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Purpose: To evaluate the integrity of the photoreceptor inner segment/outer segment (IS/OS) junction using spectral-domain optical coherence tomography (SD OCT) in patients with diabetic macular edema and to correlate the relationship between the integrity of the IS/OS junction and visual acuity.Design: Retrospective, comparative, consecutive case series.Methods: Sixty-two eyes from 38 patients with diabetic macular edema underwent SD OCT imaging. For each patient, 2 experienced observers masked to visual acuity measured several SD OCT variables, including central macular thickness, retinal volume, global disruption scale of outer retina, percentage disruption of the outer retina, and history of previous treatments. Visual acuity recorded as number of Early Treatment Diabetic Retinopathy Study letters was used as the outcome variable in univariate and multivariate analysis testing the measured SD OCT variables as predictors.Results: A statistically significant correlation between percentage disruption of the IS/OS junction and visual acuity was found (P = .0312). Additionally, there was a strong trend suggesting a relationship between macular volume and visual acuity, although borderline significance was found (P = .07).Conclusions: Disruption of the photoreceptor IS/OS junction is an important predictor of visual acuity among diabetic macular edema patients. [ABSTRACT FROM AUTHOR]

Background and Objective: To evaluate the morphological and functional outcome of wet age-related macular degeneration (AMD) during antivascular endothelial growth factor therapy with bevacizumab using SLO microperimetry (SLO-MP) with eye tracking., Patients and Methods: First, reproducibility was tested over the choroidal neovascularization (CNV) in 21 eyes of 19 patients with wet AMD. Second, 21 eyes of 19 patients with active CNV were studied longitudinally during bevacizumab therapy. Best-corrected visual acuity, SLO-MP, spectral-domain optical coherence tomography and fluorescein angiography were performed., Results: There was good reproducibility with a concordance correlation coefficient of 0.85. In the longitudinal study, eyes with anatomical response demonstrated a significant increase of retinal sensitivity. Non-responders showed no change in SLO-MP. Retinal sensitivity at baseline had a significant predictive value for the change in retinal sensitivity during therapy with bevacizumab (P=.032)., Conclusion: SLO-MP is able to analyze retinal function overlying lesions in wet AMD and can be a useful tool to monitor therapy in patients with macular diseases., (Copyright 2015, SLACK Incorporated.)

Purpose: To evaluate clinical results after the use of a novel integrated imaging and laser device to perform focal retinal navigated laser photocoagulation in perifoveal abnormalities and retinovascular disease., Methods: Interventional case series of 25 consecutive eyes with perifoveal and retinovascular diseases treated with a navigated laser photocoagulator Navilas (OD-OS, Berlin, Germany). We treated eyes with perifoveal telangiectasia (n = 3), central serous chorioretinopathy (n = 2), and diabetic macular edema with focal leakage (n = 20)., Results: The treatments were performed without a contact lens and without topical anesthesia. There was no inadvertent photocoagulation of the fovea, and all laser applications accurately hit the preplanned points. Mean and median (± standard deviation) foveal thickness at baseline was 535 ± 171 μm and 402 ± 152 μm, respectively. Mean and median (± standard deviation) foveal thickness at 6 months was 318 ± 112 μm and 221 ± 127 μm, respectively. This represents a statistically significant decrease in foveal thickness (P = 0.003). Mean and median visual acuity at baseline was 20/80 and 20/50, respectively. Mean and median visual acuity at 6 months was 20/50 and 20/40, respectively, which represents a significant improvement (P = 0.011)., Conclusion: Precise retinal targeting with a navigated laser photocoagulator resulted in highly accurate perifoveal laser application and no foveal damage. At 6 months after the treatment, significant decreases in central foveal thickness and significant improvements in visual acuity were identified.

