Retinal nerve fibre layer testing measures the thickness of the layer formed by retinal ganglion cell axons around the optic nerve. It is a key structural marker in glaucoma and other optic neuropathies.
Method
Optical coherence tomography is commonly used to obtain circular scans around the optic disc or widefield macular-disc maps. Software calculates average and sectoral thickness values and compares them with normative data.
- Non-contact and quick to perform
- Colour-coded deviation maps highlight areas thinner than expected
- Reproducibility allows reliable detection of progression
- Signal strength must meet quality thresholds for valid interpretation
Clinical Role
Thinning of the retinal nerve fibre layer often precedes detectable visual field loss in glaucoma, making it valuable for early diagnosis. It also helps assess damage from optic neuritis, ischaemia, or compression.
- Serial measurements show whether structural loss is ongoing or stable
- Sectoral patterns correlate with specific field defects
- High myopia and anatomical variants can influence measurements
- Results are considered alongside disc appearance and functional tests
