Colored overlays are transparent, tinted plastic sheets or films designed to be placed directly over printed text. These tools are primarily used to alleviate visual discomfort experienced by some individuals when reading. While often sought by people with dyslexia, these overlays address a distinct visual phenomenon rather than the core language processing difficulty. Their function is to alter the contrast and light spectrum of the page, which can make text appear more stable and reduce symptoms of visual strain.
Understanding Visual Stress
Visual stress, sometimes referred to as Scotopic Sensitivity Syndrome, involves experiencing unpleasant symptoms when looking at printed text, particularly high-contrast black letters on a bright white background. For affected individuals, this high contrast can cause a hyper-excitability in the visual cortex of the brain.
Symptoms of this over-activity include the perception that words are blurring, moving, shimmering, or that white “rivers” are running through the text. This visual distortion makes sustained reading difficult and can lead to physical discomfort, such as eye strain, fatigue, and headaches. By filtering specific wavelengths of light, a colored overlay can reduce this excessive stimulation, stabilizing the visual input pathway.
Although visual stress is not the same as dyslexia, the two conditions frequently coexist, leading many individuals with reading difficulties to seek out this intervention. When visual stress is present, addressing it can significantly improve reading endurance and fluency.
The Necessity of Personalized Color Selection
There is no single color overlay that is universally beneficial, contrary to the common search for a “best” color. The ideal tint is highly specific to the individual’s unique visual processing sensitivities.
The filtering effect of the overlay works by blocking the specific wavelength of light that causes overstimulation in a person’s visual system. Colors often tested include shades of blue, yellow, green, or rose, but the precise combination of hue, saturation, and brightness is what truly matters. The selection is not based on personal color preference but on finding the exact filter that neutralizes the neurological trigger causing the visual distortions.
Specialized Testing for Optimal Overlays
Determining the correct color requires a methodical assessment by a trained specialist, such as an optometrist or a vision therapist. The initial step involves a colored overlay assessment using a series of plastic sheets to screen for a beneficial tint that reduces visual stress symptoms.
If a positive effect is noted, the next step involves a more precise procedure called colorimetry testing. This specialized examination often uses an instrument like the Intuitive Colorimeter, which systematically manipulates the three components of color—hue, saturation, and brightness.
This detailed process allows the practitioner to explore thousands of potential color combinations to pinpoint the exact spectral filter needed to maximize visual comfort. The assessment also frequently includes a timed reading test, such as the Wilkins Rate of Reading Test, to objectively quantify any improvement in reading speed and accuracy when using the selected tint. The result is a highly tailored color prescription, which is much more precise than a standard colored overlay.
Integrating Overlays into Reading Practice
Once an optimal color is identified, consistent use of the overlay is necessary to gauge its long-term effectiveness. While overlays are inexpensive and effective as a first step, they are limited to printed pages and can be cumbersome for writing or copying from a whiteboard.
For greater convenience, many individuals transition to wearing precision tinted lenses, which can be used for all visual tasks. Note that the optimal color for a plastic overlay may differ from the color needed for these spectacle lenses. Overlays function as one tool within a broader strategy and do not replace other necessary educational interventions for reading development.