Ravi S. J. Singh

Subconjunctivally Implantable Hydrogels with Degradable and Thermoresponsive Properties for Sustained Release of Insulin to the Retina

The objective of this work is to develop subconjunctivally implantable, biodegradable hydrogels for sustained release of intact insulin to the retina to prevent and treat retinal neurovascular degeneration such as diabetic retinopathy. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide (NIPAAm) monomer and a dextran macromer containing multiple hydrolytically degradable oligolactate-(2-hydroxyetheyl methacrylate) units (Dex-lactateHEMA) in 25:75 (v:v) ethanol:water mixture solvent. Insulin is loaded into the hydrogels during the synthesis process with loading efficiency up to 98%. The hydrogels can release biologically active insulin in vitro for at least one week and the release kinetics can be modulated by varying the ratio between NIPAAm and Dex-lactateHEMA and altering the physical size of the hydrogels. The hydrogels are not toxic to R28 retinal neuron cells in culture medium with 100% cell viability. The hydrogels can be implanted under the conjunctiva without causing adverse effects to the retina based on hematoxylin and eosin stain, immunostaining for microglial cell activation, and electroretinography. These subconjunctivally implantable hydrogels have potential for long-term periocular delivery of insulin or other drugs to treat diabetic retinopathy and other retinal diseases.

Differential Roles of Hyperglycemia and Hypoinsulinemia in Diabetes Induced Retinal Cell Death: Evidence for Retinal Insulin Resistance

Diabetes pathology derives from the combination of hyperglycemia and hypoinsulinemia or insulin resistance leading to diabetic complications including diabetic neuropathy, nephropathy and retinopathy. Diabetic retinopathy is characterized by numerous retinal defects affecting the vasculature and the neuro-retina, but the relative contributions of the loss of retinal insulin signaling and hyperglycemia have never been directly compared. In this study we tested the hypothesis that increased retinal insulin signaling and glycemic normalization would exert differential effects on retinal cell survival and retinal physiology during diabetes. We have demonstrated in this study that both subconjunctival insulin administration and systemic glycemic reduction using the sodium-glucose linked transporter inhibitor phloridzin affected the regulation of retinal cell survival in diabetic rats. Both treatments partially restored the retinal insulin signaling without increasing plasma insulin levels. Retinal transcriptomic and histological analysis also clearly demonstrated that local administration of insulin and systemic glycemia normalization use different pathways to counteract the effects of diabetes on the retina. While local insulin primarily affected inflammation-associated pathways, systemic glycemic control affected pathways involved in the regulation of cell signaling and metabolism. These results suggest that hyperglycemia induces resistance to growth factor action in the retina and clearly demonstrate that both restoration of glycemic control and retinal insulin signaling can act through different pathways to both normalize diabetes-induced retinal abnormality and prevent vision loss.

Outer retinal structure after closed-globe blunt ocular trauma.

Purpose: To evaluate outer retinal structural abnormalities in patients with visual deficits after closed-globe blunt ocular trauma. Methods: Nine subjects with visual complaints after closed-globe blunt ocular trauma were examined between 1 month after trauma and 6 years after trauma. Spectral domain optical coherence tomography was used to assess the outer retinal architecture, whereas adaptive optics scanning light ophthalmoscopy was used to analyze the photoreceptor mosaic integrity. Results: Visual deficits ranged from central scotomas to decreased visual acuity. Spectral domain optical coherence tomography defects included focal foveal photoreceptor lesions, variable attenuation of the interdigitation zone, and mottling of the outer segment band, with one subject having normal outer retinal structure. Adaptive optics scanning light ophthalmoscopy revealed disruption of the photoreceptor mosaic in all subjects, variably manifesting as foveal focal discontinuities, perifoveal hyporeflective cones, and paracentral regions of selective cone loss. Conclusion: We observe persistent outer retinal disruption in subjects with visual complaints after closed-globe blunt ocular trauma, albeit to a variable degree. Adaptive optics scanning light ophthalmoscopy imaging allows the assessment of photoreceptor structure at a level of detail not resolvable using spectral domain optical coherence tomography or other current clinical imaging tools. Multimodal imaging seems to be useful in revealing the cause of visual complaints in patients after closed-globe blunt ocular trauma. Future studies are needed to better understand how photoreceptor structure changes longitudinally in response to various traumas.

