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Voluntarily Adjusting Pupil Size in Human seems Scientifically Impossible

The central opening of the iris on the inside of our eye is called the pupil. A black hole that allows light to strike the retina. The black appearance of the pupil is caused by the light rays entering the pupil that is either absorbed by the tissues inside directly from the eye or absorbed after diffuse reflections within the eye that are mostly exiting the narrow pupil.

The pupil gets narrower in light and wider in the dark. This response is a reflex that is controlled by the nervous system in regards to when light is detected, the response goes straight to the spinal cord and the response is immediately signaled back through the motor neurons. To control voluntarily over the autonomic nervous system is vigorous beyond the reach of mostly bare humans. But still, in Germany, a 23-year-old man (known as D.W.) appears to have acquired this extraordinary ability.

"This man can dilate and constrict his pupil at will, thus achieving something that has been deemed scientifically impossible" according to the International Journal of Psychophysiology in their report case.

The size of the pupil normally changes in response to fluctuation in light that occurs automatically or as a result of activation. This process cannot be manipulated through thinking as with other reflex actions, this is absolutely independent of conscious control.

The Discussion of Case Report conducted by the International Journal of Psychophysiology stated that: "In this study, we present evidence from a case that challenges the broad agreement among pupillometric researchers that voluntary changes in pupil size cannot be induced directly by mere volitional effort. So far, in a number of experiments, we have tested possible indirect strategies subserving changes in pupil size. Quantitative pupillometry revealed that D.W. was able to constrict his pupil on command to the extent of −2.4 mm and to dilate his pupil on command to the extent of +0.8 mm (both measures relative to baseline).

Pupillometric assessments demonstrated relatively mild effects of accommodation on pupil size as induced by the distances of 30 cm and 90 cm relative to 60 cm. While accommodation could in principle account to some extent for constrictions, particularly sudden, stark dilations should not be produced this way (e.g., Kasthurirangan and Glasser, 2005). Combining eye-tracking results with optometric testing demonstrated that voluntary constriction was associated with a change in accommodation, whereas voluntary dilation was not, or only very mildly associated with a change in accommodation, which is in line with assumptions on the effects of the near response.

Additionally, we could demonstrate that the near point could be shifted closer to the active eye at maximal accommodation when D.W. was voluntarily constricting his pupil. Such an increase in visual acuity can be explained only by activating the pupillary musculature because accommodation should be maxed out at the near point. Furthermore, D.W. could also change pupil sizes with both eyes open without considerable changes in vergence. For the monocularly tested eyes, no substantial inward/outward rotation of the eyes could be found during voluntary changes relative to the other conditions".

Although the authors of this study reported that D.W. is capable of expanding his pupils up to 0.8 millimeters and contract them by 2.4 millimeters by demand and can do by "feeling and activating the pupillary musculatice directly"- author Christoph Strauched said to Live Science.

"D.W.'s ability is astonishing, as it was thought to be impossible" he added.

The researchers explained in their write-up that D.W. first learned his unusual ability when he was 16. He was trying to relax his eyeball at that time after long hours of a game session when his friend noticed the pupil on his left eye became smaller than that of his right. From then on, D.W. has honed his technique for seven years.

Some people can alter their pupil size through "indirect methods", according to the study authors. Such as thinking about light and dark. However, in his case, after conducting a series of tests, he implements none of these, instead, he is able to directly control the sphincter muscle in his eyes.

For instance, to produce an expansion of the pupil, intense mental concentration is required. Nevertheless, the most strenuous mental tasks only produce a maximum dilation of 0.5 millimeters in the previous research. But D.W. is capable of expanding his pupils more than this and amazingly demonstrated his ability with ease while speaking with the researchers.

Another indirect method by which pupil size can be manipulated is by shifting focus between near and far objects known as the accommodation process. So far, eye tracking tests show that D.W. does not use this trick to adjust his ocular openings. Surprisingly, he can even constrict his pupils beyond the maximum degree when focusing on near objects that allows him to improve his visual acuity and decrease the distance at which he is able to focus sharply.

D.W.'s brain was scanned by using functional Magnetic Resonance Imaging or fMRI while he was adjusting his pupils. The study authors distinguished an activity increased in the prefrontal cortex and the adjacent motor areas that indicate voluntary muscle movement.

Although this is the first recorded example of an individual that can deliberately control this certain reflex, Strauch stated that he has been reached out by a number of people who claimed to possess this kind of unique ability.

He is hoping to study the phenomenon to these people for better understanding.


About the Writers:

Marie Rosales is a professional in the field of security. She is currently a full-time Content Writer and AVCreativity Studio's Virtual Assistant. She enjoys cooking and reading. She spends most of her spare time with her children.

Pamela Elizabeth, Editor-in-Chief at AVCreativity Studio. Earned a Bachelor’s Degree of Secondary Education Major in English. She loves going on little adventures alongside reading good books. She is enthusiastic about her work and ensures that her clients receive the finest service possible.

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