Radiation<unk>  is the calculation of absorbed dose in matter and tissue resulting from the exposure to ionizing radiation.  It is a scientific subspecialty in the fields of health physics and medical physics that is focused on the calculation of internal and external doses from ionizing radiation.
Dose is reported in gray (Gy) for the matter or sieverts (Sv) for biological tissue, where 1 Gy or 1 Sv is equal to  1 joule per kilogram. Non-SI units are still prevalent as well, where dose is often reported in rads and dose equivalent in rems.  By definition, 1 Gy = 100 rad and 1 Sv = 100 rem.
Dosimetry
Optometry
Ophthalmoscope
Intraocular pressure
Spectrophotometry
Rapid Visual Imaging
Visual acuity
Pathergy test