Intraoperative optical coherence tomographic findings in patients undergoing subretinal gene therapy surgery

Abstract

Background: To analyze intraoperative OCT (iOCT) findings during subretinal gene therapy. Methods: A single-center, retrospective, observational, case series study of twenty one eyes submitted to subretinal gene therapy. Intrasurgical high definition videos were included for analyzes. Cases with absence of iOCT video or unsuccessful bleb creation were excluded. Sharp needle tip (SNT) or blunted needle tip (BNT) and their interaction with neurosensory retina were evaluated. Presence of subretinal air bubbles, visible opened retinotomy, and medication reflux were also correlated and analyzed. Results: Nineteen of twenty-one eyes were included. Of the two excluded eyes, subretinal bleb creation was unsuccessful in one and technical issues prevented OCT image acquisition in the other. Immediately before subretinal injection, needle indention/penetration of the neurosensory retina with temporary indentation of the RPE/choroid was evident in 16 (84%) of the 19 eyes. Complete RPE/choroid indentation was needed with BNT use compared to SNT (p = 0.0114). An open retinotomy was identified in 14 (74%) of 19 eyes at the conclusion of bleb injection and was more commonly associated with SNT (p = 0.0108). Conclusions: iOCT provides valuable real-time feedback of cross-sectional retinal anatomy during subretinal gene therapy surgeries. The type of needle tip and its use during the gene therapy procedure seems to influence in the bleb creation and presence of visible open retinotomy. Further studies of iOCT findings during gene therapy delivery procedures are likely to help refine the surgical technique.

Current Clinical Applications of In Vivo Gene Therapy with AAVs

“…Vitreoretinal surgeons well versed in subretinal gene therapy have reported the utility of intraoperative optical coherence tomography (OCT), allowing in vivo real-time feedback during surgical cases. 97 The creation of the subretinal bleb with a microneedle (typically a 38- to 41-gauge, Teflon-tipped, either extendable or nonextendable, cannula that is placed through a pars plana trocar) is a challenging and critical step in the procedure. 98 The needle-penetration step has a narrow margin of error: excessively deep penetration of the needle tip can result in hemorrhage, cannula tip obstruction, unintentional suprachoroidal delivery of vector, or permanent RPE injury; however, too shallow needle penetration can create retinoschisis by intraretinal hydration during bleb formation.…”

Characterization of Gene Therapy Associated Uveitis Following Intravitreal Adeno-Associated Virus Injection in Mice

“…However, during subretinal injection, reflux from the subretinal bleb into the vitreous humor can occur and may be a factor contributing to the development of vitritis in some eyes. 24 , 25 A vitrectomy is performed before subretinal injection in human and NHP studies and this step cannot be replicated in the mouse model; however, understanding the immune response to AAV therapies that escape the subretinal space will help to clarify the importance of this variable on patient outcomes. Among the clinical trials utilizing an intravitreal approach, the ongoing X-linked retinoschisis trial (NCT02317887) found dose-related inflammation in multiple subjects as well as a dose-related increase in serum AAV8 antibodies.…”

“…After OCT imaging, the animal was euthanized and both right (injected) and left (fellow, uninjected) eyes were enucleated and intraocular contents collected separately as described by John et al 14 Briefly, each eye was rinsed in a flow buffer, placed in 50 μL of flow buffer, the cornea and lens removed, and the aqueous humor, iris, vitreous, retina, and retinal pigmented epithelium were collected. The intraocular contents were incubated with 10 mg/mL of DNAse (Roche, Germany) and 0.5 mg/mL of collagenase (Roche, Germany) at 37°C for 25 [30-F11, 565967]) for 30 minutes at 4°C. After staining, cells were washed and fixed with 1% paraformaldehyde in PBS.…”

Gene Therapy in Inherited Retinal Diseases: An Update on Current State of the Art

“…Of course, SRI is a delicate procedure, requiring a vitrectomy, retinotomy, and the development of a transitory iatrogenic neuroretinal displacement and it is potentially associated with a number of complications, including retinal tears, cataract progression, or retinal/choroidal hemorrhages. With respect to SRI, vitreoretinal subspecialists have reported the utility of in vivo real-time monitor of the surgical act through integrated optical coherence tomography (OCT) operating microscope (33).…”