Effectiveness and Safety of a phototherapeutic contact lens for Diabetic Retinopathy

Purpose : Diabetic retinopathy (DR) is a leading complication of diabetes. It is thought that increased rod metabolism under dark adaptation exacerbates hypoxia in diabetic retina. Nowadays most treatments for DR are invasive and need multiple clinic visits. Recently a phototherapeutic contact lens has been designed to provide illumination to retina as a means to supress dark adaptation. It may be possible to delay the progression of DR. The purpose of this study is to explore the bioactivity and safety of this device. Methods : Six eyes from three healthy mature white New Zealand rabbits were used. The phototherapeutic contact lens was placed on treated eye. An non-phototherapeutic contact lens was used on the fellow eye as a control. To determine bioactivity of photoreceptors, an ERG was performed. Flash response, including amplitude and implicit time on scotopic condition were analyzed at different flash intensities (100, 300, 1000, 3000, 10000, 25000 mcd.s/m^2, respectively). Animals were under a 20-minutes period of dark adaption before any ERG. Then the contact lens were swapped on the eyes and the ERG were repeated. The whole process was performed in a dark room under dim red light. Once ERG were completed, the phototherapeutic contac lens was sutured to the eye for a long–term period (28 days) to verify safety. There will be a statistical analysis using Graph Pad Prism 7.0, determining the degree of correlation between the groups. Histological analysis will be performed to determine safety. Results : The ERG showed that both the amplitude and implicit time of b-wave in the treated eye were significantly shorter than the untreated eye under scotopic conditions (Figure 1). No significant difference in the amplitude and implicit time of a-wave was observed. A representative plot (Figure 2) shows significant depression of b-wave, both in the amplitude and implicit time (amplitude: p=0.01; implicit time: p<0.001). Conclusions : The phototherapeutic contact lens can effectively reduce the bioactivity of the retina, without ocular side effects in an acute follow-up. Further studies should be performed for a long-term placement in both healthy and retinal ischemic animal models to determine whether this device can reduce oxygen consumption in retina and delay disease progression. Long-term histology from contact lens safety is on going and will be presented

Effectiveness and Safety of a phototherapeutic contact lens for Diabetic Retinopathy

Purpose : Diabetic retinopathy (DR) is a leading complication of diabetes. It is thought that increased rod metabolism under dark adaptation exacerbates hypoxia in diabetic retina. Nowadays most treatments for DR are invasive and need multiple clinic visits. Recently a phototherapeutic contact lens has been designed to provide illumination to retina as a means to supress dark adaptation. It may be possible to delay the progression of DR. The purpose of this study is to explore the bioactivity and safety of this device. Methods : Six eyes from three healthy mature white New Zealand rabbits were used. The phototherapeutic contact lens was placed on treated eye. An non-phototherapeutic contact lens was used on the fellow eye as a control. To determine bioactivity of photoreceptors, an ERG was performed. Flash response, including amplitude and implicit time on scotopic condition were analyzed at different flash intensities (100, 300, 1000, 3000, 10000, 25000 mcd.s/m^2, respectively). Animals were under a 20-minutes period of dark adaption before any ERG. Then the contact lens were swapped on the eyes and the ERG were repeated. The whole process was performed in a dark room under dim red light. Once ERG were completed, the phototherapeutic contac lens was sutured to the eye for a long–term period (28 days) to verify safety. There will be a statistical analysis using Graph Pad Prism 7.0, determining the degree of correlation between the groups. Histological analysis will be performed to determine safety. Results : The ERG showed that both the amplitude and implicit time of b-wave in the treated eye were significantly shorter than the untreated eye under scotopic conditions (Figure 1). No significant difference in the amplitude and implicit time of a-wave was observed. A representative plot (Figure 2) shows significant depression of b-wave, both in the amplitude and implicit time (amplitude: p=0.01; implicit time: p<0.001). Conclusions : The phototherapeutic contact lens can effectively reduce the bioactivity of the retina, without ocular side effects in an acute follow-up. Further studies should be performed for a long-term placement in both healthy and retinal ischemic animal models to determine whether this device can reduce oxygen consumption in retina and delay disease progression. Long-term histology from contact lens safety is on going and will be presented

Sympathetic Effects of Internal Carotid Nerve Manipulation on Choroidal Vascularity and Related Measures

Purpose: To investigate specific effects of denervation and stimulation of the internal carotid nerve (ICN) on the choroid and retina. Methods: Female Sprague Dawley rats underwent unilateral ICN transection (n = 20) or acute ICN electrical stimulation (n = 7). Rats in the denervation group were euthanized 6 weeks after nerve transection, and eyes were analyzed for changes in choroidal vascularity (via histomorphometry) or angiogenic growth factors and inflammatory markers (via ELISA). Rats in the stimulation group received acute ICN electrical stimulation with a bipolar cuff electrode over a range of stimulus amplitudes, frequencies, and pulse widths. Choroidal blood flow and pupil diameter were monitored before, during, and after stimulation. Results: Six weeks after unilateral ICN transection, sympathectomized choroids exhibited increased vascularity, defined as the percentage of choroidal surface area occupied by blood vessel lumina. Vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2) protein levels in denervated choroids were 61% and 124% higher than in contralateral choroids, respectively. TNF-α levels in denervated retinas increased by 3.3-fold relative to levels in contralateral retinas. In animals undergoing acute ICN electrical stimulation, mydriasis and reduced choroidal blood flow were observed in the ipsilateral eye. The magnitude of the reduction in blood flow correlated positively with stimulus frequency. Conclusions: Modulation of ICN activity reveals a potential role of the ocular sympathetic system in regulating endpoints related to neovascular diseases of the eye

