Wolf A. Lagrèze

Valproic acid-mediated neuroprotection and regeneration in injured retinal ganglion cells.

PURPOSE Valproic acid (VPA) has been demonstrated to have neuroprotective effects in neurodegenerative conditions. VPA inhibits histone-deacetylases (HDAC) and delays apoptosis in degenerating neurons. The authors investigated whether VPA delays retinal ganglion cell (RGC) death and enhances axonal regeneration after optic nerve crush (ONC). Furthermore, potential molecular targets involved in VPA-mediated protection were analyzed. METHODS ONC was performed on the left eye of rats, which received VPA or Ringers solution subcutaneously (SC; 300 mg/kg twice daily) or intravitreally (single postlesional injection). Densities of fluorogold-labeled RGC were analyzed in retinal flatmounts after 5 or 8 days. Retinal tissue was also harvested and processed to quantify axon growth in retinal explants; evaluate caspase-3 activity; analyze transcription factor cAMP response element binding protein (CREB); and determine acetylated histone 3 and 4, as well as phosphorylated extracellular signal-regulated kinase (pERK) 1/2. RESULTS Five and 8 days after ONC, 93% and 58% RGC survived after subcutaneous VPA treatment in comparison to Ringers solution (62% and 37% viable RGC), respectively (P < 0.001). Likewise, a single intravitreal injection of VPA immediately after injury significantly delayed apoptosis in RGC (P = 0.0016). Injured RGC treated with VPA showed better regeneration of their axons in culture (196 axons/explant) than the crushed controls receiving Ringer (115 axons/explant). RGC axons of the right control eyes regenerated more after VPA treatment. VPA-mediated neuroprotection and neuroregeneration were accompanied by decreased caspase-3 activity, CREB induction, pERK1/2 activation, but not by altered histone-acetylation. CONCLUSIONS VPA provided neuroprotection and axonal regrowth after ONC. Alterations were observed in several pathways; however, the precise mechanism of VPA-mediated protection is not yet fully understood.

A mathematical description of nerve fiber bundle trajectories and their variability in the human retina

We developed a mathematical model wherein retinal nerve fiber trajectories can be described and the corresponding inter-subject variability analyzed. The model was based on traced nerve fiber bundle trajectories extracted from 55 fundus photographs of 55 human subjects. The model resembled the typical retinal nerve fiber layer course within 20 degrees eccentricity. Depending on the location of the visual field test point, the standard deviation of the calculated corresponding angular location at the optic nerve head circumference ranged from less than 1 degrees to 18 degrees , with an average of 8.8 degrees .

The APOSTEL recommendations for reporting quantitative optical coherence tomography studies.

Objective: To develop consensus recommendations for reporting of quantitative optical coherence tomography (OCT) study results. Methods: A panel of experienced OCT researchers (including 11 neurologists, 2 ophthalmologists, and 2 neuroscientists) discussed requirements for performing and reporting quantitative analyses of retinal morphology and developed a list of initial recommendations based on experience and previous studies. The list of recommendations was subsequently revised during several meetings of the coordinating group. Results: We provide a 9-point checklist encompassing aspects deemed relevant when reporting quantitative OCT studies. The areas covered are study protocol, acquisition device, acquisition settings, scanning protocol, funduscopic imaging, postacquisition data selection, postacquisition data analysis, recommended nomenclature, and statistical analysis. Conclusions: The Advised Protocol for OCT Study Terminology and Elements recommendations include core items to standardize and improve quality of reporting in quantitative OCT studies. The recommendations will make reporting of quantitative OCT studies more consistent and in line with existing standards for reporting research in other biomedical areas. The recommendations originated from expert consensus and thus represent Class IV evidence. They will need to be regularly adjusted according to new insights and practices.

Quantification of ischemic damage in the rat retina: a comparative study using evoked potentials, electroretinography, and histology.

