Optic Nerve Transection Research Articles

Novel laser model of optic nerve transection provides valuable insights about the dynamics of optic nerve regeneration

Optic nerve (ON) injury causes blindness in adult mammals as their retinal ganglion cells (RGCs) cannot regenerate axons. However, amphibian RGC axons do not experience the same regenerative failure. Studying the regeneration process of the ON in amphibians holds profound implications for regenerative medicine and human health. Using transgenic tadpoles and laser micro-optics, we developed a reproducible ON transection and regeneration model. Through microscopy of axon dynamics, functional testing to assess visual pathway recovery, TUNEL cell death and EdU cell proliferation assays, and RNA-seq of the retina and optic nerve, we characterized the optic nerve injury response and subsequent recovery. Our model suggests no chemoattractant gradient exists early in regeneration, with defasciculated axons sprouting in random directions from the globe-proximal cut end. Once individual axons reach the appropriate targets in the brain, their tract is reinforced by other regenerating axons, restoring normal ON morphology. Thus, guidance cues or scaffolding from brain-innervating axons likely support later stages of regeneration. After 14 days, the regenerated ON is morphologically indistinguishable from the naïve ON, and visual function is restored. We found no evidence of RGC death or new RGC formation in the model, suggesting that ON regeneration involves remodeling of injured axons of pre-existing RGCs.

Novel laser model of optic nerve transection provides valuable insights about the dynamics of optic nerve regeneration.

Optic nerve (ON) injury causes blindness in adult mammals as their retinal ganglion cells (RGCs) cannot regenerate axons. However, amphibian RGC axons do not experience the same regenerative failure. Studying the regeneration process of the ON in amphibians holds profound implications for regenerative medicine and human health. Using transgenic tadpoles and laser micro-optics, we developed a reproducible ON transection and regeneration model. Through microscopy, functional testing, TUNEL, EdU assays, and RNA-seq, we characterized the ON injury response and recovery. Our model suggests no chemoattractant gradient exists early in regeneration, with defasciculated axons sprouting in random directions from the globe-proximal cut end. Once individual axons reach the appropriate anatomical insertion point in the brain, their tract is reinforced by other regenerating axons, restoring normal ON morphology. Thus, guidance cues or scaffolding from brain-innervating axons likely support later stages of regeneration. After 14 days, the regenerated ON is morphologically indistinguishable from the naïve ON, and visual function is restored. We found no evidence of RGC death or new RGC formation in the model, suggesting that only pre-existing RGCs are involved in ON regeneration.

Intra-orbital Foreign Body

Abstract Background: This case report describes a young man with an intra-orbital foreign body (FB) in both eyes. Case Report: Intra-orbital FBs are rare, with few cases reported in the literature. This is because the orbit protects the globe from external forces, and the orbit is a closed cavity with one opening. This report details the case of a 28-year-old man who presented to the emergency unit with an 11-hour history of an intra-orbital FB. The patient was lying on a bench when a stationary motorcycle fell on him. He noticed that he was unable to open both eyes and was rushed to a peripheral hospital, then subsequently referred to this tertiary center. On examination, he was ill-looking and anxious but not febrile or pale. Systemic examination did not reveal any abnormality. Unaided visual acuity in the right eye (OD) was nil perception of light, while left eye visual acuity (OS) was counting fingers. The right eyelid was ptotic due to edema. He underwent basic laboratory investigations that were all normal. A plain X-ray revealed a radio-opaque FB penetrating the left orbit, fracturing the medial walls into the right orbit, with the round end positioned behind the right globe. The FB was identified as a broken part of a brake/clutch lever from the motorcycle. A computerized tomography scan showed a metallic object in both orbits, accompanied by pneumocephalus, and suggested transection of the right optic nerve. The patient was prepared for FB removal and repair of the lid penetration under general anesthesia, following review by the ENT surgeon and neurosurgeon. The brake lever was successfully removed, and the patient was administered antibiotics. Post-operatively, visual acuity in the right eye remained at nil perception of light, while that in the left eye improved to 6/9 upon discharge. Conclusion: There is no established protocol for managing intra-orbital FBs, as removal depends on factors such as the size, composition, and potential compression damage to structures around the globe, which could further compromise vision or function. Small inert objects may be left in place if removal would cause damage. However, in this case, removal was deemed necessary for several reasons.

