by Merrill D. Bowan, O.D.

What is Aliasing?

Why should a child who sees 20/20 need glasses?

The application of low plus reading lenses and prisms, either separately or in combination, can have remarkable impact upon students and adults with reading and comprehension problems. This has been known and researched for many years but there has been little actual understanding of just why lenses that had so little optical significance might be creating such dramatic changes.  The lenses and prisms commonly result in changes in reading speed, word decoding, storytelling, fluency, comprehension, fewer headaches, and improved grades, and these changes are seen to occur in a very high percentage of cases.

More is now being uncovered and  the problem is surprising: the physical lines of print appear to create an irritating set of mirages in up to 50% of all readers whose brains are hyperreactive to most sensory inputs. These illusions take a number of forms, but most frequently make the print seem to move on the page with a flowing, rippled look or a swirling of the text in the periphery of one’s vision.  (These are well illustrated in The Light Barrier, by Rhonda Stone, St. Martin’s Press, 2002.) Children will note that the words seem to move (or get "wiggly") on the page. Pastel rainbow colors can appear between the lines of print under certain circumstances. We have known for decades that certain readers can get severe, unexplained, often migraine-like headaches and/or nausea while attempting to read for more than just a few minutes. These people seem to have a more severe form of the aliasing problem.

Aliasing is a confusion of sounds or images caused when two or more slightly different data signals are blended together, but mismatch, and so a third, approximated signal results. If you have seen this on the Aliasing Syndrome Grate (see HERE), this grate represents the lines of text in your child’s—or your—book. The mirages vary according to print size and the spacing layout of the lines. Most people have seen this before with tie and suit patterns on TV, prompting one pre-teen in our office to quip, “Oh, then it’s the “TV Tie Syndrome!” (….weeellll…, he did kind of “get it.”)

Not every reader will benefit from these aliasing-reducing lenses. But almost all of those who do, demonstrate improvement almost instantaneously. Parents reading this pamphlet in the examination room have just seen and heard this happen. This brochure is meant to explain more thoroughly what is happening and why lenses are important for your child's learning ease.

Why does it work?

This application works because many of these children suffer from visual function and visual processing problems.  It is thought that the brain is having trouble with the sampling of the images (the image processing sharpness) retinally as well as between the two hemispheres. The lenses reduce the distress at two levels: one, in the visual functioning, due to the very mild optical benefits. The second is in the actual processing of the images. There is early evidence that the novelty of the slightly enlarged, different images may release important chemicals like Dopamine from the retina of the eye, but this is only beginning to become defined, the present evidence is circumstantial.

The Brain craves to learn. The Brain wants to experience new events, and actively searches for them (which may be part of the reason behind much ADHD).  While all five senses pour data into the Brain, the fastest method by which the brain receives data is by reading. Reading is a highly complex task in which the sounds making up words are put into a letter code. We then reconvert them back into the thoughts and actions contained in the words. At least 80% of all our learning occurs through the visual sense, and after young childhood, much of that is through reading.

Reading, however, is a very stressfultask for the Brain.  It actually provokes an avoidance response much like the "fight or flight" response: the heart rate increases; the pupils dilate; respiration can increase; adrenaline is produced; the perspiration rate increases – just as if an emergency were occurring. Two studies demonstrated this and also that plus lenses reduced the effects of these responses. These stress effects further complicate any visual aliasing effects that may be present.  For a while, the Brain can stand the shock, but after 10-20-30 minutes, its comfort zone is challenged and will either signal the person to stop reading with symptoms of eyestrain or it will demand energy that has been going to decoding of the words. When this happens, the reading almost turns into "Greek" and the reader gets to the bottom of the page without absorbing anything. This happens to all of us at times. The third thing that can happen is that the structures of the eye can change to become nearsighted, a functional change which will reduce the stress because the eye is then focused for reading distance.

So, what do lenses do?

The small optical effect of the lenses and prisms is to reduce the stress by neuro-optically pushing the target just far enough away to reduce the demand upon the Brain's balancing act. This keeps the visually problemed student from fatiguing as quickly, and allows the processing of language to occur with much more effectiveness. In the cortically hypersensitive Brains that we have been discussing here, the plus and/or prism reduces or eliminates the mirages and may affect thinking and reading processes directly for poorly understood (at present) – but clinically easily observed – reasons. The lenses remove a significant barrier to learning in children who have these visual processing and function difficulties.  The reduction in distress can also indirectly affect behavior.  Any risk-to-benefit ratio is extremely positive.

Let me share one case with you: a young child received a pair of plus/prism lenses, but the father was not present for the very dramatic demonstration that had confirmed the benefit of this lens prescription. He hesitantly agreed to the lenses.  The father walked by the child's room a few days later while she worked on her computer. He heard the slow "ticky-tick" of the keys. Looking in, he noticed that she was working without her new lenses. The father asked her to stop and get the glasses, because of our instruction for her to use them at the computer. As he started to leave the room, he heard his daughter, now with glasses in place, typing again - but now, he heard a faster typing - as he put it, a "tickety-tickety-tickety" of the computer keys.

The daughter was now working three times faster, and in this way, the father got to "hear" the glasses in action. Any doubts he had were now gone, her mother later told me. This was in addition to the dramatic reading changes that had occurred. This is just one anecdotal example of the performance changes that can occur when these lenses are used as part of the solution to learning problems.