P
- pantoscopic angle
- perimeter
- perimeter decibel scale
- peripheral field
- permanent engraving
- photochromatic material
- photochromic fatigue
- photochromic lens
- photochromic material
- photoretinits
- plano lens
- plastic frame
- plus-power lens
- polarizing lens
- positiv lens
- power
- power, equivalent
- predecentration
- primary position
- Principal curvature direction
- principal meridian
- principal meridians of a surface
- principal power
- principal section of a prism
- printing
- prism base
- prism dioptre
- prism reference point
- prism thinning
- prismatic deviation
- prismatic effect
- prismatic power
- prismatic power lens
- prismatic power prism
- Prismatic test lenses
- progression zone
- progressive power lens
- progressive power semifinished lens blank
- progressive side
- progressive surface
- progressive-addition lens
- progressive-addition semi-finished lens blank
- projection perimeter
- protective lens
perimeter decibel scale
Logarithmic scale used to express, in decibels, the differential light sensitivity, S, where the value of the backtround luminance, LB, is replaced within the formula by the defined maximum stimulus luminance of the specific instrument, Lmax, and where 0 dB represents this maximum stimulus luminance. S(in dB)=10log10[Lmax/DLT] NOTE: The same scale is used to express stimulus luminance, LS, by replacing the treshold differential luminance DLT within the formula with the differential luminance DL.