Mouse Pupil (image) Johns Hopkins Medicine Share Print E-Mail Caption Mouse sphincter muscle fibers (green), with melanopsin-containing fibers shown in red. The dotted line marks the boundary between the pupil and sphincter. Credit Johns Hopkins Medicine Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.