Using texture based features from the continuous wavelet transform of the electroretinogram to predict glaucoma.

Glaucoma is an optic neuropathy resulting in the progressive loss of retinal ganglion cells (RCGs). The photopic negative response (PhNR) of the electroretinogram (ERG) has been used to objectively measure RCG function. This study sought to explore whether the usage of textural features extracted from the continuous wavelet transform of the ERG combined with ERG amplitude markers were more effective at predicting glaucoma severity than using the ERG markers alone.

Time-Frequency Analysis of ERG With Discrete Wavelet Transform and Matching Pursuits for Glaucoma.

Purpose: To examine the performance of two time-frequency feature extraction techniques applied to electroretinograms (ERGs) for the prediction of glaucoma severity.

Methods: ERGs targeting the photopic negative response were obtained in 103 eyes of 55 patients with glaucoma. Features from the ERG recordings were extracted using two time-frequency extraction techniques based on the discrete wavelet transform (DWT) and the matching pursuit (MP) decomposition.

Repeatability and Reproducibility of Retinal Fractal Dimension Measured with Swept-Source Optical Coherence Tomography Angiography in Healthy Eyes: A Proof-of-Concept Study.

The retinal vascular network fractal dimension (FD) could be a promising imaging biomarker. Our objective was to evaluate its repeatability and reproducibility in healthy eyes. A cross-sectional study was undertaken with young, healthy volunteers who had no reported cardiac risk factors or ocular disease history.

Prediction of glaucoma severity using parameters from the electroretinogram.

Glaucoma is an optic neuropathy that results in the progressive loss of retinal ganglion cells (RGCs), which are known to exhibit functional changes prior to cell loss. The electroretinogram (ERG) is a method that enables an objective assessment of retinal function, and the photopic negative response (PhNR) has conventionally been used to provide a measure of RGC function. This study sought to examine if additional parameters from the ERG (amplitudes of the a-, b-, i-wave, as well the trough between the b- and i-wave), a multivariate adaptive regression splines (MARS; a non-linear) model and achromatic stimuli could better predict glaucoma severity in 103 eyes of 55 individuals with glaucoma.

Pupillometric recordings to detect glaucoma.

. Glaucoma is the second cause of vision loss with early diagnosis having significantly better prognosis. We propose the use of hippus, the steady-state pupil oscillations, obtained from an eye-tracker for computerised detection of glaucoma.

Sample entropy analysis of pupillary signals in glaucoma patients and control via light-induced pupillometry.

This paper evaluated the pupillary light reflex of glaucomatous eyes in the presence of constant lighting via light-induced pupillometry using sample entropy. The study used 20 patients and 15 controls, applied three different light intensities to their eyes, and recorded the behavior of the pupil. This study has validated that there is a difference in the entropy of pupillary data in glaucoma and healthy eyes.

Relation Between Retinal Vasculature and Retinal Thickness in Macular Edema.

This study has investigated the relationship of the retinal vasculature and the retinal thickness for Macular Edema (ME) subjects. Ninety sets of Fluorescein Angiograph (FA) and Optical Coherence Tomography (OCT) of 54 participants were analyzed. Multivariate analysis using the binary logistic regression model was used to study the association between vessel parameters and retinal thickness.

Association between Optical Coherence Tomography and Fluorescein Angiography based retinal features in the diagnosis of Macular Edema.

The association between optical coherence tomography (OCT) and the geometrical vascular parameters obtained from the fluorescein angiography (FA) of the eyes with macular edema (ME) was investigated. Data from 82 untreated eyes with ME were studied. Fractal dimension (FD), simple tortuosity, branching angle, total angle count and vessel to background ratio were the five vasculature parameters from FA that were studied.

Agreement study between color and IR retinal images based on retinal vasculature morphological parameters.

Background: Color fundus photography have been extensively used to explore the link between retinal morphology changes associated with various disease i.e. Diabetic Retinopathy, Glaucoma.

A Comparison of the RETeval Sensor Strip and DTL Electrode for Recording the Photopic Negative Response.

Purpose: To compare the RETeval sensor strip and Dawson-Trick-Litzkow (DTL) electrodes for recording the photopic negative response (PhNR) using a portable electroretinogram (ERG) device in eyes with and without glaucoma.

Methods: Twenty-six control and 31 glaucoma or glaucoma-suspect participants were recruited. Photopic ERGs were recorded with sensor strip and DTL electrodes in random order using the LKC RETeval device.

ISCEV extended protocol for the photopic negative response (PhNR) of the full-field electroretinogram.

The International Society for Clinical Electrophysiology of Vision (ISCEV) Standard for full-field electroretinography (ERG) describes a minimum procedure, but encourages more extensive testing. This ISCEV extended protocol describes an extension to the ERG Standard, namely the photopic negative response (PhNR) of the light-adapted flash ERG, as a well-established technique that is broadly accepted by experts in the field. The PhNR is a slow negative-going wave after the b-wave that provides information about the function of retinal ganglion cells and their axons.

More than blindsight: Case report of a child with extraordinary visual capacity following perinatal bilateral occipital lobe injury.

