The influence of subretinal injection pressure on the microstructure of the monkey retina

The 1-Step Versus 2-Step Subretinal Injection Trial (1,2-SIT)-A Randomized Controlled Trial to Compare Drug Reflux Following Subretinal Injection

PURPOSE

To estimate in humans, in vivo, drug retention in the subretinal space following either 1- or 2-step subretinal injection (SRI).

DESIGN

A single-masked, randomized, controlled trial.

METHODS

Patients presenting with submacular hemorrhage secondary to age-related macular degeneration were randomly allocated to receive subretinal tissue plasminogen activator (50 µg in 0.1 mL) with sodium fluorescein (10 µg in 0.1 mL) as an optical label either as a 1-step (n = 6) procedure, in which the drug defines the subretinal space, or as a 2-step (n = 6) procedure, in which balanced salt solution is first used to define the subretinal space, following pars plana vitrectomy. All patients underwent air-for-fluid exchange at the completion of surgery with subsequent 20% sulfahexafluoride gas and bevacizumab injection. Reflux of subretinally injected drug was calculated by performing fluorophotometry on the fluid collected at the end of air-for-fluid exchange. Patients received intravitreal anti-VEGF at 4-weekly intervals to the final follow-up at 12 weeks. The primary outcome measure was the proportion of drug reflux. Secondary outcomes included duration of surgery, change in visual acuity (VA), final VA, final foveal thickness, and change in foveal thickness. To determine our fluorophotometric technique's applicability to gene and cell therapy, real-time quantitative polymerase chain reaction was employed to determine adeno-associated viral (AAV) yields following exposure to 0.1 mg/mL sodium fluorescein and its effects on retinal progenitor cells (RPCs) was assessed using a cell viability assay.

RESULTS

Mean reflux was 4.8% ± 3.1% (mean ± SEM, range 0.4%-19.5%) for 1-step SRI and 3.9% ± 0.9% (range 1.7%-5.3%) for 2-step SRI (no significant difference in means; P = .0155 for the difference in variance). There was no significant difference in the duration of surgery (26.8 ± 1.2 minutes vs 30 ± 2.7 minutes), final VA (1.1 ± 0.26 [Snellen 20/252] vs 1.1 ± 0.32 [Snellen 20/252] logMAR), change in BCVA (-0.45 ± 0.27 vs -0.27 ± 0.23 logMAR) or foveal thickness (139.2 ± 33.2 µm vs 129.8 ± 21.1 µm). Quantitative polymerase chain reaction confirmed that AAV titers are not affected by 0.1 mg/mL sodium fluorescein in vitro, and viability assays suggest that it does not adversely affect RPC viability.

CONCLUSIONS

This study demonstrates that drug loss following SRI ranged from 0.4% to 19.8% (mean 4.3%). There is no significant difference between 1-step and 2-step SRI in the mean proportion of drug reflux, duration of surgery, change in neural retinal thickness, or change in BCVA. However, there is a significantly greater variability in reflux for 1-step injection compared to 2-step injection. AAV yields are not affected by 0.1 mg/mL sodium fluorescein, nor is RPC viability. These data suggest that sodium fluorescein may be an appropriate means of tracking subretinal AAV gene therapy and retinal cell therapy quantitatively and that the 2-step SRI approach is preferable to 1-step SRI to ensure consistency in drug delivery.

Fundus autofluorescence after vitrectomy with ILM peeling and subfoveal injection in diabetic macular edema

PurposeTo determine whether subretinal injections cause defects in the RPE that are visible on fundus autofluorescence (FAF).MethodsThis retrospective study analyzed twenty-six eyes after vitrectomy with ILM peeling and subretinal injection of balanced salt solution for diabetic macular edema (DME). FAF was performed before and 36 months after surgery. Four FAF patterns were distinguished: grade 1 -normal autofluorescence, grade 2 -one or more hyperautofluorescent spots, grade 3 -central increased autofluorescence, grade 4 -central decreased autofluorescence.ResultsVisual acuity improved from 0.18 to 0.26 Snellen (p = 0.03). Retinal thickness decreased (p = 0.01). The injection site would not be possible to spot on postoperative FAF without reviewing surgical videos. Grade 1 pattern was visible in 31% operated and 36% fellow eyes, Grade 2 pattern was observed in 11% operated and in 43% fellow eyes, Grade 3 pattern in 31% operated and in 14% fellow eyes and grade 4 pattern in 31% operated and in 14% fellow eyes.ConclusionNo abnormal FAF patterns were observed at the subretinal injection sites. ILM peeling likely decreases the pressure required to perform the injection and protects the RPE from iatrogenic damage. Anomalous autofluorescence patterns are most likely associated with long-standing disease.

