Intravitreal Pharmacotherapy

Foundations & Agents - Drug Delivery Drama

• Intravitreal (IVT) Route:
  • Direct drug delivery to vitreous.
  • Bypasses blood-retinal barrier (BRB).
  • Achieves high local drug concentration.
  • Minimizes systemic side effects.
• Key Risks:
  • Endophthalmitis
  • Retinal detachment (RD)
  • ↑Intraocular Pressure (IOP)
  • Cataract (with steroids)

Common IVT Agents:

Key Indications - Retina's Rescue Remedies

• Wet AMD (wAMD):
  • Patho: CNV (VEGF-driven).
  • Drugs: Anti-VEGF (Ranibizumab, Aflibercept, Bevacizumab, Brolucizumab).
• Diabetic Macular Edema (DME):
  • Patho: ↑VEGF, inflammation → ↑permeability.
  • Drugs: Anti-VEGF; Corticosteroids (Dexamethasone, Fluocinolone implants).
• Retinal Vein Occlusion (RVO) Macular Edema:
  • Patho: Ischemia → ↑VEGF → edema.
  • Drugs: Anti-VEGF; Corticosteroids.
• Myopic CNV (mCNV):
  • Patho: CNV in pathologic myopia (VEGF).
  • Drugs: Anti-VEGF.
• Non-infectious Posterior Uveitis:
  • Patho: Inflammation → macular edema/vitritis.
  • Drugs: Corticosteroids.
• Infectious Endophthalmitis:
  • Patho: Intraocular infection.
  • Drugs: Antibiotics (Vancomycin+Ceftazidime); Antifungals (Amphotericin B, Voriconazole).

⭐ Wet Age-Related Macular Degeneration (wAMD) and Diabetic Macular Edema (DME) are the most frequent indications for intravitreal anti-VEGF injections.

The Injection Journey - Precision Pokes

• Goal: Deliver drug to vitreous, minimize complications.
• Key Prep:
  • Anesthesia (topical/subconjunctival).
  • Antisepsis: Povidone-iodine 5% or 10% (crucial!).
• The Poke:
  • Needle: 30G or 32G.
  • Site: 📌 SIT (SuperoTemporal preferred, also InferoTemporal).
  • Distance from limbus: Phakic 3.5-4 mm; Pseudophakic/Aphakic 3-3.5 mm.
  • Angle: Perpendicular to sclera.

⭐ Strict aseptic technique, including topical povidone-iodine application, is paramount to minimize the risk of post-injection endophthalmitis.

Risks & Roadblocks - Cautionary Tales

• Common/Mild (Usually Self-Limiting):

  • Subconjunctival hemorrhage
  • Transient ocular pain, foreign body sensation
  • Floaters (e.g., air bubble)
  • Transient IOP ↑ (monitor if >21 mmHg)
  • Corneal abrasion

• Serious/Vision-Threatening:

  • Endophthalmitis: Incidence ~0.05% per injection. ⚠️ Most feared!
    • Key signs: 📌 RSVP (Redness, Severe pain, ↓Vision, Pus/hypopyon)
  • Retinal Detachment (RD): Incidence ~0.01-0.7%
  • Vitreous Hemorrhage
  • Lens Damage / Cataract (esp. phakic eyes)
  • Sustained IOP ↑ / Glaucoma
  • Sterile Uveitis / Intraocular Inflammation
  • Systemic (rare): e.g., thromboembolic events (anti-VEGF)

⭐ Post-injection endophthalmitis, though rare (~0.05%), is the most devastating complication, typically presenting with pain, vision loss, and hypopyon within days.

High‑Yield Points - ⚡ Biggest Takeaways

• Anti-VEGF agents (Ranibizumab, Bevacizumab, Aflibercept) are primary for wet AMD, DME, and RVO.
• Ranibizumab is an antibody fragment; Bevacizumab is a full antibody (used off-label).
• Aflibercept is a potent VEGF trap binding VEGF-A, VEGF-B, and PlGF.
• Intravitreal steroids (Triamcinolone, Dexamethasone implant) treat inflammatory conditions like uveitis, DME, RVO.
• Key risks: endophthalmitis, retinal detachment, increased IOP (↑IOP), and cataract.
• Ozurdex (Dexamethasone implant) is biodegradable; Iluvien (Fluocinolone implant) is non-biodegradable.