Patient Guide to Your Medical Test: Purpose, Procedure, and Preparation
A non-invasive eye imaging test that measures the thickness of the retinal nerve fiber layer to detect early signs of glaucoma and other optic nerve diseases.
{"Uses light waves to create detailed cross-sectional images of the retina","Measures the thickness of the nerve fiber layer in the inferior temporal region","Helps detect glaucoma and monitor disease progression","Quick, painless procedure taking about 10-15 minutes","No special preparation or fasting required"}
Key facts at a glance
- LOINC
- 86287-0
- Short code
- RNFL IT OD OCT
- Synonyms
- R ret RNFL inf temp thickness OCT
- Category
- cardiac
- Sample
- serum
- Container
- N/A - Imaging procedure
- Units
- N/A
- Ref low
- 100
- Ref high
- 140
- Critical range
- 50 N/A – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 371632004
- Specimen volume
- N/A - Non-invasive retinal imaging
- Stability
- N/A - Imaging test performed immediately at time of acquisition
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–24 hours
- Order
- routine
What is this test? This test is a medical evaluation used to gather information about your health, help identify possible causes of symptoms, or monitor a known condition. Your healthcare professional will explain what the results may show and how they fit into your overall care.
Optical Coherence Tomography (OCT) is an advanced imaging technique that uses light waves to take cross-sectional pictures of your retina. The retinal nerve fiber layer (RNFL) is a thin layer of nerve tissue that carries visual information from your retina to your brain. This test specifically measures the thickness of the RNFL in the inferior temporal region of your right eye.
How is the test performed? The procedure depends on the specific test and may involve a blood, urine, or other sample, a physical measurement, imaging, or another clinical method. Your healthcare professional will explain each step, answer questions, and help you remain as comfortable as possible.
During the test, you will sit in front of an OCT machine and rest your chin on a support. You will be asked to look at a fixed target while the machine scans your eye. The test is completely painless and does not involve any radiation. Your pupils may be dilated with eye drops for better imaging, which may cause temporary blurred vision and light sensitivity.
How should I prepare for the test? Preparation varies by test and may include fasting, changing or withholding certain medicines, avoiding specific foods or activities, or arriving with a full bladder. Follow the instructions from your healthcare professional, and ask what to do if you are unsure or cannot follow them.
No special preparation is needed. However, if your eyes will be dilated, consider bringing sunglasses and arranging for someone to drive you home. Remove eye makeup before the test. Bring your current eyeglasses or contact lens prescription information.
Reference range
Normal Retinal Nerve Fiber Layer (RNFL) thickness in the inferior temporal quadrant for the right eye is typically 100-140 micrometers. Values below 100 micrometers may indicate early glaucomatous changes, while values below 70 micrometers suggest significant nerve fiber loss.N/A
Patient should remove contact lenses prior to imaging. Pupils may need to be dilated for optimal image quality. Inform the technician of any eye surgery history, glaucoma, or neurological conditions affecting the optic nerve.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to detect and monitor glaucoma, a disease that damages the optic nerve. Thinning of the RNFL may indicate early glaucomatous damage even before vision loss occurs. The test helps ophthalmologists track disease progression over time and evaluate treatment effectiveness. It can also help differentiate glaucoma from other optic nerve disorders.
Frequently asked questions
Does the test hurt?
How long does the test take?
When will I get my results?
How often should I have this test?
Are there any side effects?
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