Head-mounted surgical robots are an enabling technology for subretinal injections

Therapeutic protocols involving subretinal injection, which hold the promise of saving or restoring sight, are challenging for surgeons because they are at the limits of human motor and perceptual abilities. Excessive or insufficient indentation of the injection cannula into the retina or motion of the cannula with respect to the retina can result in retinal trauma or incorrect placement of the therapeutic product. Robotic assistance can potentially enable the surgeon to more precisely position the injection cannula and maintain its position for a prolonged period of time. However, head motion is common among patients undergoing eye surgery, complicating subretinal injections, yet it is often not considered in the evaluation of robotic assistance. No prior study has both included head motion during an evaluation of robotic assistance and demonstrated a significant improvement in the ability to perform subretinal injections compared with the manual approach. In a hybrid ex vivo and in situ study in which an enucleated eye was mounted on a human volunteer, we demonstrate that head-mounting a high-precision teleoperated surgical robot to passively reduce undesirable relative motion between the robot and the eye results in a bleb-formation success rate on moving eyes that is significantly higher than the manual success rates reported in the literature even on stationary enucleated eyes.

Insights into the effects of subretinal voretigene neparvovec-rzyl in RPE65-associated Leber congenital amaurosis

OBJECTIVE

Assess safety and effectiveness of subretinal gene replacement therapy at 18 months post treatment.

DESIGN

Retrospective, longitudinal study conducted at the Hospital for Sick Children in Toronto, Canada.

PARTICIPANTS

Patients with bi-allelic RPE65 variants, early onset retinal degeneration, and residual viable retina who underwent voretigene neparvovec r-zyl gene replacement therapy.

METHODS

Data collected included demographic information, molecular genetic results, and comprehensive ocular assessment results from preoperataive and postoperative visits up to 18 months. To assess the treatment's efficacy, postoperative best corrected visual acuity, full-field stimulus test (FST), visual field (VF) area, optical coherence tomography, and global satisfaction were compared to preoperative findings.

RESULTS

The procedures were safe with no complications. There was no significant improvement in visual acuity. Three eyes showed a slight reduction in VF area. All showed a reduction in ellipsoid zone thickness and area, but the outer nuclear layer thickness and area were stable. All had a significant improvement in retinal sensitivity, as per FST, allowing better navigation in a dim environment. All 3 patients reported being "very satisfied".

CONCLUSION

Following a safe gene replacement therapy, the 3 first Canadian cases had an improvement in retinal sensitivity as per FST, and our patients described their experience as positively life changing.

12-month outcomes after voretigene neparvovec gene therapy in paediatric patients with RPE65-mediated inherited retinal dystrophy

AIMS

To report main outcomes and complications following voretigene neparvovec (Luxturna) treatment in paediatric patients.

METHODS

Records of patients under the age of 17 treated by subretinal administration of voretigene neparvovec for confirmed biallelic RPE65-mediated inherited retinal dystrophy were retrospectively reviewed. Best-corrected visual acuity (BCVA) and data from spectral-domain optical coherence tomography, ultra-wide-field fundus imaging and Goldmann visual field (VF) were analysed at 12 months follow-up.

RESULTS

12 eyes of six patients (mean age: 7.8 years) were analysed. No intraoperative complications occurred. BCVA significantly improved at 12-month follow-up (mean LogMAR (logarithm of the minimal angle of resolution) BCVA: 1.0±0.8 at baseline vs 0.6±0.3 at 12 months, p=0.001). Mean central macular thickness and central outer nuclear layer thickness did not change at 12 months follow-up. VF V4e isopter did not show significant changes. Postoperatively complications included: elevated intraocular pressure in two eyes of the same patient, a parafoveal lamellar hole at 3 months post-treatment and atrophy on the injection site observed in all eyes except one, which significantly enlarged during 12 months (p=0.008).

CONCLUSIONS

Most paediatric patients treated by voretigene neparvovec showed a significant increase in visual function at 12 months follow-up. None of the postoperative complications prevented gains in visual function.

