|Title||The relationship between clinical measures of proximal convergence|
|Author, Co-Author||Emmanuel Owusu, Aaron Zimmerman, Nicklaus Fogt|
Purpose: Proximal convergence is said to be driven cognitively by an “awareness of nearness”. At least two methods have been proposed to assess proximal vergence clinically, and vergence facility may be driven largely by proximal inputs. The purpose of this study was to compare the results from two clinical methods for measuring proximal convergence, and to determine whether these are correlated with vergence facility.
Methods: 38 individuals aged 22 to 40 years underwent a battery of near binocular clinical tests. These tests included distance (6m) and near (40cm) heterophorias (cover test), near heterophoria through +1.00D and +2.50D lenses, base-in and base-out vergence ranges, and near vergence facility. The different near heterophoria tests were randomized and separated in time by 5 minutes. Proximal convergence was calculated using the difference between the Gradient and Calculated AC/As (ACA method), and the change in vergence calculated from the distance heterophoria and the near heterophoria through +2.50D lenses (+2.50D method). A PD of 64mm was used in all calculations.
Results: The average proximal values obtained by the two methods were 1.87Âż ± 4.86 and 4.18Âż ± 3.91 for the ACA and +2.50 methods respectively. The two proximal vergence measures were highly correlated (Spearman correlation: r = +0.81, p < 0.0001) with good agreement between the two tests (Bland-Altman: 95% LoA = 2.83 Âż) However, the mean proximal value using the +2.50D method tended to be larger than that obtained using the ACA method (Bland-Altman: bias = 2.3Δ). There was no correlation between either proximal measure and vergence facility (p > 0.05).
Conclusion: While the two clinical methods for measuring proximal vergence are correlated, proximal measures obtained by the +2.50D method tended to be higher than those obtained by the ACA method. Vergence facility does not correlate with steady-state proximal measures
|Affiliation of Co-Authors||The Ohio State University College of Optometry, The Ohio State University College of Optometry|