Optic Ganglion Research Articles

Neural Network Model for Detection of Edges Defined by Image Dynamics.

Insects can detect the presence of discrete objects in their visual fields based on a range of differences in spatiotemporal characteristics between the images of object and background. This includes but is not limited to relative motion. Evidence suggests that edge detection is an integral part of this capability, and this study examines the ability of a bio-inspired processing model to detect the presence of boundaries between two regions of a one-dimensional visual field, based on general differences in image dynamics. The model consists of two parts. The first is an early vision module inspired by insect visual processing, which implements adaptive photoreception, ON and OFF channels with transient and sustained characteristics, and delayed and undelayed signal paths. This is replicated for a number of photoreceptors in a small linear array. It is followed by an artificial neural network trained to discriminate the presence vs. absence of an edge based on the array output signals. Input data are derived from natural imagery and feature both static and moving edges between regions with moving texture, flickering texture, and static patterns in all possible combinations. The model can discriminate the presence of edges, stationary or moving, at rates far higher than chance. The resources required (numbers of neurons and visual signals) are realistic relative to those available in the insect second optic ganglion, where the bulk of such processing would be likely to take place.

Comparison of Structural Defects between Optic Disc and Ganglion Cell Complex in Patients with Glaucoma

Purpose: To evaluate the agreement of glaucomatous structural defects of the ganglion cell complex (GCC) detected with the spectral domain optical coherence tomography (sdOCT) with the optic nerve head alterations detected with the Heidelberg retina tomography (HRT), of glaucoma patients with ocular hypertension or open angle glaucoma.
 Material and Methods: Ninety patients eyes with structural glaucomatous defects were enrolled. All of them underwent imaging examination of GCC with sdOCT and the optic disk with HRT. The Cohen's kappa coefficient of agreement was used.
 Results: The agreement between the optic disc and GCC using the parameters of the programs analysis of the HRT, the moorfields regression analysis (MRA) and glaucoma probability score (GPS) was not significant. Instead between MRA and GPS a good agreement was calculated. Significant agreements were found between MRA and GPS on one hand and GCC on the other, considering location and length of the glaucomatous damage, while non significant agreements were found between GPS and GCC for the location and the length of the glaucomatous structural defect.
 Conclusions: There is no significance (Please explain further if you are referring to significance in terms of the difference, similarity or agreement) between HRT and sdOCT for the detection of the glaucomatous damage between the optic nerve head and the ganglion cell complex. Instead MRA and GCC detect comparable areas and lengths of the glaucomatous damage. On the other hand GPS records larger deficits relative to MRA and has not a significant agreement with the study of GCC.

Differential Tuning to Visual Motion Allows Robust Encoding of Optic Flow in the Dragonfly.

Visual cues provide an important means for aerial creatures to ascertain their self-motion through the environment. In many insects, including flies, moths, and bees, wide-field motion-sensitive neurons in the third optic ganglion are thought to underlie such motion encoding; however, these neurons can only respond robustly over limited speed ranges. The task is more complicated for some species of dragonflies that switch between extended periods of hovering flight and fast-moving pursuit of prey and conspecifics, requiring motion detection over a broad range of velocities. Since little is known about motion processing in these insects, we performed intracellular recordings from hawking, emerald dragonflies (Hemicordulia spp.) and identified a diverse group of motion-sensitive neurons that we named lobula tangential cells (LTCs). Following prolonged visual stimulation with drifting gratings, we observed significant differences in both temporal and spatial tuning of LTCs. Cluster analysis of these changes confirmed several groups of LTCs with distinctive spatiotemporal tuning. These differences were associated with variation in velocity tuning in response to translated, natural scenes. LTCs with differences in velocity tuning ranges and optima may underlie how a broad range of motion velocities are encoded. In the hawking dragonfly, changes in LTC tuning over time are therefore likely to support their extensive range of behaviors, from hovering to fast-speed pursuits.SIGNIFICANCE STATEMENT Understanding how animals navigate the world is an inherently difficult and interesting problem. Insects are useful models for understanding neuronal mechanisms underlying these activities, with neurons that encode wide-field motion previously identified in insects, such as flies, hawkmoths, and butterflies. Like some Dipteran flies, dragonflies exhibit complex aerobatic behaviors, such as hovering, patrolling, and aerial combat. However, dragonflies lack halteres that support such diverse behavior in flies. To understand how dragonflies might address this problem using only visual cues, we recorded from their wide-field motion-sensitive neurons. We found these differ strongly in the ways they respond to sustained motion, allowing them collectively to encode the very broad range of velocities experienced during diverse behavior.