Purpose: To describe the appearance on spectral domain optical coherence tomography of the peripheral retina and overlying vitreous after scleral buckling surgery., Methods: Retrospective case series of patients who underwent scleral buckle surgery and had subsequent scanning laser ophthalmoscopy/spectral-domain optical coherence tomography images over the area of buckled retina. Twelve eyes from 11 patients were identified and show a variety of retinal anatomies, vitreous configurations, and clinical applications., Results: Twelve eyes from 11 patients were studied, and in all eyes, the peripheral retina could be visualized with 10 cases of successful retinal reattachment and 2 cases of scleral buckle failure. Vitreous including strands to the causative retinal tear was seen in three eyes and overlying vitreous in four additional eyes. The scleral buckle indentation was seen in nine eyes, and in the two failed scleral buckles, unsupported retinal breaks, residual vitreous traction, and persistent subretinal fluid over the scleral buckle could be visualized and followed as it resolved., Conclusion: Simultaneous scanning laser ophthalmoscopy/spectral-domain optical coherence tomography allows detailed examination of the peripheral retina and overlying vitreous after scleral buckle surgery. Along with confirmation that the retina is attached and retinal breaks are closed, the scanning laser ophthalmoscopy/spectral-domain optical coherence tomography can be used in the postoperative management of scleral buckles to identify residual vitreous traction and monitor areas of subretinal fluid.

Purpose: To evaluate the clinical use and accuracy of a new retinal navigating laser technology that integrates a scanning slit fundus camera system with fluorescein angiography (FA), color, red-free, and infrared imaging capabilities with a computer steerable therapeutic 532-nm laser., Design: Interventional case series., Participants: Eighty-six eyes of 61 patients with diabetic retinopathy and macular edema treated by NAVILAS., Methods: The imaging included digital color fundus photographs and FA. The planning included graphically marking future treatment sites (microaneurysms for single-spot focal treatment and areas of diffuse leakage for grid pattern photocoagulation) on the acquired images. The preplanned treatment was visible and overlaid on the live fundus image during the actual photocoagulation. The NAVILAS automatically advances the aiming beam location from one planned treatment site to the next after each photocoagulation spot until all sites are treated. Aiming beam stabilization compensated for patient's eye movements. The pretreatment FA with the treatment plan was overlaid on top of the posttreatment color fundus images with the actual laser burns. This allowed treatment accuracy to be calculated. Independent observers evaluated the images to determine if the retinal opacification after treatment overlapped the targeted microaneurysm., Main Outcome Measures: Safety and accuracy of laser photocoagulation., Results: The images were of very good quality compared with standard fundus cameras, allowing careful delineation of target areas on FA. Toggling from infrared, to monochromatic, to color view allowed evaluation and adjustment of burn intensity during treatment. There were no complications during or after photocoagulation treatment. An analysis of accuracy of 400 random focal targeted spots found that the NAVILAS achieved a microaneurysm hit rate of 92% when the placement of the treatment circle was centered by the operating surgeon on the microaneurysm. The accuracy for the control group analyzing 100 focal spots was significantly lower at 72% (P<0.01)., Conclusions: Laser photocoagulation using the NAVILAS system is safe and achieves a higher rate of accuracy in photocoagulation treatments of diabetic retinopathy lesions than standard manual-technique laser treatment. Precise manual preplanning and positioning of the treatment sites by the surgeon is possible, allowing accurate and predictable photocoagulation of these lesions., Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references., (Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to use spectral domain-optical coherence tomography in imaging retina and vitreoretinal relationship in healed cytomegalovirus (CMV) retinitis., Methods: Patients with a history of confirmed CMV retinitis and a healed CMV scar on clinical examination underwent spectral domain-optical coherence tomography examinations using a Spectralis Heidelberg retinal angiograph/optical coherence tomography instrument (Heidelberg Engineering, Heidelberg, Germany). Horizontal and vertical cross-sectional B-scans 6 mm x 6 mm passing through the center and margins of healed CMV scars and adjacent retina were obtained. We analyzed the integrity of retinal layers in the area of the CMV scar, integrity of retinal layers at the margins of the CMV scar, margins of the scar and adjacent nonaffected retina, and any structural alterations in the retina or vitreous., Results: Eleven eyes (50%) had vitreous detached, and 11 eyes attached over the area of healed retinitis. Nineteen eyes (86%) had an epiretinal membrane, and 12 eyes (54%) had vitreoretinal gliosis present over the healed retinitis or in its vicinity. The epiretinal membrane and vitreoretinal gliosis occurred concomitantly in 10 eyes and could be well differentiated on scans. None of these were found in control eyes., Conclusion: This first in vivo study of vitreoretinal interface in inactive CMV retinitis shows that the vitreoretinal interface in healed CMV is pathologically changed. The presence of epiretinal membranes, vitreoretinal gliosis, and traction may help explain the higher incidence of retinal elevation, retinal breaks, and retinal detachment in these eyes.

