What is the cylinder axis tolerance for cylinder powers between 0.75 and 1.50 diopters according to ANSI Z80.1?

The cylinder axis tolerance for cylinder powers between 0.75 and 1.50 diopters is specified by ANSI Z80.1. According to this standard, the appropriate tolerance for cylinder axes within this range is +/-3 degrees. This means that if an eye care practitioner prescribes a cylindrical power within these limits, the actual axis measured in the finished lens can deviate by up to 3 degrees from the prescribed axis.

The significance of this tolerance is rooted in ensuring that the corrective lenses produced provide the intended visual correction and comfort to the wearer. Maintaining this level of accuracy, especially in cylinder power prescriptions, is crucial for effective vision correction, as the axis determines the orientation of the cylindrical component designed to address astigmatism. The value of +/-3 degrees is a compromise between manufacturing capabilities and the need for precise optical performance that meets patient requirements.