Localized RPE Removal with a Novel Instrument Aided by Viscoelastics in Rabbits

Fabian Thieltges; Zengping Liu; Ralf Brinken; Norbert Braun; Warapat Wongsawad; Sudawadee Somboonthanakij; Martina Herwig; Frank G Holz; Boris V Stanzel

doi:10.1167/tvst.5.3.11

Localized RPE Removal with a Novel Instrument Aided by Viscoelastics in Rabbits

Transl Vis Sci Technol. 2016 Jun 1;5(3):11. doi: 10.1167/tvst.5.3.11. eCollection 2016 Jun.

Authors

Fabian Thieltges¹, Zengping Liu², Ralf Brinken¹, Norbert Braun³, Warapat Wongsawad⁴, Sudawadee Somboonthanakij⁴, Martina Herwig¹, Frank G Holz¹, Boris V Stanzel⁵

Affiliations

¹ Department of Ophthalmology, University of Bonn, Bonn, Germany.
² Department of Ophthalmology, University of Bonn, Bonn, Germany ; Present address: Zengping Liu, Department of Ophthalmology, National University of Singapore, Singapore.
³ Geuder AG, Heidelberg, Germany.
⁴ Mettapracharak Eye Institute, Raikhing, Nakhon Pathom 73210, Thailand.
⁵ Department of Ophthalmology, University of Bonn, Bonn, Germany ; Present address: Singapore National Eye Center, Singapore.

Abstract

Purpose: We developed a surgical method for localized and atraumatic removal of the retinal pigment epithelium (RPE) with a novel instrument.

Methods: Bleb retinal detachments (bRD) were raised with balanced salt solution (BSS) following vitrectomy in 27 rabbits. The RPE was scraped with 3 loop variants (polypropylene [PP], 0.1 mm; PP, 0.06 mm; metal, 0.1 mm) of a custom-made instrument. Stabilization of bRDs with BSS or various concentrations (0.1%-0.5%) of hyaluronic acid (HA) was video analyzed. Perfusion-fixed samples of scraped areas and controls were studied by light and transmission electron microscopy.

Results: The bRDs were sufficiently stabilized by ≥0.25% HA. Using the PP 0.1 mm loop with a single forward/backward stroke, an area of ca. 2.5 × 1.5 mm was nearly devoid of RPE, yet did show occasional Bruch's membrane (BM) defects combined with choriocapillaris hemorrhages in 13% of the bRDs. A single scrape with PP 0.06 mm resulted in unsatisfactory RPE denudement, while repeated scraping maneuvers caused more BM defects and hemorrhages. The metal loop resulted in incomplete RPE removal and massive intraoperative subretinal hemorrhages. Histologically, intact photoreceptor outer segments (POS) were observed above the RPE wounds in bRDs. Controls with bRDs alone showed an intact RPE monolayer with microvilli, with few engulfed remains of POS.

Conclusions: Localized removal of RPE in HA stabilized bRD can be achieved by a PP 0.1 mm loop instrument.

Translational relevance: Removal of degenerated RPE may aid RPE cell replacement strategies.

Keywords: AMD; Bruch's membrane; RPE transplantation; cell replacement; cell-based therapy; hyaluronic acid; hydrogel; retina; retinal surgery; tissue engineering.