Biomedicine: An improved gel for detached retinas.


Detachment of the retina is a serious condition that must be surgically corrected to avoid permanent sight loss. The surgery involves replacement of the vitreous body — a clear gel that allows light from the cornea and lens to be transmitted to the back of the eye. For more than 50 years, eye surgeons have been using gases or silicone oil as vitreous-body replacements, but this strategy has potentially harmful side effects. Writing in Nature Biomedical Engineering, Hayashi et al. describe a gel that can be easily implanted as a vitreous-body replacement. If it stands up to further testing, the gel could revolutionize the treatment of retinal detachment and other ocular disorders. In young people, the vitreous body is viscous, acting as a shock absorber that decelerates the inertial forces on the retina during eye movement. Age-related changes can cause the vitreous body to liquefy and collapse, pulling on the retina and heightening the risk of tears in the retina. Eye movement and swirling currents in the vitreous body allow fluid to pass through a tear, separating the retina from the wall of the eye and causing retinal detachment. Vitrectomy is the most common way to repair a detached retina. The vitreous body is cut and aspirated, removing the traction from the retinal tears. The retina is then reattached surgically and lasers are applied to the tears so that the retina adheres to the back of the eye, preventing the passage of fluid under the retina. A gas bubble or silicone oil is then used to fill the space left by the vitreous body, keeping the retina in position until strong adhesion occurs. Gases are absorbed by the body after a month or two, and replaced by natural aqueous humour (a main component of the vitreous body), whereas silicone oil can later be removed from the eye. However, many aspects of this strategy are problematic. For instance, because both gas and silicone oil are less dense than water, they rise to the top of the eye. As a result, patients must tilt their heads forward into a prone position — sometimes for weeks — to keep the gas or oil bubble pushing against the retina, and to allow nutrients from the surrounding fluid to flow around the bubble and reach the lens to prevent the development of a cataract. Recurrent retinal detachments occur more commonly at the bottom of the eye, because the bubble rises when the head is not prone. Denser oils have been developed to push against the lower retina, but have not been approved for use in the United States. In addition, the presence in the eye of both gases and silicone oil can impair vision, because they refract light differently from the vitreous fluid. The use of gas bubbles also temporarily limits air travel, because a sudden rise in altitude results in expansion of the bubble and a rapid increase in intraocular pressure, which can close the central retinal artery. And if silicone oil is left in place long-term, tiny droplets can break off, blocking the eye’s drainage channels and causing a subsequent rise in intraocular pressure that can damage the optic nerve — a condition called glaucoma that may persist even after the oil’s removal. An inert, biocompatible hydrogel (a waterabsorbing network of crosslinked polymers) could be better suited than gas or silicone oil for vitreous-body replacement. A gel that has the mechanical stability to hold the retina in place would not require head positioning, and would allow patients to maintain normal activities during their recovery. Such a gel might also be a safe repository for drugs to treat different disorders of the retina, because B I O M E D I C I N E

DOI: 10.1038/nature21898

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@article{Chang2017BiomedicineAI, title={Biomedicine: An improved gel for detached retinas.}, author={Stanley Chang}, journal={Nature}, year={2017}, volume={543 7645}, pages={319-320} }