Aniridia, also known by the medical synonyms iris aplasia and irideremia, refers to a congenital defect of the iris, or iris, of both eyes. It is a rare hereditary disease that may be associated with diseases in other parts of the body. The disease is considered incurable, but general life expectancy is not limited.
What is aniridia?
Literally translated, the term means aniridia without iris. It refers to the partial or complete absence of the iris. It is a genetic malformation of the visual organ with complex influences on further development during adolescence. Due to the fact that the iris is partially absent or not present at all in both eyes, the pupils cannot close or cannot close properly and regulate the incidence of light into the eyes, as is the case at all times in a person with normal vision. In the case of the genetically caused visual disorder, the vision of the affected person is always severely impaired, and in fulminant courses of the disease, complete blindness may occur. However, there are also milder forms known in which those affected have almost no problems and can even obtain a driver’s license. In the course of adult life, patients suffer not only from irideremia, but also from the many concomitant diseases that can, but do not have to, manifest themselves over time as a result of the genetic defect. Whether or not a new symptom that has appeared is directly related to the absence of iridescence can only be assessed by the physician.
Causes
The causes of aniridia lie in a genetic defect called a chromosomal aberration. This genetic defect is congenital and will accompany affected individuals throughout their lives. Human genetic studies from blood samples of the affected individuals have shown that this is a defect of the 11th chromosome. The affected PAX6 gene is located on the 11th chromosome and is considered to be the trigger of the disease. The malfunction of this gene causes a developmental delay of both eyes, i.e. the complete maturation of the eye function is completed too early and is not completed at the beginning of birth. It is a so-called autosomal dominant chromosomal dysfunction. The risk of developing aniridia is statistically 1:100000, both sexes are equally affected. In the special form of so-called sporadic aniridia, the rare chromosomal mutation occurs in a child whose parents do not have the disease. In every third case of the absence of the iris it is such a de novo mutation. In both forms, the gene for the development of both eyes plays a role, therefore both eyes are affected by the disease. Nevertheless, a few individual cases in which only one eye was affected by aniridia have also been documented in the world medical literature.
Symptoms, complaints, and signs
A lack of luminal stem cells results in a variety of symptoms affecting the cornea of the eye, such as chronic and difficult-to-treat keratitis. Whether an isolated aniridia or an aniridia in the context of other genetic aberrations, for example a WAGR syndrome, can only be found out on the basis of further human genetic differential diagnostics. The diagnosis is usually made by the pediatrician immediately after birth. Many patients complain of visual disturbances such as double vision or veil vision. Often, the overall visual ability is impaired and the affected person suffers from accompanying symptoms such as dizziness or headaches. Furthermore, aniridia can lead to chronic keratitis. Such a corneal inflammation manifests itself by light sensitivity and the characteristic cloudy cornea. In addition, eye pain and dry eyes may occur. If photophobia has already developed as a result of aniridia, signs such as involuntary eye movements, redness around the eyes and inflammation are added. Irreversible damage to the optic nerve may develop due to increased intraocular pressure. As a result, complete loss of vision may occur, which is announced by restrictions in the field of vision, flickering and other symptoms. The severely clouded lens may cause accompanying symptoms such as permanent headaches or malaise. Externally, aniridia can be recognized by the visible enlargement of the iris and the absence of iris tissue.The iris appears almost completely monochromatic and is usually dark gray to black. Some patients present with bleeding or inflammation. Diagnosis can be made quickly based on these symptoms.
Diagnosis and course
The course of aniridia is always protracted and chronic, so that patients have to suffer from the disease itself and its consequences throughout their lives. Few affected individuals develop any accompanying symptoms other than the actual visual impairment. A typical symptom is photophobia, a general hypersensitivity to light that impedes the visual process and is accompanied by vegetative symptoms such as constant headaches or malaise. Those affected also suffer from constant involuntary eye movements, the so-called nystagmus. The increased intraocular pressure, narrow-angle glaucoma, can lead to irreversible damage to the optic nerve and subsequently to complete loss of vision. The lens is moderately to severely opacified in most aniridia patients, which is called a cataract.
Complications
Aniridia cannot be cured; however, there is no decreased life expectancy in affected individuals. Most patients experience visual impairment as a result of aniridia. This is usually already present in childhood and is not acquired in the course of life. Aniridia also causes a strong sensitivity to light. This means that bright light causes pain in the eye and impairs the visual process. Those affected are thus unable to cope with everyday life without special visual aids and are dependent on them. The strong sensitivity to light leads to severe headaches and a feeling of dizziness. In most cases, patients also experience eye movements that cannot be controlled voluntarily. In the worst case, a defect of the optic nerve can occur, whereby the patient loses his eyesight and goes blind. Treatment is not possible. However, it can limit the symptoms such as visual impairment or headaches relatively well. The doctor can also prescribe special glasses or contact lenses for the patient to mitigate the symptom. No further complications occur, but the patient’s life is limited.
When should you see a doctor?
