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Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

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JournalInvestigative ophthalmology & visual science
DateE-pub ahead of print - 29 Jan 2015
DatePublished (current) - 19 Feb 2015
Issue number2
Volume56
Number of pages9
Pages (from-to)1208-1216
Early online date29/01/15
Original languageEnglish

Abstract

Purpose. Visual deficits in amblyopia are neural in origin, yet are difficult to characterize with functional magnetic resonance imagery (fMRI). Our aim was to develop an objective electroencephalography (EEG) paradigm that can be used to provide a clinically useful index of amblyopic deficits.

Methods. We used steady-state visual evoked potentials (SSVEPs) to measure full contrast response functions in both amblyopic (n = 10, strabismic or mixed amblyopia, mean age: 44 years) and control (n = 5, mean age: 31 years) observers, both with and without a dichoptic mask.

Results. At the highest target contrast, the ratio of amplitudes across the weaker and stronger eyes was highly correlated (r = 0.76) with the acuity ratio between the eyes. We also found that the contrast response function in the amblyopic eye had both a greatly reduced amplitude and a shallower slope, but that surprisingly dichoptic masking was weaker than in controls. The results were compared with the predictions of a computational model of amblyopia and suggest a modification to the model whereby excitatory (but not suppressive) signals are attenuated in the amblyopic eye.

Conclusions. We suggest that SSVEPs offer a sensitive and objective measure of the ocular imbalance in amblyopia and could be used to assess the efficacy of amblyopia therapies currently under development.

Bibliographical note

© 2015, The Association for Research in Vision and Ophthalmology, Inc.

    Research areas

  • Amblyopia, Steady-state EEG, Dichoptic masking, Contrast

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