Intravitreal implants

Intravitreal implants are micro device-like inserts injected into the posterior segment of the eye to treat retinal diseases releasing therapeutic drugs at a set rate over a desired period of time.[1][2] The posterior segment of the eye consists of the sclera, choroid, fovea, vitreous humor, optic nerve, and retina.[3][4]

Anatomical diagram of a human eye

Applications

Non-biodegradable implants

Inserts made with non-biodegradable materials such as polymers require a surgical removal of the implant after the end of the treatment period.[2] Examples of these materials consist of polymers such as ethylene-vinyl acetate (EVA), polyvinyl alcohol (PVA), polyurethane (PU) and poly siloxane (PS).[4] An advantage to these non-biodegradable implants is that they do not cause any immune response towards the retina and the release of the drug substance can be controlled by "layering polymers of different permeability."[2]

Biodegradable implants

Biodegradable implants are made of materials, typically, either water-soluble or metabolizable to degrade into un-harmful byproducts which can be safely excreted by the human body.[2][4] It is important to note the release of the therapeutic drug is determined by the degradation of the implant and the diffusion rate of the drug substance.[2] Indicating that the higher the molecular weight of the polymer and drug substance used, the slower the release of the drug into the vitreous humor.[2]

References
  1. Tawfik M, Chen F, Goldberg JL, Sabel BA (December 2022). "Nanomedicine and drug delivery to the retina: current status and implications for gene therapy". Naunyn-Schmiedeberg's Archives of Pharmacology. 395 (12): 1477–1507. doi:10.1007/s00210-022-02287-3. PMC 9630211. PMID 36107200.
  2. Orlova ER, Gorobets AV, Dorofeev DA, Kirilik EV, Kozlova IV (2022-06-25). "Intravitreal Systems For Targeted Drug Delivery To The Posterior Eye Segment: A Systematic Review". Russian Open Medical Journal. 11 (2): e0213. doi:10.15275/rusomj.2022.0213. S2CID 252724853.
  3. Bajpai A, Bajpai J, Saini RK, Agrawal P, Tiwari A (2016-12-19). Smart Biomaterial Devices (0 ed.). CRC Press. doi:10.1201/9781315371559. ISBN 978-1-4987-0701-5.
  4. García-Estrada P, García-Bon MA, López-Naranjo EJ, Basaldúa-Pérez DN, Santos A, Navarro-Partida J (May 2021). "Polymeric Implants for the Treatment of Intraocular Eye Diseases: Trends in Biodegradable and Non-Biodegradable Materials". Pharmaceutics. 13 (5): 701. doi:10.3390/pharmaceutics13050701. PMC 8151640. PMID 34065798.
  5. Abdulla D, Ali Y, Menezo V, Taylor SR (April 2022). "The Use of Sustained Release Intravitreal Steroid Implants in Non-Infectious Uveitis Affecting the Posterior Segment of the Eye". Ophthalmology and Therapy. 11 (2): 479–487. doi:10.1007/s40123-022-00456-4. PMC 8800436. PMID 35092605.
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