Simulation of murine retinal hemodynamics in response to tail suspension

The etiology of spaceflight-associated neuro-ocular syndrome (SANS) remains unclear. Recent murine studies indicate there may be a link between the space environment and retinal endothelial dysfunction. Post-fixed control (N = 4) and 14-day tail-suspended (TS) (N = 4) mice eye samples were stained and imaged for the vessel plexus and co-located regions of endothelial cell death. A custom workflow combined whole-mounted and tear reconstructed three-dimensional (3D) spherical retinal plexus models with computational fluid dynamics (CFD) simulation that accounted for the Fåhræus-Lindqvist effect and boundary conditions that accommodated TS fluid pressure measurements and deeper capillary layer blood flow distribution. TS samples exhibited reduced surface area (4.6 ± 0.5 mm2 vs. 3.5 ± 0.3 mm2, P = 0.010) and shorter lengths between branches in small vessels (<10 μm, 69.5 ± 0.6 μm vs. 60.4 ± 1.1 μm, P < 0.001). Wall shear stress (WSS) and pressure were higher in TS mice compared to controls, particularly in smaller vessels (<10 μm, WSS: 6.57 ± 1.08 Pa vs. 4.72 ± 0.67 Pa, P = 0.034, Pressure: 72.04 ± 3.14 mmHg vs. 50.64 ± 6.74 mmHg, P = 0.004). Rates of retinal endothelial cell death were variable in TS mice compared to controls. WSS and pressure were generally higher in cell death regions, both within and between cohorts, but significance was variable and limited to small to medium-sized vessels (<20 μm). These findings suggest a link may exist between emulated microgravity and retinal endothelial dysfunction that may have implications for SANS development. Future work with increased sample sizes of larger species or spaceflight cohorts should be considered.

Correlation between subretinal tissue plasminogen activator and air injection rates with pressure in a retina mimicking model

By investigating the correlation between the injection rate and pressure of subretinal tissue plasminogen activator (tPA) and air using a standard Viscous Fluid Control (VFC) system with a 38-gauge cannula, we aimed to establish guidelines for stable injections. We fabricated a retina mimicking model (RMM) with 0.25% agarose solution and an aluminum plate, and substituted submacular hemorrhage (SMH) and tPA with blood-mimicking fluid (BMF) and balanced salt solution (BSS), respectively. The diameter of the pre-bleb mimicking SMH in RMM was 1.30 ± 0.16 cm, increasing to 1.98 ± 0.24 cm and 1.83 ± 0.22 cm after bleb propagation with BSS and air, respectively. BSS injection rates were 2.86 ± 0.04 µl/sec, 6.74 ± 0.48 µl/sec and 8.55 ± 0.16 µl/sec at 8, 12, and 16 psi, respectively. Air injection rates were 37.98 ± 3.11 µl/sec, 79.01 ± 5.13 µl/sec and 156.06 ± 13.72 µl/sec at 2, 3 and 4 psi, respectively. By experimenting with different pressures in the RMM, we found 12 psi to be the minimum for proper BSS injection and 2 psi for air. These findings provide crucial parameters for safer surgery to prevent irreversible damage.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of Nonrodent Ocular Tissues

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/ inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in ocular tissues (eyes and glands and ocular adnexa) from laboratory nonrodent species (rabbits, dogs, minipigs, and nonhuman primates) used in nonclinical safety studies with an emphasis on ocular-targeted dosing. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes descriptions and visual depictions of spontaneous lesions and lesions induced by exposure to various test materials. A widely accepted and utilized internationally harmonized nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Dose-Dependent Progression of Chorioretinal Atrophy at the Injection Site After Subretinal Injection of rAAV2/8 in Nonhuman Primates

Objective

Progressive retinal atrophy has been described after subretinal gene therapy utilizing the adeno-associated virus (AAV) vector platform. To elucidate whether this atrophy is a consequence of inherent properties of AAV, or if it is related to the surgical trauma of subretinal delivery, we analyzed data from an Investigational New Drug-enabling study for PDE6A gene therapy in nonhuman primates.

Design

Animal study (nonhuman primates), retrospective data analysis.

Subjects

Forty eyes of 30 healthy nonhuman primates (macaca fascicularis) were included in the analysis. Two AAV dose levels (low: 1x10E11, high: 1x10E12) were compared with sham injection (balanced saline solution; BSS). Twenty untreated eyes were not analyzed.

Methods

Animals were treated with a sutureless 23G vitrectomy and single subretinal injections of AAV.PDE6A and/or BSS. The follow-up period was 12 weeks. Atrophy development was followed using fundus autofluorescence (AF), OCT, fluorescence angiography, and indocyanine green angiography.

Main Outcome Measures

Area [mm2] of retinal pigment epithelium atrophy on AF. Presence of outer retinal atrophy on optical coherence tomography. Area [mm2] of hyperfluorescence in fluorescence angiography and hypofluorescence in indocyanine green angiography.

Results

Progressive atrophy at the injection site developed in 54% of high-dose-treated, 27% of low-dose-treated, and 0% of sham-treated eyes. At the end of observation, the mean ± SD area of atrophy in AF was 1.19 ± 1.75 mm2, 0.25 ± 0.50 mm2, and 0.0 ± 0.0 mm2, respectively (sham × high dose: P = 0.01). Atrophic lesions in AF (P = 0.01) and fluorescence angiography (P = 0.02) were significantly larger in high-dose-treated eyes, compared with sham-treated eyes. Rate of progression in high-dose-treated eyes was 4.1× higher compared with low-dose-treated eyes.

