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.
Over-the-Counter Eye Drops vs. Prescription Eye Drops. Eye drops and ointments can be broken down into two categories: over-the-counter (OTC) eye drops and prescription (Rx) eye drops. Over-the-counter eye drops are appropriate in many cases, and can be cheaper and more convenient.here's an eye drop or ointment to relieve the symptoms of most eye problems  whether you have dry eyes, pink eye (conjunctivitis), red eyes or itchiness. Determining which kind of eye drop or ointment is best depends on what kind of eye condition you have: 1  Dryness.