Short-Term Effects of Low-Addition Progressive Lenses on Binocular Vision

The study investigated the one-month effect of low-addition progressive lenses on binocular vision (BV) in healthy Chinese young adults.
Participants: 120 subjects with a mean age of $29 \pm 5.4$ years (range 22 to 44 years).
Experimental Design: Subjects were divided into two groups of 60:
- Low-addition progressive lenses with blue cut coating (Essilor Eyezen™).
- Normal anti-reflective coated single vision lenses (control group).
Key Measurements: Amplitude of accommodation (AA), near point of convergence (NPC), distance and near phoria, AC/A ratio, negative relative accommodation (NRA), positive relative accommodation (PRA), positive/negative fusional vergences (PFV/NFV), vergence facility (VF), and accommodative facility (AF).

General Results: No significant differences were found in the majority of optometric tests between baseline and the one-month follow-up.
Amplitude of Accommodation (AA): Baseline value of $11.5 \pm 5.3\,D$ showed no significant change compared to the one-month measurement of $11.4 \pm 4.9\,D$ ( $p = 0.19$ ).
Near Point of Convergence (NPC): Baseline measurement of $6.3 \pm 2.3\,cm$ showed no significant change compared to the one-month measurement of $6.9 \pm 2.3\,cm$ ( $p = 0.65$ ).
Fusional Vergence: A statistically significant increase was observed in the recovery value of PFV, rising from $14.3 \pm 7\,PD$ at baseline to $16.6 \pm 8\,PD$ after one month ( $p = 0.02$ ).
Facility Improvements: Significant improvements in VF and AF (both monocularly and binocularly) were noted in both the low-addition progressive and single vision lens groups, suggesting these improvements were not specific to the progressive lenses.

Wearing low-addition progressive lenses for one month does not significantly impact the baseline binocular vision performance, including AA and NPC, for most wearers.