Purpose: The purposes of this study were to evaluate with spectral domain-optical coherence tomography the relationship between the retina and overlying silicone oil tamponade after macular hole surgery and to evaluate how this relationship changes with patient positioning., Methods: We studied a retrospective consecutive case series of 10 eyes from 9 patients who underwent macular hole surgery with silicone oil tamponade and subsequent spectral domain-optical coherence tomography scans. Four of the included eyes were also imaged with patients in face-down posture to determine whether the silicone-retina apposition changes with prone positioning. Finally, a single patient was also scanned in the lateral and supine positions., Results: The posterior surface of the silicone oil bubble was well visualized in all 10 eyes. In the majority of eyes (7 of 10), the oil tamponade bridged the macular hole, creating a prefoveal fluid space, but in 3 eyes the silicone oil filled the macular hole and was seen in touch with the underlying foveal depression or retinal pigment epithelium. In 75% of eyes (3 of 4), the silicone oil-retinal approximation did not vary with face-down position. Supine positioning clearly floated the silicone tamponade anteriorly and off the retinal surface., Conclusion: Silicone oil tamponade can either bridge macular holes or, in a novel finding, fill the underlying foveal depression or macular hole space. Generally, the oil position is stable between face-forward and prone spectral-domain optical coherence tomography images, suggesting that either of these patient positions allows waterproofing of the underlying macular hole. Finally, our images confirm that supine positioning should be avoided postoperatively because it leads to loss of oil-retinal tamponade.

Purpose: The purpose of this study was to evaluate the predictive value of spectral domain-optical coherence tomography-determined integrity of the photoreceptor inner segment/outer segment (IS/OS) junction on visual acuity in patients with epiretinal membranes (ERMs)., Methods: This is a retrospective consecutive case series of 54 eyes from 48 patients with primary ERMs who underwent spectral domain-optical coherence tomography scans. Regression analysis was used to calculate the relative contribution of several variables, including photoreceptor IS/OS disruption, grade of IS/OS disruption, macular thickness, and ERM grade on fundus imaging to visual acuity., Results: The strongest individual predictor of visual acuity among patients with ERM was central retinal thickness on spectral domain-optical coherence tomography (r(2) = 0.16, P = 0.0024), but the most efficient model was the combination of macular thickness and presence or absence of photoreceptor IS/OS disruption (r(2) = 0.24, P = 0.0008). Additional measured variables did not significantly contribute to visual acuity prediction. Inner segment/outer segment layer integrity was also an independent predictor of visual acuity, and patients with IS/OS disruption were 6.88 times as likely to have 20/50 or worse vision than patients with intact photoreceptor layers (odds ratio: 6.88, confidence interval: 1.56-30.43, P = 0.01)., Conclusion: Disruption of the photoreceptor IS/OS junction is a statistically significant predictor of poor visual acuity among patients with ERM and is most useful when combined with central retinal thickness measurement.

Purpose: To determine the ability to detect normal vitreous structure, evolving posterior vitreous detachment (PVD), and related vitreoretinal changes with combined spectral-domain optical coherence tomography (SD-OCT) and scanning laser ophthalmoscopy (SLO)., Design: Observational cross-sectional study., Methods: Simultaneous SD-OCT and SLO imaging instruments (SD-OCT/SLO) were used to image both eyes of patients with symptoms of PVD. The vitreous cortex, preretinal lacunae, hyaloid, and its relations to the retinal surface were analyzed. In addition, ultrasound was performed in a subset of patients to determine the stage of PVD., Results: Two-hundred two eyes of 113 subjects were scanned. There was a high correlation between diagnosis of complete PVD by clinical examination and OCT (95 vs 93 eyes, respectively; kappa, 0.82). A partial PVD was detected more frequently by SD-OCT/SLO than by biomicroscopy examination (45 vs 7 eyes; P < .0001). Ultrasound was performed in a subset of 30 eyes. A high agreement was found between ultrasound and SD-OCT/SLO results for both complete PVD (kappa, 0.933) and incomplete PVD (kappa, 0.91). Vitreous cortex was detected in 181 eyes, and posterior precortical vitreous pocket was detected in 85 eyes. The effects of PVD, including vitreoretinal traction, paravascular lamellar holes, and fine changes at the fovea, could be visualized reliably in detail only with SD-OCT/SLO. In all these eyes, SD-OCT/SLO allowed improved visualization of the vitreoretinal relationship., Conclusions: SD-OCT/SLO provides unprecedented in vivo information about the physiologic and pathologic vitreous structure; it allows an extremely detailed analysis of the vitreoretinal interface, and it is particularly useful for defining focal changes and PVD., (Copyright 2010 Elsevier Inc. All rights reserved.)

