Measuring visual electrophysiological responses in individuals with low-functioning autism: a feasibility and pilot study

Background Although visual abnormalities are considered common in individuals with autism spectrum disorders, the associated electrophysiological markers have remained elusive. One impediment has been that methodological challenges often preclude testing individuals with low-functioning autism (LFA). Methods In this feasibility and pilot study, we tested a hybrid visual evoked potential paradigm tailored to individuals with LFA that combines passively presented visual stimuli to elicit scalp-recorded evoked responses with a behavioral paradigm to maintain visual attention. We conducted a pilot study to explore differences in visual evoked response patterns across three groups: individuals with LFA, with high-functioning autism (HFA), and with typical development. Results All participants with LFA met criteria for study feasibility by completing the recordings and producing measurable cortical evoked waveform responses. The LFA group had longer (delayed) cortical response latencies on average as compared with the HFA and typical development groups. We also observed group differences in visually induced alpha spectral power: the LFA group showed little to no prestimulus alpha activity in contrast to the HFA and typical development groups that showed increased prestimulus alpha activity. This observation was confirmed by the bootstrapped confidence intervals, suggesting that the absence of prestimulus alpha power may be a potential electrophysiological marker of LFA. Conclusion Our results confirm the utility of tailoring visual electrophysiology paradigms to individuals with LFA in order to facilitate inclusion of individuals across the autism spectrum in studies of visual processing.

Bee sting presumed endophthalmitis: a devastating ocular outcome

Background To report a rare case of bee sting presumed endophthalmitis that resulted in a devastating ocular outcome. Case presentation A 43-year-old patient presented 24 h after bee sting ocular injury in his left eye. He had a mild inflammatory sign at presentation, and he underwent surgical exploration to rule out a scleral defect, which revealed a sealed defect. During his hospital course, he developed signs of endophthalmitis 48 h following trauma for which he received vitreous tap and intravitreal antibiotic. Microbial culture revealed gram-negative rods, Pseudomonas aeruginosa, and Aeromonas veronii. Condition escalated to reach the panophthalmitis stage and cellulitis like picture with visual acuity of no light perception. Visual evoked response (VER) demonstrated a flat response. Infection was controlled by evisceration of the globe at the end as salvage therapy against the spreading of infection Conclusions Bee sting ocular injury is an exceedingly rare type of ocular trauma. Concomitant infection can happen, and severity depends on the pathogen involved. It is crucial to have insight and start appropriate treatment based on to the patient presentation.

EEG signatures of contextual influences on visual search with real scenes

The use of scene context is a powerful way by which biological organisms guide and facilitate visual search. Although many studies have shown enhancements of target-related electroencephalographic activity (EEG) with synthetic cues, there have been fewer studies demonstrating such enhancements during search with scene context and objects in real world scenes. Here, observers covertly searched for a target in images of real scenes while we used EEG to measure the steady state visual evoked response to objects flickering at different frequencies. The target appeared in its typical contextual location or out of context while we controlled for low-level properties of the image including target saliency against the background and retinal eccentricity. A pattern classifier using EEG activity at the relevant modulated frequencies showed target detection accuracy increased when the target was in a contextually appropriate location. A control condition for which observers searched the same images for a different target orthogonal to the contextual manipulation, resulted in no effects of scene context on classifier performance, confirming that image properties cannot explain the contextual modulations of neural activity. Pattern classifier decisions for individual images was also related to the aggregated observer behavioral decisions for individual images. Together, these findings demonstrate target-related neural responses are modulated by scene context during visual search with real world scenes and can be related to behavioral search decisions.Significance StatementContextual relationships among objects are fundamental for humans to find objects in real world scenes. Although there is a larger literature understanding the brain mechanisms when a target appears at a location indicated by a synthetic cue such as an arrow or box, less is known about how the scene context modulates target-related neural activity. Here we show how neural activity predictive of the presence of a searched object in cluttered real scenes increases when the target object appears at a contextual location and diminishes when it appears at a place that is out of context. The results increase our understanding of how the brain processes real scenes and how context modulates object processing.

