Indirect traumatic optic neuropathy

Investigation of the effects of Gamma Knife radiosurgery on optic pathways using diffusion tensor MRI within the first year after treatment

PURPOSE

To investigate the radiation-induced effects of Gamma Knife radiosurgery (GKRS) for sellar-parasellar tumors on optic pathways using DTI parameters within the first year after treatment.

METHODS

Twenty-five patients with sellar-parasellar tumors underwent MRI before and 3 months after GKRS, including T1WI, DTI, T2WI. Moreover, 21 patients underwent follow-up DTI 6-8 months after radiosurgery. ROIs were set on optic nerves, optic radiations, and control localizations; DTI parameters for each were calculated. Pre- and post-radiosurgery differences in DTI values were statistically compared and assessed with respect to tumor size changes.

RESULTS

Following GKRS, DTI parameters, notably ADC, FA, and RD, showed statistically significant changes in optic nerves and anterior optic radiations. DTI changes were more significant in the group of cases with tumor shrinkage. In this group, DTI of the anterior optic radiations further deteriorated 3 months post-GKRS, whereas acute changes in DTI parameters of the optic nerves resolved within 6-8 months. DTI of central and posterior optic radiations did not differ significantly following radiosurgery; 6-8 months after radiosurgery, visual function was stable in 14 (56%) patients and improved in 11 (44%), showing no correlation with tumor size changes or DTI parameters.

CONCLUSION

White Matter (WM) injury in the optic pathways can be induced by Gamma Knife radiosurgery targeted to sellar and parasellar tumors. Following GKRS, microstructural abnormalities occurred in the optic radiations as well as the optic nerves within the first post-treatment year. Our findings could support modifications to radiosurgical treatment strategies to minimize the risk of permanent WM injury.

Appropriate patient population for future visual system axon regeneration therapies

A number of blinding diseases caused by damage to the optic nerve result in progressive vision loss or loss of visual acuity. Secondary glaucoma results from traumatic injuries, pseudoexfoliation or pigmentary dispersion syndrome. Progressive peripheral vision loss is common to all secondary glaucoma irrespective of the initial event. Axon regeneration is a potential therapeutic avenue to restore lost vision in these patients. In contrast to the usual approach of having the worst possible patient population for initial therapies, axon regeneration may require consideration of appropriate patient population even for initial treatment trials. The current state of axon regeneration therapies, their potential future and suitable patient population when ready is discussed in this perspective. The selection of patients are important for adoption of axon regeneration specifically in the areas of central nervous system regenerative medicine. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology Neurological Diseases > Biomedical Engineering Metabolic Diseases > Molecular and Cellular Physiology.

Diffusion basis spectrum imaging detects subclinical traumatic optic neuropathy in a closed-head impact mouse model of traumatic brain injury

Introduction

Traumatic optic neuropathy (TON) is the optic nerve injury secondary to brain trauma leading to visual impairment and vision loss. Current clinical visual function assessments often fail to detect TON due to slow disease progression and clinically silent lesions resulting in potentially delayed or missed treatment in patients with traumatic brain injury (TBI).

Methods

Diffusion basis spectrum imaging (DBSI) is a novel imaging modality that can potentially fill this diagnostic gap. Twenty-two, 16-week-old, male mice were equally divided into a sham or TBI (induced by moderate Closed-Head Impact Model of Engineered Rotational Acceleration device) group. Briefly, mice were anesthetized with isoflurane (5% for 2.5 min followed by 2.5% maintenance during injury induction), had a helmet placed over the head, and were placed in a holder prior to a 2.1-joule impact. Serial visual acuity (VA) assessments, using the Virtual Optometry System, and DBSI scans were performed in both groups of mice. Immunohistochemistry (IHC) and histological analysis of optic nerves was also performed after in vivo MRI.

Results

VA of the TBI mice showed unilateral or bilateral impairment. DBSI of the optic nerves exhibited bilateral involvement. IHC results of the optic nerves revealed axonal loss, myelin injury, axonal injury, and increased cellularity in the optic nerves of the TBI mice. Increased DBSI axon volume, decreased DBSI λ||, and elevated DBSI restricted fraction correlated with decreased SMI-312, decreased SMI-31, and increased DAPI density, respectively, suggesting that DBSI can detect coexisting pathologies in the optic nerves of TBI mice.

Conclusion

DBSI provides an imaging modality capable of detecting subclinical changes of indirect TON in TBI mice.

Visual-evoked potential predicts the efficacy of the optical canal decompression for traumatic optic nerve neuropathy showing blindness: A case report

Background

The indication for surgical optic canal decompression (OCD) for traumatic optic neuropathy (TON) remains controversial because there is no reliable predictor of a good outcome. We report the case of a blind patient with TON whose remaining visual-evoked potential (VEP) suggested recovery potential of the injured optic nerve after OCD.

Case Description

A 48-year-old man had fallen from a height of 7 m, striking his head. He immediately complained of right-eye blindness. He had no light perception and the direct light reflex disappeared from the right pupil, although there was no fracture or traumatic lesion on computed tomography and magnetic resonance imaging. Because the amplitude of the VEP with the right eye stimulation remained unchanged, we performed the right OCD. During surgical OCD, the amplitude and latency of VEP began to improve. Finally, the visual field improved in almost all directions, and eyesight improved to 0.2.

Conclusion

The retained VEP activity in TON may suggest the recovery potential of the injured optic nerve, even in cases of blindness. It is possible that VEP is an indicator of aggressive treatment for TON such as OCD.

