Coloured Overlays and Visual Stress

Visual Stress - Also known as Meares-Irlen syndrome

Visual stress is a condition which causes reading difficulties as a result of eyestrain, headaches, light sensitivity and exposure to disturbing visual patterns.

Typical symptoms of visual stress are:

Print moving or blurring
Letters changing shape or size
Patterns appearing on the print
Colours appearing on the print
Rapid fatigue

A good example is the visual discomfort that we often experience on looking at for example a striped shirt. This pattern effect, when viewing print, is a typical symptom for someone suffering from visual stress.

Is visual stress the same as dyslexia?
No - Dyslexia is a specific learning difficulty that affects the ability to read and spell. However, visual stress has been found to be present in a significant number of people with dyslexia and its presence can be an additional burden on reading and writing performance.

Visual stress is not a condition that is restricted to children. In a number of cases, the problem goes undiagnosed and the attendant reading difficulties can affect an adult's career prospects and quality of life generally.

Coloured Overlays

Coloured overlays are sheets of transparent plastic that are placed over the text when reading.

Before carrying out an assessment with coloured overlays, it is important to carry out a full eye examination, with particular emphasis on how the two eyes are working together. Any underperformance in this area can affect reading ability and can often be corrected with spectacles, contact lenses or eye exercises.

In the examination with overlays, a wide variety of colours are used by the examiner to determine if a specific colour will be of benefit in reducing visual stress, thus improving comfort and fluency when reading.

What if the overlays are helpful?

The initial examination determines if coloured overlays may be helpful and identifies the specific colour from which the patient is liable to gain the greatest benefit. It is possible at this stage to measure the rate of reading with and without the chosen overlay. These measurements can then be compared with future readings after the overlay has been used at home or at school.

It is routine to issue the chosen overlay for a period of four to six weeks.

In the case of a child, parents are advised not to prompt the child to use the overlay as , where the child benefits , the improvement will be sufficient for the child to seek out the overlay and use it for reading.

Tinted Spectacle Lenses

If after the trial period, the overlay has been shown to be of help at improving the patient's ability to read, referral can be made to the Hospital Eye Service for further assessment.

Here, an instrument called a "Colorimeter" is used to determine the optimum tint required in the form of a spectacle lens - a more convenient arrangement than an overlay for long term use.

It is important to note that the colour chosen for the overlay will often be different from the tint required in a spectacle lens

How much does it cost?

There is no provision within the NHS for coloured overlay assessment and it therefore has to be funded privately.

Cost of initial overlay assessment £25.00
Overlay cost per sheet £5.00

If the patient is referred to the Hospital Eye Service for further assessment this examination is carried out within the NHS.