## IOL Materials and Refractive Index **Key Point:** Among the commonly used IOL materials listed, PMMA (Polymethylmethacrylate) has the **highest refractive index of approximately 1.49**, which is higher than Collamer (~1.43–1.45), Silicone (~1.41–1.46), and standard hydrophilic acrylic (~1.41–1.46). ### Refractive Index Comparison | IOL Material | Refractive Index | Notes | |---|---|---| | **PMMA** | **~1.49** | Highest RI; rigid, requires large incision | | Silicone | ~1.41–1.46 | Foldable; lower RI variants common | | Collamer | ~1.43–1.45 | Hydrophilic acrylic-collagen copolymer; foldable | | Acrylic (hydrophobic) | ~1.41–1.55 | Wide range; some high-RI variants exist | **High-Yield:** A higher refractive index allows: - **Thinner optic design** for the same dioptric power - **Reduced spherical aberration** due to flatter lens curvature - Better optical quality and contrast sensitivity **Clinical Pearl:** Although PMMA has the highest refractive index among the classic IOL materials (making lenses theoretically thinner), it is **rigid** and requires a large surgical incision (~6 mm), making it largely obsolete in modern cataract surgery. Foldable materials (acrylic, silicone, Collamer) are preferred today despite their comparatively lower refractive indices, because they allow small-incision phacoemulsification. [Reference: Yanoff & Duker, Ophthalmology, 6th ed., Ch. 7; Kanski's Clinical Ophthalmology, 9th ed.] **Exam Tip:** When a NEET PG question specifically asks for the **highest refractive index** among standard IOL materials, the answer is **PMMA (~1.49)**. When asked about the best *modern* or *foldable* IOL, consider hydrophobic acrylic or Collamer. 
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