RETINAL DETACHMENT

Intraocular magnetic microparticles may offer a potentially safe and effective method of sealing retinal tears and overcoming some of the current drawbacks of traditional retinal detachment surgery. “This novel device draws on advances in nanotechnology and could be potentially used in retinal detachment to seal retinal tears by means of pressure and also adjusted to surpass tractional forces in proliferative vitreoretinopathy (PVR) cases,†according to Diego Ruiz-Casas MD.

In recognition of their ground-breaking research, Dr Ruiz-Casas, Ramon Y Cajal University Hospital, Madrid, Spain, and his team of co-workers were awarded first prize in the EURETINA Innovation Awards, a prize established by EURETINA in 2011 to support and encourage innovation in the field of retinal medicine. In a presentation summarising his team’s research, Dr Ruiz-Casas said that using magnetic microparticles may help to overcome some of the drawbacks associated with current retinal detachment (RD) techniques such as scleral buckling, pneumatic retinopexy and vitrectomy. “Some of the main drawbacks of current treatments include the eye wall deformation by scleral buckle, the delayed effect with retinopexy and the need for an intraocular tamponade by means of interfacial tension,†he said. He noted that there was a clear need for more effective treatments for RD.

“Rhegmatogenous retinal detachment occurs in approximately seven to 18 out of 100,000 people a year, which means that anywhere between four and 12 million people worldwide will have it,†said Dr Ruiz-Casas. Discussing the concept behind his team’s research, Dr Ruiz- Casas explained that there are two principal components to the proposed ocular magnetic device (OMD). First, a scleral magnetic explant (SME) is sutured to the sclera. The magnet, which is 6.0mm in diameter and 2.0mm in height, requires no indentation and is coated with different biocompatible layers where drugs can be attached.

The second part of the proposed solution comes in the form of suspended magnetic microparticles of about 100 microns, which are directed towards the area of the retinal tear through the magnetic field created by the magnet sutured to the sclera. Much of the research effort by Dr Ruiz-Casas’ team has been directed at determining the optimal target pressure that needs to be exerted between the explant and the microparticles to keep the retina attached.

Noting that mild local retinal damage is acceptable to induce retinopexy, a target pressure of 0.75 mmHg was defined as the optimal value, which is about the pressure of a 10.0mm bubble of air in water. To test the performance of the device in vitro, an eye model was used to understand the magnetic interaction between the microparticles and the explant. In a test lasting 30 days, the microparticles were shown to migrate from one magnet to another, and they maintained their position at the end of the trial.

In vivo testing of the OMD also showed stable biomechanics and good biocompatibility of the device, with no movement of the microparticles during follow-up in rabbits’ eyes, he said. The microparticles were found to be located directly under the explant in 100 per cent of cases, and the specimens with iatrogenic RD kept the retina attached where the ocular magnetic device was located by pressure, said Dr Ruiz-Casas. In terms of an objective evaluation of the OMD, Dr Ruiz-Casas said the approach offered several advantages, including the delivery of localised treatment of retinal tears by using pressure.

The fact that the magnet is sutured to the sclera also eliminates the need for the patient to maintain an uncomfortable posture in the immediate postoperative period. Other benefits of the OMD include the maintenance of a clear visual axis with preservation of the non-treated retina. Furthermore, the pressure used is adjustable, with no eye wall deformation and therefore offering potentially multiple uses in vitreoretinal surgery.

Among the downsides of the proposed device, Dr Ruiz- Casas said that multiple tears would require multiple scleral magnetic explants, and potential issues of retinopexy/necrosis on the outer retinal layers and toxicity risk/siderosis also required further investigation. Summing up, Dr Ruiz-Casas said that the OMD could be potentially used in retinal detachment to seal retinal tears by means of pressure and also adjusted to surpass tractional forces in PVR cases. Other intriguing possible applications include vitreoretinal dissection/drainage, localised drug release and treatment of intraocular tumours, he said.