Analysis of the Causes of Non-Amblyopic Functional Low Vision in Children

Objective: To analyze the causes of non-amblyopic functional low vision in children. Methods: One hundred and seven non-amblyopic functional low vision children aged 8.3±1.9 years were selected from Puyang Eye Hospital from June 2015 to May 2019 in this serial case study. The initial best near-far corrected visual acuity (BCDVA, BCNVA), monocular and binocular accommodative sensitivity (MAF, BAF), accommodation amplitude (AMP), accommodative convergence (BCC), positive and negative relative accommodation (PRA, NRA), near-far horizontal oblique lens power (DLP, NLP), accommodative convergence/accommodation (AC/A), and spherical equivalent (SE) were measured. Decimal visual acuity was converted into a 5-point expression by Muir's method. The univariate multiple linear regression analysis was used to study the relationship between corrected vision before training and independent variables of related visual function parameters. Results: Seventy-nine patients (73.8%) had a BCDVA lower than 5.0 in both eyes and 28 patients (26.2%) had a BCDVA lower than 5.0 in one eye. Seventy-one patients (66.4%) had a BCNVA below 5.0 in both eyes and 22 patients (20.6%) had a BCNVA below 5.0 in one eye. Visual function examination showed that the accommodative range of all eyes with low vision was lower than normal, 59 patients were diagnosed with convergence insufficiency and 18 patients were diagnosed with simple exotropia, accounting for 55.1% and 16.8% of the total cases, respectively, accounting for 97.5% of all eyes with a BCDVA lower than 5.0. There were 27 patients with a simple accommodative abnormality, accounting for 25.2% of the total patients, and 96.4% of those had a monocular BCDVA lower than 5.0. The best corrected visual acuities of far and near were positively correlated with AMP (r=0.563, P=0.035; r=0.587, P=0.029), both negatively correlated with NLP (r=-0.413, P=0.031; r=-0.409, P=0.030), which had no significant correlation with BCC, PRA, NRA, DLP, AC/A, or SE (P>0.05). Conclusions: ①Patients with convergence insufficiency and simple exotropia are characterized mainly by binocular BCDVA abnormalities, while patients with simple accommodation abnormalities are mainly characterized by monocular BCDVA abnormalities. ②The formation of the children's non-amblyopic functional vision impairment is related to the AMP and the near horizontal cryptogamy anomaly, of which the AMP anomaly is the root cause and the near horizontal cryptogamy anomaly is the secondary cause. Key words: convergence insufficiency; accommodative; children; low vision