PURPOSE To identify objective criteria to quantify visual function in the rat for developing therapeutic strategies to protect neuronal cells after ischemia. The impact of ocular ischemia on luminance and frequency-modulated contrast vision was compared with the function of outer retinal cells and the number of intact retinal ganglion cells (RGCs). METHOD Ischemia was induced in Brown-Norway rats by elevating the intraocular pressure to 120 mm Hg for 30, 45, 60, and 90 minutes. Visual function was evaluated by visual evoked potentials (VEPs) in awake, freely moving rats. Retinal function was analyzed with scotopic and photopic electroretinography (ERG). RGCs were quantified in retinal flatmounts after postischemic injection of tracer into the superior colliculus. RESULTS The response to flicker stimulation in VEP recordings decreased as the ischemic episodes increased. The susceptibility to ischemic damage was more pronounced when potentials were evoked with stimuli at higher frequencies. In ERG recordings, ischemia reduced oscillatory potentials and photopic flicker responses more intensely than scotopic a- and b-waves. In counting the RGCs, the reduced cell density correlated significantly with all electrophysiological parameters. The duration of ischemia with half-maximal inhibitory effect was between 36 and 58 minutes for VEPs and between 36 and 41 minutes for ERG, and it was 51 minutes for RGCs. CONCLUSIONS The amounts of reduction in VEPs, ERG, and RGCs differed as the duration of ischemia increased. The electrophysiological parameters presented in this study may serve as a useful addition to morphologic evaluations in future neuroprotection studies in vivo.

Dependence of the optic nerve sheath diameter on acutely applied subarachnoidal pressure – an experimental ultrasound study

Purpose:  To determine the distensibility and elastic characteristics of the optic nerve sheath for development of a basic understanding of ultrasound studies aimed to measure optic nerve sheath diameter (ONSD) for detection of acutely elevated intracranial pressure (ICP).

Visual contrast response functions in Parkinson's disease: evidence from electroretinograms, visually evoked potentials and psychophysics

OBJECTIVES Visual contrast detection thresholds and suprathreshold contrast discrimination thresholds were compared to luminance and flash/pattern electroretinograms (ERG) and visually evoked potentials (VEP) in patients with Parkinsons disease (n = 31), patients with multiple system atrophy (n = 6), patients with progressive supranuclear palsy (n = 6) and control patients without central nervous disease (n = 33). METHODS The stimuli were luminance modulated full-field (flash) or horizontally oriented sinewave gratings (pattern), the latter having either a low (0.5 cycles/deg) or medium (4.0 cycles/deg) spatial frequency. Stimulus contrast ranged from 10 to 80% so that contrast response functions could be derived. RESULTS Contrast thresholds were higher in the patients with Parkinsons disease than in the control patients. Contrast discrimination thresholds were also somewhat elevated in patients with Parkinsons disease. Pattern ERG amplitudes were significantly reduced in patients with Parkinsons disease for the medium spatial frequency stimulus, but less for the low spatial frequency and flash stimuli. CONCLUSIONS Our results suggest that Parkinsons disease impairs contrast processing in the retina. VEP amplitudes did not significantly differ between the groups for the conditions tested. Patients with progressive supranuclear palsy also showed impaired contrast perception and reduced ERG amplitudes, whereas patients with multiple system atrophy were less impaired.

VEGF-A, VEGFR-1, VEGFR-2 and Tie2 levels in plasma of premature infants: relationship to retinopathy of prematurity

Aim: To study prospectively the plasma levels of vascular endothelial growth factor (VEGF-A), its soluble receptors sVEGFR-1, sVEGFR-2 and soluble Tie2 in premature infants. To identify their changes related to the onset of retinopathy of prematurity (ROP). Methods: Blood samples of 63 preterm infants born at a postmenstrual age (PMA) of 23–32 weeks were obtained between 5 days and 15 weeks after birth. 42 infants had no ROP, two had stage 1, nine stage 2 and 10 stage 3. Of these, four infants were treated with retinal photocoagulation. VEGF-A, sVEGFR-1, sVEGFR-2, and sTie2 were measured in the plasma with a sandwich enzyme immunoassay using factor-specific monoclonal mouse antibodies. The time course of concentrations plotted by kernel smoothing in infants with and without ROP were compared and a paired subgroup with analysis of variance was analysed. Results: ROP patients had raised plasma levels of sVEGFR-2 and sTie2 compared with premature infants without ROP. VEGF-A and sVEGFR-1 levels were similar in both groups. Analysis of a subgroup with pairs of measurements, one before 32 weeks and one after 36 weeks, showed a significant increase in sTie2 after 36 weeks of PMA independent of ROP (p = 0.03). Conclusion: This is the first study to measure plasma levels of angiogenic factors in ROP. Similar VEGF-A plasma levels in infants with and without ROP suggest that pathogenic retinal angiogenesis in ROP is mainly driven by local VEGF-A synthesis. Elevated plasma levels in active ROP were observed for sVEGFR-2 and sTie2. These increases have yet to be confirmed as predictive values for ROP.

