Generality
Orthokeratology is a particular technique used in ophthalmology for the purpose of correcting various types of visual defects.
More in detail, orthokeratology - or better, nocturnal orthokeratology - makes use of contact lenses that must be used at night in order to correct sight defects such as myopia, hypermetropia, astigmatism and presbyopia.
Orthokeratology can represent a valid alternative to the surgical treatment of the aforementioned visual defects, however, it presents some limitations and disadvantages that will be illustrated during the article.
What is that
What is Orthokeratology?
Orthokeratology - also known as nocturnal orthokeratology, ortho-k or OK - is a non-surgical technique used in ophthalmology for the correction of visual defects.
The orthokeratology treatment involves the programmed application of particular night-time contact lenses, rigid and gas-permeable, made in a personalized manner for each patient. These lenses have a particular shape, defined as " inverse geometry " which allows to temporarily correct the visual defect that afflicts the individual.
The foundations of orthokeratology were laid around the 1960s, but it was only in the 1990s that the use of this technique began to spread significantly. Nowadays, the use of orthokeratology is considered as an alternative for those patients who do not want or cannot undergo surgery to correct ametropia (myopia, astigmatism and hyperopia) and presbyopia.
Indications
Orthokeratology is indicated in cases where various types of ametropia are to be corrected, such as myopia, astigmatism and hypermetropia. However, in some cases, orthokeratology is also useful in the temporary treatment of presbyopia.
The use of orthokeratology is also indicated to slow down the progression of myopia in children and adolescents.
Currently, it seems that the main use of orthokeratology concerns precisely the correction or arrest of the progression of myopia.
However, it should be pointed out that not all patients can use hortocheratological lenses. The decision to resort to orthokeratology or not, therefore, it is only up to the ophthalmologist who after an accurate visit will evaluate, case by case, which treatment is most suitable for each patient.
Action mechanism
How Does Orthokeratology Work?
The purpose of night-time lenses used in orthokeratology is to modify the shape of the corneal surface that is altered in patients with visual defects.
Short Insight: Importance of Cornea
The regularity of the corneal surface is of fundamental importance for the correct vision. Not by chance, this structure is one of the most important dioptric means of the eye and its surface behaves like a converging lens able to convey - in association with the crystalline lens - the light rays towards the retina, favoring the perception of sharp images .
Normal contract lenses are designed so as to interfere as little as possible with the cornea; on the contrary, the hortocheratological lenses are specifically designed to modify - naturally, in a controlled manner - the corneal profile. This change is made possible by the pressure exerted on the corneal surface by the tear deposit that is created between the rigid lens and the cornea. In other words, the lens is designed in such a way as to leave a sort of impression on the corneal surface, shaping it according to the specific needs of the patient (correction of myopia, astigmatism, hypermetropia or presbyopia).
Through the modification of the cornea profile - with a certain plasticity - it is possible to correct the refractive error that characterizes the visual defect of the patient. Unfortunately, this remodeling is temporary.
Preliminary Tests and Controls
What tests do I need to carry out before using Orthokeratology?
Not all patients can wear hortocheratologic lenses, for this reason, before using them, it is necessary to undergo some tests.
First of all, it is necessary to evaluate the patient's eye health conditions through an accurate eye examination, after which it is essential to carry out the so-called corneal topography which allows to obtain the topographic map of the cornea, or rather, the mapping of the anterior corneal surface. This map shows in detail the shape and the curvature of the cornea, providing essential information to be able to create night-time lenses for orthokeratology customized and adaptable to the eyes and the needs of the patient.
What checks should be carried out after the first night of use?
After the first application of the lenses, the patient must be checked again by the ophthalmologist (or possibly by the contactologist) and a new corneal topography will be performed in order to verify the variations obtained on the corneal surface after the first night of orthokeratological treatment. In some cases, in fact, it may be necessary to make some changes to the lenses in order to improve the results obtained.
Once the ideal hortocheratological lenses have been identified and designed for the patient, the doctor will set up periodic checks to constantly check the health of the eyes, the integrity of the lenses and the efficacy of orthokeratology treatment.
Effectiveness and Results
What results can be obtained with orthokeratology?
When the hortocheratologic lenses are applied, the patient should have a clear and sharp vision immediately, as if he were wearing traditional contact lenses. Spent the night, after the removal of the lenses, the cornea should maintain the modified shape conferred by them and the patient's vision should remain clear for a period of about 24 hours, but in some cases, the duration of the effect can even last for 48 hours.
However, improved vision does not necessarily occur immediately after the first night of use, as some patients may take longer to achieve the desired result.