Randomly weighted receptor inputs can explain the large diversity of colour-coding neurons in the bee visual system

True colour vision requires comparing the responses of different spectral classes of photoreceptors. In insects, there is a wealth of data available on the physiology of photoreceptors and on colour-dependent behaviour, but less is known about the neural mechanisms that link the two. The available information in bees indicates a diversity of colour opponent neurons in the visual optic ganglia that significantly exceeds that known in humans and other primates. Here, we present a simple mathematical model for colour processing in the optic lobes of bees to explore how this diversity might arise. We found that the model can reproduce the physiological spectral tuning curves of the 22 neurons that have been described so far. Moreover, the distribution of the presynaptic weights in the model suggests that colour-coding neurons are likely to be wired up to the receptor inputs randomly. The perceptual distances in our random synaptic weight model are in agreement with behavioural observations. Our results support the idea that the insect nervous system might adopt partially random wiring of neurons for colour processing.

Novel Strategies for the Generation of Neuronal Diversity: Lessons From the Fly Visual System.

Among all organs of an adult animal, the central nervous system stands out because of its vast complexity and morphological diversity. During early development, the entire central nervous system develops from an apparently homogenous group of progenitors that differentiate into all neural cell types. Therefore, understanding the molecular and genetic mechanisms that give rise to the cellular and anatomical diversity of the brain is a key goal of the developmental neurobiology field. With this aim in mind, the development of the central nervous system of model organisms has been extensively studied. From more than a century, the mechanisms of neurogenesis have been studied in the fruit fly Drosophila melanogaster. The visual system comprises one of the major structures of the Drosophila brain. The visual information is collected by the eye-retina photoreceptors and then processed by the four optic lobe ganglia: the lamina, medulla, lobula and lobula plate. The molecular mechanisms that originate neuronal diversity in the optic lobe have been unveiled in the past decade. In this article, we describe the early development and differentiation of the lobula plate ganglion, from the formation of the optic placode and the inner proliferation center to the specification of motion detection neurons. We focused specifically on how the precise combination of signaling pathways and cell-specific transcription factors patterns the pool of neural stem cells that generates the different neurons of the motion detection system.

Photoreceptor projection from a four-tiered retina to four distinct regions of the first optic ganglion in a jumping spider.

Jumping spiders have four pairs of eyes (ocelli) of which only the principal eyes (PEs) are used to detect features of objects. Photoreceptors in the retina of the PEs form four layers (PL1-4) and terminate in the first optic ganglion (FOG). Here, we focus on Hasarius adansoni because it has unique depth vision besides color vision and its FOG appears to contribute to the initial processing of these visual modalities. We first investigated the neuroanatomical organization of the FOG. The three-dimensional structure of the FOG revealed by synapsin immunostaining is horseshoe-shaped and consists of four terminal zones (TZ1-4). Then, we traced single photoreceptors through serial sections and found that green-sensitive receptors of PL1 and 2 terminate in TZ1 and 2, respectively, by keeping retinotopic organization. In contrast to TZ1 and 2, TZ3 receives terminals of ultraviolet-sensitive receptors from lateral regions of both PL3 and 4, while photoreceptors of the medial region of PL3 and 4 terminate in TZ4. We further studied details of photoreceptor terminals and the branching pattern of interneurons in the FOG in Golgi stained preparations. Photoreceptors have long lateral processes in each terminal zone. Some photoreceptors terminating in TZ3 have branches innervating TZ1, indicating that TZ1 receives different spectral information. A type of interneuron connects TZ1 and 2, while others have branches within a single terminal zone or in the entire FOG. These results suggest that TZ1 and 2 contribute to color, shape, and depth vision, while TZ3 and 4 have specific roles for UV vision.

