Type II cadherins guide assembly of a direction-selective retinal circuit.

Complex retinal circuits process visual information and deliver it to the brain. Few molecular determinants of synaptic specificity in this system are known. Using genetic and optogenetic methods, we identified two types of bipolar interneurons that convey visual input from photoreceptors to a circuit that computes the direction in which objects are moving. We then sought recognition molecules that promote selective connections of these cells with previously characterized components of the circuit. We found that the type II cadherins, cdh8 and cdh9, are each expressed selectively by one of the two bipolar cell types. Using loss- and gain-of-function methods, we showed that they are critical determinants of connectivity in this circuit and that perturbation of their expression leads to distinct defects in visually evoked responses. Our results reveal cellular components of a retinal circuit and demonstrate roles of type II cadherins in synaptic choice and circuit function.

SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING OF THE MACULA AND VITREOMACULAR INTERFACE IN PERSISTENT FETAL VASCULATURE SYNDROME WITH POSTERIOR INVOLVEMENT.

PURPOSE: To describe the microstructural features of the macula and vitreomacular interface in persistent fetal vasculature syndrome (PFVS) with posterior involvement managed with early vitrectomy or with observation, with functional correlation. METHODS: We retrospectively identified 45 consecutive pediatric patients with PFVS with posterior involvement treated from 2005 to 2016. The eyes that could be imaged with spectral domain optical coherence tomography were included, and images were correlated with best-corrected visual acuity. RESULTS: Thirty-eight imaging sessions were performed on 10 eyes from 9 patients, including 7 that had been managed with vitrectomy for PFVS-related tractional retinal detachment, and 3 that had been observed. Mean age of the patients who were imaged was 9.1 years and their average length of follow-up was 5.9 years. Best-corrected visual acuities of the eyes imaged ranged from 20/30 to count fingers, with mean best-corrected visual acuity 20/163. All eyes imaged had microstructural anomalies identified. The main anomalous features included posterior hyaloidal organization, vitreoretinal traction, vitreopapillary traction, diminished foveal contour, foveal displacement, and disruption of the ellipsoid zone. Posterior hyaloidal organization (P = 0.043), diminished foveal contour (P = 0.019), and disruption of the ellipsoid zone (P = 0.014) were associated with worse best-corrected visual acuity. CONCLUSION: Macular and vitreomacular interface anomalies were identified in all pediatric patients with posterior PFVS imaged with spectral domain optical coherence tomography. These microstructural findings, together with functional measures, may inform the diagnosis and management of PFVS with posterior involvement.

STEM CELL THERAPIES, GENE-BASED THERAPIES, OPTOGENETICS, AND RETINAL PROSTHETICS: Current State and Implications for the Future.

PURPOSE: To review and discuss current innovations and future implications of promising biotechnology and biomedical offerings in the field of retina. We focus on therapies that have already emerged as clinical offerings or are poised to do so. METHODS: Literature review and commentary focusing on stem cell therapies, gene-based therapies, optogenetic therapies, and retinal prosthetic devices. RESULTS: The technologies discussed herein are some of the more recent promising biotechnology and biomedical developments within the field of retina. Retinal prosthetic devices and gene-based therapies both have an FDA-approved product for ophthalmology, and many other offerings (including optogenetics) are in the pipeline. Stem cell therapies offer personalized medicine through novel regenerative mechanisms but entail complex ethical and reimbursement challenges. CONCLUSION: Stem cell therapies, gene-based therapies, optogenetics, and retinal prosthetic devices represent a new era of biotechnological and biomedical progress. These bring new ethical, regulatory, care delivery, and reimbursement challenges. By addressing these issues proactively, we may accelerate delivery of care to patients in a safe, efficient, and value-based manner.

Long-Term Outcomes of Total Exudative Retinal Detachments in Stage 3B Coats Disease.

PURPOSE: To evaluate the long-term outcomes of treatment of total exudative retinal detachments (ERDs) secondary to Coats disease (stage 3B) and the role of vitrectomy. DESIGN: Retrospective, observational case series. PARTICIPANTS: A total of 16 eyes in 16 patients undergoing treatment for total ERDs secondary to Coats disease with at least 5 years of follow-up. METHODS: We reviewed the records of patients with stage 3B Coats disease. The interventions, including the timing of vitrectomy if used, and clinical course were recorded. MAIN OUTCOME MEASURES: The primary outcome measures were visual acuity at the most recent appointment, whether there was progression to neovascular glaucoma (NVG) or phthisis bulbi, and need for enucleation. RESULTS: All patients received ablative treatment (photocoagulation or cryotherapy), with 8 having scleral buckling (SB) and 6 having external drainage of subretinal fluid (XD). Of the 12 patients who had pars plana vitrectomy (PPV), 8 had early PPV (EV) in the first year after presenting, and 4 of 8 in the expectant management group had late PPV (late vitrectomy) at a mean of 4.3 years post-presentation for treatment of significant traction retinal detachment (TRD). The other 4 patients of 8 in the expectant management group did not require vitrectomy. Mean follow-up overall was 9 1/2 years. At the date of last follow-up, 50% had no light perception or light perception vision, which was consistent across the subgroups that underwent EV (4/8), late vitrectomy (2/4), or no PPV (2/4). A total of 4 of 16 patients had progression to NVG or phthisis, 1 of whom required enucleation. CONCLUSIONS: In this retrospective series of patients with Stage 3B Coats disease, ablative therapy with a combination of PPV, XD, or SB was effective in preventing progression to NVG or phthisis in the majority of patients, thus preserving the globe. Half of the patients (4/8) in this series who did not undergo PPV in the early vitrectomy group developed late-onset TRD, suggesting a possible role for early prophylactic vitrectomy with possible SB and XD; however, this is balanced by the other half (4/8) in the expectant management group who did not require any vitrectomy.

Direction-selective retinal ganglion cells arise from molecularly specified multipotential progenitors.

Single progenitors can give rise to any and all of the main retinal cell types: photoreceptors, interneurons (horizontal, bipolar, and amacrine cells), retinal ganglion cells (RGCs), and glia. Many of these types are divisible into multiple functionally, structurally, and molecularly distinct subtypes (e.g., ~25 for RGCs). It remains unknown when and how progenitors become committed to generate such subtypes. Here, we determine the origin of RGCs that respond selectively to vertical motion and express cadherin 6 (cdh6). Using Cre recombinase-based lineage tracing, we show that these RGCs arise from progenitors that themselves express cdh6. These progenitors are capable of generating all major retinal cell types, but the RGCs they generate are predominantly of the single direction-selective subtype. In contrast, cdh6-positive progenitors retain the ability to generate multiple subtypes of amacrine and bipolar cells. Our results demonstrate that type and subtype specification are regulated in different ways and suggest that multipotential but fate-restricted progenitors contribute to subtype specification in retina.

Retinal ganglion cells with distinct directional preferences differ in molecular identity, structure, and central projections.

The retina contains ganglion cells (RGCs) that respond selectively to objects moving in particular directions. Individual members of a group of ON-OFF direction-selective RGCs (ooDSGCs) detect stimuli moving in one of four directions: ventral, dorsal, nasal, or temporal. Despite this physiological diversity, little is known about subtype-specific differences in structure, molecular identity, and projections. To seek such differences, we characterized mouse transgenic lines that selectively mark ooDSGCs preferring ventral or nasal motion as well as a line that marks both ventral- and dorsal-preferring subsets. We then used the lines to identify cell surface molecules, including Cadherin 6, CollagenXXVα1, and Matrix metalloprotease 17, that are selectively expressed by distinct subsets of ooDSGCs. We also identify a neuropeptide, CART (cocaine- and amphetamine-regulated transcript), that distinguishes all ooDSGCs from other RGCs. Together, this panel of endogenous and transgenic markers distinguishes the four ooDSGC subsets. Patterns of molecular diversification occur before eye opening and are therefore experience independent. They may help to explain how the four subsets obtain distinct inputs. We also demonstrate differences among subsets in their dendritic patterns within the retina and their axonal projections to the brain. Differences in projections indicate that information about motion in different directions is sent to different destinations.

PHENOTYPIC HETEROGENEITY IN A FAMILY WITH X-LINKED FAMILIAL EXUDATIVE VITREORETINOPATHY WITH PREVENTION OF VISUAL LOSS IN AN AFFECTED MALE CHILD WITH LASER TREATMENT IN INFANCY.

PURPOSE: To present the scope of prenatal diagnosis and early treatment of patients with clinically heterogeneous phenotypic retinal dysplasia associated with NDP gene variants. METHODS: Retrospective. Review of electronic medical records. RESULTS: Twenty-nine-year-old woman known to carry a NDP gene variant presented to the eye clinic for consultation and risk assessment at her second pregnancy. Her 11-year-old son had bilateral retinal detachment, despite surgical treatment. The family declined prenatal testing. The patient was born full term, was examined, and underwent genetic testing after birth. He was found to have bilateral retinal avascular periphery abnormalities and preretinal hemorrhages on the left eye. The patient received bilateral laser treatment at 2 months of age. He was found to be doing well at 16 months after treatment with adequate visual acuity and flat maculae. The asymptomatic mother and maternal grandfather of the proband were found to have retinal periphery abnormalities with unremarkable posterior pole and excellent visual acuity. CONCLUSION: NDP gene variants associated with X-linked familial exudative vitreoretinopathy phenotype benefit from early treatment. Providers who take care of these patients need to monitor closely the pregnancy and delivery of a male child born to a female carrier to offer appropriate and timely treatment.

Cone Spacing Correlates With Retinal Thickness and Microperimetry in Patients With Inherited Retinal Degenerations.

Purpose: To determine whether high-resolution retinal imaging measures of macular structure correlate with visual function over 36 months in retinal degeneration (RD) patients and normal subjects. Methods: Twenty-six eyes of 16 RD patients and 16 eyes of 8 normal subjects were studied at baseline; 15 eyes (14 RD) and 11 eyes (6 normal) were studied 36 months later. Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) was used to identify regions of interest (ROIs) with unambiguous cones at baseline to measure cone spacing. AOSLO images were aligned with spectral-domain optical coherence tomography (SD-OCT) and fundus-guided microperimetry results to correlate structure and function at the ROIs. SD-OCT images were segmented to measure inner segment (IS) and outer segment (OS) thickness. Correlations between cone spacing, IS and OS thickness and sensitivity were assessed using Spearman correlation coefficient ρ with bootstrap analyses clustered by person. Results: Cone spacing (ρ = 0.57, P < 0.001) and macular sensitivity (ρ = 0.19, P = 0.14) were significantly correlated with eccentricity in patients. Controlling for eccentricity, cone spacing Z-scores were inversely correlated with IS (ρ = -0.29, P = 0.002) and OS thickness (ρ = -0.39, P < 0.001) in RD patients only, and with sensitivity in normal subjects (ρ = -0.22, P < 0.001) and RD patients (ρ = -0.38, P < 0.001). After 36 months, cone spacing increased (P < 0.001) and macular sensitivity decreased (P = 0.007) compared to baseline in RD patients. Conclusions: Cone spacing increased and macular sensitivity declined significantly in RD patients over 36 months. High resolution images of cone structure correlated with retinal sensitivity, and may be appropriate outcome measures for clinical trials in RD.

Partial Cone Loss Triggers Synapse-Specific Remodeling and Spatial Receptive Field Rearrangements in a Mature Retinal Circuit.

Resilience of neural circuits has been observed in the persistence of function despite neuronal loss. In vision, acuity and sensitivity can be retained after 50% loss of cones. While neurons in the cortex can remodel after input loss, the contributions of cell-type-specific circuits to resilience are unknown. Here, we study the effects of partial cone loss in mature mouse retina where cell types and connections are known. At first-order synapses, bipolar cell dendrites remodel and synaptic proteins diminish at sites of input loss. Sites of remaining inputs preserve synaptic proteins. Second-order synapses between bipolar and ganglion cells remain stable. Functionally, ganglion cell spatio-temporal receptive fields retain center-surround structure following partial cone loss. We find evidence for slower temporal filters and expanded receptive field surrounds, derived mainly from inhibitory inputs. Surround expansion is absent in partially stimulated control retina. Results demonstrate functional resilience to input loss beyond pre-existing mechanisms in control retina.

Parental comprehension following informed consent for pediatric cataract surgery.

OBJECTIVE: To investigate the effectiveness of information transfer by the pediatric cataract surgeon to the parents or guardians of children during the informed-consent process. DESIGN: Prospective observational case series. PARTICIPANTS: Parents of 31 children undergoing cataract surgery. METHODS: Parents were enrolled from the clinical practice of 1 pediatric cataract surgeon. Using a checklist developed in consultation with other pediatric cataract surgeons, the surgeon discussed the nature of the disease, the course without surgical intervention, the surgical procedure, the risks and benefits, and the postoperative care. Immediately after the discussion, parents were invited to complete a questionnaire assessing information recall. Analysis of variance and the t test were used to determine associations between questionnaire scores and demographic variables. The surgeon subsequently called parents and discussed again the issues that they had not remembered correctly, as identified by the questionnaire responses. The study and data accumulation were carried out with the approval of the Research Ethics Board at The Hospital for Sick Children, Toronto, Ont. Informed consent for the research was obtained from the parents or legal guardians of the children enrolled in the study. The study adhered to the tenets of the Declaration of Helsinki. RESULTS: Of 31 parents, 18 (58%) overestimated their understanding of the informed-consent discussion. Parents scored well on questions about the nature of the disease and the postoperative follow-up but scored lower on questions regarding surgical risks and outcomes. Parents identified several barriers to understanding, including the large amount of information, stress, and preoccupation with the child. No association was noted between the level of understanding and demographic factors. CONCLUSIONS: Parents may overestimate their understanding of informed-consent discussions. Some parents may be overly optimistic about risks and outcomes. The surgeon's follow-up communication with parents that addressed aspects insufficiently understood during the initial discussion provided a way of improving comprehension.