# Comparison of accommodation and vergence parameters in early and late-onset myopic adults

## TL;DR

Late-onset myopic adults show reduced eye focusing and coordination abilities compared to those with early-onset myopia, suggesting the need for tailored treatment.

## Contribution

The study reveals that late-onset myopia is associated with distinct accommodative and vergence impairments compared to early-onset myopia.

## Key findings

- Late-onset myopes have significantly reduced accommodative facility compared to early-onset myopes.
- Late-onset myopes show lower negative and positive fusional vergence at distance.
- Age of myopia onset influences accommodative and binocular vision behavior in adulthood.

## Abstract

Myopia is a growing public health concern, and understanding the visual function differences among adults with different ages of myopia onset is essential for effective management. This study demonstrated that late-onset myopic adults have significantly reduced accommodative facility and lower fusional vergence amplitudes at distance compared to early-onset myopes. These findings highlight that the age of myopia onset influences accommodative and binocular vision behavior in adulthood, emphasizing the need for individualized clinical management strategies such as accommodative and vergence training in late-onset myopia.

This study aimed to assess and compare the accommodation and vergence parameters in early and late-onset myopic adults.

This cross-sectional observational study was carried out at the Department of Ophthalmology, Kasturba Medical College and Optometry Clinic, Manipal. A total of 60 participants aged 18-35 years with mild to moderate defined as a spherical equivalent refractive error of –0.50 D to -6.00D were included in the study. A comprehensive eye examination was done to confirm eligibility criteria. Those who met the inclusion criteria were categorised into two groups: one with those who had early-onset myopia (EOM) and another with late-onset myopia (LOM). Accommodation and vergence parameters such as the amplitude of accommodation, accommodative facility, accommodative response, AC/A ratio, near point of convergence, positive fusional vergence, negative fusional vergence and vergence facility were measured.

A total of 60 participants (30 EOM and 30 LOM) were enrolled in the study. The mean age at presentation of the early-onset myopic individual was 21.8± 2.3, and the late-onset myopic individual was 21.9± 2.6. There was a statistically significant difference between EOM and LOM in both monocular and binocular accommodative facility, negative fusional vergence and positive fusional vergence for distance. Accommodative facility was reduced in late-onset myopes compared with early-onset myopes (OD: 8.5 ± 4.7 vs. 12.5 ± 4.5 cpm, p < 0.001; OS: 8.5 ± 4.1 vs. 12.0 ± 5.0 cpm, p = 0.001; OU: 9.2± 4.8 vs. 12.8± 4.3 cpm, p = 0.002;). Late-onset myopes also demonstrated lower negative fusional vergence at distance (break: 7.0 ± 5.5 vs 10.0 ± 4.0 PD, p = 0.002; recovery: 6.0 ± 5.5 vs 8.0 ± 4.0 PD, p = 0.005;) and positive fusional vergence at distance (break: 9.0 ± 8.0 vs 12.0 ± 11.0 PD, p = 0.018; recovery: 7.0 ± 8.0 vs 10.0 ± 11.0 PD, p = 0.024). Other parameters showed no significant difference between EOM and LOM.

This study concluded that late-onset myopic individuals have reduced accommodative facility and lower negative and positive fusional vergence for distance compared to early-onset myopic individuals. These findings indicate that the age of myopia onset may influence visual performance, and the consideration of its characteristics of onset should be included in clinical evaluation and treatment.

• Myopic individuals often exhibit altered accommodative and vergence functions compared to emmetropes.

• Accommodation and vergence dysfunctions have been widely studied in children, but limited data exist comparing adults with early and late-onset myopia.

•This study demonstrates that late-onset myopes have significantly reduced monocular and binocular accommodative facility compared to early-onset myopes.

• It reveals that late-onset myopic adults also show lower negative and positive fusional vergence at distance.

• These findings suggest that the age at which myopia develops may influence how the accommodative and vergence systems function in adulthood. Understanding these differences can help clinicians tailor management strategies.