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
Spherical test lenses
Lenses used for the calibration of the dioptric power measurements by focimeters, in which the power of each lens is expressed as its back vertex power in dioptres (D).