Human amnionic progenitor cell secretome mitigates the consequence of traumatic optic neuropathy in a mouse model

Traumatic optic neuropathy (TON) is a condition in which acute injury to the optic nerve from direct or indirect trauma results in vision loss. The most common cause of TON is indirect injury to the optic nerve caused by concussive forces that are transmitted to the optic nerve. TON occurs in up to 5% of closed-head trauma patients and there is currently no known effective treatment. One potential treatment option for TON is ST266, a cell-free biological solution containing the secretome of amnion-derived multipotent progenitor (AMP) cells. We investigated the efficacy of intranasal ST266 in a mouse model of TON induced by blunt head trauma. Injured mice treated with a 10-day regimen of ST266 showed an improvement in spatial memory and learning, a significant preservation of retinal ganglion cells, and a decrease in neuropathological markers in the optic nerve, optic tract, and dorsal lateral geniculate nucleus. ST266 treatment effectively downregulated the NLRP3 inflammasome-mediated neuroinflammation pathway after blunt trauma. Overall, treatment with ST266 was shown to improve functional and pathological outcomes in a mouse model of TON, warranting future exploration of ST266 as a cell-free therapeutic candidate for testing in all optic neuropathies.

A hypothermia mimetic molecule (zr17-2) reduces ganglion cell death and electroretinogram distortion in a rat model of intraorbital optic nerve crush (IONC)

Introduction: Ocular and periocular traumatisms may result in loss of vision. Our previous work showed that therapeutic hypothermia prevents retinal damage caused by traumatic neuropathy. We also generated and characterized small molecules that elicit the beneficial effects of hypothermia at normal body temperature. Here we investigate whether one of these mimetic molecules, zr17-2, is able to preserve the function of eyes exposed to trauma. Methods: Intraorbital optic nerve crush (IONC) or sham manipulation was applied to Sprague-Dawley rats. One hour after surgery, 5.0 µl of 330 nmol/L zr17-2 or PBS, as vehicle, were injected in the vitreum of treated animals. Electroretinograms were performed 21 days after surgery and a- and b-wave amplitude, as well as oscillatory potentials (OP), were calculated. Some animals were sacrificed 6 days after surgery for TUNEL analysis. All animal experiments were approved by the local ethics board. Results: Our previous studies showed that zr17-2 does not cross the blood-ocular barrier, thus preventing systemic treatment. Here we show that intravitreal injection of zr17-2 results in a very significant prevention of retinal damage, providing preclinical support for its pharmacological use in ocular conditions. As previously reported, IONC resulted in a drastic reduction in the amplitude of the b-wave (p < 0.0001) and OPs (p < 0.05), a large decrease in the number of RGCs (p < 0.0001), and a large increase in the number of apoptotic cells in the GCL and the INL (p < 0.0001). Interestingly, injection of zr17-2 largely prevented all these parameters, in a very similar pattern to that elicited by therapeutic hypothermia. The small molecule was also able to reduce oxidative stress-induced retinal cell death in vitro. Discussion: In summary, we have shown that intravitreal injection of the hypothermia mimetic, zr17-2, significantly reduces the morphological and electrophysiological consequences of ocular traumatism and may represent a new treatment option for this cause of visual loss.

Mitochondrial Triglyceride Dysregulation in Optic Nerves Following Indirect Traumatic Optic Neuropathy

The purpose of this work is to identify mitochondrial optic nerve (ON) lipid alterations associated with sonication-induced traumatic optic neuropathy (TON). Briefly, a mouse model of indirect TON was generated using sound energy concentrated focally at the entrance of the optic canal using a laboratory sonifier (Branson Digital Sonifier 450, Danbury, CT, USA) with a microtip probe. We performed an analysis of a previously generated dataset from high-performance liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS). We analyzed lipids from isolated mitochondria from the ON at 1 day, 7 days, and 14 days post-sonication compared to non-sonicated controls. Lipid abundance alterations in post-sonicated ON mitochondria were evaluated with 1-way ANOVA (FDR-adjusted significant p-value < 0.01), debiased sparse partial correlation (DSPC) network modeling, and partial least squares-discriminant analysis (PLS-DA). We find temporal alterations in triglyceride metabolism are observed in ON mitochondria of mice following sonication-induced optic neuropathy with notable depletions of TG(18:1/18:2/18:2), TG(18:1/18:1/18:1), and TG(16:0/16:0/18:1). Depletion of mitochondrial triglycerides may mediate ON damage in indirect traumatic optic neuropathy through loss energy substrates for neuronal metabolism.

Resting-state functional MRI of the visual system for characterization of optic neuropathy

Optic neuropathy refers to disease of the optic nerve and can result in loss of visual acuity and/or visual field defects. Combining findings from multiple fMRI modalities can offer valuable information for characterizing and managing optic neuropathies. In this article, we review a subset of resting-state functional magnetic resonance imaging (RS-fMRI) studies of optic neuropathies. We consider glaucoma, acute optic neuritis (ON), discuss traumatic optic neuropathy (TON), and explore consistency between findings from RS and visually driven fMRI studies. Consistent with visually driven studies, glaucoma studies at rest also indicated reduced activation in the visual cortex and dorsal visual stream. RS-fMRI further reported varying levels of functional connectivity in the ventral stream depending on disease severity. ON patients show alterations within the visual cortex in both fMRI techniques. Particularly, higher-than-normal RS activity is observed in the acute phase and decreases as the disease progresses. A similar pattern is observed in the visual cortex of TON-like, open globe injury (OGI), patients. Additionally, visually driven and RS-fMRI studies of ON patients show recovery of brain activity in the visual cortex. RS-fMRI suggests recovery of signals in higher-tier visual areas MT and LOC as well. Finally, RS-fMRI has not yet been applied to TON, although reviewing OGI studies suggests that it is feasible. Future RS-fMRI studies of optic neuropathies could prioritize studying the fine scale RS activity of brain areas that visually driven studies have identified. We suggest that a more systematic longitudinal comparison of optic neuropathies with advanced fMRI would provide improved diagnostic and prognostic information.