Injury to the primary visual cortex (V1, striate cortex) and the geniculostriate pathway in adults results in cortical blindness, abolishing conscious visual perception. Early studies by Larry Weiskrantz and colleagues demonstrated that some patients with an occipital-lobe injury exhibited a degree of unconscious vision and visually-guided behaviour within the blind field. A more recent focus has been the observed phenomenon whereby early-life injury to V1 often results in the preservation of visual perception in both monkeys and humans.

Photopic Negative Response Obtained Using a Handheld Electroretinogram Device: Determining the Optimal Measure and Repeatability.

Purpose: To determine the measure of the photopic negative response (PhNR) of the full-field electroretinogram (ERG) that exhibits the optimal level of test-retest repeatability, and examine its repeatability under different conditions using a handheld, nonmydriatic ERG system and self-adhering skin electrodes.

Methods: Multiple ERG recordings (using 200 sweeps each) were performed in both eyes of 20 normal participants at two different sessions to compare its coefficient of repeatability (CoR; where 95% of the test-retest difference is expected to lie) between different PhNR measures and under different testing conditions (within and between examiners, and between sessions).

Results: The ratio between the PhNR trough to b-wave peak and b-wave peak to a-wave trough amplitude (PhNR/B ratio) exhibited the lowest CoR relative to its effective dynamic range (30 ± 4%) when including three recordings.

Test-Retest Variability of Fundus-Tracked Perimetry at the Peripapillary Region in Open Angle Glaucoma.

Purpose: To examine the association between the measured level and local gradient of visual sensitivity on the magnitude of test-retest variability of its measurements at the peripapillary region using fundus-tracked perimetry in eyes with glaucoma.

Methods: A total of 30 participants with open angle glaucoma underwent three examinations in one eye on fundus-tracked perimetry using a stimulus pattern that sampled the peripapillary region densely. Factors associated with the magnitude of test-retest variability at each location were examined.

Application-Dedicated Selection of Filters (ADSF) using covariance maximization and orthogonal projection.

Visible and near-infrared (Vis-NIR) spectra are generated by the combination of numerous low resolution features. Spectral variables are thus highly correlated, which can cause problems for selecting the most appropriate ones for a given application. Some decomposition bases such as Fourier or wavelet generally help highlighting spectral features that are important, but are by nature constraint to have both positive and negative components.

Measuring the Photopic Negative Response: Viability of Skin Electrodes and Variability Across Disease Severities in Glaucoma.

Purpose: The purpose of this study was to determine the feasibility of measuring the photopic negative response (PhNR) of the full-field electroretinogram (ERG) using skin electrodes compared to conjunctival electrodes and its test-retest variability over a range of disease severities in open-angle glaucoma.

Methods: Recordings were performed twice (100 sweeps each) within the same session in 43 eyes of 23 participants with glaucoma to determine its intrinsic variability. The ratio between the PhNR and B-wave amplitude (PhNR/B ratio) was determined for each trace and computed across 5 to 100 sweeps of each recording.

Vitamin A Deficiency Presenting with 'Itchy Eyes'.

We present the case of an 88-year-old female living in metropolitan Melbourne, Australia who developed vitamin A deficiency manifesting as 'itchy eyes' due to a bizarre dietary habit. Slit lamp examination revealed Bitot's spots and a subsequent vitamin A serum level test revealed severe deficiency. An electroretinogram showed grossly reduced a- and b-wave amplitudes consistent with generalised rod and cone dysfunction - these parameters showed marked improvement 5 months post supplementation.

Neuronal activity-dependent regulation of retinal blood flow.

Blood flow in the retina is intrinsically regulated to meet the metabolic demands of its constituent cells. Flickering light or stationary contrast reversals induce an increase in blood flow within seconds of the stimulus onset. This phenomenon is thought to compensate for an increase in ganglion cell activity and energy consumption.

Relationship between diabetes and grayscale fractal dimensions of retinal vasculature in the Indian population.

Background: Diabetes mellitus is rapidly increasing in the Indian population. The purpose of this study was to identify changes in the retinal vasculature of diabetic people, ahead of visual impairments. Grayscale Fractal Dimension (FD) analysis of retinal images was performed on people with type 2 diabetes from an Indian population.

The Test-Retest Reliability of the Photopic Negative Response (PhNR).

Purpose: The photopic negative response (PhNR) may be useful as a tool to monitor longitudinal change in retinal ganglion cell (RGC) function. The goal was to assess PhNR test-retest reliability, and to estimate the amount of change between tests that is likely to be statistically significant for an individual test subject.

Methods: Photopic electroretinograms (ERGs) were recorded from 49 visually normal subjects (mean age, 38.

A fast automated method for calculating the EOG Arden ratio.

Background: Recording of the dark trough/light peak of the electrooculogram (EOG) remains a useful electrodiagnostic tool. Manual analysis of the recording is tedious and lengthy, and automated analysis needs to deal with artefacts due to suboptimal patient cooperation.

Methods: We present a novel method of automating the processing and analysis of raw EOG data using the open-source statistical software R.

Nasolacrimal duct screening to minimize post-cataract surgery endophthalmitis.

Background: To examine unrecognized nasolacrimal duct obstruction as a risk factor for developing endophthalmitis post-cataract surgery in order to assess the value of preoperative lacrimal system screening.

Design: Prospective case-control study.

Participants: A random sample of patients undergoing phacoemulsification cataract surgery (control group) and a consecutive series of patients admitted to our hospital with post-cataract surgery endophthalmitis.