Etomidate protects retinal ganglion cells from hydrogen peroxide-induced injury via Nrf2/HO-1 pathway.

To determine whether etomidate (ET) has a protective effect on retinal ganglion cells (RGCs) injured with hydrogen peroxide (H2O2) and to explore the potential mechanism underlying the antioxidative stress effect of ET. Cultured RGCs were identified by double immunofluorescent labeling of microtubule-associated protein 2 and Thy1.1. An injury model of H2O2-induced RGCs oxidative stress was established in vitro. Cells were pretreated with different concentrations of ET (1, 5, and 10 µmol/L) for 4h, followed by further exposure to H2O2 at 1000 µmol/L. Cell counting kit 8 and Annexin V/propidium iodide assays were applied to detect the viabilities and apoptosis rates of the RGCs at 12, 24, and 48h after H2O2 stimulation. The levels of nitric oxide, malondialdehyde, and glutathione in culture media were measured at these time points. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were performed to observe the effects of ET on the messenger RNA and protein expression of inducible nitric oxide synthase (iNOS), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), glutathione peroxidase 1 and the level of conjugated acrolein in RGCs at 12, 24, and 48h after H2O2 stimulation and in the retina at 12h after optic nerve transection (ONT). The applications of 5 and 10 µmol/L of ET significantly increased the viability of RGCs. Results from qRT-PCR indicated a decrease in the expression of iNOS and an increase in the expressions of Nrf2 and HO-1 in ET-pretreated RGCs at 12, 24 and 48h after H2O2 stimulation, as well as in ET-treated retinas at 12h after ONT. Western blot analysis revealed a decrease in the expression of iNOS and levels of conjugated acrolein, along with an increase in the expressions of Nrf2 and HO-1 in ET-pretreated RGCs in vitro and ET-treated retinas in vivo. ET is a neuroprotective agent in primary cultured RGCs injured by H2O2. The effect of ET is dose-dependent with the greatest effect being at 10 µmol/L. ET plays an antioxidant role by inhibiting iNOS, up-regulating Nrf2/HO-1, decreasing the production of acrolein, and increasing the scavenge of acrolein.

Gross-total resection in optic nerve sheath meningiomas: minimally invasive and cosmetic pleasing

PurposeThe optic nerve sheath meningioma (ONSM) is one of the most challenging tumors in orbital surgery. From the perspective of mental health and patient needs, we analyzed the necessity and importance of the endoscopic transnasal approach (ETA) combined with optic nerve transection (ONT) in gross-total resection (GTR) in ONSM patients with residual vision and aim to broaden the use of ONT for specific people.MethodsThe authors included patients with ONSMs who were treated between 2014 and 2022. We divided those cases into two groups named ETA group and lateral orbitotomy approach (LOA) group. We present the application of ETA and analyze the preoperative indication of the ONT and compared the advantages and disadvantages between ETA and LOA. The degree of tumor resection was based on imaging and surgical evaluation.ResultsA total of 23 patients with ONSM were included. Sixteen patients underwent ETA, and seven underwent LOA. Among ETA cases, GTR was achieved in 14 patients with ONT and most patients maintained normal eye movement function (75%) and morphology (93.75%). In the ETA group, 14 patients experienced vision loss, while two other patients saw improvements in vision. And proptosis was alleviated (5.20 ± 2.34 vs 0.27 ± 0.46, p < 0.0001). Six patients with blindness and proptosis of the LOA group resulted in GTR with ONT and ophthalmectomy. Although intracranial extension and recurrence included no cases in the two groups, a significant psychological gap was presented due to cosmetic problems.ConclusionsUnder the premise of reducing damage and improving aesthetics, the selection of ETA combined with ONT to gross-total resect ONSMs successfully provides a minimally invasive access with acceptable complications. As an important adjunct to GTR in the surgical treatment of ONSM, the scope of ONT application should be expanded to relieve the patient’s psychological burden.

