(Originais Teachy 2024) - Question Medium of Sciences

To understand how light is captured and processed by the human eye, let's follow the path that light takes from the moment it enters the eye until the image is formed on the retina. The light first passes through the cornea, which is the transparent front part of the eye. The cornea helps focus the light in the eye and protects the internal structures. Next, the light passes through the pupil, which is the opening in the center of the iris. The iris is the colored part of the eye and can contract or dilate to control the amount of light entering the eye, thus regulating the intensity of light reaching the retina. After passing through the pupil, light travels through the lens, which is a flexible lens that adjusts its shape to help focus light on the retina. The retina contains light-sensitive cells that convert light energy into electrical signals, which are then transmitted to the brain by the optic nerve. The brain interprets these signals as the image we see. Now, let's analyze the specific role of some eye structures: The cornea is responsible for the initial light focus and provides about two-thirds of the eye's focusing power. The lens adjusts its shape to focus light from near or far, allowing vision at different distances, a process known as accommodation. The iris acts as a kind of 'diaphragm' of a camera, controlling the pupil's aperture and, consequently, the amount of light entering the eye. Now, the importance of adequate lighting for visual health is significant. Inadequate light can strain the eye to work harder to see clearly, which can lead to visual fatigue and headaches. On the other hand, excessive light can cause glare and discomfort. Changes in the structure or function of the eye can result in different visual conditions. For example, in myopia, the eye can focus light in front of the retina instead of on the retina itself, resulting in difficulty seeing distant objects clearly. In hyperopia, the opposite occurs, with light focused behind the retina, leading to difficulties in seeing close objects. Presbyopia is an age-related condition in which the lens loses some of its accommodation capacity, making reading and viewing close objects more difficult. These conditions can be corrected with the use of glasses, contact lenses, or refractive surgeries, which alter how light is focused in the eye, allowing the image to be correctly formed on the retina.