of the average person in the mid 1800's combined to give people who wore spectacles an appearance
indicative of that period; a defining frame-to-face
ratio. Today we are physically larger than we were
in the 1800's and original period spectacles are just too small for most of us.
Unlike modern eyeglasses
that are considered to
fit properly when they are the same width as the
wearer's face, a good rule of thumb for spectacle
size is approximately two-thirds the width of the
face, eyes centered horizontally in the lens portion of the
spectacles. As we are physically larger today than in
the past, spectacle sizes can
be increased to comfortably fit the wearer, while
maintaining the approximate frame-to-face ratio
of the past.
Pupillary Distance (PD)
Patient PD or Pupillary Distance is the distance between the centers of the pupils.
In the illustration above, A to B. This information can be obtained from you optical professional.
Frame P.D. is the distance between the center of the right lens and the center of the left lens.
In order to emulate an authentic period appearance, the patient P.D. should closely match the frame P.D.
In effect, horizontally centering the eyes (right to left - left to right) in the spectacle frame, as illustrated above. On the vertical plane (top to bottom) the eyes should be located in the mid to upper portion of the frames allowing adequate room for bifocals or progressive lenses, if necessary.