Retinal Prostheses: Engineering and Clinical Perspectives for Vision Restoration.

A retinal prosthesis, also known as a bionic eye, is a device that can be implanted to partially restore vision in patients with retinal diseases that have resulted in the loss of photoreceptors (e.g., age-related macular degeneration and retinitis pigmentosa). Recently, there have been major breakthroughs in retinal prosthesis technology, with the creation of numerous types of implants, including epiretinal, subretinal, and suprachoroidal sensors. These devices can stimulate the remaining cells in the retina with electric signals to create a visual sensation. A literature review of the pre-clinical and clinical studies published between 2017 and 2023 is conducted. This narrative review delves into the retinal anatomy, physiology, pathology, and principles underlying electronic retinal prostheses. Engineering aspects are explored, including electrode-retina alignment, electrode size and material, charge density, resolution limits, spatial selectivity, and bidirectional closed-loop systems. This article also discusses clinical aspects, focusing on safety, adverse events, visual function, outcomes, and the importance of rehabilitation programs. Moreover, there is ongoing debate over whether implantable retinal devices still offer a promising approach for the treatment of retinal diseases, considering the recent emergence of cell-based and gene-based therapies as well as optogenetics. This review compares retinal prostheses with these alternative therapies, providing a balanced perspective on their advantages and limitations. The recent advancements in retinal prosthesis technology are also outlined, emphasizing progress in engineering and the outlook of retinal prostheses. While acknowledging the challenges and complexities of the technology, this article highlights the significant potential of retinal prostheses for vision restoration in individuals with retinal diseases and calls for continued research and development to refine and enhance their performance, ultimately improving patient outcomes and quality of life.

Effects of physiological fluctuations on the estimation of vascular flow in eyes with idiopathic macular pucker.

OBJECTIVES: To evaluate the macular vascular flow in eyes with idiopathic macular pucker (EyeiMP), pre and post pars plana vitrectomy with epiretinal and limiting membranes peeling, and to compare it with the vascular flow in the healthy fellow eyes (Eyefellow), taken as physiological reference value. METHODS: 40 eyes of 40 patients were recruited. Best-corrected visual acuity (BCVA) was evaluated. Spectral domain optical coherence tomography (SD-OCT) and OCT-angiography parameters were central foveal thickness (CFT), choroidal thickness (CT), foveal avascular zone (FAZ) area, vessel area density (VAD), vessel length fraction (VLF), vessel density index (VDI) of superficial capillary plexus (SCP) and deep vascular complex (DVC), choriocapillaris (CC) flow. Absolute and relative difference calculation was applied to evaluate macular vascular flow in EyeiMP adjusted for physiological changes detected in Eyefellow. FOLLOW-UP: 6 months. RESULTS: BCVA improved (p = 0.003) in all cases following surgery. CFT reduced postoperatively (p = 0.0138). FAZ area was smaller in EyeiMP than Eyefellow (p = 0.0071) preoperatively and postoperatively it shrank further (p = 0.0027). After surgery, inverse correlation between FAZ area and BCVA was detected (r-0.683). VAD of SCP was pre- and post-operatively higher in EyeiMP than Eyefellow (baseline p = 0.0344, 6th month p = 0.0466). Relative difference of VDI of SCP (p = 0.0096) and CC flow (p = 0.0013) at 6 months reduced. DVC flow changed significantly only in Eyefellow. CT increased post-operatively in both EyeiMP (p = 0.0345) and Eyefellow (p = 0.00423), but relative difference did not change. CONCLUSIONS: Vascular flow indices monitoring demonstrated significant changes in both eyes: EyeiMP and Eyefellow. Relative difference of vascular flow provided objective estimate of changes due to iMP surgery taking into account physiological changes in Eyefellow.

The Role of Widefield and Ultra Widefield Optical Coherence Tomography in the Diagnosis and Management of Vitreoretinal Diseases.

BACKGROUND: This study reports on the advantages of wide-field (WF)- and ultra-widefield (UWF)- optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in managing different vitreoretinal diseases in a real-life setting using the new WF-Swept Source (SS)-OCT Xephilio S1 (Canon, Tokyo, Japan). METHODS: We conducted an observational retrospective case series study involving 1472 eyes that underwent retinal scans with Canon Xephilio® OCT-S1 between 1 March 2021 and 1 December 2021 at Eyecare Clinic (Brescia, Italy). All patients underwent routine ophthalmologic examinations along with WF and UWF color fundus retinography with Clarus 500™ (Carl Zeiss Meditec, Inc., Dublin, CA, USA) and Xephilio® OCT-S1. WF SS-OCT, UWF-OCT, WF-OCTA, and UWF-OCTA were taken by using Xephilio® OCT-S1. RESULTS: We analyzed 122 peripheral retinal lesions, 144 retinal detachment, 329 high myopic eyes, 37 pediatric cases, 60 vascular retinopathies, 15 choroidal lesions, and 90 eyes as follow-up post vitreoretinal surgery. The OCT-S1 was the only reliable and diagnostic exam for peripheral lesions, pediatric and high myopic cases, and significantly influenced the management in 10% of cases and the postoperative follow-up. CONCLUSIONS: WF and UWF OCT and OCTA imaging may help in the management of several vitreoretinal diseases, becoming an indispensable tool for the high-quality management of patients.

