Converting a written prescription from plus to minus cylinder form is known as:

Converting a written prescription from plus cylinder form to minus cylinder form is referred to as toric transposition. This process involves changing the format of the cylindrical power and its axis to maintain the same visual correction but in a different notational system.

In plus cylinder form, the positive cylinder denotes the meridian with the least curvature, while in minus cylinder form, the negative cylinder indicates the meridian with the greatest curvature. This transposition is crucial in ensuring that the patient's correction is represented correctly for fabrication of lenses.

The method of toric transposition allows eye care professionals to communicate accurate prescription details clearly and effectively, accommodating various lens manufacturing practices and patient needs. It is an essential skill for those involved in dispensing eyewear to ensure optimal vision correction for their clients.