Simultaneous perception of prosthetic and natural vision in AMD patients.

Loss of photoreceptors in atrophic age-related macular degeneration (AMD) results in severe visual impairment. Since the low-resolution peripheral vision is retained in such conditions, restoration of central vision should not jeopardize the surrounding healthy retina and allow for simultaneous use of the natural and prosthetic sight. This interim report, prespecified in the study protocol, presents the first clinical results with a photovoltaic substitute of the photoreceptors providing simultaneous use of the central prosthetic and peripheral natural vision in atrophic AMD. In this open-label single group feasibility trial (NCT03333954, recruitment completed), five patients with geographic atrophy have been implanted with a wireless 2 x 2 mm-wide 30 µm-thick device, having 378 pixels of 100 µm in size. All 5 patients achieved the primary outcome of the study by demonstrating the prosthetic visual perception in the former scotoma. The four patients with a subretinal placement of the chip demonstrated the secondary outcome: Landolt acuity of 1.17 ± 0.13 pixels, corresponding to the Snellen range of 20/460-20/565. With electronic magnification of up to a factor of 8, patients demonstrated prosthetic acuity in the range of 20/63-20/98. Under room lighting conditions, patients could simultaneously use prosthetic central vision and their remaining peripheral vision in the implanted eye and in the fellow eye.

A novel nonsense variant in REEP6 is involved in a sporadic rod-cone dystrophy case.

Rod-cone dystrophy (RCD), also called retinitis pigmentosa, is the most common form of progressive inherited retinal disorders secondary to photoreceptor degeneration. It is a genetically heterogeneous disease characterized by night blindness, followed by visual field constriction and, in most severe cases, total blindness. The aim of our study was to identify the underlying gene defect leading to severe RCD in a 60-year-old woman. The patient's DNA was investigated by targeted next generation sequencing followed by whole exome sequencing. A novel nonsense variant, c.267G>A p.(Trp89*), was identified at a homozygous state in the proband in REEP6 gene, recently reported mutated in 7 unrelated families with RCD. Further functional studies will help to understand the physiopathology associated with REEP6 mutations that may be linked to a protein trafficking defect.

Multimodal imaging and functional correlations identify unusual cases of macular retinal pigment epithelium hypopigmentation occurring without functional loss.

PURPOSE: Patients with unusual macular retinal pigment epithelium (RPE) hypopigmentation are described and analyzed using retinal multimodal imaging. METHODS: We report three cases of patients with unilateral (2) or bilateral (1) macular lesions discovered incidentally on fundoscopy. A comprehensive ophthalmic examination including visual acuity, fundoscopy, spectral-domain optical coherence tomography (SD-OCT), short-wavelength light and near-infrared autofluorescence, fluorescein angiography, microperimetry, multifocal electroretinogram, adaptive optics (AO), and OCT-angiography (OCT-A) has been performed. RESULTS: Visual acuity was 20/20 in both eyes of all patients. The lesion appeared hyperautofluorescent on short-wavelength light and hypoautofluorescent on near-infrared light. Fluorescein angiography revealed a sharply demarcated macular hyperfluorescence without any leakage, suggesting a window defect. Interestingly, SD-OCT revealed only a choroidal hyperreflectivity in relation to the lesions without any abnormality of the outer retinal layers. Microperimetry was normal except for 1 patient with bilateral lesion and subtle decrease in macular sensitivity. Mf ERG was normal in all three patients. AO showed a well-preserved cone mosaic, suggesting that the abnormality was localized under the photoreceptor layers. OCT-A revealed hyperreflectivity just below the RPE layer, corresponding to the macular lesion observed on fundoscopy and the choroidal hyperreflectivity seen on SD-OCT. CONCLUSIONS: Macular RPE hypopigmentation should be considered in case of an isolated macular lesion without functional visual impairment or anatomical defect on SD-OCT.

ARL2BP mutations account for 0.1% of autosomal recessive rod-cone dystrophies with the report of a novel splice variant.

We report a novel ARL2BP splice site mutation after whole-exome sequencing (WES) applied to a Moroccan family including two sisters affected with autosomal recessive rod-cone dystrophy (arRCD). Subsequent analysis of 844 index cases did not reveal further pathogenic chances in ARL2BP indicating that mutations in ARL2B are a rare cause of arRCD (about 0.1%) in a large cohort of French patients.

[Hereditary retinal pathologies and AMD: new therapeutic perspectives]. / Pathologies rétiniennes d'origine héréditaire et DMLA: nouvelles perspectives thérapeutiques.

This article summarizes our current knowledge on two types of retinal diseases: hereditary retinal degeneration and wet aged-related macular degeneration. Our understanding of retinal physiopathology in hereditary retinal degeneration and the successful experimental therapeutic results on animal models call for a new approach to these patients to prepare future clinical trials. Longitudinal follow-up of the functional alteration rhythm based on international standards and by expert centers is an essential prerequisite to including these patients in future clinical trials. Creating international databases that include data on follow-up using electrophysiological, psychophysical and morphological analyses would require standards defining how each of these procedures should be carried out. Furthermore, the relevance and value of the various examinations would then be evaluated in a longitudinal manner. The repeated use of these procedures in the various centers would bring to light any limitations these techniques may have for use in prospective studies. Continuous re-evaluation of these investigative techniques will therefore be necessary, a crucial factor in the preparation of multicenter clinical studies. The inclusion of patients phenotyped at different centers would require that certification procedures be set up for these centers. A great leap forward, clinical trials on new antiangiogenic approaches for the treatment of neovascular AMD are currently underway. The reasons for the switch between the neovascular and atrophic forms of AMD are as yet unknown, but these new approaches are based on the events that occur sequentially during the angiogenic response.

Protective effect of trimetazidine in a model of ischemia-reperfusion in the rat retina.

Trimetazidine is an anti-ischemic agent which is frequently prescribed as a prophylactic treatment of episodes of angina pectoris and as a symptomatic treatment of vertigo and tinnitus. It has also shown beneficial effects in models of visual dysfunction, but the mechanism(s) by which this occurs is as yet undefined. The present study was intended to evaluate the influence of trimetazidine on retinal damage induced by ischemia-reperfusion in a rat model. Retinal ischemia was induced by increasing intraocular pressure to 160 mm Hg for 60 min. Trimetazidine or buffer controls were administered 3 days before the ischemia or in the postischemic period. The degree of retinal damage was assessed after 15 and 30 days of reperfusion after the ischemic insult by histopathologic study according to Hughes' quantification of ischemic damage. Retinal ischemia led to significant reductions in thickness and cell number, mainly in the inner retinal layers. The results from the study demonstrate that treatment with intraperitoneally injected trimetazidine conferred significant protection against retinal ischemic damage. Better results were obtained in the pretreatment group after 15 days of reperfusion. Trimetazidine protects the rat retina from pressure-induced ischemic injury and might be considered a potential therapeutic modality for combating retinal ischemia.

Rod-cone interactions: developmental and clinical significance.

During the last decade, numerous research reports have considerably improved our knowledge about the physiopathology of retinal degenerations. Three non-mutually exclusive general areas dealing with therapeutic approaches have been proposed; gene therapy, pharmacology and retinal transplantations. The first approach involving correction of the initial mutation, will need a great deal of time and further development before becoming a therapeutic tool in human clinical practice. The observation that cone photoreceptors, even those seemingly unaffected by any described anomaly, die secondarily to rod disappearance related to mutations expressed specifically in the latter, led us to study the interactions between these two photoreceptor populations to search for possible causal links between rod degeneration and cone death. These in vivo and in vitro studies suggest that paracrine interactions between both cell types exist and that rods are necessary for continued cone survival. Since the role of cones in visual perception is essential, pending the identification of the factors mediating these interactions underway, rod replacement by transplantation and/or neuroprotection by trophic factors or alternative pharmacological means appear as promising approaches for limiting secondary cone loss in currently untreatable blinding conditions.

Selective transplantation of rods delays cone loss in a retinitis pigmentosa model.

BACKGROUND: Rod-cone retinal degenerations (retinitis pigmentosa) are typified by initial rod loss followed by secondary cone death. Rod death, predominantly caused by gene mutations expressed specifically in these cells, induces scotopic vision loss. Cone death, the overriding cause of blindness, has no current explanation. Disease progression and preliminary data suggest that cone survival depends on rods. OBJECTIVE: To establish whether rod transplantation into mutant rodless retinas could halt cone loss. METHODS: We transplanted pure sheets of rods isolated from normal-sighted mice into the subretinal space of recipient retinal degeneration mice lacking rods but possessing approximately 30% residual cones. Control animals were unoperated on or grafted with inner retinal cells from young normal donors, entire retinas from aged retinal degeneration mice, or gelatin. Two weeks after surgery, we quantified by an unbiased method the numbers of host retinal cones after immunolabeling with specific markers. RESULTS: Only mice receiving rod-rich transplants demonstrated statistically significant greater cone numbers, with rescue of 40% of host cones normally destined to die during this period. CONCLUSION: Cone survival depends specifically on rods. CLINICAL RELEVANCE: Such findings indicate that transplantation of rods could limit loss of cones, thus preserving useful vision in human retinitis pigmentosa. Arch Ophthalmol. 2000;118:807-811

Glial cell line-derived neurotrophic factor induces histologic and functional protection of rod photoreceptors in the rd/rd mouse.

PURPOSE: To evaluate the neuroprotective potential of glial cell line-derived neurotrophic factor (GDNF) in the retinal degeneration (rd/rd) mouse model of human retinitis pigmentosa. METHODS: Subretinal injections of GDNF were made into rd/rd mice at 13 and 17 days of age and electroretinograms (ERGs) recorded at 22 days. Control mice received saline vehicle injections or underwent no procedure. At 23 days of age, retinas from treated and control mice were fixed and processed for wholemount immunohistochemistry using an anti-rod opsin antibody, and rod numbers were estimated using an unbiased stereological systematic random approach. Subsequent to counting, immunolabeled retinas were re-embedded and sectioned in a transverse plane and the numbers of rods recalculated. RESULTS: Although ERGs could not be recorded from sham-operation or nonsurgical rd/rd mice at 22 days of age, detectable responses (both a- and b-waves) were observed in 4 of 10 GDNF-treated mice. Stereological assessment of immunolabeled rods at 23 days showed that control rd/rd retinas contained 41,880+/-3,890 (mean +/- SEM; n = 6), phosphate-buffered saline (PBS)-injected retinas contained 61,165+/-4,932 (n = 10; P < 0.001 versus control retinas) and GDNF-injected retinas contained 89,232+/-8,033 (n = 10; P < 0.001 versus control retinas, P < 0.002 versus PBS). This increase in rod numbers after GDNF treatment was confirmed by cell counts obtained from frozen sections. CONCLUSIONS: GDNF exerts both histologic and functional neuroprotective effects on rod photoreceptors in the rd/rd mouse. Thus rescue was demonstrated in an animal model of inherited retinal degeneration in which the gene defect was located within the rods themselves, similar to most forms of human retinitis pigmentosa. GDNF represents a candidate neurotrophic factor for palliating some forms of hereditary human blindness.

[A new mode of recording retinal activity: multifocal ERG]. / Nouveau mode d'enregistrement de l'activité rétinienne: ERG multifocal.

Global ERG recordings are only modified in conditions with diffuse or extensive retinal involvement. The use, over the last 6 months, of a new functional testing device: VERIS (visual evoked response imaging system) allows accurate detection and quantification of localized retinal function defects. Our preliminary experience shows that a careful preparation of subjects, standardized testing protocols and a good understanding of the device technology, especially software parameters are mandatory. We report our results on a series of 28 normal volunteers, grouped by age and describe the various graphic presentation of data collected. This technology should allow accurate detection and quantification of retinal functional defects in patients with age related macular degeneration as well as evaluation of visual function in retinitis pigmentosa patients before and after photoreceptor transplantation.

Gangliosides and neurotrophic growth factors in the retina. Molecular interactions and applications as neuroprotective agents.

Polypeptide growth factors and gangliosides can both be considered as trophic agents involved in almost all stages of neural cell development, differentiation, survival, and pathology. In most cases their physiological roles are still not clear due to the considerable complexity in their regulation. Several growth factors [e.g., basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF)] and one species of ganglioside (GM1) have been shown to exert interactions with each other and also to exhibit neuroprotective effects against retinal ischemia in vivo and cerebral excitotoxicity in vitro. Different experimental models are used to investigate their relevance to ischemic and excitotoxic conditions in the retina, and it is shown that (1) both bFGF and EGF show very effective neuroprotection for rat retinal neurones exposed to toxic levels of glutamate or its nonphysiological agonist kainate in vitro; (2) GM1 (10(-5M) used under the same conditions does not afford protection; (3) retinal glial cells also suffer morphological perturbations following glutamate or kainate treatment, but this effect is dependent on neuron-glial interactions, indicating the existence of intermediate neuron-derived messenger molecules; (4) these glial changes can be corrected by posttreatment with either bFGF or EGF in vitro; (5) using an in vivo animal model involving anterior chamber pressure-induced ischemia in adult rats, it is shown that either pretreatment by intraperitoneal injection of GM1, or posttreatment by intraocular injection of the same ganglioside, reduces significantly histological damage to inner nuclear regions; and (6) in cultured retinal Müller glial cells the existence of molecular and metabolic interactions between both types of trophic factors is demonstrated. Hence both these groups of trophic molecules show interesting features for retinal ischemic treatment.

Normal retina releases a diffusible factor stimulating cone survival in the retinal degeneration mouse.

The role of cellular interactions in the mechanism of secondary cone photoreceptor degeneration in inherited retinal degenerations in which the mutation specifically affects rod photoreceptors was studied. We developed an organ culture model of whole retinas from 5-week-old mice carrying the retinal degeneration mutation, which at this age contain few remaining rods and numerous surviving cones cocultured with primary cultures of mixed cells from postnatal day 8 normal-sighted mice (C57BL/6) retinas or retinal explants from normal (C57BL/6) or dystrophic (C3H/He) 5-week-old mice. After 7 days, the numbers of residual cone photoreceptors were quantified after specific peanut lectin or anti-arrestin antibody labeling by using an unbiased stereological approach. Examination of organ cultured retinas revealed significantly greater numbers of surviving cones (15-20%) if cultured in the presence of retinas containing normal rods as compared with controls or cocultures with rod-deprived retinas. These data indicate the existence of a diffusible trophic factor released from retinas containing rod cells and acting on retinas in which only cones are present. Because cones are responsible for high acuity and color vision, such data could have important implications not only for eventual therapeutic approaches to human retinal degenerations but also to define interactions between retinal photoreceptor types.

Growth factors and gangliosides as neuroprotective agents in excitotoxicity and ischemia.

1. At least two different groups of molecules can be considered neurotrophic factors because they exert a variety of effects upon neural cells. The first consists of the numerous families of polypeptide growth factors known to take part in almost all stages of neural cell growth and functioning, including development, differentiation, survival and pathology. The second group also is characterized by extensive complexity of multiple forms, and consists of the sialic acid-containing glycosphingolipids or gangliosides. These molecules also take part in the transfer of information from the extracellular milieu to the cell interior, and, similarly to growth factors, are participants in such aspects as development, differentiation and functioning. 2. In this short overview, we consider the existing data on the neuroprotective effects of growth factors [e.g., basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and brain-derived neurotrophic factor] and one species of ganglioside (GM1) against retinal ischemia in vivo and cerebral excitotoxicity in vitro. 3. We used three different experimental models to investigate their relevance to ischemic and excitotoxic conditions in the retina and have shown that: (a) both bFGF and EGF show highly effective neuroprotection for rat retinal neurons exposed to toxic levels of glutamate or its nonphysiological agonist kainate in vitro (b) retinal glial cells suffer morphological perturbations after glutamate or kainate treatment, and this effect depends on neuron-glial interactions; (c) these glial changes can also be corrected by posttreatment with either bFGF or EGF in vitro; (d) with the use of an in vivo animal model involving anterior chamber pressure-induced ischemia in adult rats, either pretreatment by intraperitoneal injection of GM1 or posttreatment by intraocular injection of the same ganglioside significantly reduces histological damage to inner nuclear regions. 4. Hence both groups of trophic molecules show interesting features for retinal ischemic treatment.

