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Optical Coherence Tomography (OCT) of the Retinal Nerve Fiber Layer, Lower Nasal Area, Left Eye

Published: August 9, 2026Updated: August 17, 2026

A non-invasive eye imaging test that uses optical coherence tomography (OCT) to measure the thickness of the retinal nerve fiber layer in the lower nasal area of the left eye.

Quick summary

{"Uses light waves to create detailed cross-sectional images of the retina","Measures the thickness of retinal nerve fiber layer to detect eye diseases","Helps diagnose and monitor conditions like glaucoma","The test is quick, painless, and requires no blood sample","Results help doctors assess the health of your optic nerve"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
86272-2
Short code
RNFL-NI-L
Synonyms
L ret RNFL nasal inf thickness OCT
Category
cardiac
Sample
serum
Container
Non-specimen imaging procedure - no container required
Units
N/A
Ref low
67
Ref high
95
Critical range
50 N/A – 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 - Imaging study
Stability
N/A - Images acquired in real-time during examination
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), an advanced imaging technology that uses light waves to take cross-sectional pictures of your retina. Specifically, it measures the thickness of the retinal nerve fiber layer (RNFL) in the nasal inferior region of your left eye. The RNFL is a layer of nerve fibers that carries visual information from the retina to the brain.

How is the test performed?

During the test, you will sit in front of an OCT machine and rest your chin on a support. The device will scan your eye without touching it. You will need to remain still and look at a target for a few seconds while the images are captured. The procedure is completely painless and takes only a few minutes.

Why is this test important?

Measuring RNFL thickness helps doctors detect early changes in the optic nerve, often before vision loss occurs. Thinning of the RNFL can indicate damage to the optic nerve, which is crucial information for diagnosing and managing various eye and neurological conditions.

Reference range

Normal RNFL thickness range for nasal inferior quadrant: 67-95 microns. Values below 67 microns may indicate RNFL thinning suggestive of glaucomatous damage or other optic neuropathies.N/A

Specimen: serum

Patient should remove contact lenses prior to imaging. Pupillary dilation may be performed for better visualization. Inform technician of any eye surgery history, glaucoma, or optic nerve disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is primarily used for detecting and monitoring glaucoma, a condition that damages the optic nerve. It can also help identify other optic nerve disorders, such as optic neuritis (inflammation of the optic nerve), ischemic optic neuropathy (reduced blood flow to the optic nerve), and neurological conditions like multiple sclerosis. Early detection of RNFL thinning allows for timely treatment to prevent further vision loss.

Frequently asked questions

Do I need to fast before this test?
No, fasting is not required. This is an imaging test that does not involve blood samples. You can eat and drink normally before the test.
Is the test painful?
No, the OCT test is completely painless. You may experience mild discomfort from keeping your eyes open, but there is no pain or physical contact with the eye.
How long does the test take?
The actual scanning takes only a few seconds to a minute per eye. The entire appointment, including preparation, typically lasts about 10-15 minutes.
When will I get my results?
Your doctor will analyze the images and discuss the results with you, usually at a follow-up appointment. The report compares your measurements to normal values and tracks changes over time.
Are there any side effects?
There are no known side effects. The test uses harmless light waves and does not involve radiation or invasive procedures.
  1. 1
    American Academy of Ophthalmology - Understanding OCTSource
  2. 2
    National Eye Institute - GlaucomaSource

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.

Medical Disclaimer

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