Conclusion

Subretinal injection of AAV.PDE6A induced dose-dependent, progressive retinal atrophy at the site of injection. Findings from multimodal imaging were in line with focal, transient inflammation within the retina and choroid and secondary atrophy. Atrophic changes after gene therapy with AAV-based vector systems are not primarily due to surgical trauma and increase with the dose given.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Biomechanical considerations for optimising subretinal injections

Subretinal injection is the preferred delivery technique for various novel ocular therapies and is widely used because of its precision and efficient delivery of gene and cell therapies; however, choosing an injection point and defining delivery parameters to target a specified retinal location and area is an inexact science. We provide an overview of the key factors that play important roles during subretinal injections to refine the technique, enhance patient outcomes, and minimise risks. We describe the role of anatomical and physical variables that affect subretinal bleb propagation and shape and their impact on retinal integrity. We highlight the risks associated with subretinal injections and consider strategies to mitigate reflux and retinal trauma. Finally, we explore the emerging field of robotic assistance in improving intraocular manouvrability and precision to facilitate the injection procedure.

Liquid-Driven Microinjection System for Precise Fundus Injection

Microinjection is usually applied to the treatment of some retinal disorders, such as retinal vein cannulation and displaced submacular hemorrhage. Currently, the microinjection procedure is usually performed by using the viscous fluid control of a standard vitrectomy system, which applies a fixed air pressure through foot pedal activation. The injection process with the fixed pressure is uncontrollable and lacks feedback, the high flow rate of the injected drug may cause damage to the fundus tissue. In this paper, a liquid-driven microinjection system with a flow sensor is designed and developed specifically for fundus injection. In addition, a PID sliding mode control (SMC) method is proposed to achieve precise injection in the injection system. The experimental results of fundus simulation injection demonstrate that the microinjection system meets the requirements of fundus injection and reduces the impact of the injection process on the fundus tissue.

Predicting Language in Children with ASD Using Spontaneous Language Samples and Standardized Measures

This longitudinal study examined the degree to which standardized measures of language and natural language samples predicted later language usage in a heterogeneous sample of children with autism spectrum disorder (ASD), and how this relationship is impacted by ASD severity and interventions. Participants with a diagnosis of ASD (N = 54, 41 males) completed standardized assessments of language and social functioning; natural language samples were transcribed from play-based interactions. Findings indicated that standardized language measures, natural language measures, and ADOS severity were each unique predictors of later lexical use. Intervention types also appeared to impact later language; in particular, participation in mainstream inclusion accounted for significant amounts of variance in children's mean length of utterance at T3.

Injection pressure levels for creating blebs during subretinal gene therapy

Retinal damage has been associated with increased injection pressure during subretinal gene therapy delivery in various animal models, yet there are no human clinical data regarding the pressures required to initiate and propagate subretinal blebs. This study characterized the intraoperative pressure levels for subretinal gene therapy delivery across eight retinal conditions. A total of 116 patients with retinal degenerative diseases have been treated with subretinal gene therapy at OHSU-Casey Eye Institute as of June 2020; seventy patients (60.3%) were treated using a pneumatic-assisted subretinal delivery system. All retinal blebs were performed using a 41-gauge injection cannula, and use of a balanced salt solution (BSS) "pre-bleb" prior to gene therapy delivery was performed at the discretion of the surgeon. Patient age and intraoperative data for BSS and vector injections were analyzed in a masked fashion for all patients who received pneumatic-assisted subretinal gene therapy. The median age of the patients was 35 years (range 4-70). No significant differences in injection pressures were found across the eight retinal conditions. In this study, patient age was shown to affect maximum injection pressures required for bleb propagation, and the relationship between age and pressure varied based on retinal condition. These data have important implications in optimizing surgical protocols for subretinal injections.

Subretinal Injection Techniques for Retinal Disease: A Review

Inherited retinal dystrophies (IRDs) affect an estimated 1 in every 2000 people, this corresponding to nearly 2 million cases worldwide. Currently, 270 genes have been associated with IRDs, most of them altering the function of photoreceptors and retinal pigment epithelium. Gene therapy has been proposed as a potential tool for improving visual function in these patients. Clinical trials in animal models and humans have been successful in various types of IRDs. Recently, voretigene neparvovec (Luxturna^®) has been approved by the US Food and Drug Administration for the treatment of biallelic mutations in the RPE65 gene. The current state of the art in gene therapy involves the delivery of various types of viral vectors into the subretinal space to effectively transduce diseased photoreceptors and retinal pigment epithelium. For this, subretinal injection is becoming increasingly popular among researchers and clinicians. To date, several approaches for subretinal injection have been described in the scientific literature, all of them effective in accessing the subretinal space. The growth and development of gene therapy give rise to the need for a standardized procedure for subretinal injection that ensures the efficacy and safety of this new approach to drug delivery. The goal of this review is to offer an insight into the current subretinal injection techniques and understand the key factors in the success of this procedure.

