Relationship between reading performance and saccadic disconjugacy in patients with convergence insufficiency type intermittent exotropia.
OBJECTIVE
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).
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
Masakazu
M
Hirota
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
Hiroyuki
H
Kanda
Department of Ophthalmology, Osaka University Graduate School of Medicine, Suita-shi, Osaka, Japan.
Takao
T
Endo
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.|Department of Ophthalmology, University Hospital Aachen RWTH Aachen University, Aachen, Nordrhein-Westfalen, Germany.
Tibor Karl
TK
Lohmann
Department of Integrative Physiology, Osaka University Graduate School of Medicine, Suita-shi, Osaka, Japan.
Tomomitsu
T
Miyoshi
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan.
Takeshi
T
Morimoto
Department of Applied Visual Science, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan. fujikado@ophthal.med.osaka-u.ac.jp.
Takashi
T
Fujikado
D000293:Adolescent; D000328:Adult; D005099:Exotropia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D015835:Ocular Motility Disorders / Q000503:physiopathology*; D011932:Reading; D012438:Saccades / Q000502:physiology*; D015348:Vision, Binocular; D055815:Young Adult
Convergence insufficiency; Eye movement; Intermittent exotropia; Reading