Prevalence of Heterophoria in Tibetan Grade-One Students: The Lhasa Childhood Eye Study

Abstract

Introduction. The study aims to explore the prevalence of heterophoria and associate factors in Tibetan grade-one students. Methods. The Lhasa Childhood Eye Study (LCES) is a school-based cohort study. 1942 grade-one students from 7 elementary schools were randomly sampled by stratified cluster sampling. Ocular examinations were performed in participants, including ocular motility, distance and near visual acuity, cycloplegic autorefraction, and stereoacuity. The near (33 cm) and distance (6 m) fixation cover test was used to differentiate orthophoria, heterophoria, and heterotropia, and the magnitude of the phoria was measured by the Maddox rod and prisma. Results. Of 1856 grade-one students completing all the ocular examinations, 1852 participants finished the ocular alignment test. The mean age was 6.82 ± 0.46 years (range 6∼10 years); 981 (52.97%) were males, and 871 (47.03%) were females. The prevalence of phoria was 22.89% (n = 424). At distance fixation, the prevalence of heterophoria, exophoria, and esophoria was 4.64%, 4.21%, and 0.43% separately, while at near fixation, the prevalence was 22.73%, 22.35%, and 0.38%. No vertical phoria was detected. The mean magnitude of heterophoria at near and distance fixation was −7.63 ± 5.15 PD (exo: −7.83 ± 4.91 PD, eso: +5.67 ± 3.61 PD) and −4.84 ± 5.94 PD (exo: −6.26 ± 4.20 PD, eso: +8.13 ± 3.04 PD). The prevalence of esophoria was associated with hyperopia (OR = 6.38, 95% CI: 1.15–35.28, P = 0.03; OR = 5.42, 95% CI: 1.04–28.24, P = 0.04) and amblyopia (OR = 16.02, 95% CI: 1.81∼141.96, P = 0.01; OR = 11.37, 95% CI: 1.34∼96.52, P = 0.03) at near and distance fixation. The prevalence of exophoria was associated with myopia at near fixation (OR = 2.43, 95% CI: 1.47–4.00, P <0.01). In the near heterophoria group, the proportion of children with abnormal stereoacuity was 23.26% (n = 97), significantly higher (χ2 = 5.70, P = 0.017) than that in orthophoria (17.99%, n = 244). Conclusions. In Lhasa, grade-one pupils have a lower prevalence of heterophoria. Near exophoria was associated with myopia, while esophoria was related to hyperopia and amblyopia both near and distance. Heterophoria may be one of the affected factors for reducing stereoacuity.

Heterophoria, fusional vergence, and near point of convergence in Sudanese hospital-based population

“…Conversely, the condition where heterophoria does not exist and the dissociated position is the same as the active position is known as orthophoria. 1 A review of studies 5,6,7,8 on prevalence rates of heterophoria among children may vary depending on the specific populations age and diagnostic criteria used. However, exophoria appears to be the more prevalent phoria in young children and school-aged children from Australia, 5 China, 6 Tibet, 8 and South Africa.…”

“…1 A review of studies 5,6,7,8 on prevalence rates of heterophoria among children may vary depending on the specific populations age and diagnostic criteria used. However, exophoria appears to be the more prevalent phoria in young children and school-aged children from Australia, 5 China, 6 Tibet, 8 and South Africa. 7 Normal binocular vision needs correct alignment of both eyes, in addition to motor and sensory mechanisms of fusion.…”

Maternal Hypertensive Disorder in Pregnancy and Childhood Strabismus in Offspring

“…1 If the deviation is absent when both eyes are open for viewing, it is considered latent strabismus; otherwise, it is considered manifest strabismus. The prevalence rate ranges from 4% to 58.3% for latent strabismus [2][3][4][5][6][7] and from 0.8% to 5.7% for manifest strabismus. [8][9][10][11][12][13] The etiology and pathogenesis of childhood strabismus remain to be elucidated.…”