Prospective study to evaluate incidence and indicators for early detection of ethambutol toxicity

AimsTo evaluate incidence of toxic optic neuropathy in patients receiving ethambutol (EMB) for 6 months and to identify its early indicators.MethodsWe included 50 patients on anti-tubercular therapy (ATT) including EMB (HRE regimen) based on total body weight for 6 months. Best-corrected visual acuity (ETDRS), colour vision (Ishihara pseudo-isochromatic plates), contrast sensitivity (Pelli-Robson chart), Humphrey visual field analysis (HVF 30-2 SITA FAST), pattern visual evoked response (VER) and spectral-domain optical coherence tomography (SDOCT) for ganglion cell inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) analysis were assessed at baseline and at 2, 4 and 6 months after starting ATT.ResultsMean age of the patients was 36.5±14.7 years with male:female ratio of 2.5:1. Mean daily dosage of EMB was 17.5±1.3 mg/kg/day. No significant change was observed in visual acuity, contrast sensitivity, color vision and mean or pattern SD on HVF at 6 months. Significant increase in VER latency of >2 SD (>125 ms) was observed in 46% eyes on follow-up indicating subclinical toxicity. Significant loss of mean RNFL (from 100.79±16.05 μm to 89.96±13.79 μm) and GCIPL thickness (from 83.1±5.60 μm to 79.85±6.45 μm) was observed at 6 months (p=0.001 for both). Patients with subclinical toxicity had significantly greater damage in temporal RNFL quadrant, supero-nasal and infero-nasal GCIPL sectors compared with others.ConclusionThe incidence of clinical EMB optic neuropathy was <2%, though subclinical damage in the form of increase in VER latency, and decrease in RNFL and GCIPL on OCT was seen in 46% eyes.

Variation in Spontaneous Activity and Visual Evoked Response in Primary Visual Cortex of the S334ter-3 Rats

S334ter-3 retinal degeneration (RD) rats have been widely used to investigate degenerative diseases of the retina. In this model, morphological and electrophysiological changes have been observed in the retina, superior colliculus and primary visual cortex (V1). In this study, experimental rats (S334ter-3) carried one copy of the mutant transgene. We measured the extracellular responses in the primary visual cortex to three stimulus contrast levels (spontaneous activity, medium contrast, and high contrast) at the preferred parameters of each recorded cell under classical receptive field (CRF) stimulation. Then we compared the responses (spontaneous activity and the visual evoked responses) in RD rats with those in wildtype rats. Our results show that V1 cells in the RD group exhibit stronger spontaneous activity but weaker stimulus-evoked responses at medium and high contrasts. At the same time, compared with WT group, RD group also showed a narrow dynamic range. These results indicate the decrease in discriminating the stimuli contrast and loss in responses and lower signal to noise ratio after retina degeneration.

Visual-Evoked-Response-Supported Outcome of Intravitreal Erythropoietin in Management of Indirect Traumatic Optic Neuropathy

Purpose. Investigating the efficacy of intravitreal injection of erythropoietin (EPO) in managing indirect traumatic optic neuropathy (ITON) of different durations.Methods. A case series that included two groups of ITON patients: recent ITON group (<3 months trauma duration; 7 eyes) and old duration ITON group (3–36 months; 7 eyes). Diagnostic computerized tomography (CT) and baseline flash visual evoked response (VER) were performed at the presentation time. At the initial visit and each follow-up, all patients had undergone assessment of best-corrected visual acuity (BCVA), pupil reaction, and anterior and posterior segments. VER was repeated 1 and 3 months after injection. All patients received an intravitreal injection of 2000 IU EPO in 0.2 ml of commercially available sterile EPREX 4000 solution, Jansen Cilag, Zug, Switzerland. Five patients had received a second injection 3 months later.Results. Significant improvement was found in BCVA, VER amplitude, and latency (P<0.0001, 0.0154, and 0.0291, respectively). Initial values of BCVA, VER amplitude, and latency correlated significantly to the final values. Differences between recent and old trauma groups were insignificant in the three parameters. In patients who received second injection, further clinical but statistically insignificant improvement was noted in BCVA in 60% of patients, VER amplitude in 50% of patients, and in VER latency in 100% of patients. No complications were recorded.Conclusion. Intravitreal injection of EPO may be effective and safe in treatment of recent and old indirect traumatic optic neuropathy.