Consensual pupillary light response in the red-eared slider turtle (Trachemys scripta elegans)

Purpose of this study was to determine if the turtle has a consensual pupillary light response (cPLR), and if so, to compare it to its direct pupillary light response (dPLR) One eye was illuminated with different intensities of light over a four log range while keeping the other eye in darkness. In the eye directly illuminated, pupil diameter was reduced by as much as similar to 31% In the eye not stimulated by light, pupil diameter was also reduced but less to similar to 11%. When compared to the directly illuminated eye, this generated a ratio, cPLR-dPLR, equal to 0 35. Ratio of slopes for log/linear fits to plots of pupil changes versus retinal irradiance for non-illuminated (-1 27) to illuminated (-3.94) eyes closely matched at 0.32. cPLR had time constants ranging from 0.60 to 1.20 min: however, they were comparable and not statistically different from those of the dPLR. which ranged from 1.41 to 2 00 min. Application of mydriatic drugs to the directly illuminated eye also supported presence of a cPLR. Drugs reduced pupil constriction by similar to 9% for the dPLR and slowed its time constant to 9.58 min while simultaneous enhancing constriction by similar to 6% for the cPLR. Time constant for the cPLR at 1.75 min, however. was not changed Results support that turtle possesses a cPLR although less strong than its dPLR. (C) 2010 Elsevier Ltd All rights reserved