Cataract Operation: How Does the Brain Assimilate Visual Changes?

The operation of cataracts, although it is a simple surgery, involves structural changes in the eye that force the brain to process the sense of sight in a different way. Learn more about this re-adaptation process.

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Although cataracts have been considered as the leading cause of blindness worldwide, there is a simple surgical intervention that eliminates the problem and restores vision in affected people. However, this cataract operation involves a series of complexities that are interesting to know.

Eye cataracts are a fairly common visual problem. In fact, according to various studies, more than 60% of the world population from 75 years old will develop some type of cataract. Therefore, cataracts are perceived as a threat as they mature.

In addition, the symptoms of this ocular pathology are part of popular knowledge: people who suffer from them suffer a progressive impairment of the functionality of their vision that can become disabling.

People suffering from this problem report glare, poor visual acuity, distortion of the forms, and a whole series of visual limitations that, if not treated surgically, can lead to blindness.

What is a cataract?

What is clinically understood as ocular cataract is nothing more than the opacification of the lens. The lens is the transparent lens inherent to the eye under which it can focus, which is behind the iris and the pupil.

When cataracts appear, this lens becomes progressively cloudy; due to an accumulation of epithelial cells that change color for pathological reasons.

These cells proliferate and impede the normal passage of light through the lens, given that, due to their translucent features and brown tone, they represent a physical barrier to this step. It is as if the world were observed through a fogged windshield. In this way, the vision is affected.

“The only thing worse than not having sight is not having vision”.

-Helen Adams Keller-

There is another clinical picture: secondary cataracts. These are a pathological ocular condition very similar to the previous one. It arises after the surgical removal of the cataract and is due to the remains of that darkened epithelium that have remained dormant and have proliferated again, dulling the structures of the eye.

The resulting symptomatology is similar to the one that causes the primary cataract, but the ocular lesion is milder and less extensive. Thus, all that is required for its correction is the elimination of that layer of tissue by laser. It is a quick, painless and risk-free intervention.

Around 50% of people who have received a cataract operation – technically called a phacoectomy – will develop a secondary cataract within a few months.

As a consequence of the formation of the cataract, in a progressive manner -and more or less quickly depending on the type of cataract involved-, the affected person will experience the following visual discomforts:

  • Decreased visual acuity.
  • Photophobia and glare.
  • Alteration of the chromatic perception – the colors lose intensity and melt.
  • Alteration of the perception of the surrounding space.
  • And, in general, any visual modification that may arise as a result of the light reflected by the objects can not penetrate the eye or if it does so, in a darkened and distorted manner.

It is because of this progressive and disabling nature – since sight is possibly the most important of the senses – that symptoms can go unnoticed at the beginning or interpreted as symptoms of something else, until the person presents a visual decrease such that it makes obvious that There is an underlying problem.

In addition, as a confounder, while the cataract is in the process of extension, the different degrees of dilation or contraction of the pupil may mask or exacerbate the symptoms.

Thus, if the pupil is very dilated, much of the light that enters the eye will “dodge” the cataract and the vision will be closer to normal. Now, if it is very contracted -in low light environments-, the light will be at the cataract in its path and the vision will be very impoverished.

Causes of ocular cataract

Of all the causes, the most widely accepted is the normal aging process of the body. In this sense, developing cataracts would be a logical consequence of reaching advanced ages, although it is well

It is not the case that only susceptible people will develop them.

In a certain number of cases, the cause is genetic and the problem is called a congenital cataract. Therefore, there is a small percentage of babies born with this deficit. For our peace of mind, surgical correction is indicated at that age and the results are usually good.

In addition to the above, and leaving aside those paintings of unknown or unaffiliated origin (idiopathic cataracts), three other causes are posited as the possible origin of this oculopathy:

  • A high degree of myopia – which influences ocular morphology.
  • Ocular trauma.
  • Long-term steroid-based drug treatments, especially corticosteroids -as occurs with chronic cortisone intake regimens in rheumatism or antiallergics in people with allergies-.

Whatever the cause of this problem, the result impacts in such a way the daily performance of the person suffering from cataracts usually brings with it a whole constellation of psychological discomforts, among which stress anxiety and depression.

“To go ahead of others, you need to see more than them.”

-Josep Pla-

What is the operation of cataracts?

Considered as a simple and safe surgery and given its ambulatory nature, this is a type of surgery that should not scare us. Hundreds of them are practiced every day around the world and the success rate is very high.

In summary, the intervention consists in the physical extraction of the cataract through instruments that are inserted in the anterior part of the eyeball.

