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Relationship between reading performance and saccadic disconjugacy in patients with convergence insufficiency type
Masakazu Hirota1, Hiroyuki Kanda1, Takao Endo2
1Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
Purpose:
To determine the relationship between re-reading the same line and saccadic disconjugacy in patients with convergence insufficiency-type intermittent exotropia [CI-type X(T)].
Methods:
Eight patients with CI-type X(T) 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-in. liquid crystal monitor placed 60 cm from the eyes. The sentences were displayed horizontally and read from left to right. The number of unintentional re-readings of the same line was counted, and the disconjugacy at the median of the saccade between the end of a line and the next line was determined.
Results:
The number of re-readings of the same line in patients with CI-type X(T) was 4.9 ± 2.3 times which was significantly higher than that in the controls at 0.2 ± 0.4 times (P < 0.001). The saccadic disconjugacy was significantly larger in patients with CI-type X(T) at -1.70° ± 0.72° than that in the controls at -0.40°± 0.30° (P < 0.001). The number of re-readings of the same line was significantly and positively correlated with the saccadic disconjugacy (R = 0.84, R (2) = 0.71, P < 0.01).
Conclusions:
The results of our study indicate that saccadic disconjugacy is associated with re-reading the same line in patients with CI-type X(T).
