Re-Reading the Same Line in Intermittent Exotropia is Related to the Saccadic Disconjugacy
Takashi Fujikado, MD; Masakazu Hirota, MS
Osaka University Graduate School of Medicine
Introduction: Difficulty of reading is a typical symptom of intermittent exotropia (IXT) and is coupled with re-reading the same line. We investigated the relationship between the re-reading the same line and saccadic disconjugacy in patients with IXT.
Methods: Seven patients with IXT and ten healthy orthophoric individuals were studied. Video oculography was used to assess the eye movements during the reading of a Japanese novel displayed on a 23-inch liquid crystal monitor placed 60-cm from the eyes. The sentences were displayed horizontally and read from left-to-right. The rate of unintentional re-reading the same line was counted, and the disconjugacy at the median of the saccade between the end of a line to the next line was determined.
Results: The rate of the re-reading of the same line in the patients with IXT was 5.0±2.5 times which was significantly higher than that in the controls at 0.2±0.4 times (P<0.001). The rate of re-reading of the same line was significantly and positively correlated with the saccadic disconjugacy (P<0.01, R2=0.79) but was not correlated with the angle of strabismus at near(P=0.18, R2=0.28).
Discussion: Re-reading in IXT may be caused by the disturbance of binocular coordination during saccade from the end of a line to the next line.
Conclusion: The re-reading in IXT is related to the saccadic disconjugacy but not significantly related to the angle of strabismus at near .
References: Saunte JP, Christensen T. Improvement in reading symptoms following botulinum toxin A injection for convergence insufficiency type intermittent exotropia. Acta Ophthalmol. 2015;93:e391-2.