Correlation of relative afferent pupillary defect and estimated retinal ganglion cell loss

Abstract · Background: The relative afferent pupillary defect (RAPD) is an important parameter for quantifying the loss of neuronal function in asymmetric optic nerve disease. We wanted to assess its correlation with retinal ganglion cell loss, estimated from visual field defects, using a recently described method. · Methods: In 36 patients with unilateral optic nerve disease, the RAPD was measured using an automated, computerized infrared pupillometer. The percentage of ganglion cell loss was estimated with clear templates. · Results: We found a highly significant correlation between the RAPD and estimated ganglion cell loss. The correlation was higher for Humphrey visual fields than for Goldmann visual fields measured with the I4e and I2e stimulus. · Conclusion: The RAPD correlates well with estimated retinal ganglion cell loss in optic nerve disease. Humphrey visual fields seem to reflect the ganglion cell loss better than Goldmann visual fields. The spatial distribution of pupillomotor retinal ganglion cells seems to be proportional to the distribution of light-sensitive ganglion cells projecting to the lateral geniculate nucleus.

Comparison of the new perimetric GATE strategy with conventional full-threshold and SITA standard strategies

PURPOSE A new, fast-threshold strategy, German Adaptive Thresholding Estimation (GATE/GATE-i), is compared to the full-threshold (FT) staircase and the Swedish Interactive Thresholding Algorithm (SITA) Standard strategies. GATE-i is performed in the initial examination and GATE refers to the results in subsequent examinations. METHODS Sixty subjects were recruited for participation in the study: 40 with manifest glaucoma, 10 with suspected glaucoma, and 10 with ocular hypertension. The subjects were evaluated by each threshold strategy on two separate sessions within 14 days in a randomized block design. RESULTS SITA standard, GATE-i, and GATE thresholds were 1.2, 0.6, and 0.0 dB higher than FT. The SITA standard tended to have lower thresholds than those of FT, GATE-i, and GATE for the more positive thresholds, and also in the five seed locations. For FT, GATE-i, GATE, and SITA Standard, the standard deviations of thresholds between sessions were, respectively, 3.9, 4.5, 4.2, and 3.1 dB, test-retest reliabilities (Spearmans rank correlations) were 0.84, 0.76, 0.79, and 0.71, test-retest agreements as measured by the 95% reference interval of differences were -7.69 to 7.69, -8.76 to 9.00, -8.40 to 8.56, and -7.01 to 7.44 dB, and examination durations were 9.0, 5.7, 4.7, and 5.6 minutes. The test duration for SITA Standard increased with increasing glaucomatous loss. CONCLUSIONS The GATE algorithm achieves thresholds that are similar to those of FT and SITA Standard, with comparable accuracy, test-retest reliability, but with a shorter test duration than FT.

Preconditioning with Inhalative Carbon Monoxide Protects Rat Retinal Ganglion Cells from Ischemia/Reperfusion Injury

PURPOSE. Retinal ischemia/reperfusion (I/R) injury damages retinal neurons. Carbon monoxide (CO) recently attracted attention as cytoprotective because of its anti-inflammatory and antiapoptotic effects. Rapid preconditioning of retinal neurons by inhaled CO before I/R injury may reduce inflammation and apoptosis in retinal ganglion cells (RGCs). METHODS. I/R injury was performed on the left eyes of rats (n = 8) with or without inhaled CO preconditioning (250 ppm) for 1 hour before ischemia. Densities of fluorogold-prelabeled RGCs were analyzed 7 days after injury in whole-mounts. Retinal tissue was further harvested to analyze protein expression of TNF-alpha, HSP-70, and mitogen-activated protein kinases (MAPKs) pERK1/2 and p-p38. DNA-binding activities of the transcription factors NF-kappaB, AP-1, CREB, and HSF-1 were determined to elucidate a possible pathway of neuroprotection. RESULTS. Seven days after I/R injury, RGC death decreased by 52% in the CO preconditioning group compared with controls receiving room air (P < 0.001). Similarly, CO inhalation resulted in attenuated caspase-3 activity and TNF-alpha protein expression. In contrast, HSP-70 protein expression was elevated in the retina after CO. CREB and HSF-1 showed CO-dependent regulation and p-p38 MAPK. CONCLUSIONS. Rapid preconditioning with CO mediates anti-inflammatory and antiapoptotic effects in retinal I/R injury, thus making it neuroprotective. Further studies are needed to evaluate whether CO posttreatment may represent a therapeutic option counteracting ischemic neuronal injury.