June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Amblyopia disrupts balanced ocular dominance (OD) activity in humans
Author Affiliations & Notes
  • Shahin Nasr
    Radiology, Harvard Medical School, Boston, Massachusetts, United States
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Jan Skerswetat
    Psychology, northeastern university, Boston, Massachusetts, United States
  • Bryan Kennedy
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Saralla Nikita Malladi
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Panharath Sok
    Psychology, northeastern university, Boston, Massachusetts, United States
  • Iman Aganj
    Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
    Radiology, Harvard Medical School, Boston, Massachusetts, United States
  • Peter Bex
    Psychology, northeastern university, Boston, Massachusetts, United States
  • David G Hunter
    Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States
    Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
  • Eric D Gaier
    Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States
    Ophthalmology, Massachusetts Eye and Ear, Boston, Massachusetts, United States
  • Footnotes
    Commercial Relationships   Shahin Nasr None; Jan Skerswetat PerZeption Inc., Code O (Owner); Bryan Kennedy None; Saralla Malladi None; Panharath Sok None; Iman Aganj None; Peter Bex PerZeption, Code I (Personal Financial Interest), PerZeption, Code O (Owner), FInD and AIM patents owned by Northeastern University, Code P (Patent); David Hunter Luminopia, Inc., Code I (Personal Financial Interest), Rebion, Inc., Code O (Owner); Eric Gaier Stoke Therapeutics Inc., Code C (Consultant/Contractor), Luminopia Inc., Code I (Personal Financial Interest), Luminopia, Inc., Code P (Patent), Luminopia, Inc., Code S (non-remunerative)
  • Footnotes
    Support  NIH Grant R01EY030434
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 527. doi:
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      Shahin Nasr, Jan Skerswetat, Bryan Kennedy, Saralla Nikita Malladi, Panharath Sok, Iman Aganj, Peter Bex, David G Hunter, Eric D Gaier; Amblyopia disrupts balanced ocular dominance (OD) activity in humans. Invest. Ophthalmol. Vis. Sci. 2023;64(8):527.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Amblyopia affects the development of OD columns in V1. Functional evidence for this phenomenon is mostly limited to single-cell studies in animal models, which show that amblyopia decreases the proportion of cells that respond to the amblyopic eye (AE). Here we used advanced neuroimaging to probe analogous evidence directly in humans and to test the impact of this phenomenon on downstream areas V2, V3, and V3A.

Methods : Adults with strabismic (n=8), anisometropic (n=6), and deprivation (n=1) amblyopia, along with controls (n=6), participated in this study. Using high-resolution functional MRI (voxel size=1mm isotropic), we measured OD response to stimulating the central (r≤10°) visual field of each eye separately (Nasr et al., 2016).

Results : Control subjects demonstrated OD responses mainly in V1 (Fig. 1A). The spatial distribution of the response was consistent with prior histological results of OD columnar organization (Adams et al., 2007). The median of V1 activity remained close to zero (mean±SD; 0.19±0.20) suggesting weak (if any) OD bias in controls.
In subjects with strabismic amblyopia, we found a significant (p<0.05) increase in the level of OD bias favoring the fellow eye (FE) (Fig. 1B-C). This bias extended to areas V2-V3A in all subjects. Nevertheless, AE-preferring clusters were found within V1 and beyond. Compared to control subjects, FE and AE clusters appeared larger, even after median V1 activity adjustment for overall OD bias.
We also found a significant (p<0.01) increase in OD bias in V1-V3A in individuals with anisometropic/deprivation amblyopia (Fig. 1D-F), but with fewer and smaller AE-preferring clusters compared to strabismic amblyopia. However, after adjusting for overall bias, the distribution of OD clusters resembled those in strabismic amblyopia.

Conclusions : Amblyopia affects the mesoscale functional organization of V1. This phenomenon extends to downstream visual areas.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Differential fMRI response to stimulation of fellow (dominant) vs. amblyopic (non-dominant) eye in subjects with normal (A), strabismic (B-C), anisometropic (D-E) and deprivation (F) amblyopia, along their eyesight tests. Activity maps were overlaid on the subject’s own flattened cortex, shown before (left) and after (right) adjusting the V1 median to zero. V1 border (dashed black line) and fovea position (asterisk) were defined for each subject retinotopically. Scale bar indicates 1 cm.

Differential fMRI response to stimulation of fellow (dominant) vs. amblyopic (non-dominant) eye in subjects with normal (A), strabismic (B-C), anisometropic (D-E) and deprivation (F) amblyopia, along their eyesight tests. Activity maps were overlaid on the subject’s own flattened cortex, shown before (left) and after (right) adjusting the V1 median to zero. V1 border (dashed black line) and fovea position (asterisk) were defined for each subject retinotopically. Scale bar indicates 1 cm.

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