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Intraocular Lenses (IOLs): Types, Surgery, and Outcomes

Intraocular Lenses: Restoring Vision After Cataract or Refractive Surgery

An intraocular lens (IOL) is an artificial lens implanted to replace the eye's natural crystalline lens (cataract surgery) or to correct refractive error (refractive lens exchange).

IOL Types

1. Monofocal

  • Single focal point (usually distance).
  • Requires glasses for near/intermediate.
  • Highest optical quality, least dysphotopsia.
  • Monovision option (one eye distance, one near).

2. Multifocal (Diffractive/Refractive)

  • Multiple focal points (distance + near ± intermediate).
  • Reduces spectacle dependence (~80% spectacle-free).
  • Trade-offs: Halos, glare, reduced contrast sensitivity (especially night).
  • Not ideal for macular disease, high visual demand professions.

3. Extended Depth of Focus (EDOF)

  • Single elongated focal range (distance to intermediate).
  • Less dysphotopsia than multifocal; near vision may need readers.

4. Toric

  • Corrects corneal astigmatism (cylinder power aligned at surgery).
  • Available in mono-, multi-, EDOF platforms.

5. Accommodating

  • Designed to shift position/shape with ciliary muscle contraction.
  • Clinical accommodation modest; Crystalens (FDA approved) — variable results.

6. Light-Adjustable (LAL)

  • Post-op UV light treatments fine-tune power (non-invasively).
  • Requires UV-protective glasses until lock-in.

Cataract Surgery Workflow

  1. Topical/local anesthesia.
  2. Corneal incision (2.2–2.8 mm).
  3. Capsulorhexis (circular anterior capsule opening).
  4. Phacoemulsification: Ultrasound emulsifies lens → aspirated.
  5. IOL injection into capsular bag.
  6. Incision self-seals (usually sutureless).

Outcomes and Risks

  • Success: >95% achieve 20/40 or better uncorrected (monofocal distance).
  • Risks: Infection (endophthalmitis <0.1%), retinal detachment (~0.5–1%), CME, IOL dislocation, posterior capsule opacification (PCO — 20–30%, treated with YAG laser).

Patient Selection

Surgeon discusses: Visual goals, lifestyle, ocular comorbidities (dry eye, glaucoma, macular disease), astigmatism, cost (premium IOLs often out-of-pocket).

Future Directions

Trifocal, pinhole (IC-8 Apthera), drug-eluting, smart IOLs (sensors).

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