Lretrnfl5oclockthicknessoct
A non-invasive eye imaging test that measures the thickness of the retinal nerve fiber layer in the left eye to detect glaucoma and optic nerve damage.
{"Uses OCT technology to capture detailed cross-sectional images of the retina","Measures the retinal nerve fiber layer (RNFL) thickness at clock hour 5 of the left eye","Helps detect early signs of glaucoma and monitor disease progression","The test is quick, painless, and does not require any eye drops or blood draw","Results are compared to normal ranges to assess eye health"}
Key facts at a glance
- LOINC
- 86297-9
- Short code
- OCT RNFL LH5
- Synonyms
- L ret RNFL 5 o'clock thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- Not applicable (imaging study, not a specimen collection)
- Units
- N/A
- Ref low
- 70
- Ref high
- 85
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 399550006
- Specimen volume
- Not applicable
- Stability
- Not applicable
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–24 hours
- Order
- routine
What is this test?
This test uses Optical Coherence Tomography (OCT) to measure the thickness of the retinal nerve fiber layer (RNFL) at a specific location (clock hour 5) in your left eye. The retina is the light-sensitive tissue at the back of your eye, and the RNFL contains nerve fibers that carry visual information to your brain. OCT is a advanced imaging technology that uses light waves to create detailed cross-sectional images of your retina, similar to how ultrasound uses sound waves.
Why is this test performed?
This test is primarily performed to: (1) Detect early signs of glaucoma, a disease that damages the optic nerve; (2) Monitor the progression of glaucoma or other optic nerve disorders; (3) Evaluate changes in the retinal nerve fiber layer due to neurological conditions; (4) Assess the effectiveness of glaucoma treatment; and (5) Screen for optic nerve damage in patients at risk for eye diseases.
How is the test done?
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 machine scans your eye. The scan is quick and completely painless - you will not feel anything. No eye drops or injections are required. The entire procedure takes about 5-10 minutes. You may need to avoid blinking during the scan for a few seconds.
How to prepare for the test?
No special preparation is needed for this test. You can eat and drink normally before the appointment. However, you should inform your doctor about any eye conditions, surgeries, or medications you are taking. If you wear contact lenses, you may be asked to remove them before the test. Avoid wearing eye makeup on the day of the test as it may interfere with the imaging.
Understanding your results
Your test results will show the RNFL thickness measurement at clock hour 5 of your left eye, measured in micrometers (μm). The results will be compared to a database of normal healthy eyes. Thinner than average RNFL may indicate potential nerve damage, while thicker than average measurements may not be concerning. Your eye doctor will interpret the results in conjunction with other eye examinations and your medical history.
Reference range
Normal RNFL thickness at clock hour 5 typically ranges from 70-85 microns in healthy adults. Full peripapillary RNFL average thickness: 95-110 microns. Reference ranges vary by instrument manufacturer and patient age.N/A
No special preparation required. Patient should remove eye makeup and contact lenses if applicable. Inform technician of any eye conditions or recent eye surgeries.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Does the OCT test hurt?
How long does the test take?
Will I need to have my pupils dilated?
How often should I have this test?
What do abnormal results mean?
Can I drive after the test?
Sources
- 1
- 2
- 3
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