Horner syndrome in children can also be a sign of a serious underlying condition, a tumour called neuroblastoma. In some children, the iris colour can also be lighter on the affected side, or the child may have a blue iris on the affected side and a brown iris on the other side.

This condition is called ‘congenital Horner syndrome’. The distance between upper and lower lid is also smaller than on the other side. When they are damaged, the pupil on the affected side is smaller, which is particularly noticeable in a dimly lit room. The same nerve fibres also travel to the eyelids. Pulling on the baby’s head during birth can damage the delicate nerve fibres in the neck which send signals to the muscle in the iris which dilates the pupil. Some people have a difference in pupil size from birth, particularly if forceps were used during delivery. This difference in pupil size is not linked with any underlying condition. This difference is the same, regardless of whether they are in a dark room or in bright light. Many people have a difference of up to 1mm between the two pupils. The pupil also becomes smaller when we focus on something close-up, thereby helping the eye to focus an image onto the back of the eye. In bright light, the pupils become smaller so the light doesn’t dazzle us. In a dark room, the pupils become bigger to let more light in, so we can still see. By changing the pupil size, light more or less enters the eye. The iris is a ring-shaped muscle - more precisely, it contains two muscles, one to make the pupil bigger, and the other to make the pupil smaller. The pupil is the ‘hole’ in the centre of the iris, the blue/brown part at the front of the eye. Is this something to be concerned about if you notice it in your child?ĭr Annegret Dahlmann-Noor, director of the children’s eye service at Moorfields Eye Hospital, London, discusses this issue in this informative article for parents and carers.

However, it’s possible that they are different sizes. The results suggest a population difference in normal pupil size influencing color observation which was exposed by the dress.It goes without saying that our pupils are an incredibly useful part of our eyes because of how they automatically adjust to light, allowing us to adapt to our environment in an instant. In a third experiment, to check whether increase in retinal illuminance will trigger a change in color in the w/g group, 6 participants were administered dilation drops that increased the pupil size by 3–4 mm, but the participants did not report a switch. A standard infinity focus experiment was then conducted on 18 participants from each group to check if there is bimodality in the population, and we found a statistically significant difference ( w / g < b / b, p - value = 0.0132). Our results showed that the w/g and switch groups had significantly lower pupil size than the b/b group ( w / g < b / b, p - value = 0.0086), suggesting a possible difference in light perception influencing pupil size. We looked at pupil size differences in a sample population of 53 individuals from these two groups and a group that switched from w/g to b/b. The fundamental question that arises from the color conundrum of #thedress is “What are the phenomena that underlie the individual differences in the reported colors when all other conditions like light and device for the display are identical?” A survey of 384 participants showed near-equal distribution into blue/black (b/b) and white/gold (w/g) groups.

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Regular pupil size