Keratoconus and corneal dystrophies are ocular pathologies that affect the cornea, the transparent front part of the eye that first interacts with the light that enters the visual system. A healthy cornea has a spherical symmetry and is perfectly transparent, these characteristics permit to light to reach the retina correctly.
Keratoconus causes the progressive weakening of the cornea’s structure, which over time thins and deforms, changing its profile from “spheric” to “conic”. This determines a fast-evolving irregular astigmatism and in some cases the appearance of lesions and scars that significantly interfere with the passage of light. In the most severe cases, keratoconus can lead to vision loss and make corneal transplantation necessary. Keratoconus has an important genetic basis; however, the timing of onset and evolution of this pathology may also depend on other factors.
Corneal dystrophies are a heterogeneous group of hereditary diseases that cause an alteration in the metabolism of the cornea, with the formation of precipitates and consequent loss of transparency. These pathologies cause important visual impediments and in the most serious cases the loss of vision and the necessity of a cornea transplant. Despite the genetic basis, corneal dystrophies can remain silent for years and then suddenly appear due to a trigger, such as a trauma (an accident a surgical intervention, etc.). Environmental and behavioral factors (for example the habit of frequently rubbing the eyes) can also affect the onset and evolution of these pathologies.
Genetic tests for keratoconus and corneal dystrophies allow to identify the presence of genetic defects responsible for these diseases before they occur. This is very important because individuals who are carriers but still asymptomatic could run very serious risks for the health of their eyes in case they underwent interventions that involve the cornea, such as refractive surgery.
Refractive surgery, performed to correct myopia, hyperopia and astigmatism, requires candidates to undergo routine pre-operative screening exams that are unable to detect very slight anomalies that may be possibly present in apparently normal clinical pictures. In a clinically healthy individual who is a carrier of a mutation responsible for corneal dystrophy, refractive surgery could act as a trigger that determines the manifestation or acceleration of the evolution of an initial and asymptomatic form of disease.
Genetic tests help prevent at-risk candidates from undergoing routine surgery that for them could imply a risk for their vision and also represent a valuable resource as they allow the implementation of prevention strategies or targeted treatments before the onset of the pathology, where the precocity of treatment can make a big difference in terms of therapeutic efficacy.
Genetic tests available today are able to analyze as many as 75 genes whose mutations could be related to keratoconus and reveal the possible presence of more than 70 mutations in the TGFBI gene responsible for granular corneal dystrophy type 1 (GCD1) and type 2 (GCD2), lattice corneal dystrophy, Reis-Bücklers corneal dystrophy (RBCD) and Thiel-Behnke corneal dystrophy (TBCD), among the most aggressive and vision-threatening inherited corneal diseases.
Samples for genetic testing are taken easily, quickly and totally painlessly by rubbing a cotton swab on the inner surface of the cheeks for a few seconds.
Genetic testing is recommended to anyone with family history or suspicious symptoms or clinical pictures. In addition, genetic examination should be strongly recommended to anyone intending to undergo refractive surgery.
The results of genetic testing can guide specialists towards a series of decisions and choices aimed at preserving the integrity and health of the patient’s cornea, such as the possibility of performing preventive treatments or choosing only certain types of surgical applications, excluding those that for certain types of patients could imply a high risk of post-operative complications that could be potentially very dangerous for their vision.