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Intravitreal implants are controlled drug delivery systems that are an emerging field in treating intraocular inflammation and other posterior segment diseases needing chronic therapy. They have the advantage of targeted delivery of high drug concentrations to the posterior segment for a prolonged period. This activity reviews the various types of intravitreal implants, their indications and contraindications, the technique of implantation, the possible complications, and the role of the interprofessional team in management and follow-up. Objectives: Describe the different types of intravitreal implants currently available and elaborate on their mechanism of action and possible complications. Review the indications for each implant and identify the situations where they might be contraindicated. Identify the techniques of implantation of the intravitreal implants along with the choice of anesthesia and instrumentation needed. Explain the role of ancillary investigations and follow-up for intravitreal implants. Access free multiple choice questions on this topic.

The intravitreal route is the main route of drug administration to treat diseases affecting the posterior segment of the eye. Intravitreal implants are specially designed to release drugs in a controlled manner over a longer duration. It helps to directly deliver the drug to the vitreous, thus overcoming systemic pathways and obtaining a high drug concentration in the vitreous chamber.[1] Intravitreal implants can either be non-biodegradable (NBI) or bio-degradable (BI). NBIs are longer lasting as they can achieve near zero-order release kinetics. Since they are non-degradable, they need surgical removal or replacement. They are larger in size; hence, a larger incision is required for implantation. They are made up of ethylene vinyl acetate (EVA), polyvinyl alcohol (PVA), or polysulfone capillary fiber (PCF). Examples of the available NBIs are Vitrasert and Retisert. BIs have the advantage of not requiring surgical removal or replacement as they degrade and disintegrate over time, thus eliminating all components from the body. They are made of polylactic acid (PLA), polyglycolic acid (PGA), PLGA, or polycaprolactones. An example of the available BI is a steroid implant containing dexamethasone called DEX Implant (Ozurdex).[2][3]

Following intravitreal implantation, complications can occur, including conjunctival hyperemia, conjunctival hemorrhage, vitreous hemorrhage, vitreous loss, hypotony, choroidal detachment, retinal detachment, accidental lens touch, intraocular inflammation, and wound dehiscence.[28] NBI requires multiple surgeries for implantation, replacement, or removal as necessary. This can lead to an increased risk of post-surgical complications such as endophthalmitis, pseudoendophthalmitis, vitreous haze and hemorrhage, cataracts, and retinal detachment.[30] Vitrasert can also lead to epiretinal membrane formation.[31]  Retisert has an additional risk of dissociating its main components leading to visual problems.[32][33] BI can have an uncontrolled release of drug load during the final burst stage of the implant, which can cause complications related to drug toxicity. BI can also cloud vision, and their movement in front of the retina or anterior chamber is a possible complication.[30] Steroid intravitreal implants are additionally associated with risks of increased intraocular pressure leading to increased IOP and glaucoma and the development or progression of cataracts. They can also migrate into the anterior chamber, which can secondarily cause damage to the corneal endothelium.[34][35] There is a greater risk of DEX implant migration into the anterior chamber in the presence of a compromised posterior capsule.[36] Ranibizumab PDS is associated with endophthalmitis, retinal detachment, implant dislocation, septum dislodgement, vitreous hemorrhage, conjunctival erosion, retraction, and bleb formation.[16][26] Follow-up Follow-up of patients with intravitreal implants is important for treatment response, monitoring of side effects, and early identification of complications. Follow-up visits depend on the disease being treated but are usually scheduled at 4 to 6 weeks to look for treatment response. Best-corrected visual acuity should be checked at every visit. IOP measurement by applanation tonometry is important, especially for intravitreal implants containing steroids. Slit lamp examination is also important to look for any anterior chamber reaction and development or progression of cataracts. In NIPU and CMV retinitis, a fundus examination should be done to look for a decrease in vitreous haze and resolution of retinitis lesions.

IOP measurement by applanation tonometry is important, especially for intravitreal implants containing steroids. Slit lamp examination is also important to look for any anterior chamber reaction and development or progression of cataracts. In NIPU and CMV retinitis, a fundus examination should be done to look for a decrease in vitreous haze and resolution of retinitis lesions. Ancillary investigations such as optical coherence tomography (OCT), OCT angiography (OCTA), and fundus fluorescein angiography (FFA) play a role in the follow-up. In conditions such as DME and RVO- ME, OCT can aid in determining the response to treatment. Central subfield thickness (CST) is assessed at every visit to look for the resolution of ME. It helps in the decision-making process of re-treatment. OCT, OCTA, and FFA can be useful in nAMD undergoing intravitreal implants to look for any signs of activity or recurrence of choroidal neovascular membranes, which will require re-treatment.

Intravitreal implants have revolutionized the treatment of posterior segment diseases. A thorough ophthalmological examination of both the anterior and posterior segments to rule out any ocular or periocular infections before planning for intravitreal steroid implants is essential. The nurse can assist the ophthalmologist in explaining to the patient the indications of the intravitreal implant and the need for follow-up to monitor response and manage complications early. Risks and possible complications of the implant should be thoroughly explained to the patient. The nurses should be aware of the implantation techniques and the use of intravitreal implants. The peri-injection precautions and the follow-up schedule should be explained to the patient. The patient should be explained the importance of periodic evaluation, including intraocular pressure check and optical coherence tomography. The clinic can play an active role by scheduling future visits in advance and sending timely reminders to the patient to attend the appointment. In case of complications, the physician or nurse should promptly identify those and institute treatment immediately. This interprofessional team approach will yield better patient outcomes. [Level 5]