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The dynamic pupil: How age impacts our ability to see the world in different light

The pupil is the structure that allows light to enter our eye and reach the retina, making it an essential aspect of our eye regarding visual acuity. When we're in a dimly lit room, the pupil can expand up to eight millimeters to allow light to reach the photoreceptors on the back of the eye. Conversely, in the brightest light, the pupil can constrict to a mere two millimeters, preventing overexposure of the sensitive retinal cells.

Often in daily life we alternate between various shades of dim and bright. A few examples include driving down the street at night while an oncoming car's headlight approach, walking outside on a bright sunny day, or opening your laptop to start your workday. In a young eye, the pupil is able to adjust to varying sizes with ease, accommodating our dynamic lifestyles. However, what happens to the pupil's ability to make these necessary changes as we age?

Researchers at the Max Planck Institue for Biological Cybernetics and the University of Basel recently studied this exact question. The pupil size of people ages 18-87 were measured under differing lighting including artificial, natural, and LED light in both indoor and outdoor conditions. Results showed pupil width declining approximately 0.4 millimeters per decade. This means younger participants had a greater ability to adjust to altered lighting conditions as opposed to older participants.

So, what does this mean for the ageing eye? Unfortunately, our pupil's ability to adjust to various lighting conditions has real impacts on the quality of our everyday life. For example, overexposure to a car's headlight while driving could create dangerous illusions that can impact driving. Walking from a dark room to light room, or vice versa, could distort an older person's ability to see clearly, resulting in increased injuries or falls. Additionally, circadian rhythms can be impacted based on how much light is reaching the eye, desynchronizing people with their environments and disrupting schedules.

Although there is no viable treatment yet, future research will hopefully give insight into how to effectively deal with the pupil's declined ability as we age and improve this troubling phenomenon.

Source: Ophthalmology News Medical Xpress

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