Fine structure of neurosecretory cells and sinus gland in the eyestalk of the freshwater crab Travancoriana schirnerae Bott, 1969 (Decapoda: Gecarcinucidae)

This study elucidated the fine structure of neurosecretory cells and sinus gland in the optic ganglia of the freshwater crab Travancoriana schirnerae Bott, 1969 (Decapoda: Gecarcinucidae). The eyestalk ganglion showed the presence of four well defined ganglia arranged below the ommatidium: lamina ganglionaris, medulla externa, medulla interna and medulla terminalis of which the lamina ganglionaris, was devoid of neurosecretory cells. Groups of neurosecretory cells seen distributed along the medulla externa, interna and terminalis regions constitute the X-organs. Electron microscopic observations of the eyestalk ganglia revealed ten types of neurosecretory cells, mostly apolar with a few unipolar and bipolar cells classified according to the size, shape and density of the cell and nucleus, cell organelles/inclusions, together with the arrangement and properties of chromatin. These cells were characterized by the presence of large nuclei with unusually condensed chromatin, inclusions like vacuoles and vesicles of varying size, shape and density and organelles like Golgi, endoplasmic reticulum, ribosomes and mitochondria and neurosecretory material. The sinus gland of T. schirnerae was positioned laterally between the externa and interna regions, composed of axonal endings of the neurosecretory cells of the optic ganglia with interspersed glial cells. The axon terminals were enclosed with several small to large membrane bound homogenously dense neurosecretory granules which also occur in the preterminal areas of the axons. Based on size, shape and density of granules and axoplasmic matrix, seven terminal types could be distinguished in the sinus gland of T. schirnerae. Mostly, the granules contained in a terminal were of the same type; rarely, the same terminal enclosed granules of varying size, shape and density. The neurosecretory cell types and axon terminal types represent the types of neurohormones they contained. A precise knowledge of the morphology and cytology of neurosecretory cells in the XO-SG complex of the eyestalk that secrete neurohormones controlling major physiological processes such as growth and reproduction is imperative for successful captive breeding of a species of aquaculture potential.

Cyanobacterial Neurotoxin Beta-Methyl-Amino-l-Alanine Affects Dopaminergic Neurons in Optic Ganglia and Brain of Daphnia magna.

The non-proteinogenic amino acid beta-methyl-amino-l-alanine (BMAA) is a neurotoxin produced by cyanobacteria. BMAA accumulation in the brain of animals via biomagnification along the food web can contribute to the development of neurodegenerative diseases such as Amyotrophic lateral sclerosis/Parkinsonism dementia complex (ALS/PDC), the latter being associated with a loss of dopaminergic neurons. Daphnia magna is an important microcrustacean zooplankton species that plays a key role in aquatic food webs, and BMAA-producing cyanobacteria often form part of their diet. Here, we tested the effects of BMAA on putative neurodegeneration of newly identified specific dopaminergic neurons in the optic ganglia/brain complex of D. magna using quantitative tyrosine-hydroxylase immunohistochemistry and fluorescence cytometry. The dopaminergic system was analysed in fed and starved isogenic D. magna adults incubated under different BMAA concentrations over 4 days. Increased BMAA concentration showed significant decrease in the stainability of dopaminergic neurons of D. magna, with fed animals showing a more extreme loss. Furthermore, higher BMAA concentrations tended to increase offspring mortality during incubation. These results are indicative of ingested BMAA causing neurodegeneration of dopaminergic neurons in D. magna and adversely affecting reproduction. This may imply similar effects of BMAA on known human neurodegenerative diseases involving dopaminergic neurons.

Assessment of macular ganglion cell complex using optical coherence tomography: Impact of a paediatric reference database in clinical practice.

