Abstract
Purpose :
In a prior prospective study, 74% of stroke survivors with strabismus failed to report diplopia (Rowe, 2010). The possible reasons were investigated hypothesizing that pathological suppression exists and is related to laterally imbalanced attentional networks, and therefore associated with hemispatial neglect (HSN) and/or visual extinction (VE) after controlling for other reasonable factors.
Methods :
A 1 year review of all inpatient vision clinic records included comprehensive eye and sensorimotor exam with 2AFC Randot E, Stereobook R+L and Randot Stereopsis, TV trainer, induced strabismus test, covertest, motorfield, motility and NPC. Evaluation for HSN included line bisection, cancellation, and VE. Failed suppression tests were tabulated and the clinician reviewer, considering all information, rated(1-10) the likelihood-certainty of suppression vs. another explanation. Hypothesized association of HSN and VE with likelihood rating and proportion of test failures was analyzed.
Results :
There were 113 consecutive records with ≥1 suppression test (median 4, range 1-10). Only 33% passed all suppression tests administered. 47% did not have diplopia with optically induced strabismus. Actual strabismus was present in 50%, of whom 49% denied diplopia. Randot stereopsis was failed in 64%, and stereobook R+L in 23%. Potential confounders reported as most limiting clinician reviewer certainty were homonymous hemianopia (HH), order effects with preceding tests potentially breaking suppression, and generalized reduction of awareness/insight. Multiple regression analysis did not support HH or interocular acuity differences as confounders. Insight and order effects could not be tested. HSN was a significant predictor of suppression certainty P=.001, controlling for age P=.004. Post hoc exploration of other possible factors via forward selection identified VE P<.001 and subsequently parietal lobe involvement P=0.03 as independent predictors, with age, HSN, and VE ultimately dropping out.
Conclusions :
Findings support the hypothesis that failure to report diplopia from strabismus after stroke is common and that there is relationship to HSN, or more specifically VE and the associated parietal corticies. Prospective studies would allow for control of potentially confounding order effects and generally reduced insight for impairment in stroke patients, while introducing psychophysical and dichoptic testing paradigms.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.