Idiosyncratic responses of RGCs to injury and protection

Objectives: The objectives of the study were to investigate the responses of different retinal ganglion cell (RGC) populations to diverse injuries [transient ischemia induced by acute ocular hypertension (AOH), excitotoxicity induced by intravitreal injection of 100 mM N‐methyl D‐aspartate (NMDA) or intra‐orbital optic nerve transection (IONT)] and protection with selective agonists of the tropomyosin related kinase B (TrkB) receptor, brain‐derived neurotrophic factor (BDNF) or 7,8‐Dihydroxyflavone (DHF) or with a voltage‐dependent calcium channel blocker (ITH12657).Methods: Adult Sprague–Dawley rats were used. In the first group, the left eye received a single intravitreal injection of 5 μL vehicle or 5 μg BDNF and was connected to a saline reservoir elevated above the eye to induce an acute ocular hypertension (AOH) and transient ischemia for 75 min. These rats were analysed at different survival intervals from 3 to 45 days.A second group were treated daily subcutaneously with vehicle or ITH5263 (10 mg/kg), or intraperitoneally with vehicle or DHF (5 mg/kg), starting 12 h prior to an intraocular injection of 100 mM N‐methyl‐D‐aspartate (NMDA) to induce retinal excitotoxicity. These rats were analysed at different survival intervals from 3 to 21 days.A third group received a left intra‐orbital optic nerve transection (IONT) to induce axotomy of the RGC population and were treated daily with an intraperitoneal injection of vehicle (0.9% NaCl containing 1% DMSO) or DHF (5 mg/kg diluted in vehicle). These rats were analysed at survival intervals from 3 to 60 days.The retinas were prepared as wholemounts and immunolabelled for Brn3a, melanopsin (m), Osteopontin (OPN) and the T‐box transcription factor T‐brain‐2 (Tbr2) to identify the following retinal ganglion cell populations: Brn3a+, melanopsin+, α‐like (OPN+), α‐ON sustained RGCs (OPN+Tbr2+), α‐ON transient RGCs (OPN+ Brn3a− Tbr2−) and α‐OFF like (OPN+Brn3a+). The labelled RGCs were quantified automatically (Brn3a) or dotted manually and quantified with a graphic software, and distribution of the different populations were represented on topographical maps.Results: Our studies document that:(i) AOH induces progressive loss of Brn3a+RGCs and a significant but not progressive loss of m+RGCs. Treatment with BDNF afforded significant long‐lasting protection for both RGC populations.(ii) Intravitreal injection of NMDA resulted at 7 days in the abrupt significant loss of Brn3a+RGCs, αRGC and αONs‐RGCs without further progression, whereas αOFF‐RGCs died massively. Both m+RGCs and αONtRGCs appear fully resistant to NMDA‐induced excitotoxicity. Both ITH12657 or DHF protect Brn3a+RGC, αRGCs and αONs‐RGCs, but not αOFF‐RGCs.(iii) IONT and vehicle treatment result in a characteristic rapid loss of Brn3a, melanopsin RGCs, αRGCs, αONs‐RGCs and αOFF‐RGCs. DHFs protect Brn3a + RGC, m + RGCs, αRGCs and αONs‐RGCs, but not αOFF‐RGCs.Conclusions: Thus, three different RGC populations (Brn3a+, m+ and α‐like) respond distinctly to different injuries and neuroprotective agents, further adding to the idea that each type of RGC has a unique response to injury and protection. Deciphering the molecular mechanisms of each RGC type will help understand neuronal responses to injury and its possible prevention.

Elemental Mapping in a Preclinical Animal Model Reveals White Matter Copper Elevation in the Acute Phase of Central Nervous System Trauma.

Understanding the chemical events following trauma to the central nervous system could assist in identifying causative mechanisms and potential interventions to protect neural tissue. Here, we apply a partial optic nerve transection model of injury in rats and use synchrotron X-ray fluorescence microscopy (XFM) to perform elemental mapping of metals (K, Ca, Fe, Cu, Zn) and other related elements (P, S, Cl) in white matter tracts. The partial optic nerve injury model and spatial precision of microscopy allow us to obtain previously unattained resolution in mapping elemental changes in response to a primary injury and subsequent secondary effects. We observed significant elevation of Cu levels at multiple time points following the injury, both at the primary injury site and in neural tissue near the injury site vulnerable to secondary damage, as well as significant changes in Cl, K, P, S, and Ca. Our results suggest widespread metal dyshomeostasis in response to central nervous system trauma and that altered Cu homeostasis may be a specific secondary event in response to white matter injury. The findings highlight metal homeostasis as a potential point of intervention in limiting damage following nervous system injury.

