keyword(s):

Visual Acuity ◽

Macular Degeneration ◽

Retinal Thickness ◽

Central Area ◽

Age Related Macular Degeneration ◽

Central Retinal Thickness ◽

Cross Sectional ◽

Age Related ◽

Low Luminance ◽

Sd Oct

Purpose/Aim: To examine whether central retinal thickness (CRT) is related to mesopic visual acuity (VA) and low luminance deficit (LLD, difference between photopic and mesopic VA) in eyes with early and intermediate age-related macular degeneration (AMD). Materials and Methods: In a cross-sectional study, 50 pseudophakic subjects older than 63 years were divided into three groups (no AMD, early AMD and intermediate AMD). Spectral domain optical coherence tomography (SD-OCT) was used to measure CRT in the 1 mm-central-area. Best-corrected distance VA was measured under photopic or mesopic luminance conditions and LLD calculated. Subjects were stratified by VA impairment to compare CRTs across these groups. Relationships were examined by stepwise multiple linear regression. Results: No significant differences in mean CRT, photopic and mesopic VA or LLD were detected between the groups no AMD, early AMD and intermediate AMD. However, mean CRTs were 20 microns and 18 microns thicker in the eyes with impaired mesopic VA (> 0.3 logMAR) and impaired LLD (⩾ 0.3 logMAR) compared to the eyes with non-impaired VA or LLD respectively (both p < 0.01). CRT and mesopic pupil size were independent predictors of mesopic VA ( p = 0.001). CRT emerged as the only independent predictor of LLD ( p = 0.004). Conclusions: Increased CRT was linked to worse retinal function when measured under mesopic conditions in eyes without AMD and eyes with early to intermediate AMD. SD-OCT imaging combined with VA measurements under low luminance conditions could be a useful tool to detect early AMD.

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Macular Thickness and Volume Assessed by Spectral-Domain Optical Coherence Tomography in Patients With Coronavirus Disease 2019: A Case-Control Study

10.21203/rs.3.rs-133611/v1 ◽

2020 ◽

Author(s):

Mojtaba Abrishami ◽

Fariba Tohidinezhad ◽

Zahra Emamverdian ◽

Ramin Daneshvar ◽

Neda Saeedian ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Retinal Thickness ◽

Spectral Domain ◽

Case Group ◽

Special Focus ◽

Optical Coherence ◽

Cross Sectional ◽

Significant Difference ◽

Normal Controls ◽

Sd Oct

Abstract Purpose: To quantify the retinal thickness and volume using spectral-domain optical coherence tomography (SD-OCT) analysis in the macular region of patients with Coronavirus Disease 2019 (COVID-19).Methods: In a comparative cross-sectional, observational study, patients recovered from COVID-19 were included. All included subjects had a reverse transcription-polymerase chain reaction (RT-PCR) - confirmed diagnosis of COVID-19. Macular SD-OCT was performed at least two weeks after recovery from systemic COVID-19. Inner, outer and full retinal thicknesses and volumes were measured in COVID-19 recovered patients versus age-matched normal controls.Results: Twenty-five patients (11 male) with a mean age of 36.4 ± 11 years and 60 healthy controls (31 males) with a mean age of 39.3 ± 7.7 years were enrolled in the study. There was no statistically significant difference in the retinal thickness or volume measures between the two groups. However, the thickness in the case group was minimally more than the controls. Conclusion: Retinal thickness in COVID-19 patients may be higher than healthy subjects. Comprehensive ocular examination with special focus on posterior segment manifestations should be considered in these patients.

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Comparison of CSV-1000 and Metrovision contrast sensitivity tests in normal eyes

Medical Hypothesis, Discovery & Innovation in Optometry ◽

10.51329/mehdioptometry127 ◽

2021 ◽

Vol 2 (2) ◽

pp. 63-70

Author(s):

Abolfazl Tahkor ◽

Javad Heravian Shandiz ◽

Abbas Azimi Khorasani ◽

Alireza Ansari Moghadam

Keyword(s):

