With earlier generation GP materials, lenses with lower Dk polymers exhibited greater dimensional stability and wettability, which translated to improved vision and comfort. 1 However, these lenses still exhibit more flexure and surface scratches than PMMA. The new material came with limitations, however, including significant protein deposition, flexure and parameter instability they were also easily broken and scratched.įluorine was later added to minimize protein deposition, maintain oxygen permeability and improve wettability of the fluorosilicone acrylate (FSA) lens materials that are commonly used today. ![]() In these early products, Dk increased in proportion to the silicone. Materials were then categorized according to oxygen permeability, or “Dk” value. In the late ’70s, silicone was added to create a silicone acrylate (SA) material, a step closer to today’s rigid GP lenses. This image depicts poor wetting of a GP lens surface. Given the material’s impermeability to oxygen and other gases, successful PMMA lens wear relied on adequate tear exchange to supply oxygen to the eye and remove metabolic byproducts. 1 PMMA was also impervious to rigorous wear and care practices and could withstand forceful handling and exposure to off-label cleaning products such as dishwashing liquid. These characteristics allowed for easy manufacturing and long replacement intervals. ![]() All but obsolete, PMMA contact lenses exhibited excellent optical qualities and lens stability and were resistant to lens deposits. How it All StartedĬontact lenses have come a long way from the days of polymethyl methacrylate acid (PMMA), a predecessor to today’s gas permeable (GP) contact lens materials. This review of the strengths and limitations of current lens materials can help you better understand why surface treatments may be the next innovation in lens wear. Scleral Lenses: Boom, Don’t Bust (Earn 2 CE Credits)Ĭontact lens experts have turned their attention to the contact lens surface and how it contributes to performance. Follow the links below to read other articles from annual update on contact lenses:
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