## IOL Materials and Refractive Index **High-Yield:** Refractive index determines the thickness of an IOL for a given power. A higher refractive index allows thinner, lighter lenses that can be inserted through smaller incisions. ### Refractive Index Comparison | IOL Material | Refractive Index | Key Features | |---|---|---| | Collamer (Visian ICL) | ~1.45 | Biocompatible, UV protection; used as phakic lens | | Silicone | ~1.46 | Foldable, moderate index; prone to glistenings | | PMMA | ~1.49 | Rigid, durable, excellent optics; requires large incision (>6 mm) | | **Acrylic** | **~1.55** | **Highest refractive index; foldable; preferred for small-incision surgery** | **Key Point:** Acrylic IOLs (both hydrophobic and hydrophilic subtypes) have the highest refractive index (~1.55) among commonly used IOL materials. This allows acrylic lenses to be made thinner for a given dioptric power, facilitating insertion through incisions as small as 2.2–2.8 mm. **Clinical Pearl:** Because of their high refractive index (~1.55), excellent biocompatibility, low posterior capsule opacification (PCO) rates, and minimal glistening, hydrophobic acrylic IOLs (e.g., AcrySof) have become the most widely used IOL material in modern phacoemulsification cataract surgery. (Reference: Kanski's Clinical Ophthalmology, 9th ed.; Yanoff & Duker Ophthalmology) **Summary of ranking (lowest to highest refractive index):** Collamer (1.45) < Silicone (1.46) < PMMA (1.49) < **Acrylic (1.55)** 
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