Fluorescent Nanosystems for Drug Tracking and Theranostics: Recent Applications in the Ocular Field

The greatest challenge associated with topical drug delivery for the treatment of diseases affecting the posterior segment of the eye is to overcome the poor bioavailability of the carried molecules. Nanomedicine offers the possibility to overcome obstacles related to physiological mechanisms and ocular barriers by exploiting different ocular routes. Functionalization of nanosystems by fluorescent probes could be a useful strategy to understand the pathway taken by nanocarriers into the ocular globe and to improve the desired targeting accuracy. The application of fluorescence to decorate nanocarrier surfaces or the encapsulation of fluorophore molecules makes the nanosystems a light probe useful in the landscape of diagnostics and theranostics. In this review, a state of the art on ocular routes of administration is reported, with a focus on pathways undertaken after topical application. Numerous studies are reported in the first section, confirming that the use of fluorescent within nanoparticles is already spread for tracking and biodistribution studies. The first section presents fluorescent molecules used for tracking nanosystems’ cellular internalization and permeation of ocular tissues; discussions on the classification of nanosystems according to their nature (lipid-based, polymer-based, metallic-based and protein-based) follows. The following sections are dedicated to diagnostic and theranostic uses, respectively, which represent an innovation in the ocular field obtained by combining dual goals in a single administration system. For its great potential, this application of fluorescent nanoparticles would experience a great development in the near future. Finally, a brief overview is dedicated to the use of fluorescent markers in clinical trials and the market in the ocular field.

Three-Year Safety Results of SAR422459 (EIAV-ABCA4) Gene Therapy in Patients With ABCA4-Associated Stargardt Disease: An Open-Label Dose-Escalation Phase I/IIa Clinical Trial, Cohorts 1-5

PURPOSE

To report on the safety of the first 5 cohorts of a gene therapy trial using recombinant equine infectious anemia virus expressing ABCA4 (EIAV-ABCA4) in adults with Stargardt dystrophy due to mutations in ABCA4.

DESIGN

Nonrandomized multicenter phase I/IIa clinical trial.

METHODS

Patients received a subretinal injection of EIAVABCA4 in the worse-seeing eye at 3 dose levels and were followed for 3 years after treatment.

MAIN OUTCOME MEASURES

The primary end point was ocular and systemic adverse events. The secondary end points were best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, multifocal ERG, color fundus photography, short-wavelength fundus autofluorescence, and spectral domain optical coherence tomography.

RESULTS

The subretinal injections were well tolerated by all 22 patients across 3 dose levels. There was 1 case of a treatment-related ophthalmic serious adverse event in the form of chronic ocular hypertension. The most common adverse events were associated with the surgical procedure. In 1 patient treated with the highest dose, there was a significant decline in the number of macular flecks as compared with the untreated eye. However, in 6 patients, hypoautofluorescent changes were worse in the treated eye than in the untreated eye. Of these, 1 patient had retinal pigment epithelium atrophy that was characteristic of tissue damage likely associated with bleb induction. No patients had any clinically significant changes in best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, or multifocal ERG attributable to the treatment.

CONCLUSIONS

Subretinal treatment with EIAV-ABCA4 was well tolerated with only 1 case of ocular hypertension. No clinically significant changes in visual function tests were found to be attributable to the treatment. However, 27% of treated eyes showed exacerbation of retinal pigment epithelium atrophy on fundus autofluorescence. There was a significant reduction in macular flecks in 1 treated eye from the highest dose cohort. Additional follow-up and continued investigation in more patients will be required to fully characterize the safety and efficacy of EIAV-ABCA4.

Two-step versus 1-step subretinal injection to compare subretinal drug delivery: a randomised study protocol

INTRODUCTION

There is increasing interest in subretinal injections as a surgical procedure, largely as a result of emerging treatments for ocular diseases which necessitate this manoeuvre. However, surgical variables in the efficacy of such treatments have to date been largely overlooked and the proportion of drug which reaches the intended compartment of the subretinal space remains unknown. Our aims are twofold: first, to determine the proportion of subretinally injected medication retained following surgical delivery and second, to compare two different techniques of injection ('1-step' vs '2-step').

METHODS

We outline a randomised controlled trial of subretinal injection of alteplase following vitrectomy for the management of submacular haemorrhage secondary to age-related macular degeneration. Patients will be randomised to receive either 1-step injection, where the therapeutic solution simultaneously defines the surgical plane or 2-step injection, where the surgical plane is first identified with balanced salt solution prior to injection of subretinal alteplase, as outlined below. Sodium fluorescein will be used as an optical label to track drug reflux into the vitreous cavity using quantitative protocols established in our laboratory. All patients will undergo fluid air exchange at the completion of surgery, with injection of bevacizumab 1.25 mg and 20% sulfahexafluoride gas as the vitreous substitute (both of which may help improve outcomes). Alteplase, sodium fluorescein and bevacizumab will all be used for off-label indications in the trial.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the South Eastern Sydney Local Health District's Human Research Ethics Committee (HREC 17/092). The results of this trial will be disseminated in peer-reviewed proceedings (associated with conference presentation) and in scholarly journals.

