A novel, minimally invasive implant for intraocular drug delivery

Abstract

Purpose : Patients undergoing intravitreal injections experience pain as the needle courses through the unanaesthetised sclera and choroid. We describe the design, development and in-vivo testing in a rabbit model of a titanium implant that allows for intravitreal injections through the implant to minimize patient discomfort.

Methods : Computer aided design of the novel implant was rendered using Solidworks®. Anodized Grade 5 titanium alloy (TiAl6V) implants were machined by conventional turning of blank rods. The holes and slots were machined using a drill press while the conical end of the implant was created by shaping tool. The implant was hand polished using 500 grit sandpaper followed by 1000 grit sandpaper. Both ex-vivo testing of the implant in enucleated goat’s eye as well as in-vivo validation in 4 rabbit eyes was carried out. The implant was placed through the pars plana via a minor surgical procedure and was sutured to the sclera and covered with conjunctiva. Subsequent intravitreal injections were administered under topical anaesthesia with a 30 gauge needle through the implant, thus delivering the drug directly into the vitreous cavity. Repeated intravitreal injections were administered every 2 weeks via the implant for 3 months in 4 rabbits. The implants were removed at 5 months and the scleral wound was sutured. One eye was enucleated for histopathological evaluation.

Results : There was no complication during the implantation. Post-implantation, eye opening of rabbits was normal. Subsequent intravitreals were easy to administer. No efflux was observed during injection. Focal cataract adjacent to the implant was observed in 1 rabbit. Complications such as vitreous haemorrhage, retinal detachment or endophthalmitis were not observed. There was no focal erosion of conjunctiva. Following explantation the sclera and overlying conjunctiva healed well. Histopathological analysis did not reveal any inflammation or necrosis.

Conclusions : The current work shows the successful design and implantation of an intraocular device that can be used repeatedly for painless minimally invasive drug delivery. The in-vivo evaluation of the implant shows promising results for future animal and human studies.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

A. Implant in rabbit’s eye covered by conjunctiva B. Fundus image showing the implant

 

Fundus images of rabbit 1 (A,B,C,D) and 2 (E,F,G,H) with implant in situ taken at 1 week, 1 month, 2 months and 3 months respectively.