Overlay Testing Kit

Many practitioners first screen their patients with an overlay to determine if the cost of tinted lenses is necessary. Colored overlays have been shown to reduce visual stress and increase reading fluency in about 20% of school children.

In order for susceptible individuals to obtain effective filter it is important to sample a large number of colors. The colors of the cerium overlays have been selected using the intuitive colorimeter to ensure that, as far as possible, all colors are represented by the overlays and that the transmissions of them are approximately equal.

The overlays consist of a robust transparent sheet that has a non-reflective surface, but one that allows the print to be clearly seen. The overlays may be superimposed on each other, but no more then two overlays should be used any one time due to the increasing density of tint. The edges are rounded for safety.

The overlays examination requires illumination similar to that under which the overlays will be used. The overlays are compared in pairs, and the best of each pair retained, the other being replaced by another overlay. If the patient finds the choice difficult, the choice is repeated when all overlays have been assessed.

Double overlays are used if symptoms remain, It is recommended that the Wilkins rateof reading test be used to check and increase in reading speed with the chosen overlay. In 6 studies of normal unselected children in mainstream schools, about 20% used their chosen overlay long term. Those that used their overlays read faster with them: 5% read more then 25% faster.

The benefits from overlays can be rapidly ascertained as an increase in reading speed, as measured by the Wilkins Rate of Reading™ Test. Although test is not a typical reading task, it has shown to predict performance when text is read silently for comprehension.

An overlay needs to be of a size sufficient to cover the text, but it does not have to cover the surround. Individuals who find colored overlays helpful usually prefer colored lenses.

The Intuitive Colorimeter® is a more accurate method of determining lens tint. There is little relationship between the chosen overlay color (selected when the eyes are adapted to white light) and the color for lenses (selected by the Intuitive Colorimeter when the eyes are adapted to colored light)

Kit includes:
Two A5 sheets sets of overlays, a pack of recording sheets, examination targets, and full instructions for assessment

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