DARK FOCUS OF ACCOMMODATION AND VERGENCE POSTURE

We evaluated the dark focus of accommodation and vergence posture in 20 boys and girls, 10 with and 10 without accommodative esotropia, before and after they wore glasses for at least 1 month. Refractive error was measured by Nidek Autorefractometer AR1600. We used two definitions of the dark focus, DFcus (Non-Cyclo R) and DFcus (Cyclo R). DFcus (Non-Cyclo R) = Dark R - Non-Cyclo R. DFcus (Cyclo R) = Dark R - Cyclo R. (Dark R: refractive state in the dark; Non-Cyclo R: non-cycloplegic refractive error, Cyclo R: cycloplegic refractive error.) Vergence posture was measured by prism cover test during distance fixation while uncorrected. DFcus (Cyclo R) was significantly greater in esotropic subjects than in non-esotropic subjects, although DFcus (Non-Cyclo R) did not differ significantly. A significant hyperopic shift in Dark R was observed after wearing glasses. DFcus (Cyclo R) was significantly decreased after wearing glasses, suggesting that wearing glasses is an important variable of the dark focus. Unlike the dark focus, the vergence posture did not change in either group after wearing glasses. The dissociation of the dark focus from vergence posture seems to be inconsistent with previous findings. It is postulated that change in dark vergence after wearing glasses is responsible for the results.