Josefin Nilsson

The negative impact of amblyopia from a population perspective: untreated amblyopia almost doubles the lifetime risk of bilateral visual impairment

Van Leewen et al’s work provides valuable data, moving us closer to determining whether preschool vision screening can be justified

Blue Flash ERG PhNR Changes Associated with Poor Long-Term Glycemic Control in Adolescents with Type 1 Diabetes

PURPOSE To investigate the relationship between long-term glycemic control and photopic negative response (PhNR) changes in the blue flash ERG in adolescents with type 1 diabetes (T1D) without diabetic retinopathy (DR). METHODS After light adaptation, ERG responses to 1.60 cd·s/m(2) blue (420 nm) flashes (blue flash ERG) and 3.0 cd·s/m(2) white flashes (LA 3.0 ERG) were recorded in 22 patients (age range, 12 to 19 years) and 28 age-similar control subjects. The primary outcome measure was the amplitude of the PhNR. Secondary outcome measures were the amplitude and implicit time of the a-wave and b-wave. Multiple regression analyses were conducted with glycated hemoglobin (HbA(1c)) values and the time since diagnosis of T1D as covariates. RESULTS Blue flash ERG PhNR amplitudes were reduced (P = 0.005) in patients compared with control subjects. Multiple regression analysis demonstrated that a 1-unit increase in HbA(1c) was associated with a 15% decrease in the blue flash ERG PhNR amplitude (r = 0.61, P = 0.003). Compared with controls blue flash ERG a-waves (P = 0.03) and b-waves (P = 0.02) were delayed in patients but were not significantly associated with HbA(1c) or time since diagnosis of T1D. None of the ERG measures in the LA 3.0 ERG were significantly different in patients compared with controls. CONCLUSIONS Poorer long-term glycemic control is associated with worsening inner retinal dysfunction involving short-wavelength cone pathways of adolescents with T1D and no clinically visible DR. Future studies are warranted to determine whether changes in the blue flash ERG PhNR are a predictive marker of subclinical DR.

Analysis of multifocal electroretinograms from a population with type 1 diabetes using partial least squares reveals spatial and temporal distribution of changes to retinal function

Spatial–temporal partial least squares (ST-PLS) is a multivariate statistical analysis that has improved the analysis of modern imaging techniques. Multifocal electroretinograms (mfERGs) contain a large amount of data, and averaging and grouping have been used to reduce the amount of data to levels that can be handled using traditional statistical methods. In contrast, using all acquired data points, ST-PLS enables statistically rigorous testing of changes in waveform shape and in the distributed signal related to retinal function. We hypothesise that ST-PLS will improve analysis of the mfERG. Two mfERG protocols, a 103 hexagon clinical protocol and a slow-flash mfERG (sf-mfERG) protocol, were recorded from an adolescent population with type 1 diabetes and an age similar control population. The standard mfERGs were analysed using a template-fitting algorithm and the sf-mfERG using a signal-to-noise measure. The results of these traditional analysis techniques are compared with those of the ST-PLS analysis. Traditional analysis of the mfERG recordings revealed changes between groups for implicit time but not amplitude; however, the spatial location of these changes could not be identified. In contrast, ST-PLS detected significant changes between groups and displayed the spatial location of these changes on the retinal map and the temporal location within the mfERG waveforms. ST-PLS confirmed that changes to diabetic retinal function occur before the onset of clinical pathology. In addition, it revealed two distinct patterns of change depending on whether the multifocal paradigm was optimised to target outer retinal function (photoreceptors) or middle/inner retinal function (collector cells).

Normal visual evoked potentials in preschool children born small for gestational age.

Aim:  Previous studies have shown visual evoked potential (VEP) abnormalities in infants and animals born small for gestational age (SGA) compared with controls. The current exploratory study aims to investigate whether VEP abnormalities persist in older ages.

Rod a-wave analysis using high intensity flashes adds information on rod system function in 25% of clinical ERG recordings.

