Red saturation test assesses the integrity of the optic nerve by testing the ocular sensitivity to the red colour. The test is used clinically for the detection of asymmetric optic nerve function and detection of neurophthalmological visual field defects such as hemianopias and quadrantopias. Nerve diseases that can cause optic neuritis include multiple sclerosis, neuromyelitis optica, Shilder´s disease. Infections that may cause optic neuritis include mumps, measles, tuberculosis, Lyme disease, and also a few other conditions like sarcoidosis, Gullain-Barre syndrome and post-vaccination reaction may cause ON to occur. Nowadays, a red marker is used in the practices and the client needs to compare the intensity of red colour monoculary.
Equipment and set-up:
The client wears their best near correction and holds the test at a distance of 30 cm under bright illumination. The test is undertaken monocularly, so one eye is occluded and the client is asked to focus the dot in the middle of the screen. Ask the client if he can spot four red circles in the corners. The client must identify the richness of the red colour of these four circles, or its faded colour. Holding the circles will slowly decrease the intensity of the red colour. Pressing the same circle again will increase the intensity of the red colour. The goal is to level the colour of all four circles. When you finish with the comparison, press the middle white dot.
Interpreting the results:
The test will give a result in percentage for each of the circles and report any relative dullness of the colour. Clients with optic neuritis have normally significantly increased desaturation.