Troland (Td) is a measure of the light stimulation entering the eye, taking into account both the luminance of the light source and the size of the pupillary aperture. It is used in visual perception, optics, and ophthalmology to quantify the light intensity reaching the retina.
Formula for Troland:
whereby:
- L = luminance of the light source (in cd/m², candela per square meter)
- A = pupillary area (in mm²)
Why is the Troland size important?
- Take pupil size into account : The larger the pupil, the more light reaches the retina.
- More accurate than luminance alone : Because the amount of light entering the eyes depends not only on the external light source, but also on how the pupil adapts.
- Used in research on vision and light sensitivity : For example, in studies of night vision, glare, and contrast perception .
Uses of Trolands:
- Research into scotopic and photopic vision (night versus day vision).
- Determining the optimal lighting conditions for readability and comfort.
- Evaluating glare levels in drivers or pilots.