Left Eye Retinal Nerve Fiber Layer (RNFL) Test by OCT (Optical Coherence Tomography)
This test uses light waves to create detailed cross-sectional images that measure the thickness of the retinal nerve fiber layer in your left eye, helping your doctor detect early signs of eye diseases like glaucoma before you notice any vision loss.
{"A non-invasive imaging test that measures nerve layer thickness in the retina","Helps detect glaucoma and other optic nerve diseases early","Takes only a few minutes with no pain or discomfort","Results are compared to normal values to assess eye health","Regular testing helps monitor changes over time"}
Key facts at a glance
- LOINC
- 86281-3
- Short code
- RNFL-NS-L
- Synonyms
- L ret RNFL nasal sup thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- Not applicable - This is an imaging test, not a blood test
- Units
- N/A
- Ref low
- 70
- Ref high
- 140
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 424689005
- Specimen volume
- Not applicable - Imaging procedure
- Stability
- Not applicable - Imaging procedure
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–48 hours
- Order
- routine
What is this test?
The Left Retina Retinal Nerve Fiber Layer (RNFL) test by OCT (Optical Coherence Tomography) is an advanced imaging test that uses light waves to create detailed cross-sectional images of your retina. Specifically, it measures the thickness of the retinal nerve fiber layer in the nasal superior region of your left eye. This layer contains nerve fibers that carry visual information from your retina to your brain.
How is the test performed?
During the test, you will sit in front of the OCT machine and rest your chin on a support. You will be asked to look at a fixed target while the device scans your eye. The test is completely painless, takes only a few minutes, and requires no special preparation. Your eyes may be dilated with eye drops before the test for better imaging.
Why is it important?
Measuring the retinal nerve fiber layer thickness helps your doctor detect damage to the optic nerve before you notice any vision loss. This is particularly important for diagnosing and monitoring glaucoma, a condition that causes progressive damage to the optic nerve. Early detection allows for timely treatment to prevent further vision loss.
Reference range
Normal Retinal Nerve Fiber Layer (RNFL) thickness for nasal superior quadrant: 70-140 microns. Values below 70 microns suggest possible nerve fiber layer thinning which may indicate glaucoma or optic neuropathy.N/A
Patient should remove contact lenses prior to imaging. Pupils may be dilated for optimal imaging quality. No special fasting required. Inform technician of any eye surgery history or current eye conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to detect and monitor glaucoma, a leading cause of irreversible blindness worldwide. Thinning of the retinal nerve fiber layer may indicate early glaucomatous damage even before visual field loss occurs. The test also helps differentiate between glaucoma and other optic nerve disorders, and provides objective measurements to track disease progression over time. Results are compared against a database of healthy eyes to determine if your measurements fall within normal ranges.
Frequently asked questions
Does the test hurt?
How long does the test take?
Do I need to fast before the test?
What do the results mean?
How often should I have this 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 16, 2026. · Read our editorial policy