Metabolomic profiling of a neurodegenerative retina following optic nerve transection.

The degeneration of retinal ganglion cells (RGCs) often causes irreversible vision impairment. Prevention of RGC degeneration can prevent or delay the deterioration of visual function. The present study aimed to investigate retinal metabolic profiles following optic nerve transection (ONT) injury and identify the potential metabolic targets for the prevention of RGC degeneration. Retinal samples were dissected from ONT group and non‑ONT group. The untargeted metabolomics were carried out using liquid chromatography‑tandem mass spectrometry. The involved pathways and biomarkers were analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and MetaboAnalyst 5.0. In the ONT group, 689 disparate metabolites were detected, including lipids and lipid‑like molecules. A total of 122 metabolites were successfully annotated and enriched in 50 KEGG pathways. Among them, 'sphingolipid metabolism' and 'primary bile acid biosynthesis' were identified involved in RGC degeneration. A total of five metabolites were selected as the candidate biomarkers for detecting RGC degeneration with an AUC value of 1. The present study revealed that lipid‑related metabolism was involved in the pathogenesis of retinal neurodegeneration. Taurine, taurochenodesoxycholic acid, taurocholic acid (TCA), sphingosine, and galabiosylceramide are shown as the promising biomarkers for the diagnosis of RGC degeneration.

Differential Responses of Retinal Neurons and Glia Revealed via Proteomic Analysis on Primary and Secondary Retinal Ganglion Cell Degeneration.

To explore the temporal profile of retinal proteomes specific to primary and secondary retinal ganglion cell (RGC) loss. Unilateral partial optic nerve transection (pONT) was performed on the temporal side of the rat optic nerve. Temporal and nasal retinal samples were collected at 1, 4 and 8 weeks after pONT (n = 4 each) for non-biased profiling with a high-resolution hybrid quadrupole time-of-flight mass spectrometry running on label-free SWATHTM acquisition (SCIEX). An information-dependent acquisition ion library was generated using ProteinPilot 5.0 and OneOmics cloud bioinformatics. Combined proteome analysis detected 2531 proteins with a false discovery rate of <1%. Compared to the nasal retina, 10, 25 and 61 significantly regulated proteins were found in the temporal retina at 1, 4, and 8 weeks, respectively (p < 0.05, FC ≥ 1.4 or ≤0.7). Eight proteins (ALDH1A1, TRY10, GFAP, HBB-B1, ALB, CDC42, SNCG, NEFL) were differentially expressed for at least two time points. The expressions of ALDH1A1 and SNCG at nerve fibers were decreased along with axonal loss. Increased ALDH1A1 localization in the inner nuclear layer suggested stress response. Increased GFAP expression demonstrated regional reactivity of astrocytes and Muller cells. Meta-analysis of gene ontology showed a pronounced difference in endopeptidase and peptidase inhibitor activity. Temporal proteomic profiling demonstrates established and novel protein targets associated with RGC damage.

Potential role of Lycium barbarum polysaccharides in glaucoma management: evidence from preclinical in vivo studies.

In recent years, the pharmacological benefits of herbal extracts have been revisited for their potential neuroprotective effects in glaucoma. The polysaccharides extracted from the fruits of Lycium barbarum L., or Lycium barbarum polysaccharides, exert their anti-aging effect through reducing oxidative stress, modulating the immune response, enhancing neuronal responses, and promoting cytoprotection. The therapeutic efficacy of Lycium barbarum polysaccharides in preserving retinal ganglion cells and their functions was demonstrated in a range of experimental models of optic neuropathies. These include the acute and chronic ocular hypertension models, the partial optic nerve transection model, and the ischemic-reperfusion injuries model. Based on these findings, Lycium barbarum polysaccharides appear to be a good candidate to be developed as a neuroprotective agent for treating multifactorial diseases. This review aims to present a comprehensive review on the latest preclinical evidence on the pre- and post-treatment benefits of Lycium barbarum polysaccharides in retinal ganglion cell neuroprotection. The possible mechanisms of Lycium barbarum polysaccharides mediating retinal ganglion cell neuroprotection will also be described. Moreover, the potential research gaps in the effective translation of Lycium barbarum polysaccharides treatment into clinical glaucoma management will be discussed.