Purpose: To review the cases of viral retinitis after intravitreal steroid administration at a single center, to estimate the incidence, and to propose risk factors for its occurrence., Design: Retrospective, observational case series., Methods: Seven hundred thirty-six intravitreal triamcinolone (IVTA) injections were administered in the clinic and operating room by 3 retina specialists at a single academic medical center between September 2002 and November 2008. Inclusion criteria were simply a history of 1 or more IVTA injections during the period. The overall incidence of viral retinitis after IVTA injection was calculated. Subsequently, a chart audit was performed to estimate the number of patients with immune-altering conditions who had received IVTA during the period, and the incidence within this subgroup was calculated., Results: Viral retinitis developed after IVTA injection in 3 patients, yielding an overall incidence of 3 in 736 or 0.41%. An estimated 334 injections were administered to patients with an immune-altering condition, including diabetes. All 3 of the patients in whom viral retinitis developed after IVTA injection possessed abnormal immune systems, yielding an incidence rate of 3 in 334 or 0.90% within this subgroup., Conclusions: Our high reported incidence for this potentially devastating complication can be attributed to multiple factors, including coexisting medical immunocompromising comorbidities, a higher dose with a longer duration of local immunosuppression in the vitreous, multiple injections, as well as previous viral retinitis. Caution with a high index of clinical suspicion and frequent follow-up is advised in patients receiving IVTA injection with potentially immune-altering conditions, even after apparent immune recovery., ((c) 2010 Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to determine the morphologic patterns of angiographic macular edema using simultaneous colocalization of fluorescein angiography and spectral-domain optical coherence tomography (SD-OCT) images in diabetes, epiretinal membrane, uveitic and pseudophakic cystoid macular edema, and vein occlusion., Methods: Eighty-seven consecutive patients (107 eyes) with macular edema from 5 different etiologies were imaged by simultaneous scanning laser ophthalmoscopy/OCT to study the morphologic patterns of edema on SD-OCT and then correlated/colocalized with the fluorescein angiographic patterns of leakage. Statistical analysis was done to analyze the differences in the morphologic OCT pattern by different diseases., Results: Spectral-domain OCT characteristics of macular edema showed a significant difference across different diseases (P = 0.037). Cystic fluid pockets were found to be more commonly seen in patients with diabetic macular edema and retinal vein occlusions, whereas those cases with macular edema secondary to epiretinal membrane showed noncystic changes on OCT. Seventy of the 107 eyes had diffuse angiographic leakage, and the remaining 37 eyes had cystoid leakage on angiography. Of the 70 eyes with diffuse leakage, 24.28% showed microcysts on SD-OCT in the area of edema, and 70% eyes had diffuse thickening or distorted architecture without cyst. All 37 eyes with cystoid leakage showed cysts in the area of edema by SD-OCT. A total of 3.73% of eyes with fluorescein angiographic leakage had no abnormalities on SD-OCT., Conclusion: Eyes with diabetic macular edema and retinal vein occlusions have a significantly higher incidence of cyst formation on SD-OCT. There was no correlation between visual acuity and cyst formation. Diffuse noncystoid angiographic macular edema may show microcysts on SD-OCT, but diffuse edema is more commonly associated with thickening or distortion of the retinal layers without cyst formation. Cystoid leakage on fluorescein angiography is always associated with cystic changes on SD-OCT.

Purpose: To study the appearance of margins of geographic atrophy in high-resolution optical coherence tomography (OCT) images and to correlate those changes with fundus autofluorescence (FAF) imaging., Design: Retrospective, observational case study., Methods: Patients with geographic atrophy secondary to dry age-related macular degeneration were assessed by means of spectral-domain OCT (Spectralis Heidelberg Retinal Angiograph/OCT; Heidelberg Engineering, Heidelberg, Germany; or OTI Inc, Toronto, Canada) as well as autofluorescence imaging (Heidelberg Retinal Angiograph or Spectralis; Heidelberg Engineering). The outer retinal layer alterations were analyzed in the junctional zone between normal retina and atrophic retina and were correlated with corresponding FAF., Results: Twenty-three eyes of 16 patients between 62 and 96 years of age were examined. There was a significant association between OCT findings and the FAF findings (r = 0.67; P < .0001). Severe alterations of the outer retinal layers at margins on spectral-domain OCT correspond significantly to increased autofluorescence; smooth margins on OCT correspond significantly to normal FAF (kappa, 0.7348; P < .0001)., Conclusions: Spectral-domain OCT provides in vivo insight into the pathogenesis of geographic atrophy and its progression. Visualization of reactive changes in the retinal pigment epithelial cells at the junctional zone and correlation with increased FAF; secondary to increased lipofuscin, together these methods may serve as determinants of progression of geographic atrophy.

