Left Eye Retinal Nerve Fiber Layer (RNFL) Nasal Thickness Test with OCT
A non-invasive eye imaging test that uses optical coherence tomography (OCT) to measure the thickness of the retinal nerve fiber layer on the nasal side of the left eye, helping doctors evaluate optic nerve health and detect conditions such as glaucoma.
{"This test measures the thickness of nerve fibers in your left retina using light waves","It helps detect early signs of glaucoma and other optic nerve diseases","The procedure is quick, painless, and does not require any blood samples","Results are compared to normal values to assess your eye health","Regular monitoring helps track changes over time"}
Key facts at a glance
- LOINC
- 86279-7
- Short code
- RNFL Nasal OS OCT
- Synonyms
- L ret RNFL nasal thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- Not applicable - This is an imaging test, not a blood collection
- Units
- N/A
- Ref low
- 50
- Ref high
- 100
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 422148006
- Specimen volume
- Not applicable - Imaging study
- Stability
- Not applicable - Imaging study
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–48 hours
- Order
- routine
What is this test used for?
The Left Retina Retinal Nerve Fiber Layer (RNFL) Nasal Thickness test is an imaging procedure that uses Optical Coherence Tomography (OCT) to measure the thickness of the retinal nerve fiber layer on the nasal side of your left eye. The retina is the light-sensitive tissue at the back of your eye, and the nerve fiber layer contains the axons of ganglion cells that transmit visual information to the brain.
How is the test performed?
During the test, you will sit in front of an OCT machine. Your chin will rest on a support while you look at a fixed point. The machine uses light waves to create detailed cross-sectional images of your retina. The scan is quick, typically taking only a few seconds, and is completely painless. No eye drops, injections, or blood samples are required.
How do I prepare for the test?
No special preparation is needed for this test. You can eat and drink normally. If you wear glasses or contact lenses, you may need to remove them for the scan. Inform your doctor about any eye conditions or surgeries you have had.
What will the results show?
The test results will show the thickness measurement of your retinal nerve fiber layer in micrometers. Your results will be compared to a database of normal values based on age and other factors. Thinner than normal RNFL measurements may indicate nerve damage, while thicker measurements are generally considered normal.
Reference range
Normal retinal nerve fiber layer (RNFL) thickness in the nasal quadrant for the left eye typically ranges from 50 to 100 microns. Values may vary slightly by instrument manufacturer and population norms. Thinner measurements may indicate glaucomatous or optic nerve damage.N/A
No special preparation required. Remove eye makeup and contact lenses before the scan. Patient should be comfortably positioned at the OCT instrument. Inform the technician of any eye conditions, surgeries, or current medications.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to detect and monitor glaucoma, a disease that damages the optic nerve. It can identify damage even before you notice vision loss. The test is also useful for monitoring other conditions that affect the optic nerve, such as optic neuritis, stroke, and certain neurological disorders. Early detection allows for timely treatment to prevent further vision loss.
Serial measurements over time help doctors track disease progression and evaluate the effectiveness of treatment. Changes in RNFL thickness as small as a few micrometers can be detected, making this test highly sensitive for monitoring subtle changes in eye health.
Frequently asked questions
Does this test cause any pain?
How long does the test take?
Do I need to fast before the test?
Will I need eye drops?
How often should I have this test?
Can I drive after the test?
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