Effects of Orthoptic Treatment on the CA/C and AC/A Ratios in Convergence Insufficiency

Abstract

Despite improvements in the fast and slow vergence mechanisms no change was found in the AC/A and CA/C ratios after orthoptic treatment in CI subjects. This finding is unexpected in light of the present understanding of CI, and an alternative theory is proposed.

Effect of Vergence Adaptation and Positive Fusional Vergence Training on Oculomotor Parameters

“…However, whether this improved vergence adaptability reducing the CA response gets reflected in the static CA/C ratio is in question. Findings of Brautaset & Jennings (2006) show no change in the CA/C ratio following vergence training in convergence insufficiency cases. Increase in the BO fusional range following training could be due to the improved vergence adaptation reducing the CA response.…”

“…From the current models, this improved ability of the vergence system to adapt following fusional vergence training is predicted to modify the cross-link ratios. Although a few studies showed the possibility of the change in the ratios (Flom, 1959;Manas, 1958;Hung et al, 1986), a recent study did not show a significant alteration with training (Brautaset & Jennings., 2006).…”

“…As noted previously, defective slow fusional vergence mechanism produces asthenopic symptoms. Literature evidence suggests that the slow fusional vergence mechanism is amenable to training to restore normalcy resulting in alleviation of near visual symptoms (Brautaset & Jennings., 2006). The ability of the oculomotor system to 20 adapt to prism induced heterophoria was evaluated before and after orthoptic treatment in a group of convergence insufficiency subjects.…”

“…Universally, positive fusional vergence training has been shown to improve near vision symptoms resulting in enhanced positive fusional amplitude (Cooper et al, 1983;Brautaset & Jennings., 2006). No significant (p>0.05) phoria adaptation or reduction in the CA response between 5, 10 and 15 minutes of viewing showing no effect of duration.…”

Effect of oculomotor rehabilitation on vergence responsivity in mild traumatic brain injury

“…This value would be expected to change only if the cross-link ratio (response accommodative convergence/accommodation) changed [71]. However, past studies have reported constancy of this cross-link following vergence training in both visually nondisabled subjects [64,72] and in symptomatic individuals manifesting binocular vision dysfunction [73].…”