Extraction of retinal tacks from subjects implanted with an epiretinal visual prosthesis

Abstract

Background: Retinal tacks, first developed for the treatment of complex retinal detachments, have more recently been used for the fixation of epiretinal electrode arrays as part of implanted visual prostheses. Here, we report on the clinical experience of extracting four such tacks after chronic implantation. The ability to safely extract retinal tacks ensures that epiretinal devices can be repositioned or removed if necessary.

Methods: Custom-built, titanium alloy retinal tacks were mechanically removed from the posterior coats after prolonged implantation (up to 19 months). The resulting wound was characterized by clinical evaluation, fundus photography, and fluorescein angiography while being monitored for stability over time. The wounds were also compared to earlier published reports of the healing response around retinal tacks in human subjects.

Results: Tack extraction was accomplished successfully, without complication, in all four subjects. The wound site was readily identified by pale scar tissue. No change in the wound size or appearance was noted over many months of post-operative observation (up to 22 months after explant). No adverse effects on overall ocular health were detected.

Conclusion: Extraction of retinal tacks from subjects implanted with epiretinal prostheses can be performed without significant complication. The long-term healing response appears to be stable and localized in eyes afflicted with retinitis pigmentosa or choroideremia. There was also minimal, if any, impact on the local circulatory system. These cases suggest that the use of retinal tacks for anchoring epiretinal visual prostheses does not preclude safe repositioning or removal of the device more than a year after implant.

Trial registration: ClinicalTrials.gov NCT00407602.

Figure 1

Argus II Retinal Tack

Figure 2

Fundus color photograph, post-extraction, Case 1. (a) 3 months. (b) 12 months.

Figure 3

Fluorescein angiogram 3 months post-extraction, late phase, Case 1.

Figure 4

Fundus color photograph, post-extraction, Case 2. (a) 1 month. (b) 16 months.

Figure 5

Fluorescein angiogram 16 months post-extraction, venous phase, Case 2.

Figure 6

Fundus color photograph, post-extraction, Case 3. (a) 3 months. (b) 22 months.

Figure 7

Fundus color photograph, post-extraction, Case 4. (a) 1 week. (b) 21 months.

Figure 8

Fluorescein angiogram 21 months post-extraction, late phase, Case 4.