Intraocular lenses

The lenses consist of two parts, the central optical zone and the support zones, which means that there are different shapes depending on the subject they have inside the eye. Most have as «legs», called haptic, which have a spring effect, others have several points of simultaneous support and others a rectangular shape that is known as «plate.»

They have an average diameter of about 12.5-13 mm, and their optical part is usually about 6 mm, in a range from 5 to 7 mm.

The graduation of the intraocular lens is calculated based on very thorough scans using an optical interferometry laser and applying specific formulas, which allows us to compensate for previous graduation defects.

There are different types of intraocular lenses, so they are classified into two groups: conventional lenses and special or Premium lenses.

Conventional lenses

Conventional lenses are known as spherical lenses and are, like the natural lens of the eye, like a microlupa. Therefore, the simplest idea is to replace the opacified lens with a similar lens, according to the basic graduation as such a microlupa that we have previously calculated.

These lenses were first implanted in 1948 by Sir Harold Ridley in England. At that time in cataract surgery, the entire natural lens of the opacified eye was removed, so a student asked him about the simple idea mentioned: if one lens was removed, why not replace it with another?

Dr. Ridley had attended in those years numerous RAF fighter pilots wounded in the eyes during the war. He remembered the good tolerance to the acrylic fragments of the cockpit that had many of them embedded in his eyes, so it occurred to him to make the first intraocular lenses in that same material.

From there began an exciting story that reaches to this day.

Premium lenses

Premium lenses are special lenses with more complex optical systems. Basically, it can be understood that they are like conventional lenses, that is, the same microlupes, to which we have added additional optical characteristics. They provide superior benefits to those of conventional ones and require additional prior and subsequent studies, all of which have a higher cost.

Aspherical, toric, multifocal and accommodative lenses are included here.

Aspherical lenses

Aspherical lenses are like conventional spherical lenses whose optical profile is improved to compensate for some optical aberrations of the cornea. Prior to surgery, both topography and corneal aberrations are studied to choose the type of aspherical lens to be implanted.

Aspherical lenses give better quality and visual acuity, especially in low light conditions

Toric lenses

Toric lenses are the best system that exists for the correction of prior astigmatism. The base of a toric lens is that microlupa that we have commented, either spherical or aspherical, to which we have incorporated a modification, called a bull, that corrects astigmatism. As this defect occurs in an axis of the eye, the toric lenses have marks to be able to fix the position of the lens intraocularly.

Its implementation requires previous studies not only to determine the amount of astigmatism to be corrected, but to obtain the reference axes for correct implantation. In Innova Ocular Clínica Dr. Soler we have developed a computer system, the Goniotrans of Dr. Soler, which greatly facilitates this task.

Toric lenses require that they remain fixed in their position once implanted and that no rotation occurs, since they would lose some of the correction effect.

The corrective bull of astigmatism can be incorporated into both a monofocal lens and a multifocal lens, so there are toric and toric multifocal monofocals.

Multifocal lenses

As is the case with glasses that are used to correct defects in far and near vision, there are monofocal or multifocal intraocular lenses. Monofocals are lenses focused on one point, so they allow you to see well or from far or near. In this way, there is a residual defect of graduation that must then be compensated with glasses, either for near, distant or both visions.

Unlike progressive glasses or a bifocals, in which the look looks in the glass for the focus area for far or near, multifocal intraocular lenses are always focused on two different points at the same time, so they allow us See far and near simultaneously.

To achieve this effect the lenses have complex optical systems added to a spherical or aspherical lens. Of these, the best known are diffractive lenses that, based on circular microscales, direct the images that enter the eye to these two different points.

The other big family are those known as refractive lenses, in which there are areas of different focus, but aimed at those two different points.

In both cases, it is the brain that selects the image we are looking for at all times, so we can see a landscape and immediately read an explanatory brochure.

Multifocal intraocular lenses are used both in cataract surgery and refractive lensectomy to correct defects from far and near. They are also used for presbyopia or tired eyesight surgery; in this case, eyes with good distance vision without glasses are intervened, but with serious dependence on the near one. To correct this, both eyes are intervened or only one, leaving the other untouched. The brain, once again, helps the integration of the images of both eyes, even if they have different optical systems. In Innova Ocular Clínica Dr. Soler we have a long and positive experience in presbyopia surgery with only one eye.

By distributing the light and the images that arrive at two points at a time, you can lower the quality of vision a little, both far and near. That is why multifocal intraocular lenses are not indicated in eyes with added eye problems that already diminish the visual capacity of the eye.

By defining as we have said two very marked points can lower visual performance in intermediate areas of vision, such as in the use of computers, sheet music, etc. This difficulty gradually disappears as the distances and approaches are adjusted.

Also, the vision of night halos around the lights is frequent at first. These halos, which are like “crowns of saint,” disappear progressively in the weeks following the intervention. Exceptionally they have had a long persistence, forcing on some rare occasion the explant of the lens.