Usually, aniridia is detected and diagnosed right after the child is born or at the latest by a pediatrician. For this reason, the doctor usually does not need to be visited again in addition. Direct treatment of this disease is also possible only to a limited extent. Those affected suffer from severe visual complaints and visual impairment. Therefore, if visual complaints occur unexpectedly or without any particular reason, they must be treated by a doctor in any case. Treatment by a doctor is also necessary in the case of photophobia. It is not uncommon for patients to also suffer from involuntary movements of the eyes, which can significantly restrict everyday life. Opacification of the lens can also be a typical complaint of aniridia and should therefore be treated by a physician in any case. It is not uncommon for aniridia to occur with other diseases, so that early treatment can have a very positive effect on the patient’s general condition. Those affected may also suffer from kidney complaints or a tumor. If kidney complaints are present, they must also be examined by a doctor.
Treatment and therapy
Although the cause of iris aplasia is clearly known, those affected unfortunately cannot be provided with a causal, i.e. cause-related, therapy to date. All treatment measures are based on the one hand on the severity and on the other hand on the ever-changing symptoms of the patients. Typically, more and more symptoms are added during the course of the disease, making treatment lengthy, complex and also cost-intensive. Adults with aniridia receive training regarding behavioral rules of constant adaptation to the environment. For example, sunglasses with extreme protective lenses and tints of 80 percent are required. Every child with aniridia should be examined genetically as soon as possible and should receive regular ophthalmological care. Regular ultrasound examination of the kidneys is also required to rule out a so-called Wilms tumor.To completely prevent the incidence of light, selected affected individuals can wear aniridia special contact lenses with artificial iris and fixed pupil. Surgical procedures can be performed only in certified eye centers.
Outlook and prognosis
The prognosis of aniridia is considered unfavorable. To date, the congenital disease cannot be cured with the available medical options. The development of the eye is prematurely terminated and cannot be regulated by the administration of hormonal preparations or surgical intervention. At the same time, under certain circumstances, the symptoms may worsen. Complications such as an increase in the internal pressure of the eye, clouding of the lens as well as the cornea can lead to an increase in symptoms. This is simultaneously accompanied by a further reduction of the already weakened vision. In addition, there is a risk that further diseases or a malfunction of the kidney activity will develop. This considerably reduces the chances of recovery. If diagnosed early and treatment is started quickly, targeted therapies to improve vision can provide some relief. This creates the best possible development of vision under the given circumstances. In addition, vision aids can lead to further but manageable improvements in vision. The prognosis prospects for a mild genetic defect are also low. There is very little impairment in everyday life, but there is still a risk that the existing symptoms will worsen in the course of life.
Prevention
Prevention of this hereditary eye disease is not possible. It has been found that amniocentesis is also not suitable to detect this malformation of both eyes already in the unborn child. Living with aniridia by adapting to rapidly changing light conditions or preventing painful glare sensations can only be made easier by consistently implementing the special rules of behavior and by adapting the surfaces in the work or school environment. This is because any glare sensation is painful for those affected, can reduce visual acuity, and can lead to movement uncertainties.
Follow-up
To date, aniridia can only be partially compensated. Therefore, follow-up care goes hand in hand with the actual treatment. As part of the therapy, the patient receives light-protective glasses, which must be regularly adjusted to the current visual acuity. Follow-up care may also include genetic clarification of the cause. Depending on the trigger, the patient may need to undergo further examinations. Follow-up care will ensure that the aniridia develops as planned and that no complications occur. If visual complaints or other problems in the eye area occur several months after treatment, follow-up is necessary. People with aniridia must have an ultrasound examination of the kidneys every three to six months, as the condition is associated with an increased risk of Wilms tumor. If the tumor is detected early, there is a 94 percent chance of cure. Patients should take advantage of the necessary examinations to detect any tumors early and improve the chances of cure. Regular screening examinations must be performed throughout the patient’s life. The responsible physician can provide further details on the necessary follow-up examinations and other aftercare measures and also advise the patient on suitable visual aids.
What you can do yourself
There are no preventive measures for this hereditary eye disease. Even amniocentesis cannot clarify whether the eye malformation is present in the unborn child. Since people affected by aniridia have an increased risk of developing glaucoma and cataracts, the ophthalmologist and optometrist should take care to preserve the visual function in regular check-ups. The usual therapy is the fitting of individual light protection glasses with a special edge filter immediately after the birth of the affected person. From the age of about two years, short-sightedness or long-sightedness can be compensated by glasses. Normal contact lenses should be avoided at all costs. However, to completely prevent the incidence of light, patients can wear special aniridia contact lenses with an artificial iris and a fixed pupil.Even if the disease is not treatable, at least the symptoms, i.e. visual impairment and headaches, can be mitigated relatively well. In addition, since any sensation of glare is associated with pain for the affected person, surfaces that reflect light well should be adapted in the work or school environment. Special rules of conduct should also be observed. For example, the affected person should avoid environments with rapidly changing light conditions.
