The OU medical abbreviation means both eyes, or more exactly each eye, from the Latin oculus uterque. When an eye drop order or an exam result says OU, it applies to the right eye and the left eye alike.
OU belongs to a trio with OD, the right eye, and OS, the left eye. You will see it written OU, ou or o.u. on prescriptions, eye exam forms and glasses orders. This page explains what it means in practice, why safety experts list it as error-prone, and the plain wording that is safer to use.
At a glance
Stands for
Each eye or both eyesLatin origin
Oculus uterque, each of the two eyesWritten as
OU, ou, o.u.Safer to write
each eye or both eyesDo not confuse with
Where you see it
Eye drop labels, exam findings, glasses prescriptions
What the OU medical abbreviation means in practice
OU tells the reader that an instruction or finding covers both eyes. For a medicine, it usually means the stated amount goes into each eye separately. So 1 drop OU calls for a drop in the right eye and another in the left eye, two drops in total, not one drop shared between them.
On an exam record, OU can summarize a finding seen in each eye, such as normal pupils or clear lenses. On a glasses prescription, it may appear next to a value that is the same for both lenses. Eye doctors also use it when they describe vision tested with both eyes open together.
Reading an eye drop order with OU
Here is how a typical both eyes order breaks down.
| Piece | Plain meaning |
|---|---|
| Artificial tears | A lubricating eye drop |
| 1 gtt | One drop |
| OU | In each eye |
| four times daily | Four times across the day |
| as needed | Only when the eyes feel dry, the meaning of PRN |
After cataract surgery, a nurse explains: "This one is for the operated eye only, but the lubricating drop on your list says OU, so that goes in both." The example shows why the eye term matters as much as the drug name. Instructions after surgery are set by the surgeon.
Why OU is considered error-prone
Medication safety experts at ISMP include OU, with its two partners, among abbreviations known to lead to errors. The concern is mainly that OU can be read as AU, which means each ear. On a handwritten order, ear drops and eye drops can be swapped by a single misread letter.
The safer practice is to write each eye or both eyes in full. Pharmacies routinely translate OU into plain words on labels, for example instill one drop into both eyes. If a label still shows only OU, or the wording seems to conflict with what the doctor said, a pharmacist can confirm it.
OD, OS, OU and the ear look-alikes compared
The eye and ear sets mirror each other, which is useful for memory but also the source of the confusion.
| Eye term | Meaning | Ear term | Meaning |
|---|---|---|---|
| OD | Right eye | AD | Right ear |
| OS | Left eye | AS | Left ear |
| OU | Each eye | AU | Each ear |
People searching od os ou medical abbreviation usually want this whole set at once. The O terms come from oculus, eye, and the A terms from auris, ear.
OU as a pharmacy abbreviation for students
For pharmacy technician and nursing students, OU is a term to read and translate rather than copy. A label should name the eye in words, and a medication record often does the same. When a drop is ordered for each eye at the same time, students also learn to wait a few minutes between different drops if more than one is ordered, so the first is not washed out, although the exact interval comes from the prescriber or pharmacist.
You may also see des OU in some notes, which is shorthand for a dry eye syndrome affecting both eyes. For the other route and timing shorthand found on orders, visit the prescription abbreviations section.
This explains the abbreviation for general understanding. How to use your own eye drops, and in which eye, should come from your eye doctor or pharmacist.
Frequently asked questions
What does OU mean on eye drops?
It means use the drops in each eye. A single drop OU equals a drop placed in each eye separately. Labels usually spell this out as both eyes.
What is the medical abbreviation for both eyes?
The traditional abbreviation is OU, from oculus uterque. Many clinics now write both eyes or each eye instead, because ISMP counts OU among error-prone abbreviations.
Is OU the same as AU?
No. OU means each eye and AU means each ear. They are easy to confuse, which is one reason safety groups recommend writing the words in full.
What do OD, OS and OU stand for?
OD names the right eye, OS names the left, and OU covers each eye. All three come from Latin terms for the eyes and are common on eye prescriptions.