Complete Blood Count (CBC): A Guide to Understanding Your Blood Test
This test uses OCT imaging to measure the thickness of the inferior retinal nerve fiber layer in the right eye, helping detect early signs of glaucoma and optic nerve damage.
{"A non-invasive eye scan that measures retinal nerve fiber layer thickness","Helps detect glaucoma and other optic nerve disorders early","Takes only a few minutes with no pain or discomfort","Results are compared to normative databases by age","Regular testing helps monitor disease progression"}
Key facts at a glance
- LOINC
- 86283-9
- Short code
- RNFL-inf-OD
- Synonyms
- R ret RNFL inf 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
- 70 N/A – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–100 years
- Method
- Optical Coherence Tomography (OCT)
- CPT
- 92134
- SNOMED
- 420576001
- Specimen volume
- Not applicable - ocular imaging test
- Stability
- Not applicable - images are captured in real-time
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 1–24 hours
- Order
- routine
This test measures the different types of cells in your blood, including red blood cells, white blood cells, and platelets. It provides valuable information about your overall health and helps detect conditions such as anemia, infection, and blood clotting problems.
Optical Coherence Tomography (OCT) is a non-invasive imaging test that uses light waves to take cross-section pictures of your retina. The Right Retina RNFL Inferior Thickness test specifically measures the thickness of the retinal nerve fiber layer (RNFL) in the lower (inferior) portion of your right eye. The retinal nerve fiber layer consists of nerve fibers that carry visual information from the retina to the brain.
For this test, a healthcare professional will draw a small sample of blood from a vein in your arm using a needle. The procedure is quick and usually takes just a few minutes. You may feel a slight pinch when the needle goes in, but the discomfort is minimal. The blood is collected into a tube and sent to a laboratory for analysis.
During the test, you will sit in front of an OCT machine and rest your chin on a support. The technician will align the machine with your right eye. You will be asked to focus on a target light while the device scans your eye. The process is completely painless, takes only a few minutes, and requires no injections or drops. No special preparation is needed before the test.
This test is important because it can help your doctor diagnose, monitor, or rule out a variety of medical conditions. It is often part of a routine checkup and can reveal issues like infections, anemia, or disorders of the blood. Early detection through this test allows for timely treatment and better management of your health.
Measuring the RNFL thickness helps ophthalmologists detect changes in the optic nerve before significant vision loss occurs. This test is particularly valuable for diagnosing and monitoring glaucoma, as the disease often causes thinning of the RNFL. Early detection allows for timely treatment to prevent further vision damage.
Reference range
Normal inferior retinal nerve fiber layer (RNFL) thickness ranges from 100-140 micrometers (μm) in healthy adult eyes. Values below 100 μm may indicate early glaucomatous damage, while values below 80 μm suggest significant nerve fiber loss.N/A
No special preparation required. Patient should remove eye makeup and contact lenses before the scan. Pupillary dilation may be performed for better image quality. Inform the technician of any eye conditions, surgeries, or recent eye injuries.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The inferior RNFL thickness measurement is clinically significant because glaucoma and other optic neuropathies often affect specific quadrants of the retinal nerve fiber layer first. Thinning of the RNFL may indicate early glaucomatous damage even before visible vision loss occurs. Comparing your results to age-matched normal databases helps determine if the thickness is within normal limits or shows abnormal thinning requiring treatment. Serial testing over time helps track disease progression and treatment effectiveness.
Frequently asked questions
Does the test hurt?
How long does the test take?
Do I need to do anything to prepare for the test?
When will I get my results?
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