Abstract: This submission will briefly review the anatomy and physiology of the optic nerve, and highlight various ischemic optic neuropathies including anterior ischemic optic neuropathies (non-arteritis and arteritic), diabetic papillopathy, posterior ischemic optic neuropathies, and ischemic optic neuropathies in the setting of hemodynamic compromise.
Abstract: Optical coherence tomography (OCT) is an ocular imaging technique that can complement the neuro-ophthalmic assessment, and inform our understanding regarding functional consequences of neuroaxonal injury in the afferent visual pathway. Indeed, OCT has emerged as a surrogate end-point in the diagnosis and follow up of several demyelinating syndromes of the central nervous system (CNS), including optic neuritis (ON) associated with: multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and anti-myelin oligodendrocyte glycoprotein (MOG) antibodies. Recent advancements in enhanced depth imaging (EDI) OCT have distinguished this technique as a new gold standard in the diagnosis of optic disc drusen (ODD). Moreover, OCT may enhance our ability to distinguish cases of papilledema from pseudopapilledema caused by ODD. In the setting of idiopathic intracranial hypertension (IIH), OCT has shown benefit in tracking responses to treatment, with respect to reduced retinal nerve fiber layer (RNFL) measures and morphological changes in the angling of Bruch’s membrane. Longitudinal follow up of OCT measured ganglion cell-inner plexiform layer thickness may be of particular value in managing IIH patients who have secondary optic atrophy. Causes of compressive optic neuropathies may be readily diagnosed with OCT, even in the absence of overt visual field defects. Furthermore, OCT values may offer some prognostic value in predicting post-operative outcomes in these patients. Finally, OCT can be indispensable in differentiating optic neuropathies from retinal diseases in patients presenting with vision loss, and an unrevealing fundus examination. In this review, our over-arching goal is to highlight the potential role of OCT, as an ancillary investigation, in the diagnosis and management of various optic nerve disorders.
Background: To compare objective electrophysiological contrast sensitivity function (CSF) in patients implanted with either multifocal intraocular lenses (MIOLs) or monofocal intraocular lenses (IOLs) by pattern reversal visual evoked potentials (prVEP) measurements.
Methods: Fourty-five cataract patients were randomly allocated to receive bilaterally: apodized diffractive-refractive Alcon Acrysof MIOL (A), full diffractive AMO Tecnis MIOL (B) or monofocal Alcon Acrysof IOL (C). Primary outcomes: 1-year differences in objective binocular CSF measured by prVEP with sinusoid grating stimuli of 6 decreasing contrast levels at 6 spatial frequencies. Secondary outcomes: psychophysical CSF measured with VCTS-6500, photopic uncorrected distance (UDVA), and mesopic and photopic uncorrected near and intermediate visual acuities (UNVA and UIVA respectively).
Results: Electrophysiological CSF curve had an inverted U-shaped morphology in all groups, with a biphasic pattern in Group B. Group A showed a lower CSF than group B at 4 and 8 cpd, and a lower value than group C at 8 cpd. Psychophysical CSF in group A exhibited a lower value at 12 cpd than group B. Mean photopic and mesopic UNVA and UIVA were worse in monofocal group compared to the multifocal groups. Mesopic UNVA and UIVA were better in group B.
Conclusions: Electrophysiological CSF behaves differently depending on the types of multifocal or monofocal IOLs. This may be related to the visual acuity under certain conditions or to IOL characteristics. This objective method might be a potential new tool to investigate on MIOL differences and on subjective device-related quality of vision.
Background: Zellweger spectrum disorder (ZSD) is an autosomal recessive disease caused by mutations in any one of 13 PEX genes whose protein products are required for peroxisome assembly. Retinopathy leading to blindness is one of the major handicaps faced by affected individuals, but treatment for this is supportive only. To test whether we could improve visual function in ZSD, we performed a proof-of-concept trial for PEX1 gene augmentation therapy using the Pex1-G844D mouse model, which bears the equivalent to a common human mutation. This model exhibits a gradual decline in scotopic ffERG response, an always residual photopic ffERG response, diminished visual acuity, and cone and bipolar cell anomalies.
