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

Abstract

PurposeTo investigate the influence of subretinal injection pressure on the microstructure of the retina in a monkey model.MethodsAfter vitrectomy, balanced salt solution was injected subretinally into one eye each of four cynomolgus monkeys while controlling the injection pressure. Initially, a pressure of 2 psi was used, and this was gradually increased to determine the minimum required pressure. Subsequent injections were performed at two pressures: minimum (n = 13) and high (n = 6). To compare the influence of these injection pressures on retinal structure, optical coherence tomography (OCT) was performed before surgery and every week afterwards. The monkeys were euthanized and their eyes were enucleated at 1 or 6 weeks after the injections. The eyes were processed for light microscopy and transmission electron microscopy (TEM) as well as for TdT-mediated dUTP nick end labeling.ResultsThe minimum pressure required to perform subretinal injection was 6 psi. After injection at this pressure, both OCT and microscopy showed that the retinal structure was well-preserved throughout the experimental period at all injection sites. Conversely, after injection at high pressure (20 psi) OCT images at all injection sites showed disruption of the ellipsoid zone (EZ) after 1 week. Microscopy indicated damage to the photoreceptor outer segment (OS) and stratification of the retinal pigment epithelium (RPE). After 6 weeks, OCT demonstrated that the EZ had become continuous and TEM confirmed that the OS and RPE had recovered. Photoreceptor apoptosis was absent after subretinal injection at both pressures.ConclusionsThe retinal damage caused by subretinal injection increases depending on pressure, indicating that clinicians should perform subretinal injection at pressures as low as possible to ensure safety.

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

“…Dose-dependent outer retinal changes with demelanization of the RPE have been reported after the administration of different vector constructs in NHPs, as well as after injection of control balance salt solutions 37, 43, 47, 48. These vector-independent abnormalities may be the consequence of low grade, immune-mediated responses within the subretinal space triggered by exposure of foreign proteins that may not be detected by the immune assays used in this work or by routine histopathology.…”

“…In contrast, the administration of rAAV2- hRPE65v2 to NHPs produces pigmentary changes within the blebs visible by fundus exam, which can be used to precisely locate a second subretinal injection in relationship to a previous one. In one animal (two eyes), a readministration of the treatment was at a site distant from the first injection to exclude mechanical (surgery-related) effects on the initially injected retina; in the other two animals, the treatment was delivered so that there was a partial or total overlap between the first and second injections 13, 43. The experiments demonstrated that ipsilateral readministration to the NHP retina was safe from an immunologic standpoint, even when readministration location coincided nearly exactly with the initially treated retinal area.…”

“…These vector-independent abnormalities may be the consequence of low grade, immune-mediated responses within the subretinal space triggered by exposure of foreign proteins that may not be detected by the immune assays used in this work or by routine histopathology. The pigmentary changes post-administration in NHPs noted on fundus examination as early as 72 h post-treatment raise the alternative possibility of acute damage to a particularly susceptible NHP POS and/or RPE to the separation between the layers caused by the subretinal injection 43, 47. The circular, ring-like autofluorescent patterns documented in these NHP experiments may represent steps of bleb formation or reabsorption that may not occur in humans (for example, Figure 4, animal 11D086; Reichel et al 48 …”

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

“…In one case, an intraoperative foveal perforation occurred at injection pressure greater than 20psi. For the remaining cases, we did not encounter any cases of foveal perforation at an injection pressure of 20psi or less [15]. In the one case of macular hole observed during chip implantation, the PRIMA microchip was implanted in the subretinal space.…”

Verschluss von persistierenden Makulalöchern durch subretinale Flüssigkeitsapplikation: technisches Vorgehen und chirurgische Überlegungen

“…3.) Senken des Druckes der Infusionsflasche auf < 20 mmHg, sodass der Augeninnendruck niedrig ist und der Widerstand gegen die Netzhaut nicht künstlich erhöht wird [11]…”