Vitreous tamponades are substances that are injected into the eye during vitreoretinal surgery to stabilize the retina and facilitate retinal reattachment after surgery. They prevent proliferative vitreoretinopathy, which is an abnormal healing response that can cause the retina to re-detach after surgery. Vitreous sealants displace the vitreous gel and fill the vitreous cavity, enabling close apposition of the retina to the underlying retinal pigment epithelium.

Types of Vitreous sealants

The main types of vitreous sealants used are gases, silicone oils and perfluorocarbon liquids. Each has their own advantages and disadvantages.

Gas Tamponades

Gas tamponades are the most commonly used vitreous sealants. The gases used include sulfur hexafluoride (SF6), perfluoropropane (C3F8) and air. They have the advantage of being absorbed by the eye over time, eliminating the need for removal surgery. However, they require keeping the eye facedown for an extended period, usually 1-3 weeks, to ensure the gas bubble presses the retina firmly against the back of the eye. This postoperative positioning can be difficult and uncomfortable for patients. The gases also diffuse rapidly, so they are only effective as tamponades for around 2-6 weeks depending on the specific gas used.

Silicone Oil Tamponades

Silicone oil is highly effective at tamponading the retina and does not require postoperative face-down positioning. However, it is not absorbable and requires another surgery for its removal once the retina is firmly attached. Its retention in the eye long-term carries risks of glaucoma and cataract formation. Additionally, being a foreign body it can cause an inflammatory reaction. However, it provides the longest and most stable retinal tamponade of any substance, often for many months.

Perfluorocarbon Liquids

Perfluorocarbon liquids such as perfluoro-n-octane are clear, inert liquids that are heavy and settle under the retina. They allow for good visualization during surgery but are eventually replaced with a gas or silicone oil tamponade prior to closing the eye. Being temporary tamponades, they reduce the need for long-term gas posture or later silicone oil removal surgery. However, they require an extra procedural step compared to other longer-acting tamponades.

Choosing a Tamponade

The choice of tamponade depends on factors like the complexity of the retinal detachment, presence of proliferative vitreoretinopathy, the surgeon’s experience and preferences, and the ability of the patient to comply with postoperative care requirements. For simple rhegmatogenous retinal detachments with no proliferative changes, gas tamponades are usually preferred. More complex or recurrent cases may benefit from longer acting silicone oil or initial use of perfluorocarbon liquid.

Recent Advances

Newer vitreous substitutes and tamponading agents aim to eliminate the need for multiple surgical procedures or compliance with positioning.

- Heavy silicone oils that sink rapidly after injection have potential to reduce required posturing time.

- Bio-absorbable tamponades made of materials like glycolic acid or tyrosine-derived polycarbonates gradually dissolve over weeks to months, eliminating removal surgery. However, none have yet demonstrated the long-term effectiveness of silicone oil.

- Heavier-than-water perfluorocarbon liquids that self-deliver more sustained tamponade are in early research.

- Drug-eluting coatings on silicone oil droplets may enable controlled release of anti-proliferative drugs to further reduce failure rates.

- Synthetic vitreous substitutes are also an ongoing area of study, though none are yet able to fully replicate the mechanical and optical properties of natural vitreous.

Conclusion

Vitreous tamponades are a crucial tool in vitreoretinal surgery, helping stabilize the retina through close apposition. Selection depends on individual factors to provide the best chance of anatomic and functional success while balancing risks and post-op compliance needs. Newer tamponades aim to overcome limitations of existing options and further improve outcomes. Careful consideration of the pros and cons of each can help surgeons choose the optimal agent for different cases.