Imaging Light Responses of Foveal Ganglion Cells in the Living Macaque Eye

The fovea dominates primate vision, and its anatomy and perceptual abilities are well studied, but its physiology has been little explored because of limitations of current physiological methods. In this study, we adapted a novel in vivo imaging method, originally developed in mouse retina, to explore foveal physiology in the macaque, which permits the repeated imaging of the functional response of many retinal ganglion cells (RGCs) simultaneously. A genetically encoded calcium indicator, G-CaMP5, was inserted into foveal RGCs, followed by calcium imaging of the displacement of foveal RGCs from their receptive fields, and their intensity-response functions. The spatial offset of foveal RGCs from their cone inputs makes this method especially appropriate for fovea by permitting imaging of RGC responses without excessive light adaptation of cones. This new method will permit the tracking of visual development, progression of retinal disease, or therapeutic interventions, such as insertion of visual prostheses

Auditory and Visual Health after Ten Years of Exposure to Metal-on-Metal Hip Prostheses: A Cross-Sectional Study Follow Up

Case reports of patients with mal-functioning metal-on-metal hip replacement (MoMHR) prostheses suggest an association of elevated circulating metal levels with visual and auditory dysfunction. However, it is unknown if this is a cumulative exposure effect and the impact of prolonged low level exposure, relevant to the majority of patients with a well-functioning prosthesis, has not been studied. Twenty four male patients with a well-functioning MoMHR and an age and time since surgery matched group of 24 male patients with conventional total hip arthroplasty (THA) underwent clinical and electrophysiological assessment of their visual and auditory health at a mean of ten years after surgery. Median circulating cobalt and chromium concentrations were higher in patients after MoMHR versus those with THA (P<0.0001), but were within the Medicines and Healthcare Products Regulatory Agency (UK) investigation threshold. Subjective auditory tests including pure tone audiometric and speech discrimination findings were similar between groups (P>0.05). Objective assessments, including amplitude and signal-to-noise ratio of transient evoked and distortion product oto-acoustic emissions (TEOAE and DPOAE, respectively), were similar for all the frequencies tested (P>0.05). Auditory brainstem responses (ABR) and cortical evoked response audiometry (ACR) were also similar between groups (P>0.05). Ophthalmological evaluations, including self-reported visual function by visual functioning questionnaire, as well as binocular low contrast visual acuity and colour vision were similar between groups (P>0.05). Retinal nerve fibre layer thickness and macular volume measured by optical coherence tomography were also similar between groups (P>0.05). In the presence of moderately elevated metal levels associated with well-functioning implants, MoMHR exposure does not associate with clinically demonstrable visual or auditory dysfunction

Un mar de soja: la nueva agricultura en Argentina y sus consecuencias

Adaptive optics is a relatively new field, yet it is spreading rapidly and allows new questions to be asked about how the visual system is organized. The editors of this feature issue have posed a series of question to scientists involved in using adaptive optics in vision science. The questions are focused on three main areas. In the first we investigate the use of adaptive optics for psychophysical measurements of visual system function and for improving the optics of the eye. In the second, we look at the applications and impact of adaptive optics on retinal imaging and its promise for basic and applied research. In the third, we explore how adaptive optics is being used to improve our understanding of the neurophysiology of the visual system

High-resolution adaptive optics fluorescence imaging of retinal cell function

Abstract The long-term goal of our research is to manipulate and/or record the physiological activity of retinal neurons optically in the living eye, both in the high-acuity, perceptually capable macaque, and in the experimentally more tractable mouse. The fine spatial scale of adaptive optics imaging makes it attractive to use recently developed neuroscience methods, such as genetically encoded calcium indicators or light-gated channels, introduced into retinal neurons, to study the function of these cells. Such studies will be fruitful if they achieve: 1. high efficiency transduction of retinal cells in order that imaging or control of neurons can be achieved with light levels low enough to be consistent with retinal safety, 2. uniform transduction of the cells across the retina, which in macaque is hampered by the dense inner limiting membrane barrier, and 3. selective transduction of chosen cell types among bipolar, amacrine or ganglion cell classes. This talk will describe the progress we are making in reaching these goals. In collaboration with the Flannery laboratory we are developing viral vectors for intravitreal injection that are tailored to the unique requirements of the mouse and macaque retina. In collaboration with the Callaway lab we are exploring the use of viral vectors that are retrogradely transported from intracranial injections to retinal neurons. A major focus of this work is the development of cell-type selective transduction, which can be accomplished by focal injection of retino-recipient nuclei that are receive input from only a single type of retinal neuron