TRIAL REGISTRATION NUMBER

ACTRN12619001121156.

Uncovering of intraspecies macular heterogeneity in cynomolgus monkeys using hybrid machine learning optical coherence tomography image segmentation

The fovea is a depression in the center of the macula and is the site of the highest visual acuity. Optical coherence tomography (OCT) has contributed considerably in elucidating the pathologic changes in the fovea and is now being considered as an accompanying imaging method in drug development, such as antivascular endothelial growth factor and its safety profiling. Because animal numbers are limited in preclinical studies and automatized image evaluation tools have not yet been routinely employed, essential reference data describing the morphologic variations in macular thickness in laboratory cynomolgus monkeys are sparse to nonexistent. A hybrid machine learning algorithm was applied for automated OCT image processing and measurements of central retina thickness and surface area values. Morphological variations and the effects of sex and geographical origin were determined. Based on our findings, the fovea parameters are specific to the geographic origin. Despite morphological similarities among cynomolgus monkeys, considerable variations in the foveolar contour, even within the same species but from different geographic origins, were found. The results of the reference database show that not only the entire retinal thickness, but also the macular subfields, should be considered when designing preclinical studies and in the interpretation of foveal data.

RELATIONSHIP BETWEEN PREOPERATIVE FOVEAL MICROSTRUCTURE AND VISUAL ACUITY IN MACULA-OFF RHEGMATOGENOUS RETINAL DETACHMENT: Imaging Analysis by Swept Source Optical Coherence Tomography

PURPOSE

To visualize foveal microstructures in macula-off rhegmatogenous retinal detachment using swept source optical coherence tomography preoperatively and postoperatively and to investigate the relationship between foveal microstructures and postoperative visual acuity.

METHODS

We retrospectively analyzed 42 eyes of 42 consecutive patients diagnosed with macula-off rhegmatogenous retinal detachment who underwent anatomically successful repair surgery and were followed up for 6 months. We used swept source optical coherence tomography to investigate the relationship between preoperative and postoperative continuity of both the external limiting membrane (ELM) and ellipsoid zone (Ez) and preoperative and postoperative best-corrected visual acuity.

RESULTS

Both preoperative ELM and Ez were continuous in 9 eyes (21%; ELM+/Ez+ eyes), only the ELM was continuous in 25 eyes (60%; ELM+/Ez- eyes), and neither was continuous in 8 eyes (19%; ELM-/Ez- eyes). Postoperative best-corrected visual acuity in ELM+/Ez+ eyes (-0.05 ± 0.04 logarithm of the minimum angle of resolution units, Snellen equivalent 20/18) was significantly better than that in both ELM+/Ez- (0.16 ± 0.16, 20/29; P = 0.03) and ELM-/Ez- (0.86 ± 0.37, 20/145; P < 0.001) eyes. Postoperative best-corrected visual acuity was significantly better in ELM+/Ez- than in ELM-/Ez- eyes (P < 0.001).

CONCLUSION

In macula-off rhegmatogenous retinal detachment, preoperative continuity of the ELM and Ez may be a predictor of postoperative best-corrected visual acuity.

Clinical Perspective: Treating RPE65-Associated Retinal Dystrophy

Until recently, there was no approved treatment for a retinal degenerative disease. Subretinal injection of a recombinant adeno-associated virus (AAV) delivering the normal copy of the human RPE65 cDNA led to reversal of blindness first in animal models and then in humans. This led to the first US Food and Drug Administration (FDA)-approved gene therapy product for a genetic disease, voretigene neparvovec-rzyl (Luxturna). Luxturna was then approved by the European Medicines Association and is now available in the US through Spark Therapeutics and worldwide through Novartis. Not only has treatment with Luxturna changed the lives of people previously destined to live a life of blindness, but it has fueled interest in developing additional gene therapy reagents targeting numerous other genetic forms of inherited retinal disease. This review describes many of the considerations for administration of Luxturna and describes how lessons from experience with Luxturna could lead to additional gene-based treatments of blindness.

Hints for Gentle Submacular Injection in Non-Human Primates Based on Intraoperative OCT Guidance

Purpose

Delivery of Advanced Therapy Medicinal Products to the submacular space is increasingly evolving into a therapeutic modality. Cell replacement for age-related macular degeneration (AMD) and gene therapy for RPE65 are recent successful examples. Herein, a nonhuman primate (NHP) model was used to investigate surgical means to detach the macula.