PURPOSE To investigate whether rod a-wave analysis using high intensity flashes adds information above that obtained with standard ERG. METHODS A total of 2,396 eyes were recorded. Patient age was 2.4 months-84.6 years. RESULTS A-wave analysis of high intensity flashes provided additional information on rod system function in 25% of eyes recorded, most importantly in subjects with midretinal disease and artificially reduced rod responses. High intensity flashes also provided measurable responses for longitudinal monitoring in rod dystrophies with non-recordable rod ERGs. CONCLUSIONS Clinical ERG testing would benefit greatly from adding high intensity flashes to its standard testing conditions.

A comparison of signal detection techniques in the multifocal electroretinogram

A common task in the analysis of the multifocal electroretinogram (mfERG) is determining which retinal areas have preserved signal in recordings which are attenuated by the effects of disease. Several automated methods have been proposed for signal detection from multifocal recordings, but no systematic study has been published comparing the performance of each. This article compares the sensitivity and specificity of expert human scoring with three different automated methods of mfERG signal detection. Recordings from control subjects were artificially modified to simulate decrease in signal amplitudes (attenuation) as well as total signal loss. Human scorers were able to identify areas with preserved signal at both low and high attenuation levels with a high specificity (minimum 0.99), sensitivities ranged from 0.2 to 0.94. Automated methods based on template correlation performed better than chance at all attenuation levels, with a slide fit method having the best performance. Signal detection based on signal to noise ratio performed poorly. In conclusion automated methods of signal detection can be used to increase signal detection sensitivity in the mfERG.

ISCEV guide to visual electrodiagnostic procedures

Clinical electrophysiological testing of the visual system incorporates a range of noninvasive tests and provides an objective indication of function relating to different locations and cell types within the visual system. This document developed by the International Society for Clinical Electrophysiology of Vision provides an introduction to standard visual electrodiagnostic procedures in widespread use including the full-field electroretinogram (ERG), the pattern electroretinogram (pattern ERG or PERG), the multifocal electroretinogram (multifocal ERG or mfERG), the electrooculogram (EOG) and the cortical-derived visual evoked potential (VEP). The guideline outlines the basic principles of testing. Common clinical presentations and symptoms are described with illustrative examples and suggested investigation strategies.

Electrophysiological changes in 12-year-old children born MLP: reduced VEP amplitude in MLP children

Aim To study the electrophysiological changes in relation to fundus morphology in moderate-to-late preterm (MLP) children with no previous history of retinopathy of prematurity. Methods Visual acuity (VA), refraction and fundus variables measured by optical coherence tomography, pattern reversal visual evoked potentials and full-field electroretinography (ff-ERG) were obtained from 22 twelve-year-old MLP children (11 male, 11 female) and 21 full-term controls. Results There were no significant differences between the MLP and control groups in VA, refraction or optic disc parameters. There was a trend for thinner papillary retinal nerve fibre layer in the MLP group. Visual evoked potential amplitudes (P100) were lower in the MLP group than in controls, that is, right eye p=0.0027, left eye p=0.0037. No differences in latencies were found. After Bonferroni adjustment for multiple testing, no ff-ERG differences were noted between MLP and controls. Lower gestational age was correlated with smaller light-adapted 3.0 b-wave amplitudes (p=0.0076, r=0.565). Conclusions Our results indicate that moderate premature birth may affect visual evoked potential amplitudes without clear retinal structural changes in MLP children at 12 years of age.

Isolating visual evoked responses--comparing signal identification algorithms.

Purpose To compare signal identification algorithms for recording visual evoked potentials (VEP). Methods VEPs were recorded both in the presence and absence of a stimulus. Four algorithms were designed to estimate the probability that a recording contains a stimulus evoked signal, and to assign weights for use in a weighted average to isolate a final VEP. Algorithms were compared on their ability to identify trials containing VEPs; the signal-to-noise (SNR) ratios of the final VEP, and the number of trials required to isolate a VEP that was significantly different from background noise. Results All the algorithms isolated VEPs that did not differ significantly in timing or amplitude from those extracted using traditional ensemble averaging. All the studied algorithms were capable of identifying and assigning a significantly greater weight to trials containing visually evoked signals compared with trials containing only noise potentials (P < 0.01). The best performing algorithm produced a ninefold increase in the signal-to-noise of the extracted waveform. Discussion The present investigation provides empirical confirmation that computational signal identification algorithms can improve the detection of VEP signal embedded in noise. When combined with weighted averaging they can reduce the number of trials required for evaluation.