In order for orthokeratology to produce appreciable and stable results, the lenses must be applied every night. Generally - although there is some variability from individual to individual - the maximum results obtainable for a patient are reached within 1-2 months from the beginning of the treatment, provided that the lenses are applied consistently and according to the indications of the doctor. Once the maximum results have been obtained, there is the possibility of reducing the frequency of application to once every two or three nights; however, even in this case there is great variability from patient to patient. Naturally, the time interval that must elapse between one application and the other can be established only and exclusively by the ophthalmologist or by the contactor.
When Is Orthokeratology Effective?
The effectiveness of orthokeratology can vary a great deal from one patient to another and therapeutic success may depend on several factors, such as:
- The severity of the refractive disorder that needs to be corrected;
- The quantity and quality of the patient's tear film;
- The stiffness of the patient's cornea (the stiffer the cornea is, the longer it will take to achieve the desired improvements).
Usually, the use of hortocheratological lenses is effective in treating conditions that are not too severe. More in detail, orthokeratology seems to be effective - allowing patients to no longer use glasses and contact lenses - in the following cases:
- Myopia up to 4-5 diopters;
- Astigmatism up to 1.50-3 diopters;
- Hyperopia up to 2-3 diopters;
- Presbyopias up to about 2 diopters.
In truth, even patients with more severe pictures can undergo orthokeratology treatment, obtaining improvements, but in all probability they will not be able to give up the use of traditional glasses or contact lenses.
Clinical studies have also shown that orthokeratology can actually be effective in slowing down and, at best, blocking the progression of myopia in children and adolescents.
Side effects
Undesirable effects and complications related to Orthokeratology
In principle, the use of orthokeratology lenses is considered safe and is well tolerated by most patients. However, this does not completely exclude the possibility of the onset of unwanted effects and complications which, in fact, are similar to those that can occur with the use of traditional contact lenses.
In detail, following the application of the hortocheratological lenses it is possible to find:
- Intolerance to the use of lenses that usually manifests itself with burning, dryness and eye irritation;
- Feelings of annoyance;
- Blurred vision;
- Appearance of "halos" during night vision;
Fortunately, the majority of the aforementioned effects are generally mild and often reversible. However, if they appear, it is a good idea to remove the lenses and consult your ophthalmologist.
Among the main complications that can occur during the treatment of orthokeratology, however, we recall the possible appearance of transient corneal edema and infectious keratitis (generally caused by incorrect or inadequate lens cleaning).
Contraindications
As repeatedly stated in the article, orthokeratology treatment cannot be performed in all patients. In fact, the use of hortocheratologic lenses is contraindicated in the presence of:
- Current eye disorders (keratitis, conjunctivitis, etc.);
- Ocular hypersensitivity;
- Any allergies.
Advantages and disadvantages
Summarizing what has been said so far, the main advantages and disadvantages associated with orthokeratology treatment are reported below.
Advantages of Orthokeratology
- Orthokeratology allows patients to achieve significant changes in their lifestyle; in fact, many of the patients who undergo this technique can avoid the use of prescription glasses or traditional contact lenses and can be free during the execution of sports, recreational or work activities, while maintaining a good vision.
- This technique allows the improvement of vision without surgery.
- The hortocheratologic lenses are customized and custom designed for each patient to ensure maximum adaptability.
- Orthokeratology lenses can be used at all ages (however, it is advisable to use this type of lens only in patients who are able to manage them independently).
- Orthokeratology treatment is completely reversible. In case of intolerance to the lenses, side effects or undesired results it is possible to interrupt the use. The corneal surface will return to the conditions prior to the start of treatment in a relatively short time.
- Since hortocheratological lenses must be worn during the night, they are more comfortable than traditional lenses. In fact, despite the first feelings of discomfort that can occur following the application of the lenses, during sleep they are not perceived.
Disadvantages of Orthokeratology
- Time and perseverance are necessary to obtain appreciable results.
- The results of orthokeratology are temporary and, to maintain them, it is necessary to wear the lenses regularly, every one, two or three nights.
- The use of hortocheratologic lenses requires periodic tests and checks, especially (but not only) during the first stages of treatment.
- The lenses must be adequately cleaned before each application, in order to avoid the occurrence of side effects and complications (in this regard, the ophthalmologist and the contactor will provide all the necessary information).
- Although orthokeratology is a usually well tolerated treatment, there is the possibility of the occurrence of side effects and complications, in addition to the presence of various contraindications.
- Orthokeratology is a technique with rather high costs (the price of a pair of hortocheratologic lenses, in fact, can vary between approximately 200 and 500 euros).