Optical coherence tomography software classifies abnormality of macular ganglion cell-inner plexiform layer thickness and macular retinal nerve fibre layer thickness based on adult series. We assessed the impact of using paediatric reference macular ganglion cell complex values instead of adult reference values. Cross-sectional study. Primary and tertiary health-care setting. Out of 140 healthy participants aged 5 to 18 years, 90% were eligible. Following a dilated eye examination and cycloplegic refraction, participants underwent optical coherence tomography ganglion cell scans (Topcon 3D OCT-2000; Topcon Corporation, Tokyo, Japan). Right eye measurements for superior, inferior, and total layer thickness and spherical equivalent were reported, together with age, sex and origin. Paediatric reference values by age and spherical equivalent were produced, and the specific agreement between paediatric and adult ganglion cell complex reference values below or equal to percentile 5 was estimated. The multivariate analysis confirmed a positive association between spherical equivalent and macular ganglion cell-inner plexiform layer thickness, and between age and macular retinal nerve fibre layer (five out of six regression coefficients P values were ≤ 0.03). Specific agreement was 25% for ganglion cell-inner plexiform layer thickness and > 80% for macular retinal nerve fibre layer. Adult-based software identified low ganglion cell values in one in seven children compared to paediatric reference values (0.8% vs 5.5%, P = 0.031). The availability of optical coherence tomography ganglion cell complex reference values for paediatric age and spherical equivalent groups can be used to improve detection of children with low cell layer thickness.

Caractéristiques de la papille chez les sujets glaucomateux et normaux à l’OCT dans une population Noire Africaine

To determine the correlations between the size of the optic disc and glaucomatous defects in black Africans. Retrospective observational study. The study was conducted over a two-year period from November 2014 to October 2016, based on records of black Togolese patients who had undergone optic nerve head (ONH) OCT or ganglion cell complex OCT for assessment of glaucoma. The population was divided into 3 groups (I, II and III) depending on the size of the ONH. The ONH was considered small (Group I) if its size was less than the mean -1 SD, medium (Group II) if its size was within 1 SD of the mean, and large (Group III) if its size was greater than the mean+1 SD. Glaucomatous lesions were qualitatively identified on RNFL and or GCC. The ONH parameters were compared in the 3 groups. The Chi-square test was used to compare the percentages, and the t test to compare the means with statistical significance of 5%. The Pearson correlation coefficient (r2) was used to measure correlations. A total of 586 eyes of 298 patients were examined, 314 glaucomatous eyes and 272 healthy eyes. The mean age was 41.0±15.7 [6; 86] years. There were 159 men vs. 137 women, with a sex ratio of 1.2. The mean surface area of the ONH was 2.80±0.55mm2. Small ONH's (Group I) were defined as a surface area of less than 2.25mm2, medium-sized ONH's (Group II) as an area between 2.25 and 3.35mm2 and large ONH's (Group III) as an area greater than 3.35mm2. Small ONH's represented 14.7%, (86 eyes), medium-sized 68.6% (408 eyes) and large ONH's 16.8% (98 eyes). The mean surface area of the neuroretinal rim, cup, the cup-disc ratio and the RNFL thickness were statistically significant in the 3 groups. Similarly, all these parameters were significant in groups of glaucomatous or non-glaucomatous eyes, except for the surface area of the cup. The RNFL thickness was weakly correlated with the surface area of the ONH (r2=0.39), moderately correlated with the surface area of the neuroretinal rim (r2=0.57). The surface area of the ONH was strongly correlated with the surface area of the cup (r2=0.7). The neuroretinal rim surface area was strongly correlated with the cup-disc ratio (r2=0.66). The size of the ONH was correlated with the size of the cup, but it was not correlated to the surface area of the neuroretinal rim or the thickness of the nerve fibers. Analysis of the RNFL and GCC is essential for the diagnosis, especially in the case of large ONH's.

Optical coherence tomography retinal ganglion cell complex analysis for the detection of early chiasmal compression.

