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

Abstract Significance 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. Purpose This study aimed to assess and compare the accommodation and vergence parameters in early and late-onset myopic adults. Methods 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. Results 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. Conclusions 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.