Development of a surgical procedure for implantation of a prototype suprachoroidal retinal prosthesis

Abstract

BackgroundCurrent surgical techniques for retinal prosthetic implantation require long and complicated surgery, which can increase the risk of complications and adverse outcomes.MethodThe suprachoroidal position is known to be an easier location to access surgically, and so this study aimed to develop a surgical procedure for implanting a prototype suprachoroidal retinal prosthesis. The array implantation procedure was developed in 14 enucleated eyes. A full-thickness scleral incision was made parallel to the intermuscular septum and superotemporal to the lateral rectus muscle. A pocket was created in the suprachoroidal space, and the moulded electrode array was inserted. The scleral incision was closed and scleral anchor point sutured. In 9 of the 14 eyes examined, the device insertion was obstructed by the posterior ciliary neurovascular bundle. Subsequently, the position of this neurovascular bundle in 10 eyes was characterized. Implantation and lead routing procedure was then developed in six human cadavers. The array was tunnelled forward from behind the pinna to the orbit. Next, a lateral canthotomy was made. Lead fixation was established by creating an orbitotomy drilled in the frontal process of the zygomatic bone. The lateral rectus muscle was detached, and implantation was carried out. Finally, pinna to lateral canthus measurements were taken on 61 patients in order to determine optimal lead length.ResultsThese results identified potential anatomical obstructions and informed the anatomical fitting of the suprachoroidal retinal prosthesis.ConclusionAs a result of this work, a straightforward surgical approach for accurate anatomical suprachoroidal array and lead placement was developed for clinical application.

The Appearance of Phosphenes Elicited Using a Suprachoroidal Retinal Prosthesis

“…4,5,27,28 In brief, the percutaneous connector and subcutaneous remote return electrode were implanted behind the ear (Fig. 1D), with the connector anchored to the temporal bone using titanium screws.…”

“…5,27,28 In comparison to epiretinal and subretinal implantation sites, the suprachoroidal approach has the advantage of a simpler surgery that does not require breaching the vitreous cavity or touching the retina. Being held in the natural cleavage plane also provides longterm mechanical stability to the implant location without the need for fixation techniques such as the retinal tacks used with epiretinal devices.…”

Spatial Restriction of Neural Activation Using Focused Multipolar Stimulation With a Retinal Prosthesis

“…The implantation procedure is detailed in our previous studies. 18,19 Briefly, following a lateral canthotomy, scleral incision, and dissection of a pocket between the sclera and choroid, the array was inserted approximately 15 mm into the suprachoroidal space until the tip was beneath the area centralis. Electrical connections to the electrodes on the array were tested using an automated impedance monitoring software developed in LabVIEW (National Instruments, Austin, TX, USA) used in previous studies.…”

“…However, suprachoroidal placement has the advantage of a relatively noninvasive implantation procedure, 18,19 albeit with higher levels of stimulation required to reach activation thresholds. 4,20,21 Higher stimulation levels have a detrimental effect on charge containment, impeding the formation of discrete phosphenes and limiting the visual resolution afforded to the patient.…”

Techniques for Processing Eyes Implanted with a Retinal Prosthesis for Localized Histopathological Analysis: Part 2 Epiretinal Implants with Retinal Tacks

“…Perceptual outcomes from clinical trials have shown promising early results and recently some devices have been approved for commercial use. Currently, there are three main anatomical locations in which clinical retinal prostheses have been positioned: epiretinally 3,4 , subretinally 5,6 and suprachoroidally 7,8 . Different devices utilise different materials and their form is customised to the location in which they are implanted.…”