To report patients with sellar tumors and chiasmal compression with normal visual fields, who demonstrate damage to the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) on optical coherence tomography (OCT). Seven patients with sellar tumors causing mass effect on the optic chiasm without definite visual field defect, but abnormal GCC are described. GCC/RNFL analyses using Cirrus-OCT were classified into centiles based on the manufacturer's reference range. In seven patients with radiologic compression of the chiasm by a sellar tumor, OCT-GCC thickness detected compressive chiasmopathy before visual defects became apparent on standard automated visual field testing. Without OCT, our patients would have been labelled as having normal visual function and no evidence of compressive chiasmopathy. With only OCT-RNFL analysis, 3/7 patients would still have been labelled as having no compression of the anterior visual pathways. These patients show that OCT-GCC analysis is more sensitive than visual field testing with standard automated perimetry in the detection of compressive chiasmopathy or optic neuropathy. These cases and previous studies suggest that OCT-GCC analysis may be used in addition to visual field testing to evaluate patients with lesions compressing the chiasm.

Patterning mechanisms diversify neuroepithelial domains in the Drosophila optic placode.

The central nervous system develops from monolayered neuroepithelial sheets. In a first step patterning mechanisms subdivide the seemingly uniform epithelia into domains allowing an increase of neuronal diversity in a tightly controlled spatial and temporal manner. In Drosophila, neuroepithelial patterning of the embryonic optic placode gives rise to the larval eye primordium, consisting of two photoreceptor (PR) precursor types (primary and secondary), as well as the optic lobe primordium, which during larval and pupal stages develops into the prominent optic ganglia. Here, we characterize a genetic network that regulates the balance between larval eye and optic lobe precursors, as well as between primary and secondary PR precursors. In a first step the proneural factor Atonal (Ato) specifies larval eye precursors, while the orphan nuclear receptor Tailless (Tll) is crucial for the specification of optic lobe precursors. The Hedgehog and Notch signaling pathways act upstream of Ato and Tll to coordinate neural precursor specification in a timely manner. The correct spatial placement of the boundary between Ato and Tll in turn is required to control the precise number of primary and secondary PR precursors. In a second step, Notch signaling also controls a binary cell fate decision, thus, acts at the top of a cascade of transcription factor interactions to define PR subtype identity. Our model serves as an example of how combinatorial action of cell extrinsic and cell intrinsic factors control neural tissue patterning.

Visual function restoring after trabeculectomy: between dream and reality

Glaucoma is characterized by the progressive degeneration of the optic nerve head (ONH) and retinal ganglion cells (RGCs). RGCs can be divided into basic regions, including the axon and synapse, the dendritic arbor, and the cell body (1). These compartments can independently be affected by degeneration processes and cause damage of the ONH (1,2).

GABA-, histamine-, and FMRFamide-immunoreactivity in the visual, vestibular and central nervous systems of Hermissenda crassicornis.

Hermissenda crassicornis is a model for studying the molecular and cellular basis for classical conditioning, based on its ability to associate light with vestibular stimulation. We used confocal microscopy to map histamine (HA), FMRF-amide, and γ-aminobutyric acid (GABA) immunoreactivity in the central nervous system (CNS), eyes, optic ganglia and statocysts of the nudibranchs. For HA immunoreactivity, we documented both consistently and variably labeled CNS structures across individuals. We also noted minor differences in GABA immunoreactivity in the CNS compared to previous work on Hermissenda. Contrary to expectations, we found no evidence for GABA inside the visual or vestibular systems. Instead, we found only FMRFamide- and HA immunoreactivity (FMRFamide: 4 optic ganglion cells, 4-5 hair cells; HA: 3 optic ganglion cells, 8 hair cells). Overall, our results can act as basis for comparisons of nervous systems across nudibranchs, and suggest further exploration of intraspecific plasticity versus evolutionary changes in gastropod nervous systems.

Substrate–inhibitor specificity of cholinesterase and monoamine oxydase from optic ganglia of the pacific squid Todarodes pacificus and commander squid Berryteuthis magister

