 The Humphery Matrix Zeiss, Dublin, California, USA; in cooperation with Welch Allyn, Skaneateles, New York, USA, which is a recently developed version of FDT perimetry, showed more improved technology to detect early glaucomatous damage. The users guide for the Humphrey Matrix Humphrey matrix visual field instrument users guide. Zeiss, Dublin, California, USA; in cooperation with Welch Allyn, Skaneateles, New York, USA; 2003 suggests that myopic refractive errors more than -3.0 D need to be corrected before the 30-2 test. However, the proper correction of the optical defocus is not always easy because of a lack of trial frame. 