Retinal Ganglion Cell Death of Guinea Pig is Slower Than Rat as Optic Nerve Transection Animal Model

Retinal Ganglion Cell Death of Guinea Pig is Slower Than Rat as Optic Nerve Transection Animal Model

Longitudinal Observation of Retinal Response to Optic Nerve Transection in Rats Using Visible Light Optical Coherence Tomography.

To characterize rat retinal responses after optic nerve transection (ONT) by visible-light optical coherence tomography (vis-OCT). Unilateral ONT was performed in Brown Norway rats (n = 8). In vivo, vis-OCT retinal imaging was performed on the experimental eyes before ONT (baseline), and two days, one week, two weeks, and four weeks (endpoint) after ONT, as well as on fellow eyes at the endpoint. The system was operated at a 70 kHz A-line sampling rate with both raster scans (512 × 2 × 512 A-lines), and circular scans (2048 × 100 A-lines) acquired around the optic disc. Retinal layers were segmented to calculate layer thicknesses and project en face images for visualization and quantifications. Vessel densities and oxygen saturation were used to evaluate the morphologic and functional impact on the retinal vasculature. After ONT, retinal nerve fiber bundles demonstrated significant degeneration, starting at two weeks, with a reduction of thicknesses quantified on the nerve fiber layer, ganglion cell complex, and total retina. Along with that, the activation of macrophage-like cells in the vitreoretinal interface was also observed. Vessel densities for all three retinal plexuses were unaffected over the period of observation. However, oxygen saturation in retinal arteries and veins was significantly reduced at four weeks after ONT. Vis-OCT can provide high-definition, in vivo characterization of retinal responses to ONT in rats. Despite a significant reduction in retinal layer thickness, this was not accompanied by alterations in vascular density. Despite this, oximetry indicates reduced retinal oxygen saturation, suggesting that altered vascular physiology is not reflected in the anatomic appearance of retinal blood vessel density alone.

Secondary Degeneration of Oligodendrocyte Precursor Cells Occurs as Early as 24 h after Optic Nerve Injury in Rats.

Optic nerve injury causes secondary degeneration, a sequela that spreads damage from the primary injury to adjacent tissue, through mechanisms such as oxidative stress, apoptosis, and blood-brain barrier (BBB) dysfunction. Oligodendrocyte precursor cells (OPCs), a key component of the BBB and oligodendrogenesis, are vulnerable to oxidative deoxyribonucleic acid (DNA) damage by 3 days post-injury. However, it is unclear whether oxidative damage in OPCs occurs earlier at 1 day post-injury, or whether a critical 'window-of-opportunity' exists for therapeutic intervention. Here, a partial optic nerve transection rat model of secondary degeneration was used with immunohistochemistry to assess BBB dysfunction, oxidative stress, and proliferation in OPCs vulnerable to secondary degeneration. At 1 day post-injury, BBB breach and oxidative DNA damage were observed, alongside increased density of DNA-damaged proliferating cells. DNA-damaged cells underwent apoptosis (cleaved caspase3+), and apoptosis was associated with BBB breach. OPCs experienced DNA damage and apoptosis and were the major proliferating cell type with DNA damage. However, the majority of caspase3+ cells were not OPCs. These results provide novel insights into acute secondary degeneration mechanisms in the optic nerve, highlighting the need to consider early oxidative damage to OPCs in therapeutic efforts to limit degeneration following optic nerve injury.

Changes in integrins αv and α5 with Nogo-A in the rat retina after optic nerve injury.

The purpose of this study was to investigate whether integrin levels are associated with axon regeneration after central nervous system (CNS) injury. By using immunohistochemistry, we performed a detailed investigation of the changes in and colocalization of integrins αv and α5, with Nogo-A in the retina after optic nerve injury. We confirmed that integrins αv and α5 were expressed in the rat retina and colocalized with Nogo-A. After optic nerve transection, we found that integrin α5 levels increased over 7 days, but integrin αv levels remained unchanged, while Nogo-A levels increased. It seems that the inhibition of axonal regeneration by the Amino-Nogo-integrin signaling pathway may not occur via changes in integrin levels.