A comparative analysis of enzymological characteristics of cholinesterase (ChE) and monoamine oxydase (MAO) from the optic ganglia was performed in the Pacific squid Todarodes pacificus and Commander squid Berryteuthis magister caught in their four habitats across the Pacific Northwest. A substrate–inhibitor analysis revealed a homogeneity of T. pacificus and B. magister ChE preparations as well as homogeneity of T. pacificus vs. heterogeneity of B. magister MAO preparations. In case of thiocholine derivatives, the rate of hydrolysis induced by T. pacificus ChE was practically independent of the structure of the acyl group, whereas in case of B. magister ChE it was found to decrease in this substrate series. It is only T. pacificus MAO that was found to be able to deaminate also a diaminooxydase substrate histamine. ChE activity was higher in T. pacificus than in B. magister for the whole substrate series, while for MAO the same activity pattern was observed for tyramine, tryptamine and serotonin. In both squids, the sensitivity of ChE to organophosphorus inhibitors containing the dimethylbutyl group was by several orders of magnitude higher than that in mammals. The sensitivity of ChE to the siloxane reversible inhibitors was lower in T. pacificus ChE and much lower in B. magister than in mammals.

Insect Bio-inspired Neural Network Provides New Evidence on How Simple Feature Detectors Can Enable Complex Visual Generalization and Stimulus Location Invariance in the Miniature Brain of Honeybees.

The ability to generalize over naturally occurring variation in cues indicating food or predation risk is highly useful for efficient decision-making in many animals. Honeybees have remarkable visual cognitive abilities, allowing them to classify visual patterns by common features despite having a relatively miniature brain. Here we ask the question whether generalization requires complex visual recognition or whether it can also be achieved with relatively simple neuronal mechanisms. We produced several simple models inspired by the known anatomical structures and neuronal responses within the bee brain and subsequently compared their ability to generalize achromatic patterns to the observed behavioural performance of honeybees on these cues. Neural networks with just eight large-field orientation-sensitive input neurons from the optic ganglia and a single layer of simple neuronal connectivity within the mushroom bodies (learning centres) show performances remarkably similar to a large proportion of the empirical results without requiring any form of learning, or fine-tuning of neuronal parameters to replicate these results. Indeed, a model simply combining sensory input from both eyes onto single mushroom body neurons returned correct discriminations even with partial occlusion of the patterns and an impressive invariance to the location of the test patterns on the eyes. This model also replicated surprising failures of bees to discriminate certain seemingly highly different patterns, providing novel and useful insights into the inner workings facilitating and limiting the utilisation of visual cues in honeybees. Our results reveal that reliable generalization of visual information can be achieved through simple neuronal circuitry that is biologically plausible and can easily be accommodated in a tiny insect brain.

Characterization and tissue distribution of neuropeptide F in the eyestalk and brain of the male giant freshwater prawn, Macrobrachium rosenbergii.

We previously analyzed the central nervous system (CNS) transcriptome and found three isotypes of long neuropeptide F (MrNPF-I, -II, -III) and four isoforms of short NPF (sMrNPF) in the giant freshwater prawn, Macrobrachium rosenbergii. We now validate the complete sequences of the MrNPF-I and -II precursor proteins, which show high similarity (91-95 %) to NPFs of the penaeus shrimp (PsNPF). MrNPF-I and -II precursors share 71 % amino acid identity, whereas the mature 32-amino-acid MrNPF-I and 69-amino-acid MrNPF-II are identical, except for a 37-amino-acid insert within the middle part of the latter. Both mature MrNPFs are almost identical to PsNPF-I and -II except for four amino acids at the mid-region of the peptides. Reverse transcription plus the polymerase chain reaction revealed that transripts of MrNPF-I and -II were expressed in various parts of CNS including the eyestalk, brain and thoracic and abdominal ganglia, with the highest expression occurring in the brain and thoracic ganglia and with MrNPF-I showing five- to seven-fold higher expression than MrNPF-II. These peptides were also expressed in the midgut hindgut, and hepatopancreas, with MrNPF-I expression in the former two organs being at the same level as that in the brain and thoracic ganglia and about 4-fold higher than NPF-II. The expression of NPFs was also detected in the testes and spermatic duct but appeared much weaker in the latter. Other tissues that also expressed a considerable amount of NPF-I included the hematopoeitic tissue, heart and muscle. By immunohistochemistry, we detected MrNPFs in neurons of clusters 2, 3 and 4 and neuropils ME, MT and SG of the optic ganglia, neurons in cluster 6 and neuropils AMPN, PMPN, PT, PB and CB of the medial protocerebrum, neurons in clusters 9 and 11 and neurophils ON and OGTN of the deutocerebrum and neurons in clusters 14, 15 and 16 and neuropils TN and AnN of the tritocerebrum. Because of their high degree of conservation and strong and wide-spread expression in tissues other than CNS, we believe that, in addition to being a neuromodulator in controlling feeding, MrNPFs also play critical roles in tissue homeostasis. This should be further explored.

