Phakic IOLs

Phakic IOLs: Fundamentals - Eyes Wide Open

• Definition: Implantable lens in an eye retaining its natural crystalline lens (phakic).
• Mechanism: Corrects refractive errors (myopia, hyperopia, astigmatism) by adding optical power within the eye.
• Advantages:
  • Preserves the eye's natural accommodation.
  • Reversibility: can be removed if needed.
  • Corrects a wide range of refractive powers.
  • Often provides excellent optical quality.
• General Indications:
  • High myopia (e.g., typically > -8 D).
  • High hyperopia (e.g., typically > +4 D).
  • Significant astigmatism.
  • Patients unsuitable for corneal laser surgery (e.g., thin corneas, very dry eyes).

⭐ Phakic IOLs excel in correcting very high myopia, often effective for powers up to or exceeding -20 D.

Phakic IOLs: Classification - Lens Lineup Logic

Categorized by placement:

• Anterior Chamber (AC):
  • Angle-supported: AC angle. E.g., AcrySof Cachet (PMMA, withdrawn).
  • Iris-fixated (claw): Anterior iris. E.g., Artisan/Verisyse (PMMA), Artiflex/Veriflex (foldable).
• Posterior Chamber (PC):
  • Sulcus-supported: Ciliary sulcus. E.g., ICL/Visian ICL (Collamer). 📌 ICL: 'I Can See Clearly'.

Phakic IOLs: Candidacy & Workup - Sizing Up Success

• Indications:
  • Stable high myopia (> -8D), hyperopia (> +4D), astigmatism.
  • Poor LASIK/PRK candidates (thin corneas, dry eyes, irregular topography).
• Contraindications:
  • Anterior Chamber Depth (ACD) < 3.0 mm (most types).
  • Endothelial Cell Count (ECC) < 2000-2500 cells/mm².
  • Active uveitis, glaucoma, cataract, progressive ectasia.
• Pre-operative Workup:
  • Refraction (Manifest, Cycloplegic), Keratometry (K-values), Pachymetry.
  • ACD, White-to-White (WTW) for sizing.
  • Endothelial cell density & morphology.
  • Gonioscopy, Dilated Fundus Exam.
• IOL Power Calculation: Van der Heijde, Olsen formulas.
• Sizing is Key: Proper sizing ensures adequate vault for Posterior Chamber IOLs, preventing complications.

⭐ Accurate White-to-White (WTW) is crucial for sizing anterior chamber phakic IOLs; ACD is key for posterior chamber IOL vault.

Phakic IOLs: Technique & Troubles - Implant Insights & Issues

• Technique Highlights:
  • Corneal incision, viscoelastic use.
  • IOL insertion & precise positioning (AC/PC).
  • PI/flow port for PC IOLs prevents pupillary block.
• Common & Serious Complications (Troubles):
  • Endothelial cell loss: Critical for AC IOLs; acceptable annual loss <5%.
  • Cataract formation: Esp. PC IOLs if vault low.

    ⭐ PC Phakic IOLs touching the crystalline lens (low vault) are a significant risk for anterior subcapsular cataract.

  • Pupil ovalization (iris-fixated IOLs).
  • Pigment dispersion syndrome/glaucoma.
  • IOL decentration/dislocation.
  • Glare/halos.
  • Uveitis.
  • Pupillary block (if PI/flow port absent/occluded).
• Management:
  • Observation, topical steroids; explantation if severe.

High‑Yield Points - ⚡ Biggest Takeaways

• Phakic IOLs provide reversible correction for high refractive errors, preserving accommodation.
• Main types: Anterior chamber (angle-supported/iris-fixated) and Posterior chamber (ICL), placed behind the iris.
• ICL sizing is crucial; incorrect sizing risks vault issues, cataract formation, or angle closure.
• Key complications: Corneal endothelial cell loss, cataract (especially with ICLs), pupillary block, and increased IOP.
• Essential prerequisites: Adequate Anterior Chamber Depth (ACD) and a healthy endothelial cell count.
• Best suited for young patients with stable, high myopia or hyperopia, who are poor candidates for laser vision correction.