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

Perc

ep

tual

di s

tort

ion

sHeadaches

Links between distortions and headachesLinks 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, 1995Wilkins, 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, 664-671.

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, 664-671.

Haemodynamic response

Spatial frequency(cycles/degree)

BO

LD S

ign

al C

han

ge in

V1

(%

)

0

1

2

3

4

0.3 1 10

Non-headachecontrols

3

fMRI

Haemodynamic response

Spatial frequency(cycles/degree)

BO

LD S

ign

al C

han

ge in

V1

(%

)

**

*

0

1

2

3

4

0.3 1 10

Non-headachecontrols

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, 664-671.

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, 664-671.

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, 257-263.

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, 257-263.

Trial lenses

SaturationHue

Brightness

Shines coloured light on text

Rose

Rose

Yellow

Blue

Turquoise

Green Orange

Purple

400 700wavelength (nm)tr

ansm

issi

on (

%)100

0

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), 925-36.

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

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

proportion when active lenses worn

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

pro

po

rtio

n w

he

n c

on

tro

l le

ns

es

wo

rn 12

6

Log oddsp<0.02

Wilkins, A.J., Patel, R. Adjamian, R., Evans, B.J.W. (2002). Tinted spectacles and visually sensitive migraine. Cephalalgia, 22, 711-719.

Wilkins, A.J., Patel, R. Adjamian, R., Evans, B.J.W. (2002). Tinted spectacles and visually sensitive migraine. Cephalalgia, 22, 711-719.

PrecisionTint

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 Allen John Findlay Ian Nimmo-Smith

Liz Ashby Nicola Grayson Tim Noakes

Debbie Ayles Sarah Haigh Duncan Nulty

John Bald Graham Harding Ragini Patel

Tom Beare Gemma Hardy Charlotte Peach

Peter Bex Samantha Harper David Pointon

Colin Binnie Pamela Heaton Lorna Scott

Alex Boyd Jie Huang Nirmal Sihra

Anne Busby Laura Hughes Anita Simmers

Edward Chronicle Stephanie Jainta Jennifer Smith

Roanna Cleave Rebecca Jeanes Lianne Smith

Chris Cooper Anita Lightstone Lynne Speedwell

Louise Coutts Amanda Ludlow Nicola Stevenson

Colleen Darby Ann Maclachlan Lynette Taylor

John Duffy Judith Martin Ruth Tyrrell

Frank Eperjesi Hazel McWhinnie Louise Wilson

Bruce Evans Brian Meldrum Wolfgang Jaschinski

Marylyn Evans Louise Mell Ben Wright

Dominic Fernandez Catherine Neary Sheila Yale

Further informationwww.essex.ac.uk/psychology/overlays/publications2.htm