Because the tissue to be removed is contiguous with the healthy ocular tissue – and in particular, the crystalline lens – it is necessary to completely or partially remove the lens. In this way, the eye remains aphakic or without its own focusing ability. Remember that it was the lens, our natural lens, that allowed such focus and, therefore, the accommodation of the view.

To replace this structural and functional lack, an intraocular lens (IOL) is implanted in the space previously occupied by the lens, which allows the focusing of the images, with characteristics that complement those of the IOL of the contralateral eye.

This is because cataracts are almost always bilateral affections, that is, they occur in both eyes at the same time; to, as a whole, form light projections focused at the level of the retina, which will later give rise to visual representation, at the brain level.

But as is well known, in many cases the artificial can hardly supply the natural. Therefore, IOLs, being artificial lenses that also remain fixed and do not have the ability of the lens to modify their focus and blur, profoundly alter and at various levels, the way in which the visual system works.

And the person in charge of constituting a final perceptual image, which is none other than the brain, must readjust to this new way of receiving the light that will be transformed into images. For this reason, it can take up to a month for the people involved to complete this readjustment. Meanwhile, his vision is more vague and uncomfortable than before.

It is thanks to the cerebral plasticity, to the capacity of our neural systems to reorganize and adapt and recover lost functionalities, that this process of readjustment culminates successfully and again enjoy a good visual capacity.

“Vision is the art of seeing invisible things.”

-Jonathan Swift-

We enumerate a series of components of the visual process that can be altered after the operation of cataracts. These are alterations that the brain will learn to correct to achieve a visual system as effective as possible.

Changes that the brain must learn to integrate

Permanent focus and focus time override

Since IOLs only focus and can not vary the degree of such focus, from the moment you have your eyes open you can see in a focused way at any distance, near or far; without having to force the eyesight, or allow a few thousandths of a second to pass before the gaze goes out of focus and focuses on another.

This situation causes sensorial strangeness at first, but over time this distortion normalizes.

Need more light to see properly

While when you suffer from cataracts you tend to avoid highly luminous spaces, since they dilate the pupil and cause visual discomfort; after cataract surgery, that is, the implantation of IOLs, the more enlightened the environment is, the better the focus and vision will be produced.

And this occurs mainly because the artificial lens does not cover the full diameter of the pupil when it is very dilated; so if it is, part of the light enters the eye from the outside of the IOL, causing double or blurred vision and halos.

Need for physical orientation

Since IOLs focus in a fixed and constant way, in order to adjust our vision to objects that are at a specific distance and with a position relative to us, we will not have the ability to adapt the lens, but we will be ourselves, moving around and By placing the head at different angles, we find the point of greatest visual acuity for that particular object.

Presbyopia residual

Generally, IOLs are more specialized in focusing medium and long distances and are less efficient for short ones. Therefore, it is not uncommon to need magnifying glasses after cataract surgery.

Visual changes to physical efforts

IOLs have a lower degree of fixation within the eye than did the crystallins in their natural state.

Therefore, marked variations in the level of intraocular tension – the pressure exerted by liquid substances within the eye – that occur as a result of physical efforts, will produce slight transient displacements of the lens that will cause distortions of the perceived image.

Tendency to eye irritation

The ocular or conjunctive epithelium, after having suffered ruptures due to surgical intervention, develops microscopic scars that will increase the degree of sensitivity of the eye to environmental irritants, such as smoke, dust, etc.

Different visual convergence

A complete final image is formed by merging two images of the same object, one from each eye.

Since IOLs are positioned somewhat differently from the original lenses, the exact point of the retina to which they project light is also different.

In this way, the two images to be fused to form a final image will come from different places, and the brain will relearn to effectively carry out that fusion.

Distortion of the visual plane and the sizes of the objects

IOLs implanted after the cataract operation produce, in general, a more flat perception of the visual field, with which the objects of initiation are perceived less rounded.

In addition, they tend to dwarf the image they focus on, so that the objects of the world are perceived as smaller than before. To all this, the brain must get used to avoid that, as a consequence, visual discomfort is generated.

Presence of visual artifacts

By artifact in Medicine it is understood the presence of any element that should not naturally be in a certain place. In the area of ​​ophthalmology, a visual artifact would be an element that is presented in the context of the functioning of the visual system and that would not have to appear.

In particular, bearers of IOLs can, under certain circumstances, perceive some components of the lens itself or even the movement of it.

This is uncomfortable and disconcerting and, at times, it reduces attentional resources to be so striking. Again, getting used to the new visual situation, thanks to neuroplasticity, will make this a minor problem.

Whether you have had cataracts or if you are suffering from them or even if there is the possibility of developing them at some point, these are some important points that, besides being interesting in themselves, it is useful to know to explain some of the results of the operation of cataracts , and especially for the personal preparation prior to the intervention.