Artificial vitreous substitute shows

Innovative vitreous substitute study

Artificial vitreous substitute shows promise in early trials. Dermot McGrath reports

Amanufactured hydrogel-based artificial vitreous has shown highly favourable biophysical characteristics in ex vivo models, strongly suggesting its further application as a potential vitreous substitute in vivo, according to a study.

“It is still early days and we need larger controlled clinical trials to fully test this hydrogel, but we are very excited by the possibilities of having a viable, safe and effective alternative to current tamponade methods, which have a lot of limitations,” said Kai Januschowski MD, FEBO.

A wide variety of artificial vitreous substitutes have been investigated over the years to repair retinal tear and detachment and for other vitreoretinal conditions, with mixed results, noted Prof Januschowski, Eye Clinic Sulzbach, Germany.

The most commonly used vitreous substitutes designed to

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produce an effective tamponade for detached retinas include expansile gases, perfluorocarbon liquids (PFCLs) and silicone oil. These can be used only as temporary substitutes, however, and they come with significant drawbacks, said Prof Januschowski.

“Whether we are putting gas or silicone oil into the eye there are limitations to hydrophobic Kai Januschowski MD, FEBO tamponades that we need to be aware of. Only one tamponade vector is possible with these agents, so a complete tamponade is physically impossible, while retracting the gas bubble has unfavourable fluid dynamics,” he said.

INITIAL TESTS Furthermore, PFCLs tend to be routinely used only intraoperatively for complicated retinal detachments because of their toxicity over longer periods of time.

To overcome these obstacles, a team around Prof Januschowski came up with a biocompatible, cross-linked, hyaluronic acid (HA)-based hydrogel.

The generated hydrogel was successfully tested as a vitreous substitute in two distinct ex vivo eye animal models in order to investigate short-term biocompatibility and IOP development.

The initial tests in the first human patients have also proved promising, said Prof Januschowski, although the experimental nature of the hydrogel means that its application has been limited to extreme rescue situations.

“The first patient that we tested this on had a severely damaged eye after multiple operations and was close to being enucleated. We performed a penetrating keratoplasty and the hydrogel stayed beautifully inside the eye. That was almost two years ago and I saw the patient recently and he was very happy,” he said.

The artificial vitreous has been successfully deployed now in nine patients: five with multiple retinal detachments, two ocular trauma cases, one case of ischaemia and another of chronic uveitis following severe hypotony.

“We are talking about very difficult situations – this is really a last option that we can offer these patients before enucleation. We managed to control the IOP and relieve the pain that these patients were experiencing. The next steps will be to try to test this in eyes where there is still some prospect of obtaining good visual acuity. However, we need to very selective because we have to be very careful about potential adverse events,” he concluded.