R
- Radiance L
- reading cap
- reading portion
- reduce-aperture trial case lens
- reduced aperture trial frame
- reduced-aperture lens
- Reference distance
- reference IOP
- Reference plane
- reference seeing distance (RSD)
- reference wavelength
- refracting angle
- refracting edge
- refractive index
- Refractor head
- relative distance magnification
- relative visual attenuation coefficient
- resolution
- resolving power of the fundus camera
- retinal hazard limit
- Retinoscope
- reverse polarity system
- round segment
Radiance L
In a given direction at a given point, the quotient of the radiant flux dÒ passing through that point and propagating within the solid angle dõ in a direction Õ divided by the product of the area of a section of that beam on a plane perpendicular to this direction containing the given point and the solid angle do (see C.1). NOTE: Radiance is expressed in milliwatts per square per steradian [mW/(cm² x sr)].