Bilateral central retinal artery occlusions in an infant with hyperhomocysteinemia

A previously healthy 7-week-old boy developed bilateral central retinal artery occlusions in the presence of hyperhomocysteinemia and elevated serum methylmalonic acid and was found to have a transcobalamin receptor mutation. Retinal arterial occlusion is uncommon in young patients and typically prompts a systemic workup. In cases of atypical retinal arterial occlusion, hyperhomocysteinemia should be investigated.

Acute Exudative Polymorphous Vitelliform Maculopathy in a Patient With Lyme Disease

Acute exudative polymorphous vitelli-form maculopathy (AEPVM) is a rare condition of unclear etiology that has been seen in association with respiratory and viral infections. It has also been reported as a paraneoplastic phenomenon in older individuals. The authors report the first case of AEPVM associated with Lyme disease with over 3.5 years of follow-up. Multimodality serial imaging suggested the lesions began as multiple serous detachments followed by accumulation of photoreceptor outer segments in the subretinal space that gradually resolved over time and gave rise to the characteristic fundus findings at various stages.

Retinal Complications Associated With Pars Plana Vitrectomy for Macular Holes or Epiretinal Membranes in Eyes With Previous Retinal Detachment Repair

Retinal Complications Associated With Pars Plana Vitrectomy for Macular Holes or Epiretinal Membranes in Eyes With Previous Retinal Detachment Repair Pars plana vitrectomy (PPV) is associated with risk of intraoperative retinal tears (RTs) and postoperative rhegmatogenous retinal detachment (RRD). Eyes undergoing RRD repair are at higher risk for developing subsequent epiretinal membranes (ERMs) that may compromise vision.1,2 For cannulated surgery as compared with standard 20-gauge PPV, we previously reported markedly lower of risk of intraoperative RT (3.3% vs 23.0%, respectively) and a trend toward reduced risk of postoperative RD (2.8% vs 5.9%, respectively).3 However, in eyes with previous RRD repair, risks of these events are not well documented. Therefore, we evaluated eyes with previous RRD repair undergoing PPV for ERMs or macular holes (MHs) and compared them with eyes without prior RRD.

CLINICAL EVALUATION OF THE RAPID ACCESS VITREAL INJECTION GUIDE: A Handheld Instrument for Assisting Intravitreal Injections.

Purpose: The Rapid Access Vitreal Injection (RAVI) guide combines the function of an eyelid speculum and measuring caliper into a single instrument for assisting intravitreal injections. This study clinically evaluated the RAVI guide with respect to patient acceptance, complication rates, and operative goals. Methods: A prospective study was performed on 54 patients undergoing intravitreal injections using the RAVI guide (n = 32) or the speculum/caliper (n = 22). Device-related pain was assessed using the Wong-Baker scoring system, scaled from 0 (no pain) to 10 (agonizing pain). Results: Mean device-related pain score did not differ significantly between the 2 groups, with scores of 0.6 and 0.7 for the RAVI guide and speculum groups, respectively. The rate of significant pain (score of ≥2) was twice as high in the speculum group (7 of 22, 32%) compared with the RAVI guide group (5 of 32, 16%), but this difference was not statistically significant (P = 0.19, Fishers exact test). Operative goals of avoiding needle touch to lashes/lids and guiding needle insertion to the intended site were achieved in all patients. Conclusion: The RAVI guide appeared equivalent to the eyelid speculum in achieving operative goals, with similarly low pain scores. It has the potential for facilitating efficient, accurate, and safe intravitreal injections.