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
retinal hazard limit
Limiting value of the spectrally weighted source radiance of an ophthalmic instrument which if exceeded, could cause damage at or to the retina. NOTE: The effect of the radiance of a source will decrease sa the light beam passes through an optical system due to filtering, absorbtion ar other loss mechanism. Thus, basing the retinal hazard on the source radiance ensures that the radiance at the retinal cannot exceed the source radiance.