Plus/Minus Cylinder Conversion Calculator

Converting Between Plus and Minus Cylinder Prescriptions

Converting between plus and minus cylinder formats is a fundamental skill in optometry, essential for accurately interpreting and transcribing eyeglass prescriptions. A prescription written in plus cylinder format indicates the correction needed to neutralize the astigmatism by adding cylindrical power to the spherical power, whereas a minus cylinder format subtracts cylindrical power from the spherical power to achieve the same result. This conversion is necessary when different optical devices or practices prefer one format over the other. To convert from plus to minus cylinder format, one must add the cylinder value to the sphere value to form the new sphere value, invert the sign of the cylinder, and adjust the axis by 90 degrees. Conversely, converting from minus to plus cylinder involves reversing this process. Mastering these conversions ensures that the prescription maintains the same optical power and effect, regardless of the format, thus allowing for seamless communication and interpretation across various optical systems and practitioners. This proficiency is vital for optometrists to provide accurate, consistent vision correction and to facilitate effective collaboration within the eye care community.

Plus/Minus Cylinder Conversion

Initial Prescription