Of the 1126 children referred, 782 (70 %) attended the eye examination, with 241 (31 %), 241 (31 %) and 300 (38 %) children in the three age groups (2nd, 5th and 10th grade).
Refractive error and visual acuity
Monocular and binocular spherical equivalent refractive errors (SER) (mean [95% CI]) are shown in Table 1. For all three age groups the mean SER was skewed towards hyperopia, and reduced significantly with age (ANOVA F2 = 26.8, p < .0001, Tukey post-hoc analysis between all groups p ≤ .0001).
Table 2 shows that most children were classified as emmetropic (60 %). Hyperopia ≥ +2.00 D decreased with age, and was present in 7 % of the 2nd grade, 6 % of 5th grade, and 1 % of the 10th grade children. Myopia increased with age, with 3 % of 2nd grade, 15 % of 5th grade and 27 % of the 10th grade children being myopic. Although almost one third of 10th grade children were classified as myopic, only 1 % had myopia -3.00 D or higher. Clinically significant astigmatism (≥ 0.75 DC) was present in 5 % of all children, and clinically significant anisometropia (≥ 1.00 D) in 3 %.
The distribution of refractive errors was similar for all three age groups over the ten year period (Figure 2). Linear regression shows no significant change in either myopia or hyperopia with time for the 2nd grade (R2 = .01, F = 2.9, p > .05), 5th grade (R2 = .01, F = 1.4, p > .05) or 10th grade children (R2 = .002, F = .45, p > .05).
Most children obtained very good correctable vision (BCVA, Table 1). As expected, binocular BCVA was slightly better than monocular. Overall, 91 % of children had BCVA of logMAR 0.0 (decimal acuity 1.0) or better in one or both eyes (Table 2). There was a slight but significant improvement with age (ANOVA F2 = 44.8, p < .0001), and 2nd graders had lower visual acuity than both older age-groups (Tukey post-hoc analysis p ≤ .05). Reduced vision was found in 2% of the children, including one 2nd grade child with BCVA > logMAR 0.5 (decimal acuity < 0.3), who was referred to an ophthalmologist due to ocular pathology.
Binocular vision and accommodation
Table 2 shows that distance and near horizontal ortophoria were present in 78 % and 77 % of children, respectively. The mean [95% CI] heterophoria was 0.8 [0.6, 1.0] exophoria for distance, and 2.3 [2.0, 2.6] exophoria for near. Exophoria was present in 13 % and 14 % of the children for distance and near, respectively (see Table 2 for criteria). Esophoria was less common, and present in 7 % and 9 % of children for distance and near.
Mean [95% CI] binocular accommodation was 14.0 [13.4, 14.6] D, 12.9 [12.3, 13.5] D, and 11.8 [11.3, 12.2] D for 2nd, 5th and 10th graders, respectively (Table 1), and reduced binocular accommodation was found in 15 % of all children (Table 2). ANOVA and post-hoc analyses showed a significant difference in accommodation between the three age groups for binocular measures (ANOVA F2 = 18.9, p < .0001, Tukey p ≤ .007 for all comparisons). Near point of convergence (NPC) was 8.2 [7.7, 8.7] cm across all children, and NPC ≥ 10 cm was found in 19 %. There was no significant difference between the age groups for NPC (ANOVA F2 = .241, p = .786).
Symptoms
Of the 782 children, 26 % experienced symptoms of vision problems, and 25 % had more than one symptom. The most prevalent symptoms were headaches (22 %), near vision problems (19 %) and reduced distance vision (14 %).
Management
Most children (650, 83 %) referred from the school screening had vision problems requiring treatment or follow up. Glasses for distance or near work was the most common management strategy (55 %), followed by vision training (7 %) and glasses combined with vision training (4 %). Glasses were recommended primarily for low hyperopia in 2nd and 5th grade and for myopia in 10th grade children. Binocular vision- and near problems due to reduced accommodation or poor NPC were prescribed low plus lenses, vision training or both. Of the 16 % of children with reduced accommodation, 42 % were given glasses, 19 % prescribed vision training and 11 % a combination. For the 14 % of children with reduced NPC, 40 % were given glasses, 31 % vision training and 20% both glasses and training. Vision training was more commonly recommended for 5th and 10th grade children, while the 2nd grade children were more likely to receive follow up. Follow up (33 %) was recommended when the child had borderline symptoms, refractive errors or binocular findings and no immediate management was required. Overall 25 (4 %) children were referred to an ophthalmologist, however, most were 2nd grade children requiring glasses to be covered by the National Insurance Scheme.