Purpose To describe the occurrence of visual loss secondary to dispersion of cells deriving from an iris strand during pupil dilation in a 35-year-old woman. Observations A 35-year-old woman presented complaining of blurring in the Left Eye 15–30 minutes following breastfeeding at night hours. On clinical examination, the uncorrected visual acuity was 20/20 in both eyes and slit-lamp examination demonstrated cells in the anterior chamber (26–50 cells in field/3+ SUN working group grading) whereas the examination of the right eye was unremarkable. Dilated examination revealed a thin pigmented strand of iris in the Left Eye spanning from one edge of the iris to the other (1st to 8th h). This strand was connected at a single point to the anterior capsule of the lens and from the point of connection red blood cells flowed in a linear configuration that ended at the lower part of the anterior chamber. Conclusions and importance In this case report a patient with persistent pupillary membrane in the form of an individual iris strand connected to the anterior lens capsule presented with episodes of monocular vision loss. This occurred due to red blood cell dispersion from the iris strand during mesopic light conditions and pupil dilation while breastfeeding. To the best of our knowledge, this is the first report in the literature.