Retinal Nerve Fiber Layer (RNFL) Thickness Test
An OCT imaging test that measures the thickness of the retinal nerve fiber layer in the lower nasal area of the right eye to assess optic nerve health.
{"Uses optical coherence tomography (OCT) to capture detailed images of the retina","Measures the thickness of the retinal nerve fiber layer (RNFL) in the right eye","Helps detect and monitor glaucoma and other optic nerve diseases","The test is non-invasive and takes only a few minutes","No special preparation or eye drops are typically required"}
Key facts at a glance
- LOINC
- 86282-1
- Short code
- RNFL-NI-OCT
- Synonyms
- R ret RNFL nasal inf 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
- 100
- 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
- Not applicable - imaging study
- Stability
- Not applicable
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
This test measures the thickness of the retinal nerve fiber layer (RNFL), the thin band of nerve fibers that runs along the surface of your retina. It is usually performed with optical coherence tomography (OCT) and helps your eye doctor evaluate the health of your optic nerve.
This test uses Optical Coherence Tomography (OCT), a non-invasive imaging technique, to measure the thickness of the retinal nerve fiber layer (RNFL) in the nasal inferior region of your right eye. The retinal nerve fiber layer consists of nerve fibers that carry visual information from the retina to the brain through the optic nerve.
The test is quick, painless, and does not touch your eye. You rest your chin and forehead on the support of the OCT machine and look at a target while the device scans your retina with light. Your doctor may use dilating eye drops, and the scan typically takes only a few minutes for each eye.
During the test, you will sit in front of an OCT machine and rest your chin on a support. The machine will scan your eye using light waves to create detailed cross-sectional images of your retina and optic nerve. The entire procedure takes about 5-10 minutes and is completely painless. No injections or eye drops are typically required.
RNFL thickness is a key indicator of optic nerve health. Thinning can be an early sign of glaucoma, often before you notice any changes in your vision, so measuring it helps your doctor detect damage early, monitor changes over time, and adjust treatment to protect your sight.
The thickness of the retinal nerve fiber layer is a critical indicator of optic nerve health. Thinning of the RNFL can be an early sign of glaucoma, optic neuritis, or other neurological conditions that affect the optic nerve. Measuring this thickness helps your doctor detect problems before you notice any vision loss.
Reference range
Normal retinal nerve fiber layer thickness varies by instrument and population. Generally, nasal inferior thickness reference range: 70-100 microns in healthy adults. Results should be compared to age-matched normative database.N/A
Patients should remove contact lenses before imaging. Pupils may need to be dilated for optimal image quality. Avoid eye makeup or creams around eyes on day of test. Inform technician of any eye surgery history, glaucoma, or optic nerve conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
RNFL thickness measurement is primarily used for glaucoma diagnosis and monitoring. In glaucoma, elevated eye pressure damages the optic nerve, causing progressive RNFL thinning. This test helps detect such damage early, often before visible vision loss occurs. It is also useful for monitoring disease progression and evaluating treatment effectiveness.
Abnormal RNFL thickness may indicate: glaucoma (most common), optic neuritis, ischemic optic neuropathy, diabetic retinopathy, and other optic nerve disorders. Your doctor will compare your results with normal reference values and track changes over time.
Frequently asked questions
Do I need to fast before this test?
Will the test hurt?
How long does it take to get results?
Do I need to stop taking my eye medications?
How often should this test be repeated?
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