Lretrnfl8oclockthicknessoct
A non-invasive imaging test that measures the thickness of the retinal nerve fiber layer in the left eye to assess optic nerve health.
{"Uses light waves to create detailed images of the retina","Helps detect and monitor glaucoma and optic nerve damage","The test is quick, painless, and requires no blood sample","Results help doctors track changes in eye health over time","No special preparation is needed before the test"}
Key facts at a glance
- LOINC
- 86300-1
- Short code
- RNFL-L-8-OCT
- Synonyms
- L ret RNFL 8 o'clock thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- N/A - This is an imaging test, not a blood collection
- Units
- N/A
- Ref low
- 100
- Ref high
- 140
- Critical range
- 70 N/A – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–80 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 397540006
- Specimen volume
- N/A - Imaging test
- Stability
- N/A - Imaging test
- 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) to measure the thickness of the retinal nerve fiber layer (RNFL) at a specific location (clock hour 8) in your left eye. The retinal nerve fiber layer consists 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.
How is the test performed?
During the test, you will sit in front of the OCT machine and rest your chin on a support. The device will scan your eye using light waves to create detailed cross-sectional images. You will need to stay still and focus on a target for a few seconds while the images are captured. The entire process takes about 10-15 minutes and is completely painless.
Why is this test important?
Measuring RNFL thickness is crucial for detecting and monitoring conditions that affect the optic nerve, particularly glaucoma. Thinning of the RNFL can indicate damage to the optic nerve, which may lead to vision loss if left untreated. This test helps your doctor catch problems early and track how your condition changes over time.
Reference range
Normal RNFL thickness at clock hour 8 (temporal-inferior quadrant) ranges from 100-140 micrometers. Values below 100 micrometers may indicate retinal nerve fiber layer thinning suggestive of glaucoma, optic neuropathy, or other optic nerve pathologies.N/A
Pupillary dilation with mydriatic eye drops is typically required 15-30 minutes before imaging. Remove contact lenses before dilation. Avoid eye makeup on test day. Inform technician of any eye conditions, surgeries, or recent eye injuries.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Frequently asked questions
Does the test require any special preparation?
Is the test painful?
How long does it take to get results?
Do I need to repeat 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 17, 2026. · Read our editorial policy