Gravel /ËÉ¡rÃ¦vÉl/ is a loose aggregation of rock fragments. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (2 to 4 mm or 0.079 to 0.157 in) and pebble gravel (4 to 64 mm or 0.2 to 2.5 in).
OD - This is shorthand for oculus dextraous which means Right Eye. OS - This is shorthand for oculus sinister which really means Left Eye. OU - This is shorthand for oculus uterque which really means Both Eyes. If you see this, you'll want to enter the prescription the same on both eyes. Sphere or Power - SPH or PWR - This is the main strength of your eyeglass prescription, and is written in 0.25 increments. If the field has 'SPH', 'PL', 'PLANO', or '00', this means your there is a 0.00 power as should be entered as so.
PD (OU), written as 62, means the Binocular PD which is for both eyes. PD (OD), means the Monocular PD for the right eye, PD (OS), means the Monocular PD for the left eye, A Monocular OD is written as two numbers, for example 32/30, 32 represents the PD for the right eye, and 30 for the left eye. Sometimes PD is written as 62/59 or they are labeled Far and Near.