Acknowledgement to: Capturing the Moment When Fusion is Lost in - - PowerPoint PPT Presentation

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In Flagrante Delicto:

Capturing the Moment When Fusion is Lost in Strabismus

Jonathan C. Horton, UCSF http://vision.ucsf.edu/hortonlab

Acknowledgement to:

• NATIONAL EYE INSTITUTE
• Research to Prevent Blindness
• Alcon Research Institute
• That Man May See
• Wayne and Gladys Valley Foundation
• Jewish Guild for the Blind

(No Financial Disclosures or Conflict of Interest)

Economides JR, Adams DL, Horton JC, Perception via the deviated eye in strabismus. J. Neuroscience, 32:10286-10295, 2012. Adams DL, Economides JR, Sincich LC, Horton JC, Cortical metabolic activity matches the pattern of visual suppression in strabismus. J. Neuroscience, 33:3752-3759, 2013. Economides JR, Adams DL, Horton JC, Eye choice for target acquisition in alternating strabismus. J. Neuroscience, 34:14578-14588, 2014. Economides, J.R., Adams, D.L., Horton, J.C., Variability of ocular deviation in strabismus. JAMA Ophthalmology, 34:63-69, 2016. Economides, J.R., Adams, D.L., Horton, J.C., Capturing the moment

• f fusion loss in intermittent exotropia. Ophthalmology, 2017.

Economides, J.R., Adams, D.L., Horton, J.C., Normal correspondence of tectal maps for saccadic eye movements in strabismus. J. Neurophysiology, 2016

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Spontaneous Right XT Spontaneous Left XT

Left Eye Fixation Right Eye Fixation

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Shutter Spontaneous

Velocity of Spontaneous & Shutter-Induced XT are Correlated r = 0.91 Velocity of Spontaneous XT & Amplitude are Correlated r = 0.81 Blue Cross, Blue Target Red Cross, Red Target

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Target Undershoot in Exotropes (n = 16) 18% 12%

Conclusions

• In alternating exotropia the deviated eye is unstable, with a standard

deviation in horizontal position of ± 2.4° .

• Even the fixating eye is slightly unsteady, compared with controls.
• The outwards eye movement that occurs spontaneously is extremely similar

to the outwards eye movement induced by occlusion.

• Therefore, once fusion is broken and the eye begins to move outwards,

visual feedback plays no role.

• The peak velocity of the outwards eye movement is correlated with the

amplitude of the exotropia.

• Although intermittent exotropia is often blamed on excess divergence tone,

in fact, adducting saccades are less accurate than abducting saccades.

• We have not yet solved the chicken or egg problem.