Women Have Bigger Pupils Than Men

Posted on April 26, 2012

Scientists did a study on emmetropic eyes. An emmetropic eye is a normal, non-pathological eye. Healthy eyes have not been studied in as much detail as myopic and hypermetropic eyes. The researchers say their study found healthy emmetropic women have a wider pupil diameter than men.

The results of the study were published here in the journal Surgical and Radiologic Anatomy. The study shows the values by gender for the central corneal thickness, minimum total corneal thickness, white to white distance and pupil diameter in a sample of 379 emmetropic subjects. Although the research states that there are no big differences between most of the parameters analyzed, healthy emmetropic women do have a wider pupil diameter than men.

Juan Alberto Sanchis-Gimeno, researcher at the University of Valencia and lead author of the study, says, "It is the first study that analyses these anatomical indexes in a large sample of healthy emmetropic subjects. It will be necessary to investigate as to whether there are differences in the anatomical indexes studied between emmetropic, myopic and hypermetropic eyes, and between populations of different ethnic origin."

The researchers also provided this explanation of how the human eye works:

Light penetrates through the pupil, crosses the crystalline lens and is projected onto the retina, where the photoreceptor cells turn it into nerve impulses, and it is transferred through the optic nerve to the brain. Rays of light should refract so that they can penetrate the eye and can be focused on the retina. Most of the refraction occurs in the cornea, which has a fixed curvature.

The pupil is a dilatable and contractile opening that regulates the amount of light that reaches the retina. The size of the pupil is controlled by two muscles: the pupillary sphincter, which closes it, and the pupillary dilator, which opens it. Its diameter is between 3 and 4.5 millimetres in the human eye, although in the dark it could reach up to between 5 and 9 millimetres.

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