Ophthalmology Research Today is a free monthly online journal that collates and summarizes the latest research about Ophthalmology, including details on eye surgery, myopia, cataracts.

Nonlinear Interactions between Excitatory and Inhibitory Retinal Synapses Control Visual Output.

Sagdullaev BT, Eggers ED, Purgert R, Lukasiewicz PD

Departments of Ophthalmology and Neurology, Weill Medical College of Cornell University, Burke Medical Research Institute, White Plains, New York 10605, Departments of Physiology and Biomedical Engineering, University of Arizona, Tucson, Arizona 85724, and Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110.

The visual system is highly sensitive to dynamic features in the visual scene. However, it is not known how or where this enhanced sensitivity first occurs. We investigated this phenomenon by studying interactions between excitatory and inhibitory synapses in the second synaptic layer of the mouse retina. We found that these interactions showed activity-dependent changes that enhanced signaling of dynamic stimuli. Excitatory signaling from cone bipolar cells to ganglion cells exhibited strong synaptic depression, attributable to reduced glutamate release from bipolar cells. This depression was relieved by amacrine cell inhibitory feedback that activated presynaptic GABA(C) receptors. We found that the balance between excitation and feedback inhibition depended on stimulus frequency; at short interstimulus intervals, excitation was enhanced, attributable to reduced inhibitory feedback. This dynamic interplay may enrich visual processing by enhancing retinal responses to closely spaced temporal events, representing rapid changes in the visual environment.

Published 21 October 2011 in J Neurosci, 31(42): 15102-12.
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Articles on Ophthalmology published 21 October 2011:

Multiplex Sequencing of Seven Ocular Herpes Simplex Virus Type-1 Genomes: Phylogeny, Sequence Variability and SNP Distribution.   Invest Ophthalmol Vis Sci.

Purpose:Little is known about the role of sequence variation in the pathology of HSV-1 keratitis virus. The goal was to show that a multiplex high-throughput genome sequencing approach was feasible for simultaneously sequencing seven HSV-1 ocular strains.Methods:The Illumina GAIIx platform was used to sequence HSV-1 ocular isolates, TFT401, 134, CJ311, CJ360, CJ394,CJ970, and OD4, in a single lane. Reads were mapped to the HSV-1 strain 17 reference genome using CLC-Bio Genomics Workbench ... [Abstract] [Full-text]

Functional Loss in the Magnocellular and Parvocellular Pathways in Patients with Optic Neuritis.   Invest Ophthalmol Vis Sci.

Purpose:To evaluate contrast threshold and contrast gain in patients with optic neuritis under conditions designed to favor mediation by either the inferred Magnocellular (MC-) or Parvocellular (PC-) pathway.Methods:Achromatic and chromatic contrast discrimination was measured in 11 patients with unilateral or bilateral optic neuritis and 18 age-matched controls with normal vision, using achromatic steady-pedestal and pulsed-pedestal paradigms to bias performance toward the MC- or PC- pathway ... [Abstract] [Full-text]

Quantitative Measurements of Autofluorescence with the Scanning Laser Ophthalmoscope.   Invest Ophthalmol Vis Sci.

Purpose:To evaluate the feasibility and reliability of a standardized approach for quantitative measurements of fundus autofluorescence (AF) in images obtained using the confocal scanning laser ophthalmoscope (cSLO).Methods:AF images (30°) were acquired in 34 normal subjects (20-55 years) using cSLOs (488nm excitation) equipped with an internal fluorescent reference to account for variable laser power and detector sensitivity. The gray levels (GL) of each image were calibrated to the ... [Abstract] [Full-text]

Enhanced Depth Imaging Detects Lamina Cribrosa Thickness Differences in Normal Tension Glaucoma and Primary Open-Angle Glaucoma.   Ophthalmology.

OBJECTIVE: To confirm the advantages of the enhanced depth imaging (EDI) mode over the standard mode of the Heidelberg Spectralis spectral domain optical coherence tomography (SD-OCT) for imaging of the lamina cribrosa, and to compare laminar thicknesses of various glaucoma types with or without disc hemorrhage in a similar state of visual field loss. DESIGN: Cross-sectional, case-control design. PARTICIPANTS: We included 137 glaucoma patients and 49 healthy controls. METHODS: Optic nerve head ... [Abstract] [Full-text]

Scleritis Therapy.   Ophthalmology.

OBJECTIVE: To delineate factors associated with a successful response to treatment in patients with various manifestations of scleritis. DESIGN: Retrospective case series. PARTICIPANTS: A total of 392 patients with noninfectious anterior scleritis. METHODS: We reviewed the electronic health records of 392 patients with noninfectious anterior scleritis seen at 2 tertiary referral centers and studied the factors associated with successful treatment. MAIN OUTCOME MEASURES: Patient characteristics ... [Abstract] [Full-text]

Pseudoexfoliation syndrome in Congolese patients.   J Fr Ophtalmol.

PURPOSE: To determine the frequency of pseudoexfoliation syndrome (PEX) in Congolese patients and its association with cataract and glaucoma. METHODS: We performed a cross-sectional and descriptive analysis of the data from patients diagnosed with PEX. Data were collected between February 2005 and June 2008 in a general practice of ophthalmology in Kinshasa. Patients aged 50 or above who attended the general practice of ophthalmology were included in the study. Each patient underwent complete ... [Abstract] [Full-text]

Relationship between minimum corneal thickness and refractive state, keratometry, age, sex, and left or right eye in refractive surgery candidates.   J Cataract Refract Surg.

PURPOSE: To evaluate the relationship between the thinnest point in corneal thickness and the refractive state, keratometry, age, sex, and the ocular side. SETTING: Eye clinics in Germany and Austria and the Department of Ophthalmology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. DESIGN: Cross-sectional study. METHODS: Medical records of refractive surgery candidates from 2006 to 2010 were reviewed. Univariate variance analysis, covariance analysis, Bravis-Pearson ... [Abstract] [Full-text]

Full-Cycle Steam Sterilization in Ophthalmic Surgery-The Effect of Wrapping Instruments.   Am J Ophthalmol.

PURPOSE: To determine if wrapping instruments in conjunction with full-cycle steam sterilization affects the incidence of postoperative infection in patients undergoing ophthalmic surgery in a dedicated eye center. DESIGN: Retrospective, consecutive-case, comparative study. METHODS: Two consecutive groups, each of approximately 19 000 ophthalmic surgical patients, were reviewed for postoperative infection. Whereas the surgical instruments for both groups were sterilized using full-cycle steam ... [Abstract] [Full-text]

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