Analysis of retinal vasculature changes in indirect traumatic optic neuropathy using optic coherence tomography angiography

AIM

To assess the retinal vasculature alterations in indirect traumatic optic neuropathy (ITON) patients following craniofacial trauma by optic coherence tomography angiography (OCTA).

METHODS

Patients diagnosed of monocular ITON were recruited from August 2016 to May 2020. OCTA was performed using the AngioVue OCT-A system for two cube scans centered at the optic nerve head and fovea. OCTA data included thicknesses of peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC), as well as proportion of capillary perfusion and data were analyzed for correlation with post-injury timepoints: within 7, 8-30, 31-90, and 91-365d.

RESULTS

A total of 73 ITON patients were studied. Significant thinning of RNFL and GCC layers and attenuation of microvascular perfusion were observed in ITON eyes as compared to contralateral unaffected eyes (for most of the analyzed sectors and quadrants, P<0.05). Without respect to surgical intervention and vision recovery, the decrease in retinal layer thicknesses and microvascular perfusion was time-dependent, and most significant within three months (P<0.001).

CONCLUSION

ITON presents with time-dependent thinning of retinal layers and attenuation of microvasculature, indicating possible degeneration of retinal ganglion cells due to reduced retinal blood supply.

[Optic nerve decompression-state of the art]

Rarely, but often with serious consequences for the patient, the optic nerve is affected during the course of head injuries. Traumatic optic nerve compression is always an emergency situation, which is why time is of the essence for both diagnosis and treatment. Precise knowledge of this accident sequelae but also of the resulting conditions, especially in terms of traumatic optic neuropathy, is indispensable for adequate patient care. The aim of this paper is to provide an overview of this clinical picture, particularly with regard to etiology, diagnosis, and treatment options, and to discuss this in the context of the current literature.

Traumatic optic neuropathy: a review of current studies

Traumatic optic neuropathy (TON) is a serious complication of craniofacial trauma that directly or indirectly damages the optic nerve and can cause severe vision loss. The incidence of TON has been gradually increasing in recent years. Research on the protection and regeneration of the optic nerve after the onset of TON is still at the level of laboratory studies and which is insufficient to support clinical treatment of TON. And, due to without clear guidelines, there is much ambiguity regarding its diagnosis and management. Clinical interventions for TON include observation only, treatment with corticosteroids alone, or optic canal (OC) decompression (with or without steroids). There is controversy in clinical practice concerning which treatment is the best. A review of available studies shows that the visual acuity of patients with TON can be significantly improved after OC decompression surgery (especially endoscopic transnasal/transseptal optic canal decompression (ETOCD)) with or without the use of corticosteroids. And new findings of laboratory studies such as mitochondrial therapy, lipid change studies, and other studies in favor of TON therapy have also been identified. In this review, we discuss the evolving perspective of surgical treatment and experimental study.

Cold protection allows local cryotherapy in a clinical-relevant model of traumatic optic neuropathy

Therapeutic hypothermia (TH) is potentially an important therapy for central nervous system (CNS) trauma. However, its clinical application remains controversial, hampered by two major factors: (1) Many of the CNS injury sites, such as the optic nerve (ON), are deeply buried, preventing access for local TH. The alternative is to apply TH systemically, which significantly limits the applicable temperature range. (2) Even with possible access for 'local refrigeration', cold-induced cellular damage offsets the benefit of TH. Here we present a clinically translatable model of traumatic optic neuropathy (TON) by applying clinical trans-nasal endoscopic surgery to goats and non-human primates. This model faithfully recapitulates clinical features of TON such as the injury site (pre-chiasmatic ON), the spatiotemporal pattern of neural degeneration, and the accessibility of local treatments with large operating space. We also developed a computer program to simplify the endoscopic procedure and expand this model to other large animal species. Moreover, applying a cold-protective treatment, inspired by our previous hibernation research, enables us to deliver deep hypothermia (4 °C) locally to mitigate inflammation and metabolic stress (indicated by the transcriptomic changes after injury) without cold-induced cellular damage, and confers prominent neuroprotection both structurally and functionally. Intriguingly, neither treatment alone was effective, demonstrating that in situ deep hypothermia combined with cold protection constitutes a breakthrough for TH as a therapy for TON and other CNS traumas.

From Provider to Advocate: The Complexities of Traumatic Brain Injury Prompt the Evolution of Provider Engagement

Treating a patient with traumatic brain injury requires an interdisciplinary approach because of the pervasive, profound and protean manifestations of this condition. In this review, key aspects of the medical history and review of systems will be described in order to highlight how the role of any provider must evolve to become a better patient advocate. Although this review is written from the vantage point of a vision care provider, it is hoped that patients, caregivers and providers will recognize the need for a team approach.