Heterozygous Pitx2 Null Mice Accurately Recapitulate the Ocular Features of Axenfeld-Rieger Syndrome and Congenital Glaucoma.

PurposeThe purpose of this analysis was to assess the utility of Pitx2+/− mice as a model for the ocular features of Axenfeld-Rieger Syndrome and for congenital glaucoma.MethodsEyes of Pitx2+/− and wild-type littermates were examined clinically using optical coherence tomography (OCT) and fundus photography. Intraocular pressures were measured using a TonoLab rebound tonometer. Eyes were examined histologically to assess PITX2 expression, structural integrity, and optic nerve and ganglion cell content.ResultsPITX2 is present postnatally in the corneal endothelium and stroma, iris stroma, trabecular meshwork, and Schlemm's canal. Reduced central corneal thickness, iris defects, and iridicorneal adhesions are all prevalent in Pitx2+/− eyes. Although optic nerve heads appear normal at postnatal day 7, IOP is elevated and optic nerve head cupping is fully penetrant in Pitx2+/− eyes by 3 weeks of age. Neurodegeneration is present in a significant percentage of optic nerves from Pitx2+/− mice by 3 weeks of age, and is fully penetrant by 2 months of age. Pitx2+/− eyes show significant reductions in specifically ganglion cell density in all four quadrants by 2 months of age.ConclusionsPitx2+/− mice model the major ocular features of Axenfeld-Rieger Syndrome and will be an important resource for understanding the molecular mechanisms leading to anterior segment dysgenesis and a high prevalence of glaucoma in this disease. In addition, these mice may provide an efficient new model for assessing the molecular events in glaucoma more generally, and for developing and testing new treatment paradigms for this disease.

Avoiding Clinical Misinterpretation and Artifacts of Optical Coherence Tomography Analysis of the Optic Nerve, Retinal Nerve Fiber Layer, and Ganglion Cell Layer.

Background:Optical coherence tomography (OCT) has become an important tool for diagnosing optic nerve disease. The structural details and reproducibility of OCT continues to improve with further advances in technology. However, artifacts and misinterpretation of OCT can lead to clinical misdiagnosis of diseases if they go unrecognized.Evidence Acquisition:A literature review using PubMed combined with clinical and research experience.Results:We describe the most common artifacts and errors in interpretation seen on OCT in both optic nerve and ganglion cell analyses. We provide examples of the artifacts, discuss the causes, and provide methods of detecting them. In addition, we discuss a systematic approach to OCT analysis to facilitate the recognition of artifacts and to avoid clinical misinterpretation.Conclusions:While OCT is invaluable in diagnosing optic nerve disease, we need to be cognizant of the artifacts that can occur with OCT. Failure to recognize some of these artifacts can lead to misdiagnoses and inappropriate investigations.

Protective Effect of ALA in Crushed Optic Nerve Cat Retinal Ganglion Cells Using a New Marker RBPMS.

In this study we first sought to determine whether RNA-binding protein with multiple splicing (RBPMS) can serve as a specific marker for cat retina ganglion cells (RGCs) using retrograde labeling and immunohistochemistry staining. RBPM was then used as an RGC marker to study RGC survival after optic nerve crush (ONC) and alpha-lipoic acid (ALA) treatment in cats. ALA treatment yielded a peak density of RBPMS-alpha cells within the peak isodensity zone (>60/mm2) which did not differ from ONC retinas. The area within the zone was significantly enlarged (control: 2.3%, ONC: 0.06%, ONC+ALA: 0.1%). As for the 10-21/mm2 zone, ALA treatment resulted in a significant increase in area (control: 34.5%, ONC: 12.1%, ONC+ALA: 35.9%). ALA can alleviate crush-induced RGC injury.