Methods

Sixteen eyes of 13 healthy macaques underwent a 25-gauge vitrectomy and subretinal injection of balanced salt solution monitored by microscope-integrated intraoperative optical coherence tomography (miOCT). The animals were followed with OCT and histology.

Results

The miOCT monitoring allowed a more precise definition of surgical trauma ranging from an initial full-thickness foveal tear, or induction of a cystoid macular edema (CME), until no foveal defect was discernible, as the technique improved. However, as the subretinal fluid wave detached the fovea, the aforementioned lesions formed, whereas persistent retinal adhesion reproducibly proved to remain in the distal parafoveal semi-annulus. Measures to reduce foveal trauma during submacular fluid injection included reducing intraocular pressure, injection volume, and velocity, as well as the retinal location for bleb initiation, use of a vitreous tamponade, and a dual-bore subretinal cannula.

Conclusions

A stable very low intraocular pressure and careful subretinal injection may avoid tangential macular stretching or mechanical CME formation, while vitreous tamponade may facilitate a more lamellar subretinal flow, all thereby reducing foveal trauma during submacular injection in NHP.

Translational Relevance

These results can be relevant to any submacular surgery procedure used today, as they synergistically reduce the risk of compromising foveal integrity.

Release and extraction of retained subfoveal perfluorocarbon liquid facilitated by subretinal BSS, vibration, and gravity: a case report

Background

Perfluorocarbon liquid (PFCL) is an effective surgical adjuvant in performing vitrectomy for severe vitreoretinal pathologies such as proliferative vitreoretinopathy and giant retinal tears. However, subretinal retention of PFCL can occur postoperatively and retained PFCL causes severe visual disorders, particularly when PFCL was retained under the fovea. Although several procedures have been proposed for subfoveal PFCL removal, such as direct aspiration or submacular injection of balanced salt solution (BSS) to dislodge the subfoveal PFCL, the retinal damage associated with these procedures has been a major problem. Here, we report a case of subfoveal retention of PFCL for which we performed a novel surgical technique that attempts to minimize retinal damage.

Case presentation

A 69-year-old man presented with subfoveal retained PFCL after surgery for retinal detachment. To remove the retained PFCL, the internal limiting membrane overlying the subretinal injection site is first peeled to allow low-pressure (8 psi) transretinal BSS infusion, using a 41-gauge cannula, to slowly detach the macula. A small drainage retinotomy is created with the diathermy tip at the inferior position of the macular bleb, sized to be slightly wider than that of the PFCL droplet. The head of the bed is then raised, and the surgeon gently vibrates the patient’s head to release the PFCL droplet to allow it to migrate inferiorly towards the drainage retinotomy. The bed is returned to the horizontal position, and the PFCL, now on the retinal surface, can be aspirated. The subfoveal PFCL is removed while minimizing iatrogenic foveal and macular damage. One month after PFCL removal, the foveal structure showed partial recovery on optical coherence tomography, and BCVA improved to 20/40.

Conclusion

Creating a macular bleb with low infusion pressure and using vibrational forces and gravity to migrate the PFCL towards a retinotomy can be considered as a relatively atraumatic technique to remove subfoveal retained PFCL.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12886-020-01698-1.

Application of subretinal fluid to close refractory full thickness macular holes: treatment strategies and primary outcome: APOSTEL study

INTRODUCTION

Persisting macular holes (PMH) after surgical release of any epiretinal traction of the vitreous and adjacent membrane may rely on secondary firm adhesions between the retracted retina and adjacent retinal pigment epithelium. Secondary application of subretinal (SR)-fluid may release these adhesions followed by an anatomical closure.

METHODS

Twelve surgeons applied in a consecutive case series SR-fluid in 41 eyes with PMH and reported retrospectively their initial surgical, anatomical and functional experience with this approach.

RESULTS

The mean duration of the MH prior to SR-fluid application was 17 months (6-96 months). The mean age of the patients at the time of surgery was 72 years (54-88). The mean preoperative aperture diameter of the opening was 1212 μm (239-4344 μm), base diameter 649 μm (SD 320 μm). The mean preoperative BCVA prior to surgery was 0.1 (0.01-0.3). All patients (41/41) complained about reduced BCVA and a significant central scotoma (negative scotoma) in their central field of vision. The secondary closure rate for our PMH was 85.36% (35 out of 41 eyes) at 6 weeks after surgery. The postoperative BCVA improved to 0.22 (0.02-0.5). The application of SR-fluid was not associated with major intraoperative adverse effects.

CONCLUSION

Remaining SR-adhesions may inhibit PMH closure. Their release by application of SR-fluid will lead to a fast and immediate anatomical closure in many cases without serious adverse events.

