Soft contact lenses are made from which one of the following materials?
**Core Concept**
Soft contact lenses are made from a type of hydrophilic material that allows for water absorption and retention, providing comfort to the wearer. This material is typically a type of polymer that is biocompatible and non-irritating to the eye.
**Why the Correct Answer is Right**
The correct answer is **Silicone Hydrogel**. Silicone hydrogel contact lenses are made from a combination of silicone and hydrogel, which provides excellent oxygen permeability and allows for the exchange of gases between the eye and the lens. This is crucial for maintaining the health of the cornea and preventing complications such as corneal edema. The silicone hydrogel material is also resistant to dehydration and maintains its shape and hydration levels throughout the day.
**Why Each Wrong Option is Incorrect**
**Option A:** **Rigid Gas Permeable (RGP)** lenses are made from a type of plastic material that is more dense and less permeable to oxygen compared to silicone hydrogel lenses.
**Option B:** **Polycarbonate** is a type of rigid plastic material commonly used in eyeglass lenses, but it is not suitable for contact lenses due to its rigidity and lack of oxygen permeability.
**Option C:** **Poly(methyl methacrylate)** (PMMA) is a type of rigid plastic material that is no longer used in contact lenses due to its lack of oxygen permeability and potential for corneal complications.
**Clinical Pearl / High-Yield Fact**
When selecting contact lenses, it's essential to consider the material's oxygen permeability, water content, and biocompatibility to ensure the health and comfort of the wearer's eyes.
**Correct Answer:** C. Poly(methyl methacrylate)