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Antoine Barbot, Krystel Huxlin, Duje Tadin, Geunyoung Yoon; Long-term adaptation to ocular aberrations alters visual processing of spatial frequency information. Journal of Vision 2016;16(12):554. doi: 10.1167/16.12.554.
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© 2017 Association for Research in Vision and Ophthalmology.
Background: Optical aberrations alter visual processing, limiting the benefits of advanced correction methods. Here, we investigated the mechanisms by which prolonged, chronic exposure to optically degraded visual inputs alters processing in normally developed adults with keratoconus (KC)–a severe and progressive corneal disease. Procedure: We used an Adaptive Optics Vision Simulator (AOVS) to fully correct and/or induce optical aberrations in both KC observers (n=7) and age-matched controls (n=7) while measuring visual performance at fixation. Specifically, we measured: visual acuity (VA) thresholds for broadband Snellen E-letter stimuli, contrast sensitivity (CS) for Gabor narrowband stimuli and CS for broadband natural images. Then, we used an external noise paradigm to characterize properties of channels selective to low (1-cpd), intermediate (3-cpd) and high (9-cpd) spatial frequencies (SF). We assessed whether sensitivity differences were due to changes in external noise filtering and/or internal noise using the Perceptual Template Model. Results: Under identical, aberration-free conditions, KC observers showed lower VA and poorer CS for high SFs relative to normal participants, consistent with previous studies. KC's impaired sensitivity at high-SFs despite full optical correction reflected both poorer external noise filtering and higher internal noise, consistent with channel reweighting. Then, we induced KC's habitual optical aberrations into normal participants using the AOVS. Under their own habitual aberration conditions, KC observers showed better VA and CS for broadband information than normal participants, but similar performance was observed using narrowband stimuli. Conclusion: Our findings provide fundamental insights into the mechanisms of long-term adaptation to optical aberrations. KC observers showed an advantage for broadband information processed through their own habitual aberrations, suggestive of a compensatory mechanism that partially restores phase congruency across SFs. Furthermore, KC observers experienced limited benefits from full optical correction, and we showed that this was likely due to reduced sensitivity to high-SFs caused by channel reweighting.
Meeting abstract presented at VSS 2016
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