Purpose: To characterize the clinical and histologic features of primary graft failure after Descemet's stripping and automated endothelial keratoplasty (DSAEK)., Design: Retrospective observational case series., Participants: Sixteen cases of DSAEK graft failure from 15 patients, all with detailed histologic examination of failed graft tissue., Methods: Hematoxylin-eosin, periodic acid-Schiff staining, and light microscopy were used to examine the failed DSAEK graft tissue from all patients., Main Outcome Measures: Examination of specimens for corneal endothelial cell viability and host-donor interface characteristics., Results: Clinical history revealed that 88% (14/16) of studied DSAEK grafts detached before failure, and pathologic examination found that 75% (12/16) of failed grafts had atrophic corneal endothelium. Examples of residual host Descemet's membrane in the graft site and improper donor trephination were also identified., Conclusions: Marked loss of the corneal endothelium is the prominent feature of primary DSAEK graft failure. Examples of surgical features, such as incomplete Descemet's stripping and residual full-thickness cornea with a DSAEK graft, are shown.

Purpose: To report a case of host-donor interface calcification after Descemet membrane stripping with automated endothelial keratoplasty (DSAEK)., Methods: Review of the patient's clinical records and histopathologic examination of the donor corneal lamella from repeat DSAEK performed subsequent to the original DSAEK., Results: Review of the clinical record of the patient revealed an ocular history of Fuchs dystrophy and pseudophakic bullous keratoplasty that was treated with DSAEK. She later developed corneal edema and a partially detached donor lamella and underwent repeat DSAEK. Histopathologic and transmission electron microscopic evaluations of the corneal lamella revealed calcium deposits in the host-donor interface., Conclusions: Calcareous degeneration of the host-donor interface after DSAEK is reported as a novel postoperative complication of DSAEK. Calcium deposits in the host-donor interface after DSAEK should be considered in the differential diagnosis of interface opacity after this procedure, particularly in patients with predisposing systemic or local risk factors such as retained phosphate-containing viscoelastic material, excessive postoperative inflammation, or use of phosphate-buffered, postoperative topical medications.

The majority of patients with incontinentia pigmenti (IP) have a mutation in the nuclear factor-kappa-beta essential modulator (NEMO) gene, and mice with a targeted deletion of NEMO exhibit skin pathology remarkably similar to the human disease. This study characterizes the retinal vascular abnormalities of NEMO-deficient mice, and compares this phenotype to known features of human IP. Nineteen heterozygous NEMO-deficient female mice, ages ranging from post-natal day 8 (P-8) through 6.5 months of life, were studied. Eyes were sectioned and stained either whole or as retinal flat mounts after incubation for enzyme histochemical demonstration of ADPase, which labels the vasculature. With maturation, retinal arteriolar abnormalities became evident at 3 months of age. Global assessment of the retinal vasculature with ADPase staining showed increased vascular tortuosity. Microscopic examination of sections of ADPase-incubated retinas revealed arteriolar luminal narrowing due to endothelial cell hypertrophy and increased basement membrane deposition. Venous morphology was normal. This study characterized the histological retinal phenotype of heterozygous NEMO-deficient female mice. Most striking were retinal arteriolar abnormalities, including luminal narrowing, endothelial cell hypertrophy, and basement membrane thickening. Retinal flat mounts revealed arteriolar tortuosity without evidence of vaso-occlusion or neo-vascularization.

Background and Purpose: The proximity of the paraclinoid segment of the internal carotid artery to the visual pathways may result in visual deficits when patients present with aneurysms in this segment. Although surgical clip ligation of these aneurysms has been the standard of care for decades, the advent of coil embolization has permitted endovascular therapy in those aneurysms with favorable dome-to-neck ratios. Although immediate nonprogressive visual loss after coil embolization of paraclinoid aneurysms has been well described, isolated progressive visual loss immediately or shortly following coil embolization, to our knowledge, has not. We have identified 8 patients who experienced progressive loss of vision, unassociated with any other neurologic deficits, developing immediately or shortly after apparently uncomplicated coil embolization of a paraclinoid aneurysm., Materials and Methods: This study is a retrospective case series of 8 patients seen at 4 separate academic institutions. Inpatient and outpatient records were examined to determine patient demographics, previous ocular and medical history, and ophthalmic status before endovascular embolization. In addition, details of the primary endovascular therapy and subsequent surgical and nonsurgical interventions were recorded. Follow-up data, including most recent best-corrected visual acuity, postoperative course, and duration of follow-up were documented., Results: Eight patients developed progressive visual loss in 1 or both eyes immediately or shortly after apparently uncomplicated coiling of a paraclinoid aneurysm. MR imaging findings suggested that the visual loss was most likely caused by perianeurysmal inflammation related to the coils used to embolize the aneurysm, enlargement or persistence of the aneurysm despite coiling, or a combination of these mechanisms. Most patients experienced improvement in vision, 2 apparently related to treatment with systemic corticosteroids., Conclusion: Patients in whom endovascular treatment of a paraclinoid aneurysm is contemplated should be warned about the potential for both isolated nonprogressive and progressive visual loss in 1 or both eyes. Patients in whom progressive visual loss occurs may benefit from treatment with systemic corticosteroids.

The response of neuronal growth cones to axon guidance cues depends on the developmental context in which these cues are encountered. We show here that the transmembrane protein semaphorin 5A (Sema5A) is a bifunctional guidance cue exerting both attractive and inhibitory effects on developing axons of the fasciculus retroflexus, a diencephalon fiber tract associated with limbic function. The thrombospondin repeats of Sema5A physically interact with the glycosaminoglycan portion of both chondroitin sulfate proteoglycans (CSPGs) and heparan sulfate proteoglycans (HSPGs). CSPGs function as precisely localized extrinsic cues that convert Sema5A from an attractive to an inhibitory guidance cue. Therefore, glycosaminoglycan bound guidance cues provide a molecular mechanism for CSPG-mediated inhibition of axonal extension. Further, axonal HSPGs are required for Sema5A-mediated attraction, suggesting that HSPGs are components of functional Sema5A receptors. Thus, neuronal responses to Sema5A are proteoglycan dependent and interpreted according to the biological context in which this membrane bound guidance cue is presented.

In the mammalian CNS, glial cells repel axons during development and inhibit axon regeneration after injury. It is unknown whether the same repulsive axon guidance molecules expressed by glia and their precursors during development also play a role in inhibiting regeneration in the injured CNS. Here we investigate whether optic nerve glial cells express semaphorin family members and, if so, whether these semaphorins inhibit axon growth by retinal ganglion cells (RGCs). We show that each optic nerve glial cell type, astrocytes, oligodendrocytes, and their precursor cells, expressed a distinct complement of semaphorins. One of these, sema5A, was expressed only by purified oligodendrocytes and their precursors, but not by astrocytes, and was present in both normal and axotomized optic nerve but not in peripheral nerves. Sema5A induced collapse of RGC growth cones and inhibited RGC axon growth when presented as a substrate in vitro. To determine whether sema5A might contribute to inhibition of axon growth after injury, we studied the ability of RGCs to extend axons when cultured on postnatal day (P) 4, P8, and adult optic nerve explants and found that axon growth was strongly inhibited. Blocking sema5A using a neutralizing antibody significantly increased RGC axon growth on these optic nerve explants. These data support the hypothesis that sema5A expression by oligodendrocyte lineage cells contributes to the glial cues that inhibit CNS regeneration.

During development, EphB proteins serve as axon guidance molecules for retinal ganglion cell axon pathfinding toward the optic nerve head and in midbrain targets. To better understand the mechanisms by which EphB proteins influence retinal growth cone behavior, we investigated how axon responses to EphB were modulated by laminin and L1, two guidance molecules that retinal axons encounter during in vivo pathfinding. Unlike EphB stimulation in the presence of laminin, which triggers typical growth cone collapse, growth cones co-stimulated by L1 did not respond to EphB. Moreover, EphB exposure in the presence of both laminin and L1 resulted in a novel growth cone inhibition manifested as a pause in axon elongation with maintenance of normal growth cone morphology and filopodial activity. Pauses were not associated with loss of growth cone actin but were accompanied by a redistribution of the microtubule cytoskeleton with increased numbers of microtubules extending into filopodia and to the peripheral edge of the growth cone. This phenomenon was accompanied by reduced levels of the growth cone microtubule destabilizing protein SCG10. Antibody blockade of SCG10 function in growth cones resulted in both changes in microtubule distribution and pause responses mirroring those elicited by EphB in the presence of laminin and L1. These results demonstrate that retinal growth cone responsiveness to EphB is regulated by co-impinging signals from other axon guidance molecules. Furthermore, the results are consistent with EphB-mediated axon guidance mechanisms that involve the SCG10-mediated regulation of the growth cone microtubule cytoskeleton.

The eye is a highly specialized structure that gathers and converts light information into neuronal signals. These signals are relayed along axons of retinal ganglion cells (RGCs) to visual centers in the brain for processing. In this review, we discuss the pathfinding tasks RGC axons face during development and the molecular mechanisms known to be involved. The data at hand support the presence of multiple axon guidance mechanisms concentrically organized around the optic nerve head, each of which appears to involve both growth-promoting and growth-inhibitory guidance molecules. Together, these strategies ensure proper optic nerve formation and establish the anatomical pathway for faithful transmission of information between the retina and the brain.

In the past several years, a great deal has been learnt about the molecular basis through which specific neural pathways in the visual system are established during embryonic development. This review provides a framework for understanding the principles of retinal ganglion cell axon guidance, and introduces some of the families of axon guidance molecules involved. In addition, the potential relevance of retinal axon guidance to human visual developmental disorders, and to retinal axon regeneration, is discussed.

Retinal axon pathfinding from the retina into the optic nerve involves the growth promoting axon guidance molecules L1, laminin and netrin 1, each of which governs axon behavior at specific regions along the retinal pathway. In identifying additional molecules regulating this process during embryonic mouse development, we found that transmembrane Semaphorin5A mRNA and protein was specifically expressed in neuroepithelial cells surrounding retinal axons at the optic disc and along the optic nerve. Given that growth cone responses to a specific guidance molecule can be altered by co-exposure to a second guidance cue, we examined whether retinal axon responses to Sema5A were modulated by other guidance signals axons encountered along the retinal pathway. In growth cone collapse, substratum choice and neurite outgrowth assays, Sema5A triggered an invariant inhibitory response in the context of L1, laminin, or netrin 1 signaling, suggesting that Sema5A inhibited retinal axons throughout their course at the optic disc and nerve. Antibody-perturbation studies in living embryo preparations showed that blocking of Sema5A function led to retinal axons straying out of the optic nerve bundle, indicating that Sema5A normally helped ensheath the retinal pathway. Thus, development of some CNS nerves requires inhibitory sheaths to maintain integrity. Furthermore, this function is accomplished using molecules such as Sema5A that exhibit conserved inhibitory responses in the presence of co-impinging signals from multiple families of guidance molecules.

Axon pathfinding relies on cellular signaling mediated by growth cone receptor proteins responding to ligands, or guidance cues, in the environment. Eph proteins are a family of receptor tyrosine kinases that govern axon pathway development, including retinal axon projections to CNS targets. Recent examination of EphB mutant mice, however, has shown that axon pathfinding within the retina to the optic disc is dependent on EphB receptors, but independent of their kinase activity. Here we show a function for EphB1, B2 and B3 receptor extracellular domains (ECDs) in inhibiting mouse retinal axons when presented either as substratum-bound proteins or as soluble proteins directly applied to growth cones via micropipettes. In substratum choice assays, retinal axons tended to avoid EphB-ECDs, while time-lapse microscopy showed that exposure to soluble EphB-ECD led to growth cone collapse or other inhibitory responses. These results demonstrate that, in addition to the conventional role of Eph proteins signaling as receptors, EphB receptor ECDs can also function in the opposite role as guidance cues to alter axon behavior. Furthermore, the data support a model in which dorsal retinal ganglion cell axons heading to the optic disc encounter a gradient of inhibitory EphB proteins which helps maintain tight axon fasciculation and prevents aberrant axon growth into ventral retina. In conclusion, development of neuronal connectivity may involve the combined activity of Eph proteins serving as guidance receptors and as axon guidance cues.