Myopia and Hyperopia

What are myopia and hyperopia?

Myopia is a refractive defect that appears as a consequence of the elongation of the eyeball. This elongation of the eyeball gives the eye the characteristics of a magnifying glass, that is:

  • ‍Very poor distance vision which starts to become apparent from a few metres away.
  • Good near vision, which leads to a tendency to move closer to objects.

Hyperopia is just the opposite. The eyeball is smaller than usual, causing it to focus behind the retina, which leads to poor near vision and good distance vision.

Astigmatism is a refractive error whereby, regardless of the length of the eye, the image refracted by the cornea is in an oblique plane with respect to the retinal plane due to an anatomical alteration of the cornea. This causes a distortion of the images.

Correction of refractive defects

Correction of the refractive defects

Both hyperopia and myopia, together with astigmatism, are what are known as refractive defects. There are basically two surgical techniques to eliminate them:

  • ‍Collamer lens.
  • Laser (LASIK or PRK).

Both techniques are completely safe and very fast. So much so that on the same day of the operation the patient can go home on their own, and the following day they can start to lead a practically normal life, without the need to wear glasses or contact lenses of any kind. The choice of one surgery or another depends mainly on the anatomical characteristics of the eye, which will be determined by a battery of diagnostic tests at our surgery.

Correction by collamer lenses

Collagen lenses for the correction of refractive defects have been around for more than 20 years. It is one of the fastest, most reliable and safest techniques. At our centre we are pioneers in the implantation of this type of lens; it is not in vain that Dr. Fernando Castanera was the first surgeon to implant collamera lenses in the country.

What is a collamer lens?

We could say that it is a kind of contact lens, but instead of being placed on the cornea, it is permanently implanted inside the eye.

One of its main characteristics is that it is very flexible. This allows it to be folded, or rather rolled up, so that it can be inserted into the eye through a minimal incision. It is also capable of correcting very high prescriptions, making it a great choice for patients with very high refractive errors.

Why choose this kind of intervention?

The main advantage of the collagen lens is that it is a fully reversible technique, i.e. no structure is affected by its implantation, so that if it were necessary to remove or replace it, the eye would remain intact.

What tests are performed during the pre-operative period?

A whole battery of diagnostic tests are carried out to determine the patient’s prescription and to find out exactly what type of lens and what power it should have. It should be borne in mind that this type of lens, in most cases, is ordered and manufactured specifically for each individual patient.

But of all the tests, one of the most important is biometry. This is a test in which we can measure exactly the space between the iris and the crystalline lens. This measurement is extremely important because it will be decisive in determining whether or not the space is sufficient to accommodate the collamer lens that will be placed in this space.

What if I am not a candidate for collagen lens implantation?

A possible alternative could be laser surgery (LASIK or PRK) or continuing to wear glasses or contact lenses. In any case, in these cases it is always best to seek the opinion of an ophthalmologist who will surely be able to offer you the best alternative.

What does the intervention involve?

As mentioned above, the lens can be folded back on itself. This allows it to be inserted into the eye with a minimal incision (2.2mm) and unfolded inside the eye.

The lens is positioned behind the iris and is held in place by the four haptics at the edges.

How long does the procedure last?

The procedure takes no more than 10 minutes per eye as no internal structures of the eye have to be altered, the lens simply has to be positioned properly behind the iris.

Will I feel any pain?

No, you will not feel any pain. The surgery is performed under local anaesthesia and light sedation, which allows the patient to be totally relaxed, in a kind of sleep, and the eye is completely anaesthetised.

Can they put me completely to sleep so that I'm not aware of anything?

It is not possible, or rather not recommended, to perform the procedure with the patient completely asleep. This is because a certain amount of cooperation is required from the patient, who has to look at a light. This will allow the eye to be fixed on a point so that the lens can be centred and positioned comfortably and quickly. Otherwise, the surgery could take longer than expected and the lens could be incorrectly positioned.

When will I start to see properly?

This is one of the best parts of having this surgical technique, as patients begin to see more than satisfactorily as soon as the operation is over. Many of them are still in the operating theatre and are surprised at how well they can see without glasses.

‍In any case, it should be borne in mind that full recovery may take a few days, no more than a week.

Laser correction (LASIK or PRK)

What does the laser technique involve?

This technique consists of altering the anatomical characteristics of the cornea by permanently modifying its curvature, and therefore its dioptric power. The remodelling is carried out in a very precise and controlled manner by vaporising the corneal tissue. Laser pulses polish the surface of the cornea with great precision until the refractive error is eliminated.

What is the difference between LASIK and PRK?

The difference between the two is that in LASIK, a thin lamella (150 microns) of the cornea is cut away so that the laser can be applied to the resulting surface. In the case of PRK, on the other hand, a very thin first layer (50 microns) of the cornea called the epithelium is removed and then the laser is applied.

The choice between one technique or the other is based solely on medical criteria.

How do I know if I can undergo laser surgery?

The suitability to be operated on or not using this technique responds solely and exclusively to medical criteria. These will be based on the results obtained in the diagnostic tests carried out during the preoperative period.

What tests are performed preoperatively?

Multiple tests are carried out, ranging from, obviously, knowing the exact prescription to be corrected, to the micrometric calculation of the thickness of the cornea. It is precisely this calculation that is one of the most decisive factors in determining whether or not you are a good candidate for the procedure. It should be borne in mind that, as we will explain below, the action of the laser on the cornea involves the removal of part of the corneal tissue and that the higher the prescription, the more corneal tissue needs to be removed. Therefore, it is essential to know whether our cornea is thick enough to withstand this subtraction. It should be noted that, if the tests indicate that we can go ahead with the operation, the safety margin is always high enough to ensure that the cornea will withstand it perfectly.

‍In any case, these are non-invasive and quick tests in which, mainly, the patient only has to look at a light and hold their eye open for a few seconds.

What if I am not eligible for this technique?

If the thickness of the cornea is not thick enough to support the removal of tissue required for our prescription, there are only two alternatives: continue wearing glasses or contact lenses or opt for collamer lens implantation surgery.

How long does the procedure last?

The procedure takes no more than 10 minutes per eye and its effects are permanent and effective from the first moment, although vision may be altered during the first few days due to the regeneration processes of the treated tissue.

Will I feel any pain?

No. Before the operation, the patient is given a sublingual relaxant to provide a relaxed state. In addition, drops of anaesthetic eye drops are instilled into the eye so that it is completely asleep before being manipulated.

When will I start to see well after surgery?

This is precisely another of the differences between these two techniques: while recovery with LASIK is more immediate (more than acceptable vision is achieved the following day), with PRK it takes between 7 and 15 days for vision to stabilise. This is due to the fact that the epithelium must regenerate completely and during this time the vision may fluctuate until it reaches its optimum state.

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