Intravitreal injection of ganglioside GM1 after ischemia reduces retinal damage in rats.

BACKGROUND AND PURPOSE: Gangliosides are normal components of cell membranes and contribute to structural rigidity and membrane function. They have been shown to protect against various insults in the brain. We have shown previously that GM1 administered intraperitoneally before the induction of retinal ischemia provides a protective effect. This study evaluates the protective effect of GM1 administered intravitreally after ischemia on retinal lesions. METHODS: We induced retinal ischemia unilaterally in Long-Evans rats by increasing intraocular pressure to 160 mm Hg for 60 minutes. GM1 (20 microL x 10(-5) mol/L) or saline (20 microL) was injected into the vitreous 15 minutes after ischemia, and the postischemic survival time was either 8 or 15 days. The degree of retinal damage was assessed by histopathological study. RESULTS: Retinal ischemia led to reductions in thickness and cell number, principally in the inner retinal layers (39% to 80%) and to a lesser extent in the outer retinal layers (26% to 45%). Postischemic treatment with intravitreally injected GM1 conferred significant protection against retinal ischemic damage after both 8 and 15 days of survival time. After 8 days of reperfusion, the ischemia-induced loss in overall retinal thickness was reduced by 15% and those of the inner nuclear and plexiform layers by 44% and 17%, respectively. Ischemic-induced ganglion cell and inner nuclear cell density losses were reduced by 37% and 27%, respectively. After 15 days of reperfusion, approximately the same statistically significant differences could be observed in comparison with the 15-day saline-injected group. CONCLUSIONS: GM1 protects the rat retina from pressure-induced ischemic injury when given intravitreally after the insult. The protection provided by GM1 after initiation of retinal damage could be of therapeutic interest.

Photoreceptor transplants increase host cone survival in the retinal degeneration (rd) mouse.

Retinal transplants offer a potentially interesting approach to treating human retinal degenerations, but so far little quantitative data are available on possible beneficial effects. We isolated photoreceptor layers from normal-sighted mice and grafted them into the subretinal space of retinal degeneration (rd) mice lacking rod photoreceptors. At 2 weeks after surgery, the numbers of residual host cone photoreceptors outside the graft zone were quantified following specific labelling. Examination of operated retinas revealed highly significantly greater numbers of surviving cones (mean of 38% more at 2 weeks) within the central field compared to sham-operated paired control retinas (p < 0.01). These are the first quantified data indicating a trophic effect of transplanted photoreceptors upon host cone cells. As cone cells are responsible for high acuity and colour vision, such data could have important implications not only for eventual therapeutic approaches to human retinal degenerations but also to understanding underlying interactions between retinal photoreceptors.

[Retinal grafts: biological problems and clinical stakes]. / Greffes de rétine: problèmes biologiques et enjeux cliniques.

Retinal transplantation, formerly perceived as unrealistic, has become over the past decade a major clinical and biological undertaking in several laboratories and eye clinics. We describe the insights gained through the pioneering experimental works of Del Cerro et al, Turner et al, Gouras et al, Aramant et al, Lund et al e.g. the survival of transplants, the lack of immune response to photoreceptors, their integration and expression of neuronal markers, but also the dysplastic arrangement into rosettes and the lack of a definitive proof for functionality. Our laboratory has undertaken to establish the trophic and synaptic functions of sheets of photoreceptors transplanted, as described by Silverman et al, in the subretinal space of mutant rd mice carrying a retinal degeneration similar to human retinitis pigmentosa. Clinical applications to this condition as well as in cases of end-stage age related macular degeneration are discussed.