Elliott B. Forrest was the first optometrist to put visual stress into a neuorological framework, looking particularly at the balance between the sympathetic and parasympathetic nervous systems. I can still recall Forrest’s brilliant lecture at a COVD meeting in the early 1980s during which he drew connections from Cannon and Selye’s physiological principles directly to visual function. In a seminal paper on the evolution of Behavioral Optometry, Birnbaum elaborates Forrest’s influence, and Elliot’s book on stress and vision remains the definite work on this subject in Optometry in the US.
Arnold Wilkins, a professor in the Department of Pscyhology at the Univesrity of Essex in the UK, has quite a different approach to visual stress. To Wilkins, visual stress is as much rooted in the stimulus as it is to the individual’s response to the stimulus. In contrast with the Forrest and Birnbaum approach to visual stress, Wilkins was drawn to the field due to his early work in stimulus patterns that triggered epileptic seizures. In following the timelines of Wilkins’ publications, you can see the progress of his work from epilepsy toward visual disturbances during reading. It is interesting to note that Wilkins’ foray into reading came roundabout through epilepsy and perhaps the common stimulus triggers of pattern glare or flicker.
This is an image of one of Wilkins’ early horizontal line grating patterns, and he spoke of visual stress in terms of the triggers induced by looking at these patterns. If you take your cursor and jiggle the screen up and down a bit, you’ll notice significant flicker of the pattern. Something that masks the flicker is to use a window guide.
Window guides such as his were originally introduced for patients with eye movement disorders, or low vision patients who had difficulty keeping their place when reading. But by masking the surround of print, these guides also serve to reduce, in Wilkins’ words, the cortical hyper-excitability induced by print patterns. Cortical excitability is a type of sensory overload or over-stimulation. But what if we could reduce the pattern sensitivity of the page of print without the need for a straight edge or window guide?
Way back when I was a student, my ophthalmic optics instructor John K. Davis, who used to work for American Optical Company (AO) would talk about the common practice of prescribing the AO Cruxite lens for office workers. The lens contained a 10% rose tint, and optometrists reported that patients found these lenses particularly helpful in reducing visual fatigue believed to be induced by the flicker rate of fluorescent lighting. John was never sure that the color itself was significant.
Back to print itself. Extremely Loud & Incredibly Close is a movie starring Tom Hanks & Sandra Bullock due to in theaters on December 25, based on the brilliant novel by Jonathan Safran Foer. This may just be one of those movies that does a novel justice, rumored to be like none other in terms of eliciting emotions through the eyes of a nine year-old whose father died on 9-11. Yet moviegoers won’t be able to visualize what Safran Foer did with the print in his book, using the printed page as a visual canvas. He created visual stress and tension by switching from liberal spacing to chapter book print to visual confusion from jumbled resolution and cortical hyper-excitability.
Merrill Bowan is a neurodevelopmental optometrist in the US who has been strongly influenced by Wilkins’ research into visual stress induced by print patterns, and has labeled the phenomenon Textual Visual Aliasing Syndrome. Whereas Bowan’s approach is the more traditional one among developmental optometrists of using low plus lens power for reading, and less conventionally the use of microprisms, Wilkins has stayed with the concept of altering light wavlength through color rather than lens or prism power.
In Phoenix in 2003 I had the pleasure of coordinating a continuing education program on the applications of light and color to reading. We invited Rhonda Stone, author of The Light Barrier and Professor Wilkins, author of Visual Stress. To lend further perspective we invited Dr. Larry Wallace, at that time President of the College of Syntonic Optometry and current President of the International Light Association. Lastly, we invited Dr. Mitchell Scheiman, one of the co-authors of the AOA’s Position Paper on Tinted Lenses and Dyslexia. Rhonda invited Helen Irlen, who sat in the audience. I had respected Irlen’s position in her book, Reading by the Colors, that before colored overlays are dispensed as an aid to reading, individuals with Scotopic Sensitivity Syndrome should be thoroughly evaluated for binocular and perceptual problems by an optometrist.
If we’re in agreement that chapter book print introduces a particularly stressful form of visual aliasing, instability, or overload to susceptible individuals, one way to combine the Wilkins and Irlen approaches has been to mask some of the text while at the same time adding beneficial color. These types of reading strips are commonly recommended by reading instructors or teachers because they are inexpensive and ostensibley do no harm. My attitude has been, if it works, it works – as long as the use of such aids doesn’t deflect from having an individual thoroughly evaluated for vision problems by a qualified optometrist, as stressed by the AOA and acknowledged by Irlen.
Owing to the work of Wilkins and colleagues, treatment of visual stress and dyslexia through colorimetry has become fairly widespread in ophthalmic practices the UK. The five part series in Optometry Today on Vision & Reading Difficulties by Allen, Evans, and Wilkins lays out an approach that has been influential. This series resulted in a book by the same authors that reviews their structured approach toward intervention. Allen, Evans, and Wilkins also have a nice toolkit of material online that helps identify who can best benefit from their approach.
– Leonard J. Press, O.D., FCOVD, FAAO