September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Surgical Correction of Strabismus in Monkeys: Longitudinal evaluation of responses of near-response cells in the Supraoculomotor Area
Author Affiliations & Notes
  • Mythri Pullela
    Optometry, University of Houston, Houston, Texas, United States
  • David K Coats
    Ophthalmology, Baylor College of Medicine, Houston, Texas, United States
  • Vallabh E Das
    Optometry, University of Houston, Houston, Texas, United States
  • Footnotes
    Commercial Relationships   Mythri Pullela, None; David Coats, None; Vallabh Das, None
  • Footnotes
    Support  NIH Grant R01 EY022723; NIH Grant P30 EY07551
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2433. doi:
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      Mythri Pullela, David K Coats, Vallabh E Das; Surgical Correction of Strabismus in Monkeys: Longitudinal evaluation of responses of near-response cells in the Supraoculomotor Area. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2433.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose : We have previously shown, in monkey models of strabismus, that plastic changes in response characteristics of Medial Rectus Motoneurons (MRMN) within the Oculomotor Nucleus plays an important role in determining the state of misalignment following surgical correction of strabismus. The MRMNs receive direct monosynaptic input from near-response cells in the Supraoculomotor Area (SOA), a structure previously implicated in maintaining the angle of horizontal misalignment in untreated animals. Therefore our goal here was to investigate responses of SOA near response (NR) cells following surgical correction of strabismus.

Methods : The study included one juvenile rhesus monkey with an exotropia (OD: ~30°,OS: ~38°) induced during infancy via optical prism rearing. Surgical correction of the strabismus involved a Medial Rectus (MR) resection and Lateral Rectus recession of the right eye only. We recorded from 19 near-response SOA cells before and after strabismus correction surgery during monocular fixation with either eye viewing. Data analysis involved computing a population SOA neural drive (potentially responsible for the static misalignment) and comparing pre- and post-surgical data.

Results : Strabismus angle was reduced to OD: ~13°,OS: ~11° immediately after surgery and gradually increased to OD: ~18°,OS: ~30° over a 6 month period. Analysis of SOA NR firing rates showed a significant decrease in population neural drive following surgical treatment during left (untreated) eye viewing (Before surgery: 41±33spks/sec, After surgery: 13±10spks/sec, t-test p-value=0.011). SOA near-response firing rates during right (treated) eye viewing decreased a little after surgery but the difference was not statistically significant (Before surgery: 120±40spks/sec, After surgery: 103±30spks/s, t-test p-value=0.306).

Conclusions : Previous studies showed that resection of the MR lead to decreased neural drive from MRMN, evidence for neural adaptation that is countering the intent of surgery. In this study, we observed a decrease in the convergent drive from the SOA to the MRMN after surgical correction that would in turn drive the eyes towards exotropia. Therefore the neural adaptation observed in the SOA may be the source of post-surgical neural plasticity observed previously at the level of oculomotor nucleus.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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