Axonopathy precedes cell death in ocular damage mediated by blast exposure

Traumatic brain injuries (TBI) of varied types are common across all populations and can cause visual problems. For military personnel in combat settings, injuries from blast exposures (bTBI) are prevalent and arise from a myriad of different situations. To model these diverse conditions, we are one of several groups modeling bTBI using mice in varying ways. Here, we report a refined analysis of retinal ganglion cell (RGC) damage in male C57BL/6J mice exposed to a blast-wave in an enclosed chamber. Ganglion cell layer thickness, RGC density (BRN3A and RBPMS immunoreactivity), cellular density of ganglion cell layer (hematoxylin and eosin staining), and axon numbers (paraphenylenediamine staining) were quantified at timepoints ranging from 1 to 17-weeks. RNA sequencing was performed at 1-week and 5-weeks post-injury. Earliest indices of damage, evident by 1-week post-injury, are a loss of RGC marker expression, damage to RGC axons, and increase in glial markers expression. Blast exposure caused a loss of RGC somas and axons—with greatest loss occurring by 5-weeks post-injury. While indices of glial involvement are prominent early, they quickly subside as RGCs are lost. The finding that axonopathy precedes soma loss resembles pathology observed in mouse models of glaucoma, suggesting similar mechanisms.

Blast mild traumatic brain injury is associated with increased myopia and chronic convergence insufficiency

While chronic visual symptom complaints are common among Veterans with a history of mild traumatic brain injury (mTBI), research is still ongoing to characterize the pattern of visual deficits that is most strongly associated with mTBI and specifically, the impact of blast-related mTBI on visual functioning. One area that has not been well explored is the potential impact of blast mTBI on refractive error. While myopic shifts have been documented following head injuries in civilian populations, posttraumatic myopic shifts have not been explored in participants with military mTBI. This study investigated the impact of blast mTBIs on a range of visual function measures including distance acuity and refractive error, in a well-characterized cohort of thirty-one Post-9/11 veterans for whom detailed clinical interviews regarding military and TBI history were available. Seventeen participants had a history of blast-related mTBI (blast mTBI + group) while 14 did not (blast mTBI- group). Results show an increased frequency of convergence insufficiency and myopia in the blast mTBI + group relative to the blast mTBI- group. Linear regression analyses further show that deficits in distance acuity and refractive error are associated with the number of blast mTBIs during military service but not the number of non-blast mTBIs or the number of lifetime non-blast TBIs and cannot be accounted for by PTSD. These results are consistent with long-lasting damage following blast mTBI to subcortical visual structures that support both vergence movements and the accommodative functions needed to see clearly objects at varying distances.

Traumatic Optic Neuropathy Is Associated with Visual Impairment, Neurodegeneration, and Endoplasmic Reticulum Stress in Adolescent Mice

Traumatic brain injury (TBI) results in a number of impairments, often including visual symptoms. In some cases, visual impairments after head trauma are mediated by traumatic injury to the optic nerve, termed traumatic optic neuropathy (TON), which has few effective options for treatment. Using a murine closed-head weight-drop model of head trauma, we previously reported in adult mice that there is relatively selective injury to the optic tract and thalamic/brainstem projections of the visual system. In the current study, we performed blunt head trauma on adolescent C57BL/6 mice and investigated visual impairment in the primary visual system, now including the retina and using behavioral and histologic methods at new time points. After injury, mice displayed evidence of decreased optomotor responses illustrated by decreased optokinetic nystagmus. There did not appear to be a significant change in circadian locomotor behavior patterns, although there was an overall decrease in locomotor behavior in mice with head injury. There was evidence of axonal degeneration of optic nerve fibers with associated retinal ganglion cell death. There was also evidence of astrogliosis and microgliosis in major central targets of optic nerve projections. Further, there was elevated expression of endoplasmic reticulum (ER) stress markers in retinas of injured mice. Visual impairment, histologic markers of gliosis and neurodegeneration, and elevated ER stress marker expression persisted for at least 30 days after injury. The current results extend our previous findings in adult mice into adolescent mice, provide direct evidence of retinal ganglion cell injury after head trauma and suggest that axonal degeneration is associated with elevated ER stress in this model of TON.

The Role of the Flash Visual Evoked Potential in Evaluating Visual Function in Patients with Indirect Traumatic Optic Neuropathy

Purpose

To assess the value of the flash visual evoked potential (FVEP) in determining final visual prognosis in patients with indirect traumatic optic neuropathy (TON).

Subjects and Methods

We included 30 patients diagnosed with indirect TON. Within one week of the onset of the trauma, visual acuity was recorded, pupillary reactions were assessed, FVEP was performed in both eyes. The amplitudes (N1p1 and N2P2) and the latency of P2 for each eye were recorded and amplitude ratio of N2P2 between the affected and normal eye was calculated. In follow-up visits, the cases underwent a complete ophthalmic examination, assessment of visual acuity, pupillary reaction, and FVEP.

Results

The study included 22 males (73.3%) and 8 females (26.7%). The right eye was involved in 16 patients (53.3%) and left eye was involved in 14 cases (46.7%). According to the findings of FVEP, there was a direct correlation between final visual acuity and initial amplitude of N1p1 and N2P2 and negative correlation with latency of P2 wave. In 20 patients in whom the N1P1 and N2P2 amplitude was within the normal range and amplitude ratio of N2P2 of normal and fellow eye was at least 0.5 and the P2 implicit time was less than 140 ms, they achieved better visual outcome and visual acuity improved in the affected eye. In other 10 patients in whom the N1P1 and N2P2 amplitude was below normal range and the N2P2 amplitude ratio between the normal and the affected eye was less than 0.5 and the P2 implicit time was more than 140 ms, the visual acuity in the affected eye was less than 0.01 and these patients achieved less or no improvement in their visual function.

Conclusion

Cases with TON usually present with severe loss of vision. FVEP is highly predictive of final visual outcome in patients having indirect TON given that the other eye is normal to be used as the patients’ internal control. More studies are needed to confirm these results.

