To compare the biometric characteristics between concomitant exotropia (XT) and orthotropia (OT) with OA2000.
This cross-sectional study collected 4–18 years old children. All subjects underwent a comprehensive ophthalmic examination and prism alternate cover test for ocular alignment measurement. Included subjects had no any eye surgery, structural ocular anomalies, amblyopia of either eyes, ptosis, cataract and nystagmus. OA-2000 was used for the measurement of ocular biological parameters. Spherical equivalent (SE, spherical power + (cylindrical power)/2), keratometry, central corneal thickness (CCT), white to white distance (WTW), pupil diameter (PD), anterior chamber depth (ACD), lens thickness (LT), axial lengths (AL) and intereye differences in SE, keratometry, CCT, WTW, PD, ACD, LT and AL were analyzed by independent sample t-tests. Pearson correlation was used for correlations assessment. Partial correlation was used to control for intereye differences in SE.
A total of 156 subjects (79 XT and 77 OT) were collected. Intereye differences in spherical equivalent (SE) (t 2.369, P 0.019), AL (t 3.423, P 0.001), ACD (t 3.782, P < 0.001), LT (t 3.136, P 0.002) and PD (t 3.229, P 0.002) were significantly larger in XT patients than OT patients. The correlation coefficient of XT with SE asymmetry was 0.187 (P 0.020), 0.265 with AL asymmetry (P 0.001), 0.289 with ACD asymmetry (P < 0.001), 0.251 with PD asymmetry (P 0.002) and 0.243 with LT asymmetry (P 0.002). Strong correlation (r 0.875) was found between anisometropia and AL asymmetry. After controlling the effect of anisometropia, the correlation coefficients slightly reduced between XT patients and intereye differences in AL (reduced to 0.213), ACD (reduced to 0.266), PD (reduced to 0.230) and LT (reduced to 0.230). Strong correlation (r 0.855) was found between intereye differences in ACD and LT.
Compared with OT subjects, intereye differences in SE, AL, ACD, LT and PD were significantly larger in XT patients and had positive correlation with XT and may be associated with the pathogenesis of XT.