LIGHT AND CONTRAST SENSITIVITY IN LOW VISION
Roberto VOLPE M.D. Ph.D.
Low Vision Service – S. Donato Hospital Arezzo
P.R.I.S.M.A. President
In low vision practice, visual acuity and visual field are considered more important than contrast sensitivity. In spite of these ideas the contrast sensitivity is often a critical aspect in everyday activities. The explanation for this statement is that relative scotomas are very sensitive to contrast changes. In other words, low contrast may transform relative scotomas in dense scotomas making more difficult reading and a lot of other tasks.
Examples are exposed and physiopathological bases are discussed. The author describes the REX test, a new low contrast reading test developed to easily assess the impact of
text contrast reduction on reading speed in subjects with normal and low vision. The REX test proved to be a reliable investigation tool for this phenomenon.
The solutions to manage the low contrast visual problems are various. Electronic devices may improve contrast in an easy way but sometimes they are not socially accepted.
Optimal light is important for functional vision and contrast enhancement. However light levels and colortemperature may be very different in low vision patients.
A useful tool is described to quantify the optimal light needs.