Exosome-Mediated Delivery of the Neuroprotective Peptide PACAP38 Promotes Retinal Ganglion Cell Survival and Axon Regeneration in Rats With Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) refers to optic nerve damage caused by trauma, leading to partial or complete loss of vision. The primary treatment options, such as hormonal therapy and surgery, have limited efficacy. Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38), a functional endogenous neuroprotective peptide, has emerged as a promising therapeutic agent. In this study, we used rat retinal ganglion cell (RGC) exosomes as nanosized vesicles for the delivery of PACAP38 loaded via the exosomal anchor peptide CP05 (EXO_PACAP38). EXO_PACAP38 showed greater uptake efficiency in vitro and in vivo than PACAP38. The results showed that EXO_PACAP38 significantly enhanced the RGC survival rate and retinal nerve fiber layer thickness in a rat TON model. Moreover, EXO_PACAP38 significantly promoted axon regeneration and optic nerve function after injury. These findings indicate that EXO_PACAP38 can be used as a treatment option and may have therapeutic implications for patients with TON.

The Relationship Between Severe Visual Acuity Loss, Traumatic Brain Injuries, and Ocular Injuries in American Service Members From 2001 to 2015

INTRODUCTION

Although traumatic brain injury (TBI) is known to cause many visual problems, the correlation between the extent of severe visual acuity loss (SVAL) and severity of TBI has not been widely explored. In this retrospective analysis, combined information from Department of Defense (DoD)/Veterans Affairs ocular injury and TBI repositories were used to evaluate the relationship between chronic SVAL, TBI, ocular injuries, and associated ocular sequelae for U.S. service members serving between 2001 and 2015.

MATERIALS AND METHODS

The Defense and Veterans Eye Injury and Vision Registry (DVEIVR) is an initiative led by the DoD and Veterans Affairs that consists of clinical and related data for service members serving in theater since 2001. The Defense and Veterans Brain Injury Center (DVBIC) is the DoD's office for tracking TBI data in the military and maintains data on active-duty service members with a TBI diagnosis since 2000. Longitudinal data from these 2 resources for encounters between February 2001 and October 2015 were analyzed to understand the relation between SVAL, and TBI while adjusting for ocular covariates such as open globe injury (OGI), disorders of the anterior segment and disorders of the posterior segment in a logistic regression model. TBI cases in DVEIVR were identified using DVBIC data and classified according to International Statistical Classification of Diseases criteria established by DVBIC. Head trauma and other open head wounds (OOHW) were also included. SVAL cases in DVEIVR were identified using both International Statistical Classification of Diseases criteria for blindness and low vision as well as visual acuity test data recorded in DVEIVR.

RESULTS

Data for a total of 25,193 unique patients with 88,996 encounters were recorded in DVEIVR from February, 2001 to November, 2015. Of these, 7,217 TBI and 1,367 low vision cases were identified, with 638 patients experiencing both. In a full logistic model, neither UTBI nor differentiated TBI (DTBI, ie, mild, moderate, severe, penetrating, or unclassified) were significant risk factors for SVAL although ocular injuries (disorders of the anterior segment, disorders of the posterior segment, and OGI) and OOHW were significant.

CONCLUSION

Any direct injury to the eye or head risks SVAL but the location and severity will modify that risk. After adjusting for OGIs, OOHW and their sequelae, TBI was found to not be a significant risk factor for SVAL in patients recorded in DVEIVR. Further research is needed to explore whether TBI is associated with more moderate levels of vision acuity loss.

A Systematic Literature Review on Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) is an uncommon vision-threatening disorder that can be caused by ocular or head trauma and is categorized into direct and indirect TON. The overall incidence of TON is 0.7–2.5%, and indirect TON has a higher prevalence than direct TON. Detection of an afferent pupillary defect in the presence of an intact globe in a patient with ocular or head trauma with decreased visual acuity strongly suggests TON. However, afferent pupillary defects may be difficult to detect in patients who have received narcotics that cause pupillary constriction and in those with bilateral TON. Mechanical shearing of the optic nerve axons and contusion necrosis due to immediate ischemia from damage to the optic nerve microcirculation and apoptosis of neurons is a probable mechanism. The proper management of TON is controversial. High-dose corticosteroid therapy and decompression of the optic nerve provide no additional benefit over observation alone. Intravenous erythropoietin may be a safe and efficient treatment for patients with TON.

Microsphere antioxidant and sustained erythropoietin-R76E release functions cooperate to reduce traumatic optic neuropathy

Wild-type erythropoietin (EPO) is promising for neuroprotection, but its therapeutic use is limited because it causes a systemic rise in hematocrit. We have developed an EPO-R76E derivative that maintains neuroprotective function without effects on hematocrit, but this protein has a short half-life in vivo. Here, we compare the efficacy and carrier-induced inflammatory response of two polymeric microparticle (MP) EPO-R76E sustained release formulations based on conventional hydrolytically degradable poly(lactic-co-glycolic acid) (PLGA) and reactive oxygen species (ROS)-degradable poly(propylene sulfide) (PPS). Both MP types effectively loaded EPO-R76E and achieved sustained release, providing detectable levels of EPO-R76E at the injection site in the eye in vivo for at least 28 days. Testing in an in vitro oxidative stress assay and a mouse model of blast-induced indirect traumatic optic neuropathy (bITON) showed that PPS and PLGA MP-mediated delivery of EPO-R76E provided therapeutic protection. While unloaded PLGA MPs inherently increase levels of pro-inflammatory cytokines in the bITON model, drug-free PPS MPs have innate antioxidant properties that provide therapeutic benefit both in vitro and in vivo. Both PLGA and PPS MPs enabled sustained release of EPO-R76E, providing therapeutic benefits including reduction in inflammation and axon degeneration, and preservation of visual function as measured by electroretinogram. The PPS-based MP platform is especially promising for further development, as the delivery system provides inherent antioxidant benefits that can be harnessed to work in complement with EPO-R76E or other drugs for neuroprotection in the setting of traumatic eye injury.

