glasses - dioptre, diamond - ?

CARAT
List of words for the clue glasses - dioptre, diamond - ? from the crossword:
UNIT FOOD DIOPTER CALORIE OPERA SPECS NEIL RIMS SPECTACLES NEZ LENS GOBLETS EYEWEAR DOC BASE EYES UMP UMPS GEM
WordClue
GEMdiamond or sapphire
FOODdioptre - glasses, calorie - ?
UNITcarat or gallon
CORPSmilitary unit size
CURIEnon-SI unit of radioactivity
FARADunit of capacitance
HERTZSI unit for frequency
JEWELdiamond or sapphire
MONTHunit of time dividing the year
OUNCEunit of mass
PENNYunit of currency in various countries
QUARTunit of volume
ZOBELdiamond
CALORIEglasses - dioptre, food - ?
DIAMONDdioptre - glasses, carat - ?
DIOPTREdiamond - carat, glasses - ?
GLASSEScarat - diamond, dioptre - ?
GOGGLESsafety glasses
RHINESTONEartificial diamond, strass
SPECTACLESglasses
SPECTACLESglasses
CALORIEglasses - dioptre, food - ?