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Rretrnfl8oclockthicknessoct

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

A non-invasive eye imaging test that measures the thickness of the retinal nerve fiber layer at a specific location to help detect and monitor eye conditions like glaucoma.

Quick summary

{"Uses optical coherence tomography (OCT) to measure retinal nerve fiber layer thickness","Helps detect early signs of glaucoma and other optic nerve diseases","The test is quick, painless, and does not require any blood sample","Results are compared to normal ranges to assess eye health","Regular testing helps track changes in eye condition over time"}

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

Key facts at a glance

LOINC
86312-6
Short code
RNFL Right CH8 OCT
Synonyms
R ret RNFL 8 o'clock thickness OCT
Category
cardiac
Sample
serum
Container
Not applicable - this is an imaging test, not a blood collection
Units
N/A
Ref low
100
Ref high
140
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Optical Coherence Tomography (OCT)
CPT
92134
SNOMED
425671006
Specimen volume
Not applicable - imaging procedure
Stability
Not applicable
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

What is this test?

The Right Retina Nerve Fiber Layer (RNFL) Thickness test is an eye imaging procedure that uses Optical Coeiherence Tomography (OCT) to measure the thickness of the retinal nerve fiber layer at the 8 o'clock position of your right eye. The retinal nerve fiber layer is a thin tissue made of nerve fibers that carry visual information from the retina to the brain. Measuring its thickness helps doctors assess the health of your optic nerve and detect conditions that may damage it.

How is the test performed?

During the test, you will sit in front of an OCT machine. You will be asked to place your chin on a support and look at a specific target. The machine will then scan your eye using light waves to create detailed cross-sectional images of your retina and measure the nerve fiber layer thickness. The test is completely painless, takes only a few minutes, and requires no blood draw or eye drops.

Why is this test important?

This test is crucial for detecting and monitoring glaucoma, which is a leading cause of vision loss. Glaucoma damages the optic nerve, causing the retinal nerve fiber layer to become thinner over time. By measuring the RNFL thickness at specific clock hours, doctors can identify early signs of damage, track disease progression, and adjust treatment plans accordingly.

What do the results mean?

Your test results will show the thickness measurement in micrometers (μm). Results are compared to a database of healthy eyes of similar age. Thinner than normal RNFL may indicate optic nerve damage from glaucoma or other conditions. Thicker than normal measurements may be less concerning but still require evaluation. Your eye doctor will interpret your results in context with other eye exam findings.

Reference range

Normal retinal nerve fiber layer (RNFL) thickness at clock hour 8 (temporal inferior quadrant) for right eye: approximately 100-140 microns. Reference ranges may vary by instrument manufacturer and population norms.N/A

Specimen: serum

No special preparation required. Patient should remove eye makeup and contact lenses if applicable. Pupils may be dilated for optimal imaging; advise against driving if dilation is performed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Does this test hurt?
No, the OCT test is completely painless. You will only need to sit still and look at a light for a few seconds while the scanner takes images of your eye.
Do I need to prepare for the test?
No special preparation is needed. You can eat and drink normally before the test. However, you should avoid wearing eye makeup on the day of the test as it may interfere with the imaging.
How long does the test take?
The actual scanning takes only about 2-5 minutes per eye. The entire appointment, including preparation and discussion with your doctor, may take 15-30 minutes.
How often should I have this test?
The frequency depends on your eye condition. For glaucoma patients, testing may be done annually or more frequently as recommended by your eye doctor. For screening purposes, your doctor will determine the appropriate interval based on your risk factors.
What happens if my results are abnormal?
If your RNFL thickness is abnormal, your eye doctor will discuss the findings with you. Additional tests may be recommended to confirm a diagnosis. If glaucoma is detected, treatment options such as eye drops, laser therapy, or surgery may be prescribed to prevent further vision loss.
  1. 1
    American Academy of Ophthalmology - OCT for GlaucomaSource
  2. 2
    National Eye Institute - Glaucoma InformationSource

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