Reversal of vision loss after traumatic optic neuropathy

Traumatic optic neuropathy is sinister sequelae of craniofacial trauma leading to vision loss. The decision between early medical or surgical intervention is usually individualised. Visual evoked potentials may guide the treatment plan. We describe a young male presenting 5 days after a road traffic accident with no perception of light vision in the right eye. He was managed medically with high dose of intravenous steroids. At the 3-month follow-up, he reported a reversal of vision loss with return of visual acuity to 3/60, which improved to 6/36 at 5 months and remained stable at 8 months.

Diffusion tensor magnetic resonance imaging of optic pathway in cases of suprasellar masses

Background

Diffusion tensor imaging (DTI) is a novel MRI technique which can provide information of the compressed tissue’s microstructural properties. The evaluation of visual function is important for the clinical management of patients with suprasellar mass lesion. Compression of the optic nerve and chiasm due to pituitary mass lesions often leads to impaired visual function. The evaluation and prognosis of visual function are important for patient management. The aim of this work is to evaluate the feasibility of DTI in the evaluation of the optic pathway in patients with suprasellar masses. Fifty patients were included in the study, 24 cases with suprasellar masses and 26 cases without suprasellar masses as a control group. All patients underwent detailed history taking, MRI of the sella with coronal and sagittal T1, and coronal T2 sequences and DTI. The region of interests (ROIs) were set on the optic chiasm as well as the anterior and posterior optic tracts. For each ROI, axial diffusivity (AD), radial diffusivity (RD), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) values were calculated. DTI parameters of cases group were compared with normal control group parameters.

Results

The result of this study showed that in cases with suprasellar masses, there were significantly lower mean AD and ADC values and higher mean FA value than control group with no masses.

Conclusion

The DTI is a useful technique in the assessment of optic pathway compression degree by suprasellar masses. This will provide the clinicians and surgeons with precise information about the degree of the visual field compromise in correlation with the clinical data.

Mitochondrial targeted therapy with elamipretide (MTP-131) as an adjunct to tumor necrosis factor inhibition for traumatic optic neuropathy in the acute setting

Traumatic optic neuropathy (TON) can occur following blunt trauma to the orbit and can lead to permanent vision loss. In this study, we investigated the effectiveness of elamipretide (MTP-131), a small mitochondrially-targeted tetrapeptide, in conjunction with etanercept, a tumor necrosis factor (TNF) inhibitor, as neuroprotective agents of retinal ganglion cells (RGCs) after optic nerve trauma with sonication-induced TON (SI-TON) in mice. Treatment with intravitreal MTP-131 and subcutaneous etanercept and MTP-131 showed a 21% increase (p < 0.01) in RGC survival rate compared to PBS-treated control eyes. Subcutaneous etanercept and MTP-131 had an 11% increase (p < 0.05) in RGC survival compared to controls. Subcutaneous etanercept only group showed 20% increase (p < 0.01) in RGC survival compared to controls, while subcutaneous MTP-131 alone showed a 17% increase (p < 0.01). Surprisingly, we did not observe a synergistic effect between the two drugs in the group receiving both etanercept and MTP-131. One possible explanation for the absence of a synergistic effect is that MTP-131 and etanercept may be acting on different portions of the same pathway.

The Biomechanics of Indirect Traumatic Optic Neuropathy Using a Computational Head Model With a Biofidelic Orbit

Indirect traumatic optic neuropathy (ITON) is an injury to the optic nerve due to head trauma and usually results in partial or complete loss of vision. In order to advance a mechanistic understanding of the injury to the optic nerve, we developed a head model with a biofidelic orbit. Head impacts were simulated under controlled conditions of impactor velocity. The locations of impact were varied to include frontal, lateral, and posterior parts of the head. Impact studies were conducted using two types of impactors that differed in their rigidity relative to the skull. The simulated results from both the impactors suggest that forehead impacts are those to which the optic nerve is most vulnerable. The mode and location of optic nerve injury is significantly different between the impacting conditions. Simulated results using a relatively rigid impactor (metal cylinder) suggest optic nerve injury initiates at the location of the intracranial end of the optic canal and spreads to the regions of the optic nerve in the vicinity of the optic canal. In this case, the deformation of the skull at the optic canal, resulting in deformation of the optic nerve, was the primary mode of injury. On the other hand, simulated results using a relatively compliant impactor (soccer ball) suggest that primary mode of injury comes from the brain tugging upon the optic nerve (from where it is affixed to the intracranial end of the optic canal) during coup countercoup motion of the brain. This study represents the first published effort to employ a biofidelic simulation of the full length of the optic nerve in which the orbit is integrated within the whole head.

Galantamine protects against synaptic, axonal, and vision deficits in experimental neurotrauma

Our goal was to investigate the neuroprotective effects of galantamine in a mouse model of blast-induced indirect traumatic optic neuropathy (bITON). Galantamine is an FDA-approved acetylcholinesterase inhibitor used to treat mild-moderate Alzheimer's disease. We exposed one eye of an anesthetized mouse to repeat bursts of over-pressurized air to induce traumatic optic neuropathy. Mice were given regular or galantamine-containing water (120 mg/L) ad libitum, beginning immediately after blast and continuing for one month. Electroretinograms and visual evoked potentials were performed just prior to endpoint collection. Histological and biochemical assessments were performed to assess activation of sterile inflammation, axon degeneration, and synaptic changes. Galantamine treatment mitigated visual function deficits induced by our bITON model via preservation of the b-wave of the electroretinogram and the N1 of the visual evoked potential. We also observed a reduction in axon degeneration in the optic nerve as well as decreased rod bipolar cell dendritic retraction. Galantamine also showed anti-inflammatory and antioxidant effects. Galantamine may be a promising treatment for blast-induced indirect traumatic optic neuropathy as well as other optic neuropathies.

Tumor Necrosis Factor Inhibition in the Acute Management of Traumatic Optic Neuropathy

Purpose

To determine the effectiveness of etanercept, a tumor necrosis factor (TNF) inhibitor, in conferring neuroprotection to retinal ganglion cells (RGCs) and improving visual outcomes after optic nerve trauma with either optic nerve crush (ONC) or sonication-induced traumatic optic neuropathy (SI-TON) in mice.

Methods

Mouse optic nerves were unilaterally subjected to ONC (n = 20) or SI-TON (n = 20). TNF expression was evaluated by using immunohistochemistry and quantitative RT-PCR (qRT-PCR) in optic nerves harvested 6 and 24 hours post ONC (n = 10) and SI-TON (n = 10). Mice in each injury group received daily subcutaneous injections of either etanercept (10 mg/kg of body weight; five mice) or vehicle (five mice) for 7 days. Pattern electroretinograms were performed on all mice at 1 and 2 weeks after injury. ONC mice were killed at 2 weeks after injury, while SI-TON mice were euthanized at 4 weeks after injury. Whole retina flat-mounts were used for RGC quantification.

Results

Immunohistochemistry and qRT-PCR showed upregulation of TNF protein and gene expression within 24 hours after injury. In both models, etanercept use immediately following optic nerve injury led to higher RGC survival when compared to controls, which was comparable between the two models (24.23% in ONC versus 20.42% in SI-TON). In both models, 1 and 2 weeks post injury, mice treated with etanercept had significantly higher a-wave amplitudes than untreated injured controls.

Conclusions

Treatment with etanercept significantly reduced retinal damage and improved visual function in both animal models of TON. These findings suggest that reducing TNF activity in injured optic nerves constitutes an effective therapeutic approach in an acute setting.

Investigating possible retinal biomarkers of head trauma in Olympic boxers using optical coherence tomography

Purpose

Changes to retina have been reported after a number of neurodegenerative conditions. The purpose of this study was to investigate retinal structures in Olympic boxers exposed to frequent head blows.

Methods

Retinal imaging offers potential as a non-invasive biomarker of neuropathology. Macula and retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography (OCT) in UK Olympic boxers attending two mandatory eye screening programs, 18 months apart. Data from the two eye screenings provide longitudinal data of retinal change over time. Sedentary healthy subjects (controls) without past or present history of concussion were also screened at the time of the second boxer screening to provide comparison of cross-sectional data.

Results

Sixteen Olympic boxers aged 20–33 years and 20 sedentary healthy controls, aged 24–45 years, were recruited. Significant macula thickening was observed over time (18 months) in 75% of right and 50% of left eye sectors. For RNFL, left eye quadrants thickened. For right eye RNFL quadrants, thickening and thinning of this layer were observed. Cross-sectional results showed thinner macula sectors and RNFL quadrants in Olympic boxers compared to controls.

Conclusion

Significant change to macula and RNFL densities, occurring over an 18 month interval is an unexpected finding in otherwise heathy elite sportsmen. In addition, macula and RNFL were thinner than healthy sedentary controls. OCT may prove clinically useful as a candidate retinal biomarker of neuropathological change after mild traumatic brain injury and/or repeat head blows.

Optic tract injury after closed head traumatic brain injury in mice: A model of indirect traumatic optic neuropathy

Adult male C57BL/6J mice have previously been reported to have motor and memory deficits after experimental closed head traumatic brain injury (TBI), without associated gross pathologic damage or neuroimaging changes detectable by magnetic resonance imaging or diffusion tensor imaging protocols. The presence of neurologic deficits, however, suggests neural damage or dysfunction in these animals. Accordingly, we undertook a histologic analysis of mice after TBI. Gross pathology and histologic analysis using Nissl stain and NeuN immunohistochemistry demonstrated no obvious tissue damage or neuron loss. However, Luxol Fast Blue stain revealed myelin injury in the optic tract, while Fluoro Jade B and silver degeneration staining revealed evidence of axonal neurodegeneration in the optic tract as well as the lateral geniculate nucleus of the thalamus and superior colliculus (detectable at 7 days, but not 24 hours, after injury). Fluoro Jade B staining was not detectable in other white matter tracts, brain regions or in cell somata. In addition, there was increased GFAP staining in these optic tract, lateral geniculate, and superior colliculus 7 days post-injury, and morphologic changes in optic tract microglia that were detectable 24 hours after injury but were more prominent 7 days post-injury. Interestingly, there were no findings of degeneration or gliosis in the suprachiasmatic nucleus, which is also heavily innervated by the optic tract. Using micro-computed tomography imaging, we also found that the optic canal appears to decrease in diameter with a dorsal-ventral load on the skull, which suggests that the optic canal may be the site of injury. These results suggest that there is axonal degeneration in the optic tract and a subset of directly innervated areas, with associated neuroinflammation and astrocytosis, which develop within 7 days of injury, and also suggest that this weight drop injury may be a model for studying indirect traumatic optic neuropathy.