Spatial Frequency ◽

Contrast Sensitivity ◽

Measurement Methods ◽

Slit Lamp ◽

Limits Of Agreement ◽

Cross Sectional ◽

Spatial Frequencies ◽

Sensitivity Tests ◽

Movement Assessment ◽

Visual Screening

Background: Measuring contrast sensitivity (CS) allows a better understanding of the visual performance of the human eye. This study aimed to examine the correlation and agreement between the results of two sinewave grating-based CS measurement methods, Metrovision and CSV-1000, in normal eyes. Methods: This cross-sectional, comparative study was performed between December 2018 and April 2019, at an optometry clinic. Subjects underwent comprehensive ocular examinations, which included pupil reflexes, subjective refraction, external eye examinations, smooth pursuit eye movement assessment, the cover–uncover test, and detailed slit-lamp examination of the anterior and posterior segments. Metrovision and CSV-1000 were employed to assess CS under photopic conditions. The correlation and agreement of the results of the two tests were evaluated. Results: CS was measured for 104 normal eyes for 3, 6, 12, and 18 cycles per degree (cpd) spatial frequencies (participants’ mean age ± standard deviation: 37.3 ± 26.4 years). The CSV-1000 measurements were significantly higher for the 3 and 6 cpd spatial frequencies (both P = 0.01); however, at higher spatial frequencies, CS scores were similar. The highest and lowest differences between the two tests were recorded for the 3 cpd spatial frequency and 18 cpd spatial frequency, respectively. Except for the 3 cpd spatial frequency, in both eyes, the findings correlated significantly between the CSV-1000 and Metrovision (P < 0.05). The narrowest and widest limits of agreement between the two tests were found for the 12 and 3 cpd spatial frequencies, respectively. Conclusions: The CSV-1000 method estimated CS higher than the Metrovision method, mostly at lower spatial frequencies. Furthermore, the agreement between the two methods was greater at higher spatial frequencies than at lower frequencies. This should be kept in mind when using the two methods interchangeably in visual screening.

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Cooperative Representation of Visual Borders

Perception ◽

10.1068/p210185 ◽

1992 ◽

Vol 21 (2) ◽

pp. 185-193 ◽

Cited By ~ 4

Author(s):

Geoffrey W Stuart ◽

Terence R J Bossomaier

Keyword(s):

Spatial Frequency ◽

Spatial Scales ◽

Receptive Fields ◽

Frequency Content ◽

Cortical Cells ◽

Firing Rates ◽

Spatial Frequencies ◽

Cooperative Coding ◽

Stimulus Features ◽

Visual Cortical

Recently it has been reported that the visual cortical cells which are engaged in cooperative coding of global stimulus features, display synchrony in their firing rates when both are stimulated. Alternative models identify global stimulus features with the coarse spatial scales of the image. Versions of the Munsterberg or Café Wall illusions which differ in their low spatial frequency content were used to show that in all cases it was the high spatial frequencies in the image which determined the strength and direction of these illusions. Since cells responsive to high spatial frequencies have small receptive fields, cooperative coding must be involved in the representation of long borders in the image.

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Hybrid motion illusions as examples of perceptual conflict

Journal of Illusion ◽

10.47691/joi.v2.7084 ◽

2021 ◽

Vol 2 ◽

Author(s):

Arthur Shapiro

Keyword(s):

Spatial Frequency ◽

Spatial Scales ◽

High Spatial Frequency ◽

Natural World ◽

Fine Scale ◽

Frequency Content ◽

Coarse Scale ◽

Trade Offs ◽

Spatial Frequencies ◽

Contrast Information

Shapiro and Hedjar (2019) proposed a shift in the definition of illusion, from ‘differences between perception and reality’ to ‘conflicts between possible constructions of reality’. This paper builds on this idea by presenting a series of motion hybrid images that juxtapose fine scale contrast (high spatial frequency content) with coarse scale contrast-generated motion (low spatial frequency content). As is the case for static hybrid images, under normal viewing conditions the fine scale contrast determines the perception of motion hybrid images; however, if the motion hybrid image is blurred or viewed from a distance, the perception is determined by the coarse scale contrast. The fine scale contrast therefore masks the perception of motion (and sometimes depth) produced by the coarser scale contrast. Since the unblurred movies contain both fine and coarse scale contrast information, but the blurred movies contain only coarse scale contrast information, cells in the brain that respond to low spatial frequencies should respond equally to both blurred and unblurred movies. Since people undoubtedly differ in the optics of their eyes and most likely in the neural processes that resolve conflict across scales, the paper suggests that motion hybrid images illustrate trade-offs between spatial scales that are important for understanding individual differences in perceptions of the natural world.

