Accommodation refers to the ability of the eye to focus in order to obtain a clear image. Its disorders cause a constant feeling of vagueness, as in cases of hyperopia or myopia.

Reminder of the light path in the eye

To understand the role of accommodation in our eye, we must briefly return to how it works. An eye is used above all to capture light: it comes from the external environment, either from the photons sent by our Sun, or those reflected on each of the objects that enter us. In order for us to see, we need a photon sensor. That’s good, the human body has not one but two: the eyes. Carpet at the bottom of each of them is the retina, a nerve tissue directly connected to the brain using the optic nerve. When a photon reaches the retina, it will activate its sensors, cones and rods, which will therefore transmit this visual information. However, if the light only entered the eye to reach the retina, it would be far too weak and scattered to remove any information. In addition, we would only see what is directly in front of us. Thanks to thousands of years of evolution, the eye has become more complex until it reaches its current version, capable of focusing rays of light at a point. This is done in two stages, first through the outside of the eye, the cornea, which allows rays coming from all directions to enter the eye in straight parallel lines. Then at crystalline, who will carry out theaccommodation.

How it works ?

Le crystalline is a small part of the eye located just behind theiris and the pupil. It is a small lens, devoid of blood vessels, and attached with fibers. Its role is vital in the perception of what surrounds us. Thanks to its elasticity, the lens can change its curvature. Thanks to this capacity, it can therefore modify the path of the light rays passing through it. Thus, it is he who realizes theaccommodation, in the sense that it will help focus the rays of the eye towards the most sensitive point of the retina, which is commonly called the macula. To be more precise, the role of the lens is above all to focus the rays coming from the objects which are close to us. Without the lens, we could still observe distant bodies thanks to the initial deflection of the cornea. This design of the eye was of interest to our ancestors, hunters and prey living in a dangerous environment, in which it was vital to spot targets in the distance.

Accommodation consists of focusing light rays on a specific point in the eye. Sometimes this focus is not sufficient, or on the contrary is too strong. In these two scenarios, we then speak of hyperopia or myopia. Conversely, normal vision is defined by a emmetropia.

Hyperopia, when accommodation is not sufficient

If the lens is not able to accommodate enough, that is to say to contract to increase the refractive power of its lens, then we speak of an eye hyperopic. In this case, the person will succeed in observing distant objects (and again, by contracting their crystalline lens!) But as soon as the object of their vision is closer, of the order of a meter or a centimeter, the image will be more cloudy. The cause lies in the bad deviation of the light rays: instead of focusing in a point, they form a spot at the back of the larger eye, the fault of the lens which cannot cross the rays on the macula. The light sensors are therefore inundated with information in all directions, the same sensor will receive different rays from different origins. The brain will be able to adjust the image it receives a little, to produce a feeling of blur.

Myopia, when the accommodation is too strong

The opposite ofhyperopia is the myopia, arguably the most well-known affliction of the eye. In this case, the accommodation is too early, and all the rays that enter the eye will be deflected too much. In this case, the eye will this time be able to see up close, since this vision requires a clear accommodation and therefore to contract the lens, but will see blurry everything that is in the distance. Short-sighted people therefore do not have to make any accommodation.

Which audiences can be reached?

Hyperopia like myopia can be an innate deformation of the eye, and therefore trigger in children during their development, or during puberty for myopia. On the other hand, with age, almost everyone develops some hyperopia. Near vision becomes cloudy, due to a gradual hardening of the lens. Less flexible and elastic than in his youth, accommodation thus becomes more and more difficult. It is for this reason that the oldest among us get into the habit of “reaching out” to see a newspaper better!

Natural and artificial solutions

Natural

Unfortunately, there is no natural solution to these disorders, as they are deeply linked to our personal development.

artificiel

The most common solution remains the wearing of prescription glasses, capable of offering a “rescue lens” to our eyes. The glasses will here take care of deflecting the light rays towards the cornea, to see better near or far depending on the individual.

Recently, the surgical placement of intraocular lenses, directly placed in the cornea, allows myopic and hyperopic people to have almost normal vision on a daily basis.