S
- second principal meridian
- segment
- segment centre
- segment depth
- segment diameter
- segment extreme point
- segment extreme point height
- segment extreme point position
- segment height
- segment lens
- segment side
- segment width
- semifinished lens blank
- shape factor
- side
- single-vision lens
- single-vision semifinished lens blank
- Slit-lamp microscope
- spatial resolution
- spectacle lens
- spectacle magnifier
- spectacle microscope
- spectacle telescopes
- Spectral radiance L l (l)
- spectral reflectance
- spectral transmittance
- Spectrally-weighted photochemical aphakic source radiance LA
- Spectrally-weighted photochemical phakic source radiance LB
- sphere
- spherical lens
- spherical power
- spherical power lens
- spherical surface
- Spherical test lenses
- spherocylindrical lens
- Spot retinoscope
- stand magnifier
- static perimeter
- stimulus duration
- stimulus luminance, LS
- straight-top bifocal
- straight-top segment
- Streak retinoscope
- supraliminal strategy
- suprathreshold strategy
- surface astigmatic power
- surface power
- Synoptophore
segment centre
Boxed centre of the rectangle formed by the horizontal and vertical tangents to the segment dividing line, or lens periphery if the segment extends to the lens edge. NOTE: This applies only to a semifinished lens blank, or to a lens where no part of the segment has been lost through surfacing or edging.