High resolution optical coherence elastography of retina under prosthetic electrode

BackgroundQuantitatively investigating the biomechanics of retina with a retinal prosthetic electrode, we explored the effects of the prosthetic electrode on the retina, and further supplemented data for a potential clinical trial.MethodsBiomechanical properties were assessed with a high resolution optical coherence tomography (OCT) based elastography (OCE) system. A shaker was used to initiate elastic waves and an OCT system was used to track axial displacement along with wave propagation. Rabbits received surgery to implant the retinal prosthetic electrode, and elastic wave speed was measured before and after implantation; anatomical B-mode images were also acquired.ResultsSpatial-temporal maps of each layer in retina with and without prosthetic electrodes were acquired. Elastic wave speed of nerve fiber to inner plexiform layer, inner nuclear to outer nuclear layer, retinal pigmented epithelium layer and choroid to sclera layer without prosthetic electrode were found to be 3.66±0.36, 5.33±0.07, 6.85±0.37, and 9.69±0.24 m/s, respectively. With prosthetic electrode, the elastic wave speed was found to be 4.09±0.26, 5.14±0.11, 6.88±0.70, and 9.99±0.73 m/s, respectively in each layer.ConclusionsOur results show that the elastic wave speed in each layer of retina is slightly faster with the retinal electrode, and further demonstrate that the retinal prosthetic electrode does not affect biomechanical properties significantly. In the future, we expect OCE technology to be used by clinicians where it could become part of routine testing and evaluation of the biomechanical properties of the retina in response to long term use of prosthetic electrodes in patients

An Oral Polyphenol Formulation to Modulate the Ocular Surface Inflammatory Process and to Improve the Symptomatology Associated with Dry Eye Disease

Due to their antioxidant, anti-inflammatory, neuroprotective, and anti-angiogenic effects, polyphenols are first-rate candidates to prevent or treat chronic diseases in which oxidative stress-induced inflammation plays a role in disease pathogenesis. Dry eye disease (DED) is a common pathology, on which novel phenolic compound formulations have been tested as an adjuvant therapeutic approach. However, polyphenols are characterized by limited stability and solubility, insolubility in water, very rapid metabolism, and a very short half-life. Thus, they show poor bioavailability. To overcome these limitations and improve their stability and bioavailability, we evaluated the safety and efficacy of an oral formulation containing among other compounds, polyphenols and omega-3 fatty acids, with the addition of a surfactant in patients with DED. Subjects were randomly assigned to one of four study groups including the study formulation (A), placebo (P), the study formulation + eye lubricant (A + L), and placebo + eye lubricant (P + L). Patients from the A and P groups were instructed to take two capsules every 24 h, while patients in the L groups also added one drop of lubricant twice a day for 12 weeks as well. Regarding safety, non-ocular abnormalities were observed during study formulation therapy. Liver function tests did not show any statistically significant difference (baseline vs. week 4). Concerning efficacy, there was a statistically significant difference between baseline, month 1, and month 3 in the OSDI (Ocular Surface Disease Index) test results in both treatment groups (group A and group A + L). Furthermore, both groups showed statistically significant differences between baseline and month 3 regarding the non-invasive film tear breakup time (NIF-BUT) score and a positive trend related to Shirmer’s test at month 3. The non-invasive average breakup time (NIAvg-BUT) score showed a statistically significant difference at month 3 when compared with baseline in the A + L group. The P + L group showed a statistically significant difference in terms of the OSDI questionary between baseline and month 3. Regarding the lissamine green staining, the A + L group showed a statistical difference between baseline and month 3 (p = 0.0367). The placebo + lubricant group did not show statistically significant differences. Finally, the placebo group did not show any data with statistically significant differences. Consequently, this polyphenol formulation as a primary treatment outperformed the placebo alone, and the polyphenol oral formulation used as an adjuvant to artificial tears was superior to the combination of the placebo and the artificial tears. Thus, our data strongly suggest that this polyphenol oral formulation improves visual strain symptoms and tear film status in patients with mild to moderate DED

Tissue Engineering Strategies for Retina Regeneration.