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The Importance of High Spatial Frequencies for Exogenous Consciousness. Evidence from the Attentional Blink Paradigm.

10.31234/osf.io/8tyjr ◽

2019 ◽

Author(s):

Mickaël Jean Rémi Perrier ◽

Louise Kauffmann ◽

Carole Peyrin ◽

Nicolas Vermeulen ◽

Frederic Dutheil ◽

...

Keyword(s):

Spatial Frequency ◽

Visual System ◽

Attentional Blink ◽

Crucial Role ◽

Conscious Perception ◽

Frequency Content ◽

Spatial Frequencies ◽

Low Pass ◽

Visual Consciousness ◽

High Pass

We attempted to highlight the respective importance of low spatial frequencies (LSFs) and high spatial frequencies (HSFs) in the emergence of visual consciousness by using an attentional blink paradigm in order to manipulate the conscious report of visual stimuli. Thirty-eight participants were asked to identify and report two targets (happy faces) embedded in a rapid stream of distractors (angry faces). Conscious perception of the second target (T2) usually improved as the lag between the targets increased. The distractors between T1 and T2 were either non-filtered (broad spatial frequencies, BSF), low-pass filtered (LSF), or high-pass filtered (HSF). The spatial frequency content of the distractors resulted in a greater disturbance of T2 reporting in the HSF than in the LSF condition. We argue that this could support the idea of HSF information playing a crucial role in the emergence of exogenous consciousness in the visual system. Other interpretations are also discussed.

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Effects of Spatial Frequency Filtering Choices on the Perception of Filtered Images

Vision ◽

10.3390/vision4020029 ◽

2020 ◽

Vol 4 (2) ◽

pp. 29

Author(s):

Sabrina Perfetto ◽

John Wilder ◽

Dirk B. Walther

Keyword(s):

Spatial Frequency ◽

Behavioral Outcomes ◽

High Spatial Frequency ◽

Frequency Content ◽

Frequency Filtering ◽

Image Content ◽

Specific Choice ◽

Spatial Frequencies ◽

Spatial Frequency Filtering ◽

Frequency Components

The early visual system is composed of spatial frequency-tuned channels that break an image into its individual frequency components. Therefore, researchers commonly filter images for spatial frequencies to arrive at conclusions about the differential importance of high versus and low spatial frequency image content. Here, we show how simple decisions about the filtering of the images, and how they are displayed on the screen, can result in drastically different behavioral outcomes. We show that jointly normalizing the contrast of the stimuli is critical in order to draw accurate conclusions about the influence of the different spatial frequencies, as images of the real world naturally have higher contrast energy at low than high spatial frequencies. Furthermore, the specific choice of filter shape can result in contradictory results about whether high or low spatial frequencies are more useful for understanding image content. Finally, we show that the manner in which the high spatial frequency content is displayed on the screen influences how recognizable an image is. Previous findings that make claims about the visual system’s use of certain spatial frequency bands should be revisited, especially if their methods sections do not make clear what filtering choices were made.

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Accessing depth-resolved high spatial frequency content from the optical coherence tomography signal

Scientific Reports ◽

10.1038/s41598-021-96619-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Sergey Alexandrov ◽

Anand Arangath ◽

Yi Zhou ◽

Mary Murphy ◽

Niamh Duffy ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Spatial Frequency ◽