Long-term Stability of Epitheliotropic Factors in Frozen Serum Eye Drops.

The objective of this experimental study was to investigate the stability of functional proteins in human serum eye drops, which are used for the treatment of ocular surface disorders, after prolonged storage of 6 months at -20°C. After obtaining whole blood from 3 volunteers and preparing 100% (S100), 50% (S50), and 20% (S20) serum eye drops, fibronectin was quantified before and after storage for 6 months at -20°C using appropriate enzyme-linked immunoassay kits. The pH and microbial contamination of preparations were also evaluated longitudinally. The fibronectin concentration showed no significant reduction in undiluted (S100) or diluted (S50 and S20) serum after 6 months of frozen storage at -20°C. None of the preparations showed any microbial contamination and no significant changes in pH were noted during storage. Frozen serum eye drops appear stable after prolonged storage at -20°C. Fibronectin in serum is temperature and time resistant after prolonged storage at -20°C. While the impact of individual serum proteins on ocular surface health remains unclear, our results suggest that freezing up to 6 months provides adequate preservation of epitheliotropic factors and a minimal risk of microbial contamination.

AMNIOTIC MEMBRANE GRAFT FOR THE TREATMENT OF LARGE REFRACTORY MACULAR HOLE.

PURPOSE: Study off-label human amniotic membrane use outcomes for giant refractory macular hole closure. MATERIALS AND METHODS: The study was performed at Lahore General Hospital, Lahore, over 52 months on patients who had undergone standard macular hole surgical procedures for treatment, but the hole failed to close. Refractory macular hole dimensions ranged from 824 µ m to 1,568 µ m. Before surgery, patients underwent slit-lamp examination, fundus photography, and optical coherence tomography for macular scan. Amniotic membrane graft (AMG) used in surgery was harvested from a human placenta 24 hours before. Before AMG application, enough internal limiting membrane peeling was performed to ensure perfect fitting and recovery. All holes were plugged with AMG and SF6 gas tamponade. RESULTS: Twenty-nine patients, 20 men and nine women, were included in this study. Mean age of patients was 58 ± 6. Patients had refractory holes of average 1,237.48 ± 151.25 µ m. Post-op, 100% macular hole closure was achieved in all patients. Type 1 closure was found in patients (37.93%) who underwent AMG surgery within 3 months after primary surgical failure. Type 2 closure was found in patients (62.07%) who were operated on 3 months after primary surgical failure. CONCLUSION: Refractory macular holes treated by AMG with SF6 gas tamponade achieve anatomical Type 1 closure if performed within 3 months of primary surgical repair.

Drug-induced corneal deposits: an up-to-date review.

This review assesses different clinical aspects of the various known drug-induced corneal deposits, based on the corneal layer involved (epithelium, stroma and/or endothelium), and based on the drug class. The most well-known condition caused by drug deposits is vortex keratopathy, or corneal verticillata, which is a whorl-like opacity in the corneal epithelium. Vortex keratopathy is commonly caused by certain cationic amphiphilic drugs such as amiodarone, antimalarials, suramin, tamoxifen, chlorpromazine and non-steroidal anti-inflammatory drugs. These deposits usually occur once a certain dose of the drug is reached. Most cases present with mild to moderate symptoms with minimal visual impairment. Most of these deposits resolve automatically, after months to years of drug cessation. Notably, other drug classes can cause deposits in all three layers of the cornea. Chlorpromazine, gold, rifabutin, indomethacin and tyrosine kinase inhibitors can cause stromal deposits, with reduced visual acuity when the anterior stroma is involved. Chlorpromazine and rifabutin can also cause deposits in the endothelial layer of the cornea. Regardless of the type of corneal deposit, local therapies such as topical lubricants or corticosteroids may help improve symptoms. Drug cessation or modification can also be helpful but should be weighed against the systemic risks of the underlying disease.

Bilateral diffuse uveal melanocytic proliferation: Report of a novel optical coherence tomography finding and clinical response to plasmapheresis.

PURPOSE: To describe a novel optical coherence tomography (OCT) finding in a case of bilateral diffuse uveal melanocytic proliferation (BDUMP) and to report the clinical response to plasmapheresis. OBSERVATIONS: We report the case of a 54-year-old man who was being treated with adjuvant immune checkpoint inhibitors for metastatic renal cell carcinoma. He had suffered from bilateral progressive vision loss without ocular pain. At presentation in the retina clinic, visual acuity was counting fingers bilaterally. Examination revealed characteristic findings suggestive of a peculiar paraneoplastic intraocular syndrome called BDUMP. Multiple choroidal nevi-like melanocytic tumors were noted bilaterally. The diagnosis was confirmed using multimodal imaging with fluorescein angiography and fundus autofluorescence, which revealed a typical leopard pattern. Ultrasonography revealed choroidal thickening extending to the ciliary body. OCT showed multiple pockets of serous retinal detachment (SRD) and bacillary layer detachment (BALAD), a newly recognized and rarely described manifestation of the disease. The clinical response to plasmapheresis was robust with resolution of the BALAD and SRD and improvement of the vision to 20/30 in both eyes at the seven-month follow-up. CONCLUSIONS AND IMPORTANCE: BALAD is a newly recognized manifestation of BDUMP. Early recognition of this paraneoplastic syndrome and prompt initiation of plasmapheresis has the potential to improve and stabilize vision.