Can Anti-Vascular Endothelial Growth Factor (anti-VEGF) intravitreal injections be administered in the presence of silicone oil in the posterior vitreous?

Anti-VEGF Intravitreal Injections with Silicone Oil in the Posterior Vitreous

Anti-VEGF intravitreal injections can be safely administered in eyes with silicone oil tamponade, though special considerations should be made regarding drug diffusion and potential complications. 1

Rationale and Considerations

• Silicone oil is used as a long-term tamponade agent in vitreoretinal surgery, particularly for patients who cannot position facedown after macular hole surgery or for complex retinal detachments 1
• The presence of silicone oil creates a different environment for drug diffusion compared to the normal vitreous, as injected particles must diffuse through this hydrophobic medium rather than the hydrated cross-linked meshwork of the natural vitreous 1
• Drug diffusion through the vitreous cavity is affected by particle size, charge, and viscosity of the media, which are all altered in the presence of silicone oil 1

Administration Technique

• When administering anti-VEGF injections in eyes with silicone oil:
  • Use standard intravitreal injection technique with povidone-iodine preparation and lid speculum 1
  • Locate the injection site 3.0-4.0mm posterior to the limbus, as with standard injections 1
  • Consider that the drug will likely form a discrete bolus within or adjacent to the silicone oil rather than dispersing evenly 1

Efficacy Considerations

• Anti-VEGF agents have demonstrated efficacy in treating macular edema from various causes, including retinal vein occlusions and diabetic macular edema, though specific studies on efficacy in silicone oil-filled eyes are limited 1
• Drug distribution may be affected by the interface between silicone oil and remaining aqueous/vitreous components, potentially creating uneven drug concentrations 1
• The hydrophobic nature of silicone oil may affect the distribution of hydrophilic anti-VEGF biologics such as ranibizumab, bevacizumab, and aflibercept 1

Potential Complications

• Additional silicone oil microdroplets may be introduced during injection if using silicone-lubricated syringes, potentially exacerbating visual symptoms 2, 3, 4
• Studies have shown varying prevalence of silicone oil microdroplets after anti-VEGF injections:
  • 78.3% with bevacizumab in BD 0.3-mL polypropylene syringes
  • 48.5% with aflibercept in BD 1.0-mL polycarbonate syringes
  • 14.4% with ranibizumab in BD 1.0-mL polypropylene or glass prefilled syringes 5
• These microdroplets can cause symptomatic floaters in approximately 39.5% of patients receiving intravitreal injections 6

Practical Recommendations

• Use silicone-free syringes when possible for intravitreal injections in eyes with silicone oil to prevent additional silicone microdroplet formation 2, 5
• Consider that drug clearance mechanisms differ in silicone oil-filled eyes, as the normal anterior and posterior clearance pathways may be altered 1
• Monitor for intraocular pressure elevation after injection, as the presence of silicone oil already occupies volume within the eye 6
• Counsel patients about the possibility of additional visual disturbances after injection, particularly if using silicone-lubricated syringes 3, 4

Conclusion

While no specific contraindications exist for administering anti-VEGF injections in silicone oil-filled eyes, clinicians should be aware of the altered pharmacokinetics and potential for additional silicone microdroplet formation. Using silicone-free syringes when available and monitoring for complications are recommended to optimize outcomes in these cases 2, 5, 6.