The retina is a complex and fragile photosensitive part of the central nervous system which is prone to degenerative diseases leading to permanent vision loss. No proven treatment strategies exist to treat or reverse the degenerative conditions. Recent investigations demonstrate that cell transplantation therapies to replace the dysfunctional retinal pigment epithelial (RPE) cells and or the degenerating photoreceptors (PRs) are viable options to restore vision. Pluripotent stem cells, retinal progenitor cells, and somatic stem cells are the main cell sources used for cell transplantation therapies. The success of retinal transplantation based on cell suspension injection is hindered by limited cell survival and lack of cellular integration. Recent advances in material science helped to develop strategies to grow cells as intact monolayers or as sheets on biomaterial scaffolds for transplantation into the eyes. Such implants are found to be more promising than the bolus injection approach. Tissue engineering techniques are specifically designed to construct biodegradable or non-degradable polymer scaffolds to grow cells as a monolayer and construct implantable grafts. The engineered cell construct along with the extracellular matrix formed, can hold the cells in place to enable easy survival, better integration, and improved visual function. This article reviews the advances in the use of scaffolds for transplantation studies in animal models and their application in current clinical trials

Tissue Engineering Strategies for Retina Regeneration

The retina is a complex and fragile photosensitive part of the central nervous system which is prone to degenerative diseases leading to permanent vision loss. No proven treatment strategies exist to treat or reverse the degenerative conditions. Recent investigations demonstrate that cell transplantation therapies to replace the dysfunctional retinal pigment epithelial (RPE) cells and or the degenerating photoreceptors (PRs) are viable options to restore vision. Pluripotent stem cells, retinal progenitor cells, and somatic stem cells are the main cell sources used for cell transplantation therapies. The success of retinal transplantation based on cell suspension injection is hindered by limited cell survival and lack of cellular integration. Recent advances in material science helped to develop strategies to grow cells as intact monolayers or as sheets on biomaterial scaffolds for transplantation into the eyes. Such implants are found to be more promising than the bolus injection approach. Tissue engineering techniques are specifically designed to construct biodegradable or non-degradable polymer scaffolds to grow cells as a monolayer and construct implantable grafts. The engineered cell construct along with the extracellular matrix formed, can hold the cells in place to enable easy survival, better integration, and improved visual function. This article reviews the advances in the use of scaffolds for transplantation studies in animal models and their application in current clinical trials

Long-Term Transplant Effects of iPSC-RPE Monolayer in Immunodeficient RCS Rats

Retinal pigment epithelium (RPE) replacement therapy is evolving as a feasible approach to treat age-related macular degeneration (AMD). In many preclinical studies, RPE cells are transplanted as a cell suspension into immunosuppressed animal eyes and transplant effects have been monitored only short-term. We investigated the long-term effects of human Induced pluripotent stem-cell-derived RPE (iPSC-RPE) transplants in an immunodeficient Royal College of Surgeons (RCS) rat model, in which RPE dysfunction led to photoreceptor degeneration. iPSC-RPE cultured as a polarized monolayer on a nanoengineered ultrathin parylene C scaffold was transplanted into the subretinal space of 28-day-old immunodeficient RCS rat pups and evaluated after 1, 4, and 11 months. Assessment at early time points showed good iPSC-RPE survival. The transplants remained as a monolayer, expressed RPE-specific markers, performed phagocytic function, and contributed to vision preservation. At 11-months post-implantation, RPE survival was observed in only 50% of the eyes that were concomitant with vision preservation. Loss of RPE monolayer characteristics at the 11-month time point was associated with peri-membrane fibrosis, immune reaction through the activation of macrophages (CD 68 expression), and the transition of cell fate (expression of mesenchymal markers). The overall study outcome supports the therapeutic potential of RPE grafts despite the loss of some transplant benefits during long-term observations

Co-grafts of Human Embryonic Stem Cell Derived Retina Organoids and Retinal Pigment Epithelium for Retinal Reconstruction in Immunodeficient Retinal Degenerate Royal College of Surgeons Rats

End-stage age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are two major retinal degenerative (RD) conditions that result in irreversible vision loss. Permanent eye damage can also occur in battlefields or due to accidents. This suggests there is an unmet need for developing effective strategies for treating permanent retinal damages. In previous studies, co-grafted sheets of fetal retina with its retinal pigment epithelium (RPE) have demonstrated vision improvement in rat retinal disease models and in patients, but this has not yet been attempted with stem-cell derived tissue. Here we demonstrate a cellular therapy for irreversible retinal eye injuries using a "total retina patch" consisting of retinal photoreceptor progenitor sheets and healthy RPE cells on an artificial Bruch's membrane (BM). For this, retina organoids (ROs) (cultured in suspension) and polarized RPE sheets (cultured on an ultrathin parylene substrate) were made into a co-graft using bio-adhesives [gelatin, growth factor-reduced matrigel, and medium viscosity (MVG) alginate]. In vivo transplantation experiments were conducted in immunodeficient Royal College of Surgeons (RCS) rats at advanced stages of retinal degeneration. Structural reconstruction of the severely damaged retina was observed based on histological assessments and optical coherence tomography (OCT) imaging. Visual functional assessments were conducted by optokinetic behavioral testing and superior colliculus electrophysiology. Long-term survival of the co-graft in the rat subretinal space and improvement in visual function were observed. Immunohistochemistry showed that co-grafts grew, generated new photoreceptors and developed neuronal processes that were integrated into the host retina. This novel approach can be considered as a new therapy for complete replacement of a degenerated retina