Amblyopic stereo vision is efficient but noisy.

People with amblyopia demonstrate a reduced ability to judge depth using stereopsis. Our understanding of this deficit is limited, as standard clinical stereo tests may not be suited to give a quantitative account of the residual stereo ability in amblyopia. In this study we used a stereo test designed specifically for that purpose. Participants identified the location of a disparity-defined odd-one-out target within a random-dot display. We tested 29 amblyopic (3 strabismic, 17 anisometropic, 9 mixed) participants and 17 control participants. We obtained stereoacuity thresholds from 59% of our amblyopic participants. There was a factor of two difference between the median stereoacuity of our amblyopic (103 arcsec) and control (56 arcsec) groups. We used the equivalent noise method to evaluate the role of equivalent internal noise and processing efficiency in amblyopic stereopsis. Using the linear amplifier model (LAM), we determined the threshold difference was due to a greater equivalent internal noise in the amblyopic group (238 vs 135 arcsec), with no significant difference in processing efficiency. A multiple linear regression determined 56% of the stereoacuity variance within the amblyopic group was predicted by the two LAM parameters, with equivalent internal noise predicting 46% alone. Analysis of control group data aligned with our previous work, finding that trade-offs between equivalent internal noise and efficiency play a greater role. Our results allow a better understanding of what is limiting amblyopic performance in our task. We find this to be a reduced quality of disparity signals in the input to the task-specific processing.

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Déclaration de conflit d'intérêts

Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Alex S. Baldwin (ASB) and Robert F. Hess (RFH) are inventors on patent(s) and other intellectual property concerning stereovision and the measurement and treatment of disorders of binocular vision such as amblyopia. Most relevant to this study is Patent Application PCT/CA2020/050051. Some of these technologies (including PCT/CA2020/050051) have been commercially licensed by McGill University to Novartis International AG. Development of these technologies for clinical use is ongoing (outside of the work reported in this manuscript) through a research agreement between Novartis and the Research Institute of the McGill University Health Centre which is supported by grants, personal fees, and non-financial support from Novartis International AG to ASB and RFH.