Breast Ultrasound: What to Expect and What the 9 O'Clock Position Means
A non-invasive eye imaging test that measures the thickness of the retinal nerve fiber layer at the 9 o'clock position of the right eye to assess optic nerve health.
{"Uses light waves to create detailed images of the eye's optic nerve","Helps detect glaucoma and other optic nerve disorders","Quick, painless procedure taking about 10-15 minutes","No special preparation needed","Results help doctors monitor eye and neurological conditions"}
Key facts at a glance
- LOINC
- 86313-4
- Short code
- RNFL 9 OS
- Synonyms
- R ret RNFL 9 o'clock thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- N/A - Imaging test not requiring specimen collection
- Units
- N/A
- Ref low
- 55
- Ref high
- 80
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92133
- SNOMED
- 371632004
- Specimen volume
- N/A - Non-invasive imaging procedure
- Stability
- N/A - Imaging test
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–24 hours
- Order
- routine
A breast ultrasound is a painless imaging test that uses high-frequency sound waves to create detailed pictures of the inside of your breast. It is often used to evaluate a lump, an area of thickening, or a finding seen on a mammogram, and it involves no radiation.
The Right Retina Retinal Nerve Fiber Layer (RNFL) Thickness test by OCT is an advanced imaging procedure that uses Optical Coherence Tomography (OCT) to measure the thickness of the retinal nerve fiber layer at the 9 o'clock position (temporal side) of your right eye. The retinal nerve fiber layer consists of nerve fibers that carry visual information from the retina to the brain. Measuring its thickness helps doctors assess the health of your optic nerve.
You will lie on your back on an exam table, and a clear gel is applied to the skin of your breast. A technologist gently moves a handheld device called a transducer across the area in slow, sweeping motions while images appear on a computer screen. The test usually takes fifteen to thirty minutes, and you can return to your normal activities right afterward.
During the test, you will sit in front of the OCT machine and rest your chin on a support. The technician will ask you to look at a specific target while the device scans your eye. The process is completely painless and does not involve any radiation or direct contact with your eye. The entire procedure takes about 10-15 minutes, and you can resume normal activities immediately afterward.
Doctors describe locations within the breast the same way you read a clock face, with twelve o'clock at the top near the collarbone and six o'clock at the bottom near the skin fold. The nine o'clock position refers to the outer side of your right breast or the inner side of your left breast, so it tells your care team exactly where a finding is located and helps them examine, monitor, or biopsy the same precise spot at follow-up visits.
The retina is divided like a clock face, with 12 o'clock being the top and 6 o'clock being the bottom. The 9 o'clock position corresponds to the temporal (outer) side of the eye. Measuring thickness at this specific location helps doctors detect early changes that may indicate glaucoma or other optic nerve conditions, as different diseases can affect different parts of the optic nerve.
Reference range
Normal Retinal Nerve Fiber Layer (RNFL) thickness at clock hour 9 (temporal quadrant) ranges from 55 to 80 micrometers (μm) in healthy adult eyes. Values may vary based on instrument manufacturer and population norms.N/A
Patient should remove contact lenses prior to imaging. Inform technician of any eye conditions, prior eye surgeries, or intraocular pressures. No fasting required. Avoid eye makeup on day of examination.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to detect and monitor glaucoma, a condition that damages the optic nerve and can lead to vision loss if untreated. It can also help identify other conditions affecting the optic nerve, such as multiple sclerosis, optic neuritis, ischemic optic neuropathy, and certain neurological disorders. The test provides baseline measurements and allows doctors to track changes over time, enabling early intervention when problems are detected.
Frequently asked questions
Do I need to fast before this test?
Is the test painful?
How long does it take to get results?
Will I need to have this test again?
Are there any side effects?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy