Distometer (or Vertex Distance) gauge is designed to accurately measure the vertex distance between the cornea and trial lens, or cornea and rear surface of the spectacle Rx lens. The Conversion Disc is used to convert any combination of lens power and vertex distance into an equivalent lens power for a different distance.

Normally a trial lens is placed 5mm to 20mm from the cornea. Spectacle Rx, when fitted correctly, should be between 8mm and 12mm from the cornea. Any difference, however, in vertex distance between the trial lenses and the resultant spectacle Rx produces an error in the effective power of the correction.

Includes instructions and conversion calculator. Measures distance between cornea and inside of glasses.

Email a Friend