Motor Fusion Amplitude Associated With Age, Spherical Equivalent

Motor fusion is associated with age and spherical equivalent (SE) in healthy adults, according to a study published in BMC Ophthalmology.

The investigators conducted the cross-sectional study between September 1, 2018, and November 30, 2019, at a single center in China to investigate the relationships between motor fusion and sex, age, and SE. All participants underwent clinical examination, including eye position, eye movement, uncorrected distance visual acuity and cover tests, stereopsis, slip lamp and fundus examinations, and subjective refraction and synoptophore tests. Motor fusion was evaluated with a synoptophore, including measurement of subjective angle (SA), divergence, convergence and fusional vergence range (FVR).

A total of 243 healthy, nonstrabismic adults, (age range 20 to 59 years, 149 women). Participants were divided into 3 groups according to SE (myopic, emmetropic and hyperopic) and were also divided into 4 groups according to age (20-29 years, 30-39 years, 40-49 years and 50-59 years). The median age was 54 years for hyperopia, 46 years for emmetropia, and 37 years for myopia (all P <.001).

For all participants, the mean value was 9.72±0.26° for divergence, 19.34±0.54° for convergence, and 29.06±0.62° for FVR. The myopic group demonstrated a higher value of divergence than the emmetropic group (10° vs 8°, respectively; P <.05). Among age groups, SE and divergence were significantly different (all P <.05). SE was correlated with divergence (P =.003), and age was correlated with SE (P <.001), divergence (P =.005), and FVR (P =.002). The proportion of SA in the comfort zone (satisfying Percival’s criterion) was significantly different among the age groups (χ² =8.283; P =.041).

“Refractive error type was correlated to divergence amplitude. Additionally, age was correlated with refractive error type, divergence and FVR. In addition, abnormal SA, which did not satisfy Percival’s criterion, was associated with age, which may be a way to predict those who are at risk of suffering from dysfunctions of motor fusion.”

Major limitations noted by the investigators include the small sample size, the uneven percentages of male and female participants, a lack of patients younger than 20 years, and older than 60 years, and no evaluation of asthenopia symptoms.

Reference

She M, Li T, Hu Q, Zhu J, Zhou X. Relationship between age, refractive errors and motor fusion in a normal Chinese adult population: a cross-sectional study. BMC Ophthalmol. 2021;21(1):345. doi:10.1186/s12886-021-02105-z