Traumatic Optic Neuropathy - Case Report with Discussion on Diagnostic Procedures and Therapy

Traumatic optic neuropathy (TON) is a serious vision threatening condition that can be caused by ocular or head trauma. Indirect damage to the optic nerve is the most common form of TON occurring in 0.5% to 5% of all closed head trauma cases. Although the degree of visual loss after indirect TON may vary, approximately 50% of all patients are left with 'light perception' or 'no light perception' vision, making TON a significant cause of permanent vision loss. We present a 47-year-old male patient with a history of right eye keratoconus following a motorcycle crash. Visual acuity was of 'counting fingers at 2 meters' on the right eye due to keratoconus and 'counting fingers at 1 meter' on the left eye as a consequence of trauma. The Octopus visual field showed diffuse re-duction in retinal sensitivity and the Ishihara color test indicated dysfunction of color perception on the left eye. Relative afferent pupillary defect was also present. Computed tomography revealed multifragmentary fracture of the frontal sinus and the roof of the left orbit without bone displacement. Based on the findings, conservative corticosteroid therapy without surgery was conducted. The patient responded well to treatment with complete ophthalmologic recovery.

Traumatic optic neuropathy treatment trial (TONTT): open label, phase 3, multicenter, semi-experimental trial

PURPOSE

Intravenously administered erythropoietin (EPO) was firstly commenced (phase 1) in patients with indirect traumatic optic neuropathy (TON) by this group in 2011. It was re-tested by another group (phase 2) in 2014. This multicenter clinical trial was designed to compare its effect with intravenous steroid and observation.

METHODS

Included were TON patients ≥5 years of age and with trauma-treatment interval of ≤3 weeks. Follow-up visits were set at 1, 2, 3, 7, 14, 30, and at least 90 days after treatment. EPO and methylprednisolone were infused intravenously every day for three consecutive days. Primary outcome measure was change in the best corrected visual acuity (BCVA). Secondary outcomes included change in color vision and relative afferent pupillary defect (RAPD), side effects, and factors affecting the final visual improvement.

RESULTS

Out of 120 patients, 100 (EPO: 69, steroid: 15, observation: 16) were finally included. All three groups showed a significant improvement of BCVA which was not significantly different between the groups (adjusted for pretreatment BCVA). Color vision was significantly improved in the EPO group. Late treatment (>3 days) (odds ratio = 2.53) and initial BCVA of NLP (odds ratio = 5.74) significantly worsened visual recovery. No side effect was observed in any group.

CONCLUSION

EPO, steroid, and observation showed a significant improvement of BCVA in patients with TON. Initial BCVA of NLP and late treatment (>3 days) were significant risk factors for visual improvement.

A Novel Mouse Model of Traumatic Optic Neuropathy Using External Ultrasound Energy to Achieve Focal, Indirect Optic Nerve Injury

Traumatic optic neuropathy (TON) is a devastating cause of permanent visual loss following blunt injury to the head. Animal models for TON exist, but most fail to recapitulate the clinical scenario of closed head indirect trauma to the nerve and subsequent neurodegeneration. Thus, we developed a clinically-relevant animal model for TON using a novel ultrasonic pulse injury modality (sonication-induced TON; SI-TON). To trigger TON, a microtip probe sonifier was placed on the supraorbital ridge directly above the entrance of the optic nerve into the bony canal. An ultrasonic pulse was then delivered to the optic nerve. After injury, the number of RGCs in the retina as well as visual function measured by PERG steadily decreased over a two-week period. In the optic nerve, pro-inflammatory markers were upregulated within 6 hours following injury. Immunohistochemistry showed activation of microglia and infiltration of CD45-positive leukocytes in the optic nerve and initiation of a gliotic response. The SI-TON model is capable of delivering a non-contact concussive injury to the optic nerve and induce TON in mice. Thus, our data indicate that the SI-TON model reliably recapitulates the pathophysiology and progressive neurodegeneration seen in the human manifestation.

Orbital Disease in Neuro-Ophthalmology

Many abnormalities of the orbit present with neuro-ophthalmic findings, such as impaired ocular motility or alignment, and sensory changes, including optic neuropathy. Comprehensive coverage of all orbital diseases is beyond the scope of this article. This review focuses on diagnosis and management of the most common and the most vision- or life-threatening orbital conditions as well as more recently discovered entities and points of active controversy. These conditions include orbital trauma, vascular disease, inflammatory and infectious diseases, and neoplasms. Common presenting symptoms and associated neuro-orbital diseases also are summarized.

Report on the National Eye Institute Audacious Goals Initiative: Replacement of Retinal Ganglion Cells from Endogenous Cell Sources

This report emerges from a workshop convened by the National Eye Institute (NEI) as part of the "Audacious Goals Initiative" (AGI). The workshop addressed the replacement of retinal ganglion cells (RGCs) from exogenous and endogenous sources, and sought to identify the gaps in our knowledge and barriers to progress in devising cellular replacement therapies for diseases where RGCs die. Here, we briefly review relevant literature regarding common diseases associated with RGC death, the genesis of RGCs in vivo, strategies for generating transplantable RGCs in vitro, and potential endogenous cellular sources to regenerate these cells. These topics provided the clinical and scientific context for the discussion among the workshop participants and are relevant to efforts that may lead to therapeutic approaches for replacing RGCs. This report also summarizes the content of the workshop discussion, which focused on: (1) cell sources for RGC replacement and regeneration, (2) optimizing integration, survival, and synaptogenesis of new RGCs, and (3) approaches for assessing the outcomes of RGC replacement therapies. We conclude this report with a summary of recommendations, based on the workshop discussions, which may guide vision scientists seeking to develop therapies for replacing RGCs in humans.