Contactology - Contact Lenses

Contactology is an examination performed by all candidates and contact lens wearers (when they have difficulties in wearing them) in order to ensure a correct adaptation and the choice of the ideal lens.

In addition to anatomical issues, such as the curvature of the eye, it is important to evaluate the quality and quantity of the tear and the wearing comfort which will promote a good adaptation, as well as the quality of vision obtained.

The patient's expectations must be understood, as well as the reason for their use. It is important to clarify which lenses are available and which one best suits the case.

The patient's visual acuity, the degree and type of ametropia, whether there are amblyopias, whether there have been previous surgeries and the existence of eye diseases, the type of environment in which the patient moves every day, the existence of allergies, medication and the general state of health must be assessed.

Contactology is an examination made up of some tests and measurements which are necessary to obtain a more efficient result. Firstly we evaluate the ocular surface through the biomicroscope (commonly known as slit lamp), with which we check for surface alterations that may prevent or advise against the use of contact lenses. By placing a fluorescein dye it is possible to detect corneal alterations, accumulated protein deposits and to evaluate the quality of the tear ( Break-Up Time Test). It also makes it possible to observe the centration and movement of the lens in the eye and to check a good adaptation of the contact lens to the eye.

Evaluation of the anterior and posterior surface of the cornea with topography is also an important examination, as well as the measurement of the pupil diameter, both in room light and in reduced light (it allows knowing, above all, the natural dilation of the pupil at night, important to evaluate the possibility of worse quality of vision under these conditions)

The tear film should be evaluated using the BUT test (break up time) in which we evaluate the time, in seconds, that the tear takes to evaporate on the surface of the eye and/or the Schirmer test, which measures the amount of tear produced during 5 minutes.

Compared to wearing glasses, contact lenses have both advantages and disadvantages.

A patient wearing contact lenses will benefit from a larger visual field (not limited to the glasses frame) and the size of the object is normal because the lens in contact with the eye does not increase the size (as in hyperopes' lenses, nor decrease it as in myopic lenses). In the case of a great difference of graduation between the two eyes (anisometropias), because the images of each eye do not have the same size, the use of contact lenses improves the binocularity (vision of the two eyes together), consequently the visual acuity and the patient will feel more comfortable.

In irregular corneas (keratoconusContact lenses, when properly fitted, can provide better visual acuity.

Wearing contact lenses takes time to stabilise and adapt, and wear should be limited to a certain number of hours per day. Correct cleansing and disinfection is also necessary.

Contact lenses may not be comfortable in dusty, smoky and air-conditioned environments.

It is important to note that wearing contact lenses does not mean you can completely replace your glasses. These must be kept up to date and must be worn in conjunction with each other in order to comply with the rest break required by the lenses.

For a correct preservation and disinfection of the lenses it is necessary to use maintenance fluids. There are unique solutions for decontamination, cleaning and storage. The lens storage case should always be clean and replaced at least every three months.

The use of contact lenses is not merely an aesthetic question, but a solution for a more satisfactory visual acuity, in refractive or visual situations such as anisometropias, high myopiairregular corneas such as keratoconusscarring, implants or complications associated with a previous surgery and even in more common ametropias, because they always improve, in any circumstance, the visual acuity as well as the field of vision.

It can also be advantageous for professional reasons, for example for athletes of high competition, actors or military or even situations in which it is not possible to use glasses as allergies (eg º the material of the frames) or anatomical problems (prominent nose or ears). There are cases in which the patient does not accept the use of glasses psychologically, and will then have to adapt to contact lenses depending on the value of ametropia, because for example, myopias greater than 1.5 dioptres already make it very difficult to see far, as well as hyperopia and/or more diopters in adults make reading or using computers, mobile phones and others very difficult.

Nowadays, hydrophilic lenses or commonly called soft lenses can correct all refractive errors. We can correct myopia e hyperopia with spherical lenses and can correct very high graduations. If these are associated with any astigmatism than 0.75 D a toric lens can be adapted (suitable for correcting that defect). Toric lenses, however, do not always achieve such a perfect correction with acuity as with spectacles. This is due to the fact that the lens must be held in position on a certain axis, which inevitably varies with blinking and eye movements.

There are also lenses that allow the correction not only of distance vision, but also of near and intermediate vision, a solution for patients with presbyopia (difficulty in seeing at close range with age).

Regarding the frequency of use, lenses can be divided into daily, fortnightly and monthly.

Daily wear lenses do not require maintenance. They are worn during the day and thrown away at the end. It is the healthiest and safest option today.

Biweekly and monthly lenses require proper cleaning and sanitizing, so that they maintain their properties, allow maximum comfort and better visual quality, avoiding complications such as infections or allergies or premature wear of lenses.