What is the wavelength stimulus of the test field for Nagel Anomaloscope?

The test field for the Nagel Anomaloscope utilizes a specific wavelength stimulus to assess color vision, particularly the ability to match colors, which is vital for diagnosing certain types of color vision deficiencies. The correct wavelength for this test field is 590 nm, which corresponds to a yellow-green light. This wavelength is particularly useful because it lies within the sensitivity range of the photoreceptor cells in the human retina that are responsible for detecting color, specifically those related to the L (long-wavelength) and M (medium-wavelength) cones.

The use of 590 nm in the anomaloscope is integral to evaluating an individual's ability to match colors that are pivotal for differentiating between normal vision and various forms of color vision deficiencies, such as red-green color blindness. Other wavelengths provided in the options do not serve the same purpose in the context of the Nagel Anomaloscope. For example, 546 nm (green light) and 495 nm (cyan light) are relevant to other types of color testing but do not match the operational wavelength of this specific instrument. The 670 nm wavelength is in the red range, which is also not applicable for the test field of the Nagel Anomaloscope.