Purified regenerating retinal neurons reveal regulatory role of DNA methylation-mediated Na+/K+-ATPase in murine axon regeneration

While embryonic mammalian central nervous system (CNS) axons readily grow and differentiate, only a minority of fully differentiated mature CNS neurons are able to regenerate injured axons, leading to stunted functional recovery after injury and disease. To delineate DNA methylation changes specifically associated with axon regeneration, we used a Fluorescent-Activated Cell Sorting (FACS)-based methodology in a rat optic nerve transection model to segregate the injured retinal ganglion cells (RGCs) into regenerating and non-regenerating cell populations. Whole-genome DNA methylation profiling of these purified neurons revealed genes and pathways linked to mammalian RGC regeneration. Moreover, whole-methylome sequencing of purified uninjured adult and embryonic RGCs identified embryonic molecular profiles reactivated after injury in mature neurons, and others that correlate specifically with embryonic or adult axon growth, but not both. The results highlight the contribution to both embryonic growth and adult axon regeneration of subunits encoding the Na+/K+-ATPase. In turn, both biochemical and genetic inhibition of the Na+/K+-ATPase pump significantly reduced RGC axon regeneration. These data provide critical molecular insights into mammalian CNS axon regeneration, pinpoint the Na+/K+-ATPase as a key regulator of regeneration of injured mature CNS axons, and suggest that successful regeneration requires, in part, reactivation of embryonic signals.

Assaying Optic Nerve Regeneration in Larval Zebrafish.

Zebrafish have a remarkable capacity for spontaneously regenerating their central nervous system. Larval zebrafish are optically transparent and therefore are widely used to dynamically visualize cellular processes in vivo, such as nerve regeneration. Regeneration of retinal ganglion cell (RGC) axons within the optic nerve has been previously studied in adult zebrafish. In contrast, assays of optic nerve regeneration have previously not been established in larval zebrafish. In order to take advantage of the imaging capabilities in the larval zebrafish model, we recently developed an assay to physically transect RGC axons and monitor optic nerve regeneration in larval zebrafish. We found that RGC axons rapidly and robustly regrow to the optic tectum. Here, we describe the methods for performing the optic nerve transections, as well as methods for visualizing RGC regeneration in larval zebrafish.

Systemic administration of 7,8‐dihydroxyflavone (DHF) after intraorbital optic nerve section in the rat produces neuroprotection of the Brn3a+retinal ganglion cell population

AbstractObjective: To investigate the short‐ and long‐term responses of different retinal ganglion cell (RGC) populations to intraorbital optic nerve transection (IONT) and their protection with systemic administration of 7,8‐dihydroxyflavone (DHF), a potent selective agonist of the tropomyosin related kinase B (TrkB) receptor,Methods: Adult anaesthetized Sprague–Dawley rats received an IONT of their left eye and daily intraperitoneal (ip) injections of vehicle (0.9% NaCl containing 1% DMSO) or of DHF (5 mg/kg in the same vehicle). One group of animals was used to investigate long term protection of DHF and was processed 7, 10, 14, 21, 30 or 60 days (n = 8 for each survival interval) after the lesion. Another group of animals was used to investigate the responses of different RGC types to DHF treatment and was processed 7, 14 or 21 days (n = 5–8 for each survival interval) after the lesion. The retinas were prepared as wholemounts and immunolabelled for Brn3a, melanopsin (m), Osteopontin (OPN) and the T‐box transcription factor T‐brain‐2 (Tbr2) to identify the following retinal ganglion cells (RGCs) populations: Brn3a+, melanopsin+, α‐ like (OPN+), α‐OFF like (OPN+Brn3a+) and M4‐like/α‐ON sustained RGCs (OPN+Tbr2+). The labelled RGCs were quantified automatically (Brn3a) or dotted manually and quantified with a graphic software, and distribution of the different populations represented on topographical logical maps.Results: IONT resulted in the loss of 83% or 59% of the Brn3a+ or m+RGC population, respectively, 14 days after vehicle treatment. The Brn3a+RGCs further diminished an additional 9% from 14 to 60 days whereas m+RGCs did not, thus at 60 days the proportion of surviving m+RGCs was almost five times greater than Brn3a+RGCs, thus showing greater resistance to IONT. Systemic administration of DHF resulted in prevention of Brn3a+RGCs loss during 21 days and permanent protection of m+RGCs. Different RGC populations showed different losses. In vehicle treated rats, IONT resulted in the rapid and massive loss of all OPN+Brn3a+RGCS, progressive and massive loss of Brn3a+RGCs and large but not progressive loss of OPN+RGCs or OPN+Tbr2+RGCs, indicating a certain resistance of the later types to IONT. DHF treatment resulted in significant prevention of the IONT‐induced loss of Brn3a+, OPN+ and OPN+‐Tbr2+ RGCs, but not of the OPN+‐Brn3a+.Conclusions: Our in vivo studies on adult rats document that IONT and vehicle treatment results in characteristic patterns of loss of the different types of RGCs including Brn3a, melanopsin, alpha and alpha‐ON sustained RGCs, although melanopsin, alpha and alpha‐ON sustained RGCs show certain resistance to the injury. DHF treatment affords in vivo protection of axotomized RGCs that lasts 21 days for the Brn3a+, m+, alpha and alpha‐ON sustained, but not for alpha‐OFF RGCs, which were not responsive to treatment.

