Optometry Research Today is a free monthly online journal that collates and summarizes the latest research about Optometry, including details on myopia, optometric practice, therapy.

Phosducin Regulates Transmission at thePhotoreceptor-to-ON-Bipolar Cell Synapse.

Herrmann R, Lobanova ES, Hammond T, Kessler C, Burns ME, Frishman LJ, Arshavsky VY

Albert Eye Research Institute, Duke University, Durham, North Carolina 27710, Center for Neuroscience and Department of Ophthalmology and Vision Science, University of California Davis, Davis, California 95618, and College of Optometry, University of Houston, Houston, Texas 77204.

The rate of synaptic transmission between photoreceptors and bipolar cells has been long known to depend on conditions of ambient illumination. However, the molecular mechanisms that mediate and regulate transmission at this ribbon synapse are poorly understood. We conducted electroretinographic recordings from dark- and light-adapted mice lacking the abundant photoreceptor-specific protein phosducin and found that the ON-bipolar cell responses in these animals have a reduced light sensitivity in the dark-adapted state. Additional desensitization of their responses, normally caused by steady background illumination, was also diminished compared with wild-type animals. This effect was observed in both rod- and cone-driven pathways, with the latter affected to a larger degree. The underlying mechanism is likely to be photoreceptor specific because phosducin is not expressed in other retina neurons and transgenic expression of phosducin in rods of phosducin knock-out mice rescued the rod-specific phenotype. The underlying mechanism functions downstream from the phototransduction cascade, as evident from the sensitivity of phototransduction in phosducin knock-out rods being affected to a much lesser degree than b-wave responses. These data indicate that a major regulatory component responsible for setting the sensitivity of signal transmission between photoreceptors and ON-bipolar cells is confined to photoreceptors and that phosducin participates in the underlying molecular mechanism.

Published 5 March 2010 in J Neurosci, 30(9): 3239-53.
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Articles on Optometry published 5 March 2010:

Age-related differences in visual sampling requirements during adaptive locomotion.   Exp Brain Res, 201(3): 467-78.

This study investigates if there are age- and falls-risk related differences in the length of time individuals need following fixation of a stepping target in order to step accurately onto it. This aim was achieved by manipulating the timing and location of stepping target presentation and comparing the effects on stepping performance between young adults, older adults characterised as having a low risk of falling and older adults characterised as having increased risk of falling (N = 10 in ... [Abstract] [Full-text]

Clinical performance of different care systems with silicone hydrogel contact lenses.   Cont Lens Anterior Eye.

PURPOSE: To assess the clinical and subjective performance of a one-step hydrogen peroxide (H(2)O(2)) lens care system compared to a multi-purpose disinfecting system (MPDS) when used with silicone hydrogel (SiH) lenses. METHODS: This was an eight-week, contralateral (lens type) clinical trial with a randomized, cross-over (care system) design. The H(2)O(2) system was Clear Care ((AO Sept Plus) CIBA VISION) and the MPDS was OPTI-FREE RepleniSH (Alcon) and the SiH materials were lotrafilcon B ... [Abstract] [Full-text]

Surgically induced astigmatism after phacoemulsification with and without correction for posture-related ocular cyclotorsion Randomized controlled study.   J Cataract Refract Surg, 36(3): 413-417.

PURPOSE: To report the impact of posture-related ocular cyclotorsion on one surgeon's surgically induced astigmatism (SIA) results and the variance in SIA. SETTING: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. METHODS: This prospective randomized controlled study included eyes that had phacoemulsification with intraocular lens implantation. Eyes were randomly assigned to have (intervention group) or not have (control group) correction for posture-related ocular cyclotorsion. ... [Abstract] [Full-text]

Optical aberrations in professional baseball players.   J Cataract Refract Surg, 36(3): 396-401.

PURPOSE: To determine the presence, type, and size of optical higher-order aberrations (HOAs) in professional athletes with superior visual acuity and to compare them with those in an age-matched population of nonathletes. SETTING: Vero Beach and Fort Myers, Florida, USA. METHODS: Players from 2 professional baseball teams were studied. Each player's optical aberrations were measured with a naturally dilated 4.0 mm pupil using a Z-Wave aberrometer and a LADARWave aberrometer. RESULTS: One ... [Abstract] [Full-text]

Articles on Optometry published 2 March 2010:

The multifunctional choroid.   Prog Retin Eye Res, 29(2): 144-168.

The choroid of the eye is primarily a vascular structure supplying the outer retina. It has several unusual features: It contains large membrane-lined lacunae, which, at least in birds, function as part of the lymphatic drainage of the eye and which can change their volume dramatically, thereby changing the thickness of the choroid as much as four-fold over a few days (much less in primates). It contains non-vascular smooth muscle cells, especially behind the fovea, the contraction of which may ... [Abstract] [Full-text]

The contribution of human cortical area V3A to the perception of chromatic motion: a transcranial magnetic stimulation study.   Eur J Neurosci, 31(3): 575-84.

Abstract Area V3A was identified in five human subjects on both a functional and retinotopic basis using functional magnetic resonance imaging techniques. V3A, along with other visual areas responsive to motion, was then targeted for disruption by repetitive transcranial magnetic stimulation (rTMS) whilst the participants performed a delayed speed matching task. The stimuli used for this task included chromatic, isoluminant motion stimuli that activated either the L-M or S-(L+M) cone-opponent ... [Abstract] [Full-text]

Articles on Optometry published 1 March 2010:

Scleral reinforcement through host tissue integration with biomimetic enzymatically degradable semi-interpenetrating polymer network.   Tissue Eng Part A, 16(3): 905-16.

Enzymatically degradable semi-interpenetrating polymer networks (edsIPNs) were explored for their biocompatibility and ability to promote new scleral tissue growth, as a means of reinforcing the posterior wall of the eye. The edsIPNs comprised thermoresponsive poly(N-isopropylacrylamide-co-acrylic acid), customizable peptide crosslinkers cleavable by matrix metalloproteinases, and interpenetrating linear poly(acrylic acid)-graft-peptide chains to engage with cell surface receptors. Rheological ... [Abstract] [Full-text]

Topical and intravenous pilocarpine stimulated accommodation in anesthetized rhesus monkeys.   Exp Eye Res.

Many studies have used pilocarpine to stimulate accommodation in both humans and monkeys. However, the concentrations of pilocarpine used and the methods of administration vary. In this study, three different methods of pilocarpine administration are evaluated for their effectiveness in stimulating accommodation in rhesus monkeys. Experiments were performed in 17 iridectomized, anesthetized rhesus monkeys aged 4-16 years. Maximum accommodation was stimulated in all these monkeys with a 2% ... [Abstract] [Full-text]

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