The ANSI 87.1 standard represents a foundational pillar in the world of optical correction, serving as the definitive American benchmark for eyeglass lens specifications. Often referenced in technical catalogs and retail descriptions, this standard dictates the fundamental shapes, dimensions, and tolerances required for lenses to ensure optical performance and physical compatibility with frames. Understanding ANSI Z87.1 is essential for anyone involved in the optical industry, from manufacturers and opticians to safety equipment suppliers, as it guarantees that lenses meet specific criteria for quality and safety.
Formally known as ANSI Z87.1, this standard is published by the American National Standards Institute (ANSI) and is developed in collaboration with the American Society for Testing and Materials (ASTM). The current major revision, Z87.1-2020, updated previous versions to reflect modern technological advancements and safety requirements. This standard applies to all kinds of eyewear, including prescription lenses, plano (non-prescription) lenses, and protective eyewear, ensuring a consistent level of safety and usability across the board.
Key Specifications and Lens Types
ANSI Z87.1 categorizes lenses based on their intended use, primarily dividing them into two main categories: prescription lenses and non-prescription lenses. For prescription lenses, the standard outlines specific requirements for sphere, cylinder, and axis measurements, ensuring that the optical power is distributed correctly across the lens surface. These specifications help prevent visual distortions, eye strain, and headaches, providing wearers with a clear and comfortable viewing experience.
Sphere Power: Defines the lens power for nearsightedness or farsightedness, measured in diopters.
Cylinder Power: Corrects astigmatism, specified in diopters along a particular axis.
Axis: The orientation of the cylindrical correction, measured in degrees from 1 to 180.
Safety and Impact Resistance
One of the most critical aspects of ANSI Z87.1 is its focus on safety, particularly for industrial and protective eyewear. Lenses intended for safety applications must undergo rigorous testing to ensure they can withstand high-velocity impact and exposure to hazardous materials. The standard specifies that lenses must pass the high-velocity impact test, where a 1/4-inch steel ball is shot at the lens at a specified velocity. Lenses that pass this test are marked with the Z87+ designation, indicating they meet the highest safety standards for impact resistance.
Beyond impact resistance, the standard also covers optical quality requirements for non-prescription lenses, ensuring they do not cause visual distortion. These lenses, often found in reading glasses or safety glasses with clear lenses, must adhere to strict tolerances for prismatic power and unwanted curvature. This ensures that even non-prescription lenses provide a clear field of view without causing visual fatigue.