Do all retinal ganglion cells respond similarly to injury and protection?

AbstractObjectives: To investigate the responses of different retinal ganglion cell (RGC) populations to diverse injuries and protection with selective agonists of the tropomyosin related kinase B (TrkB) receptor, brain‐derived neurotrophic factor (BDNF) or 7,8‐dihydroxyflavone (DHF).Methods: Adult Sprague–Dawley rats were used. A first group had their left eye connected to a saline reservoir elevated 1.5 meters above the eye to produce an acute ocular hypertension (AOH) and induce transient ischemia for 75 minutes, these were analysed at 3, 7, 14 or 45 days (d) (n = 9–14 for each survival interval). A second group received an intraocular injection of 100 mM N‐methyl‐D‐aspartate (NMDA) to induce retinal excitotoxicity and was analysed at 3, 7, 14d or 15 months (n = 7–11 for each survival interval). A third group received a left intraorbital optic nerve transection (IONT) to induce axotomy of the RGC population, these were analysed at 7, 10, 14, 21, 30 or 60d (n = 8 for each survival interval). The first group of rats received right after AOH a single intravitreal injection of 5 μl vehicle (1% Albumin in PBS) or 5 μg BDNF. Rats of the third group were treated daily with an intraperitoneal injection of vehicle (0.9% NaCl containing 1% DMSO) or DHF (5 mg/kg diluted in vehicle), while rats of the second group were untreated. The retinas were prepared as wholemounts and immunolabelled with Brn3a and melanopsin (m) antibodies to identify Brn3a+RGCs and m+RGCs, respectively. Wholemount image reconstructions were photographed; labelled RGCs were quantified and their distribution evaluated with isodensity or neighbour maps.Results: AOH with vehicle treatment results in rapid progressive loss of Brn3a+RGCs and in significant but not progressive loss of m+RGCs; BDNF treatment afforded significant prevention which was long‐lasting for both RGC populations. Intravitreal NMDA resulted at 7d in the abrupt loss of 74% of the Brn3a+RGC population but it did not progress further. The m+RGC population showed a significant diminution by 3d that recovered to control values by 7d and did not vary thereafter. IONT with vehicle treatment resulted in typical losses of RGCs that by 14d amounted to 80% or 64% of the Brn3a+ or m+RGC population, respectively. Brn3a+RGCs further decreased up to 60d whereas m+RGCs did not, so that the proportion of surviving m+RGCs was ≈five times that of Brn3a+RGCs, further showing their resilience to IONT. Systemic administration of DHF prevented Brn3a+RGC losses up to 21d while for m+RGCs such prevention was permanent.Conclusions: Our studies document that: (i) AOH induces progressive loss of Brn3a+RGCs but not of m+RGCs, and both populations respond to TrkB‐mediated protection; (ii) NMDA induced excitotoxicity results in rapid loss of Brn3a+RGCs, whereas m+RGCs survived for up to 15 months later; (iii) IONT and vehicle treatment result in characteristic rapid loss of Brn3a and melanopsin RGCs, whereas DHF treatment affords protection of axotomized RGCs. This protection is maximal at 7d and significant until 21d for Brn3a+RGCs, whereas for m+RGCs the protection was significant at 14d and permanent. Thus, two different RGC populations (Brn3a+ and m+) respond distinctly to injury and TrkB‐mediated protection.

