Long‐term endurance of adaptive shifts in tonic accommodation

Publisher Website
Google Scholar
Abstract
After an 8 min inducing period of sustained focusing on a target at the near point (NP) of accommodation, tonic accommodation was monitored at 8 min intervals over a 48 min period in darkness. A laser optometer provided evidence for asymptotically increasing tonic levels. Accordingly, eyes closed in darkness (EC) was not a condition for the relaxation or dissipation of enhanced tonic levels. Furthermore, refixating the NP target for 6 min, 24 min after the initial focusing period, provided no significant enhancement of tonic accomodation over EC. On the other hand, focusing at far point (FP) or walking within a lighted hallway (WH) significantly reduced the tonic after-effect to pre-adaptative levels, but not transiently. Tonic-effects induced by NP focusing thus appear to be remarkably resistant either to long-term attenuation or enhancement. A model based on the decay of accumulated sympathetic and parasympathetic neurotransmitters was developed to account for the contrasting fact that focusing at near targets tends to yeild complete decay of tonic after-effects.

This publication has 15 references indexed in Scilit: