Sense of Sight Introduction
The sense of sight is unique to the five senses that the human being has and, perhaps, one of the most important. When we say that “an image is worth a thousand words”, it is because we live in a world where what we can see, interpret and identify in our environment is fundamental for us.
This visual information that we capture thanks to the sense of sight is because the eye is one of the most evolved organs that the human body has.
The Eye Receptor Organ
The eye is an organ that sits in the bony cavity of the skull, called the orbit. Its external part is made up of eyelashes, eyelids, and eyebrows that protect it by preventing substances from entering it and keeping it moist, clean, and lubricate.
Parts of the Eye
The visual system detects light stimuli (electromagnetic waves), distinguishing between two characteristics of light, its intensity and wavelength (colors). However, the morning, before reaching the retina, passes through the different parts of the eye: the cornea, the aqueous humor, the pupil, the crystalline or natural lens of the eye and the vitreous humor.
In addition, the retina contains two types of photoreceptor cells. The so-called rods (responsible for peripheral and night vision) and cones (are sensitive to the color of light).
How are Images Formed?
While light passes through the cornea and lens, an inverted, actual image forms on the retina through the pupil, this inversion occurs due to different densities of the areas that light passes through so that the upper light rays are project on the lower part of the retina and the lower ones on the upper part.
According to most theories, the optic nerve carries this stimulus to the cerebral cortex, where the interpretation of the message is made through a psychic-chemical process.
Sclera, or the white colour of our eyes, is a membrane formed by collagen that, in addition to protecting the eye, regulates the passage of light. This part of the eye are the muscles that move the eyeball and its front part continues with the cornea.
The cornea is a transparent, avascular tissue of the eye that consists of five layers: the epithelium, Bowman’s membrane, the stroma, Descemet’s membrane, and the endothelium.
The cornea or ocular surface. the cornea or ocular surface
Its two main functions are protecting the intraocular content and the refraction of light. It represents almost 80% of the total refractive power.
The choroid is a dark membrane between the sclera and the retina. Its primary mission is to nourish the retina through its numerous blood vessels.
The ciliary body comprises a circle of tissue that surrounds our eye’s natural lens, or crystalline lens. These are muscle fibers that help the lens maintain its shape. It is also responsible for secreting aqueous humour in the anterior eye segment—the pupil’s magnitude and the lens’s form change when the eye focuses on an object.
The pupil is the part of the eye, or black dot (hole) that we have in the iris, which contracts (miosis) and dilates ( mydriasis ) to regulate the passage of light that will finally reach the retina. In the dark, the pupil dilates to capture more light and, the opposite, when the environment is very bright.
The iris is the cultured circle around the pupil that allows the pupil to dilate. This eye has color thanks to cells with a pigment called melanin and melanocytes.
The retina, for its part, is in charge of receiving light stimuli through its receptor cells: rods (light intensity) and cones (colour). The fovea is the one that contains the cones, which is where the light beam from the visual axis arrives.
The retina’s role is fundamental for the sense of our sight since it will depend on how that image reaches the brain, interprets it and becomes the vision that we are going to see later.
The aqueous humour is a clear fluid between the cornea and the lens. Its function is to maintain the convex shape of the cornea by exerting pressure on it, keeping it curved outwards.
Crystalline or Lens
The lens is the natural lens that our eye has and that overtime loses elasticity and becomes cloudy, forming a cataract. It is in charge of regulating the focus, allowing greater or lesser sharpness, adapting its shape from more concave to more convex thanks to the ciliary muscles.
The vitreous humour is the jelly-like fluid found in the most eyeball. It maintains its round shape between the retina and the back of the lens.
The optic nerve is responsible for transferring signals and information from the eye to our brain to be processed by the visual cortex, the hypothalamus and the occipital lobe.
Primary Eye Care
The sense of sight and, therefore, the state of our eyes is essential for the performance of our tasks daily. However, being such a delicate and small organ, it is vitally important to give it the necessary care. At least a complete ophthalmological examination is require every year to rule out any pathology that may be associate with them.
But in addition, some of the main recommendations to follow are:
- Take care of your diet: through a diet rich in vitamins A and C, essential for sight, such as carrots, asparagus, apricots and nectarines, as well as dairy products.
- Keep our eyes hydrated: mainly if we are use to working for many hours in front of the computer or very dry or humid environments.
- Correct lighting: visual fatigue can be prevent with adequate lighting. This way, we avoid excessive effort when working or reading, especially in office environments.
- Wear sunglasses with filters for ultraviolet rays every month of the year.
- Learn to relax your eyes: specialists recommend focus change techniques.
- And, of course, go to the ophthalmologist regularly to prevent any problem.