| OB-US | obstetrical ultrasound [examination of the fetus] |
|---|---|
| OC | obstetrical conjugate; occlusocervical; office call; on call; only child; optic chiasma; oral contra... |
| ECCE | Extra-Capsular Cataract Extraction |
| ECLE | Extra-Capsular Lens Extraction |
| ERBSE | Endoscopic Retrograde Balloon Stone Extraction |