Disturbing vision Arnold Wilkins University of Essex, UK © Debbie Ayles, 2004

A whistle-stop tour  Images in nature have a particular spatial structure to which we are adapted.  In the modern world images have a different structure and have become “stressful”.  This has biological consequences when the visual cortex is hyperexcitable – a variety of neurological symptoms, including headache.

Very uncomfortable stimulus  In nature there are few spatially repetitive patterns of stripes  We have not evolved to process these patterns  They are very uncomfortable.  I will now show you a very uncomfortable image. !

Very uncomfortable stimulus

  Images like this are everywhere   Here are some examples...

Discomfort, illusions and individual differences  Stripes and other spatially repetitious stimuli evoke not only discomfort but illusions.  There are individual differences in susceptibility.  The illusions are related to your headaches.  I will now demonstrate this...

red green blue yellow shimmering flickering shadowy shapes blurring Perceptual distortion

red green blue yellow shimmering flickering shadowy shapes blurring Which did you see?

Headaches and perceptual distortions are related. 12 or less more than 12 More than 2 2 or less Perceptual distortions Headaches

Links between distortions and headaches  people who see many distortions have more headaches  they see more distortions on days when they have a headache  if the headache is on one side of the head the distortions are asymmetric  people with migraine dislike the pattern  those with aura (warning of headache) see more distortions on the side of the aura Wilkins, A.J. Visual Stress Oxford University Press, 1995

Huang, J. Cooper, T. G. Satana, B. Kaufman, D. I. Cao, Y. (2003). Visual distortion associated with hyper visual neuronal activity in migraine. Headache, 43, Haemodynamic response Spatial frequency (cycles/degree) BOLD Signal Change in V1 (%) Non-headache controls 3 fMRI

Haemodynamic response Spatial frequency (cycles/degree) BOLD Signal Change in V1 (%) ** * Non-headache controls Migraine ** * 3 fMRI Y. Huang, J. Cooper, T. G. Satana, B. Kaufman, D. I. Cao, Y. (2003). Visual distortion associated with hyper visual neuronal activity in migraine. Headache, 43,

Individual differences  So the individual differences in susceptibility to illusions from strong patterns may reflect cortical hyperexcitability. .

Photophobia from hyperexcitability?  Most patients are photophobic during a migraine attack.  About 40% of patients with migraine report visual triggers of their migraine.  Perhaps flicker and patterns in the environment trigger migraine...

Tints in migraine  Some patients with migraine report tinted lenses helpful.  They do not all choose the same colour.  Which tint is best?

Intuitive Colorimeter Wilkins, A.J., Milroy, R., Nimmo-Smith,I.,Wright, A., Tyrrell, R., Holland, K., Martin, J., Bald, J., Yale, S., Miles, T., Noakes,T. (1992) Preliminary observations concerning treatment of visual discomfort and associated perceptual distortion. Ophthalmic and Physiological Optics, 12, Trial lenses Saturation Hue Brightness Shines coloured light on text

Large reduction in activation with precision tint Huang, J., Zong, X., Wilkins, A., Jenkins, B., Bozoki, A. and Cao, Y. (2011). fMRI evidence that precision ophthalmic tints reduce cortical hyperactivation in migraine. Cephalalgia, 31(8),

Summary  Some patients with migraine benefit from tinted lenses  The best tint varies from patient to patient  Patients with migraine have an abnormally large (fMRI BOLD) and short (NIRS) haemodynamic response to stressful visual stimuli  Individually selected tints make the response more normal – decreasing amplitude and lengthening the response

Clinical trial  What is the effect of tints in clinical practice?  Small pilot double–masked trial compared two tints, one that reduced discomfort from patterns and another tint that differed in color by a small amount.  Patients did not know which was which.

Pilot double-masked placebo-controlled trial Days with symptoms proportion when active lenses worn proportion when control lenses worn 12 6 Log odds p<0.02 Wilkins, A.J., Patel, R. Adjamian, R., Evans, B.J.W. (2002). Tinted spectacles and visually sensitive migraine. Cephalalgia, 22, Precision Tint Control Lens

Conclusion  Environmental stimuli, including text, can be stressful, giving headaches.  The individual differences in susceptibility may be associated with an abnormal excitability of the brain.  This may be why precision tints can sometimes improve reading speed and reduce discomfort.  Precision tints reduce days with symptoms in a small study- we now wish to extend this study to a trial in general practice.

Thanks to: Peter AllenJohn FindlayIan Nimmo-Smith Liz AshbyNicola GraysonTim Noakes Debbie AylesSarah HaighDuncan Nulty John BaldGraham HardingRagini Patel Tom BeareGemma HardyCharlotte Peach Peter BexSamantha HarperDavid Pointon Colin BinniePamela HeatonLorna Scott Alex BoydJie HuangNirmal Sihra Anne BusbyLaura HughesAnita Simmers Edward ChronicleStephanie JaintaJennifer Smith Roanna CleaveRebecca JeanesLianne Smith Chris CooperAnita LightstoneLynne Speedwell Louise CouttsAmanda LudlowNicola Stevenson Colleen DarbyAnn MaclachlanLynette Taylor John DuffyJudith MartinRuth Tyrrell Frank EperjesiHazel McWhinnieLouise Wilson Bruce EvansBrian MeldrumWolfgang Jaschinski Marylyn EvansLouise MellBen Wright Dominic FernandezCatherine NearySheila Yale Further information