[Closure of Persisting Full Thickness Macular Holes by Subretinal Fluid Application: Technical Approach and Surgical Considerations]

INTRODUCTION

Firm adhesions between the retina and adjacent retinal pigment epithelium (RPE) may prevent the closure of macular holes (MH) after chromovitrectomy. Controlled application of subretinal (SR) fluid with BSS may release these adhesions leading to closure of the retracted retina in large and or refractory macular holes.

METHODS

For a standardized procedure, it is recommended to exclude residues of epiretinal membranes on the retinal surface preoperatively at OCT or intraoperatively by means of vital dyes. Intraoperatively, a perfluorocarbon (PFO) bubble is placed above the MH and lowers the infusion bottle of 20 mmHg. Subsequently, SR-fluid blebs are applied in the upper, temporal and inferior quadrants with a subretinal 41-gauge cannula. After removing decalin bubble, the SR-detachment is enlarged toward the foveal center. This is essential to achieve a complete detachment of the outer macular edges from the RPE. The MH can be closed by a temporary gas endotamponade.

RESULTS

With a standardized procedure, the operation can be carried out safely and with minimal effort. Additional measures, such as care for bubble-free SR-fluid sands or machine assistance, were added. In a pilot study, experienced VR surgeons performed the SR-fluid application safely and without complications. The preoperative diameter of the MH was 1150 µm (651 - 2350 µm). The secondary closure rate for our PMH was 80.9%.

CONCLUSION

SR-adhesions seem to have a previously unnoticed component in persistent macular holes. An SR-fluid application can be carried out quickly, safely and with minimal material effort. The initial results show a high secondary closure rate.

PRIMA subretinal wireless photovoltaic microchip implantation in non-human primate and feline models

Purpose

To evaluate the surgical technique for subretinal implantation of two sizes of PRIMA photovoltaic wireless microchip in two animal models, and refine these surgical procedures for human trials.

Methods

Cats and Macaca fascicularis primates with healthy retina underwent vitrectomy surgery and were implanted with subretinal wireless photovoltaic microchip at the macula/central retina. The 1.5mm PRIMA chip was initially studied in feline eyes. PRIMA implant (2mm,1.5mm sizes) arrays were studied in primates. Feasibility of subretinal chip implantation was evaluated with a newly-developed surgical technique, with surgical complications and adverse events recorded.

Results

The 1.5mm implant was placed in the central retina of 11 feline eyes, with implantation duration 43–106 days. The 1.5mm implant was correctly positioned into central macula of 11 primate eyes, with follow-up periods of minimum 6 weeks (n = 11), 2 years (n = 2), and one eye for 3 years. One primate eye underwent multi-chip 1.5mm implantation using two 1.5mm chips. The 2mm implant was delivered to 4 primate eyes. Optical coherence tomography confirmed correct surgical placement of photovoltaic arrays in the subretinal space in all 26 eyes. Intraoperative complications in primate eyes included retinal tear, macular hole, retinal detachment, and vitreous hemorrhage that resolved spontaneously. Postoperatively, there was no case of significant ocular inflammation in the 1.5mm implant group.

Conclusions

We report subretinal implantation of 1.5mm and 2mm photovoltaic arrays in the central retina of feline and central macula of primate eyes with a low rate of device-related complications. The in vivo PRIMA implantation technique has been developed and refined for use for a 2mm PRIMA implant in ongoing human trials.

Safety of Same-Eye Subretinal Sequential Readministration of AAV2-hRPE65v2 in Non-human Primates

We have demonstrated safe and effective subretinal readministration of recombinant adeno-associated virus serotype (rAAV) to the contralateral eye in large animals and humans even in the setting of preexisting neutralizing antibodies (NAbs). Readministration of AAV to the same retina may be desirable in order to treat additional areas of the retina not targeted initially or to boost transgene expression levels at a later time point. To better understand the immune and structural consequences of subretinal rAAV readministration to the same eye, we administered bilateral subretinal injections of rAAV2-hRPE65v2 to three unaffected non-human primates (NHPs) and repeated the injections in those same eyes 2 months later. Ophthalmic exams and retinal imaging were performed after the first and second injections. Peripheral blood monocytes, serum, and intraocular fluids were collected at baseline and post-injection time points to characterize the cellular and humoral immune responses. Histopathologic and immunohistochemical studies were carried out on the treated retinas. Ipsilateral readministration of AAV2-hRPE65v2 in NHPs did not threaten the ocular or systemic health through the time span of the study. The repeat injections were immunologically and structurally well tolerated, even in the setting of preexisting serum NAbs. Localized structural abnormalities confined to the outer retina and retinal pigmented epithelium (RPE) after readministration of the treatment do not differ from those observed after single or contralateral administration of an AAV carrying a non-therapeutic transgene in NHPs and were not observed in a patient treated with the nearly identical, FDA-approved, AAV2-hRPE65v2 vector (voretigene neparvovec-rzyl), suggesting NHP-specific abnormalities.