Methods: We administered subretinal injections of a PEX1-containing viral vector (AAV8.CMV.hPEX1.HA) to 2 mouse cohorts of 5 or 9 weeks of age. A GFP-containing vector was used as a control in the contralateral eye of each animal. Efficient expression of the virus was confirmed by retinal histology/immunohistochemistry, and its ability to recover peroxisome import was confirmed in vitro. Preliminary ffERG and optokinetic (OKN) analyses were performed on a subset of animals at 8, 16, and 20 weeks after gene delivery. Final ffERG and OKN measures were performed when each cohort reached 32 weeks of age (23 or 27 weeks post injection).
Results: Preliminary ffERG and OKN analyses at 8 weeks post injection showed mildly better retinal response and visual acuity, respectively, in the PEX1-injected eyes, as did ffERG analysis when each cohort reached 25 weeks of age (16 or 20 weeks after gene delivery). This effect was more pronounced in the cohort treated at 5 weeks of age, when ffERG response is highest in Pex1-G844D mice. At 32 weeks of age, the ffERG response in the PEX1-injected eyes was double that of GFP-injected eyes, on average, though there was no change in OKN. Furthermore, in PEX1-injected eyes the photopic ffERG response improved over time, and the decline in scotopic b-wave amplitude was ameliorated compared to un-injected eyes.
Conclusions: AAV8.CMV.hPEX1.HA was subretinally delivered into the left eye of 5- and 9-week-old Pex1-G844D retina. Successful expression of the protein with no gross histologic side effect was observed. Neither the injection, nor exposure to the AAV8 capsid or the transgenic protein negatively altered the ERG or OKN response. At 5–6 months after gene delivery, therapeutic vector-treated eyes showed improved ERG compared to control eyes, on average, in both the “prevention” and “recovery” cohorts. This implies clinical potential of gene delivery to improve vision in patients with ZSD. Retinal immunohistochemistry (to visualize retinal cell types) and biochemical analyses will be performed on treated and untreated retinas, and may inform the mechanism of ERG improvement.
Background: Overexpression of inducible nitric oxide synthase (iNOS) has been reported in diabetic retinopathy (DR). The kinin B1 receptor (B1R) is also overexpressed in DR, and can stimulate iNOS via Gαi/ERK/MAPK pathway. We previously showed that the topical administration of a B1R antagonist, LF22-0542, significantly reduces leukocyte infiltration, increased vascular permeability and overexpression of several inflammatory mediators, including iNOS in DR. Thus, the aim of this study was to determine whether the pro-inflammatory effects of B1R are attributed to oxidative stress caused by the activation of iNOS pathway in order to identify new therapeutic targets for the treatment of DR. iNOS and B1R being absent in the normal retina, their inhibition is unlikely to result in undesirable side effects. The approach will be no invasive by eye application of drops.
Methods: Diabetes was induced in male Wistar rats (200–230 g) by a single intraperitoneal injection of streptozotocin (STZ, 65 mg/kg b.w). One week later, rats were randomly divided into four groups (N=5) and treated for one week as follows: Gr 1: control rats treated with the selective iNOS inhibitor (1,400 W, 0.06 μM twice a day by eye-drops ×7 days), Gr 2, STZ-diabetic rats treated with 1,400 W, Gr 3: control rats received a selective B1R agonist [Sar (D-Phe8)-des-Arg9-BK, 100 μg twice a week] by intravitreal injections (itrv) and treated with 1,400 W, Gr 4: STZ-diabetic rats + B1R agonist +1,400 W. At the end of treatment and two weeks post-STZ, three series of experiments were carried out to measure vascular permeability (by Evans blue dye method) and the expression of vasoactive and inflammatory mediators, including iNOS, VEGF-A, VEGF-R2, IL-1β, Cox-2, TNF-α, bradykinin 1 and 2 receptors and carboxypeptidase M/kininase 1 (by Western Blotting and qRT-PCR). The nitrosative stress (nitrosylation of proteins) was also assessed by Western Blotting. One-way Anova test with Bonferroni post hoc was used for statistical analysis.