Structural Changes ◽

High Spatial Frequency ◽

Optical Coherence ◽

Frequency Content ◽

Structural Alterations ◽

Spatial Frequencies ◽

Internal Structures ◽

Optical Coherence Tomography Signal

AbstractOptical coherence tomography (OCT) is a rapidly evolving technology with a broad range of applications, including biomedical imaging and diagnosis. Conventional intensity-based OCT provides depth-resolved imaging with a typical resolution and sensitivity to structural alterations of about 5–10 microns. It would be desirable for functional biological imaging to detect smaller features in tissues due to the nature of pathological processes. In this article, we perform the analysis of the spatial frequency content of the OCT signal based on scattering theory. We demonstrate that the OCT signal, even at limited spectral bandwidth, contains information about high spatial frequencies present in the object which relates to the small, sub-wavelength size structures. Experimental single frame imaging of phantoms with well-known sub-micron internal structures confirms the theory. Examples of visualization of the nanoscale structural changes within mesenchymal stem cells (MSC), which are invisible using conventional OCT, are also shown. Presented results provide a theoretical and experimental basis for the extraction of high spatial frequency information to substantially improve the sensitivity of OCT to structural alterations at clinically relevant depths.

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Spatial and Temporal Selectivity of Translational Glass Patterns Assessed With the Tilt After-Effect

i-Perception ◽

10.1177/20416695211017924 ◽

2021 ◽

Vol 12 (3) ◽

pp. 204166952110179

Author(s):

Andrea Pavan ◽

Adriano Contillo ◽

Filippo Ghin ◽

Rita Donato ◽

Matthew J. Foxwell ◽

...

Keyword(s):

Spatial Frequency ◽

Visual Processing ◽

Temporal Frequency ◽

Frequency Selectivity ◽

Frequency Content ◽

Global Orientation ◽

Global Form ◽

Spatial Frequencies ◽

After Effect ◽

Glass Patterns

Glass patterns (GPs) have been widely employed to investigate the mechanisms underlying processing of global form from locally oriented cues. The current study aimed to psychophysically investigate the level at which global orientation is extracted from translational GPs using the tilt after-effect (TAE) and manipulating the spatiotemporal properties of the adapting pattern. We adapted participants to translational GPs and tested with sinewave gratings. In Experiment 1, we investigated whether orientation-selective units are sensitive to the temporal frequency of the adapting GP. We used static and dynamic translational GPs, with dynamic GPs refreshed at different temporal frequencies. In Experiment 2, we investigated the spatial frequency selectivity of orientation-selective units by manipulating the spatial frequency content of the adapting GPs. The results showed that the TAE peaked at a temporal frequency of ∼30 Hz, suggesting that orientation-selective units responding to translational GPs are sensitive to high temporal frequencies. In addition, TAE from translational GPs peaked at lower spatial frequencies than the dipoles’ spatial constant. These effects are consistent with form-motion integration at low and intermediate levels of visual processing.

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Depth Interpolation with Sparse Disparity Cues

Perception ◽

10.1068/p180039 ◽

1989 ◽

Vol 18 (1) ◽

pp. 39-54 ◽

Cited By ~ 20

Author(s):

Sofia M Würger ◽

Michael S Landy

Keyword(s):

Spatial Frequency ◽

Narrow Band ◽

High Spatial Frequency ◽

Linear Interpolation ◽

Uniform Field ◽

Frequency Content ◽

Apparent Contrast ◽

Spatial Frequencies ◽

Basic Stimulus ◽

Filtered Noise

The interpolation of stereoscopic depth given only sparse disparity information was investigated. The basic stimulus was a rectangle with zero disparity at one edge, and 20 or 30 min visual angle disparity at the other. The depth assigned to the ambiguous intervening locations was measured by means of a small briefly-flashed binocular comparison spot. For a stimulus consisting of a uniform rectangle presented on a background of random dots with zero disparity, interpolated depth was greater for a high mean contrast between rectangle and background than for a low mean contrast. Relative to a linear interpolation between the edges, a larger difference in edge disparity resulted in poorer depth interpolation. Depth interpolation based on rivalrous information was examined by filling the stimulus rectangle with narrow-band filtered noise which was uncorrelated between the two eyes. Four different passbands which were matched in apparent contrast were investigated. The results demonstrate that the rivalrous low-spatial-frequency content was resistant to interpolation; rivalrous high spatial frequencies did not interfere with depth interpolation. High-spatial-frequency stimuli yielded a percept similar to the uniform-field condition, whereas low-spatial-frequency stimuli lay in a depth plane near or even behind the background. In the latter case a transparent plane was perceived which was linearly interpolated between the two edges, and which floated above the rivalrous noise.

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