Long-term efficacy of enucleation combined with primary orbital implantation in children with retinoblastoma histopathological invasion of optic nerve.

ObjectiveThis study aimed to observe the long-term effect of enucleation combined with primary orbital implantation in children with histopathologic optic nerve invasive retinoblastoma (RB).MethodsWe retrospectively analyzed the clinical data and outcomes of children with RB optic nerve invasion confirmed by histopathology who underwent enucleation combined with primary orbital implantation between March 2010 and April 2014 in Beijing Tongren Hospital. The follow-up time ranged from 81 to 129 months, with a mean follow-up of 96 ± 14 months.ResultsA total of 59 children were included in this study. There were 32 males and 27 females; 52 children were affected in one eye and seven children in both eyes. The time from onset of symptoms to visit was between 3 days and 16 months, with a mean of 2.2 ± 2.8 months. The age at the of surgery was between 2 and 65 months, with an average of 24 ± 13 months. Patients were classified based on the degree of optic nerve invasion into four grades: grade 1 (invasion of prelaminar) in 28 cases, grade 2 (invasion of laminar) in 14 cases, grade 3 (invasion of retrolaminar but not reaching the optic nerve transection) in 16 cases, and grade 4 (invasion of the optic nerve transection) in 1 case. Post-operatively, all children were treated with 0–9 cycles of intravenous chemotherapy based on histopathology results from the removed eye. Of the 59 children, 13 had postoperative complications, and one died from recurrence. The survival rate was 98% (58/59). There was one case of orbital implant exposure, one of orbital cellulitis, six of enophthalmos and superior sulcus deformity, two of blepharoptosis, one of granuloma complicated with blepharoptosis, and one with a subconjunctival cyst.ConclusionFor children with RB histopathologic invasion of the optic nerve, enucleation combined with primary orbital implantation reveals future potential treatment options when combined with a full course of intravenous chemotherapy.

Intraorbital self-inflating hydrogel expander implantation with a modified technique in congenital microphthalmia

PurposeTo investigate the long-term outcomes of intraorbital self-inflating hydrogel expander implantation with optic nerve transection in children with congenital microphthalmia. MethodsThe medical records of unilaterally blind microphthalmic pediatric patients undergoing intraconal hydrogel expander implantation with optic nerve transection were reviewed retrospectively. For each patient, the microphthalmic eye was preserved. The orbital volume and globe volume were measured and analyzed based on computed tomography scans taken preoperatively and 36 months postoperatively. The palpebral length was measured between the medial and lateral canthus at every follow-up. Surgical complications were also recorded. ResultsTwelve patients were included (median age, 44.25 ± 17.5 months). At 36 months postoperatively, the microphthalmic and contralateral orbital volumes increased by 3.07 ± 0.77 ml and 2.03 ± 0.67 ml, respectively. The mean microphthalmic/contralateral ratio (MCR) of the orbital volume increased significantly from 76.60% ± 5.46% to 83.81% ± 5.41% (P < 0.001). The microphthalmic palpebral length increased by 6.17 ± 1.85 mm, whereas the contralateral palpebral length increased by 2.67 ± 1.44 mm. Significant changes were observed in the palpebral length MCR (68.00% ± 4.83% vs 85.07% ± 3.87%; P < 0.001). There was no significant change in the microphthalmic globe volume at 36 months postoperatively (P = 0.215). For the fellow eye, the globe volume increased significantly by 0.53 ± 0.34 ml (P < 0.001). During the follow-up period, 2 patients developed a sunken prosthesis. One patient had difficulty opening the eye after wearing the conformer. There were no cases of expander rejection or extrusion. ConclusionsIn this small cohort of patients with congenital microphthalmia, intraorbital self-expanding hydrogel expander implantation with optic nerve transection led to excellent osseous and eyelid growth throughout the 36-month follow-up period.