Results: STZ-diabetic rats showed a significant increase in retinal vascular permeability (22.8 μg/g Evans blue dye per g of fresh retinas, P=0.016) compared with control rats and control treated rats (17.2 and 16.8 μg/g respectively). The injections of B1R agonist amplified the increase of vascular permeability which was normalized by the 1,400 W. The overexpression of inflammatory markers was also normalized by the 1,400 W in STZ-diabetic rats received or not the B1R agonist.
Conclusions: These results support a contribution of iNOS in the deleterious effects of B1R in this model of diabetic retinopathy. Hence, iNOS inhibition by ocular application of 1,400 W may represent a promising and non-invasive therapeutic approach in the treatment of diabetic retinopathy.
Background: The oxygen induced retinopathy rodent model is widely used, notably for the assessment of developmental dystrophies in preclinical studies of vascular retinal diseases. Typically, the quantification of vessel tufts and avascular regions is computed manually from flat mounted retinas imaged using fluorescent probes that highlight the vascular network. However, such manual measurements are time-consuming and hampered by user variability and bias, thus a rapid and objective alternative is required.
Methods: We employ a machine learning approach to segment and characterize vascular tufts. The proposed quantitative retinal vascular assessment (QuRVA) technique uses quadratic discrimination analysis and morphological techniques to provide reliable measurements of vascular density and pathological vascular tuft regions, devoid of user intervention within seconds. Our algorithms allow also delineating the whole vasculature network, and identifying and analyzing avascular regions.
Results: Our first experiment shows the high degree of error and variability of manual segmentations. In consequence, we developed a set of algorithms to perform this task automatically. We benchmark and validate the results of our analysis pipeline using the consensus of several manually curated segmentations using commonly used computer tools. We describe the method, provide details for reproducing the algorithm, and validate all aspects of the analysis.
Conclusions: Manual and semi-automated procedures for tuft detection present strong fluctuations among users, demonstrating the need for fast and unbiased tools in this highly active research field with tremendous implications for basic research and industry.
Background: Retinopathy of prematurity (ROP) is the major cause of blindness in children, mainly caused by the retinal neovascularization (NV). Mounting of evidences shown that macrophage plays a pivotal role in the regulation of angiogenesis in ROP. Numerous studies confirmed that the deletion of macrophage significantly reduce the neovascularized areas in the oxygen-induced retinopathy (OIR) model. We have been studied the effect of lymphocyte derived-microparticles (LMPs) over ten years. LMPs are extracellular vesicles derived from apoptotic human CEM T lymphocytes. Our previous studies demonstrated that LMPs possess strong anti-angiogenic effect. Recently we observed that LMPs are capable to switch the phenotype of macrophage, thus to suppress the choroidal neovascularization (CNV). However, the role of LMPs on macrophage in ROP has not been clarified. Thus, my project is to disclose the relationship between LMPs and macrophage in ROP using the OIR model. Hypothesis: LMPs may inhibit retinal NV in the OIR model through targeting at macrophage by affecting the migration of macrophage, thus to inhibit pathological angiogenesis in ROP.
Methods: Cell culture [RAW 264.7 and bone marrow-derived macrophage (BMDM)] for cell migration and viability assay. Generate the OIR model for in vivo detection of macrophage recruitment. Quantification of retinal NV, immunohistostaining of the macrophage in vivo, ex vivo retinal explants for cell migration and qPCR.
Results: LMPs do not affect RAW 264.7 and BMDM cell viability (P>0.05). LMPs significantly decrease the BMDM cell migration indirectly (P<0.05). I successfully generate the OIR model and confirm that more macrophages infiltrate during retinal angiogenesis with counting the F4/80 immunostaining in the retinal flat mount. LMPs exert inhibiting effect on retinal angiogenesis through decreasing the migration of macrophages in vivo.
Conclusions: LMPs have the negative effect on retinal angiogenesis via reducing the infiltrated macrophages to the neovascularized areas in the OIR model.
