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Leber hereditary optic neuropathy (English Leber Hereditary Optic Neuropathy - LHON) is a very rare mitochondrial disease affecting the ganglion cells of the optic nerve. It occurs more commonly in the second decade of life (between 18 and 30 years), affects males more frequently, has a prevalence of about 1 / 15.000-1 / 50.000 and is usually characterized by two phases, one acute and one chronic.
In the acute phase, the patient will present an almost complete loss of central vision in a subacute form (sudden and painless), it can occur in both eyes at the same time or after a short time from each other. Usually, patients in the initial phase notice a small central spot that over time extends to compromise vision (over several weeks) and then reaches stabilization.
On the other hand, in the chronic phase there is generally a stabilization of visual acuity and sometimes in patients in which the pathology has arisen earlier there may also be a small improvement in central visual acuity. Even if a significant visual deficit arises, the patient suffering from this pathology does not reach blindness.
Leber's hereditary optic neuropathy is caused by mutations in the DNA contained within the mitochondria (mitochondrial DNA). Transmission occurs only through the mother, so affected males do not transmit the disease to their children, while women pass it on to all subsequent generations. In addition, some patients with Leber hereditary optic neuropathy also have systemic comorbidities such as cardiac conduction defects, minor nervous system abnormalities.
Diagnosis
The diagnosis of Leber's hereditary optic neuropathy can be made during a simple eye examination as long as theophthalmoscopic examination and some instrumental tests such as:
La optical coherence tomography (OCT) to verify the alteration of the ganglion fibers of the optic nerve, in the acute phase there will be a swelling of the optic nerve head, vascular tortuosity and peripapillary telangiectasias. On the other hand, in the chronic phase, a few months after the onset of the disease, there will be the disappearance of telangiectasias and the reduction of the thickness of the ganglion fibers, initially affecting only the papillo-macular bundle, ultimately causing the atrophy of the optic nerve.
It is also very important to carry out a psychophysical examination on field of view computerized both in the acute phase to accurately visualize the extension area of the central scotoma and in the chronic phase to verify that there is no progression of the extension of the scotoma.
If the patient has difficulty performing this test, an electrophysiological test can also be performed (ERG and PEV) which can give us with objective precision the level of progression of the disease over time.
In addition, a chromatic alteration on the red-green axis was also detected in many patients, detectable by the color vision test at Farnsworth.
Treatment
The factors that determine the progression and therefore the outcome of the disease are certainly the type of genetic mutation and the age of onset of the disease, so before carrying out any type of treatment you must undergo a genetic test to accurately identify the type of mutation .
To date, there is no definitive therapy for Leber's hereditary optic neuropathy, the only therapy that has apparently proved effective in avoiding the progressive deterioration of vision is the pharmacological one with Idebenone, usable since 2007 as an orphan drug.
In recent years, several clinical studies have been underway that try to validate new therapies in addition to that with idebenone, which can be used in the treatment of this debilitating pathology. First of all, gene therapy which involves the use of a single intravitreal injection of recombined adeno-associated virus-NADH (rAAV2-ND4) and therapy with cells stem more precisely, the autologous bone marrow derived stem cells (BMSCs) which are performing well.
In addition, it is very important that patients with this disease, in order not to induce a more rapid progression, refrain from drinking alcohol, smoking and the use of certain antibiotics.
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