Juvenile open angle glaucoma is a hereditary form of this ophthalmic disease characterized by a gradual increase in intraocular pressure. Symptoms manifest in childhood or adolescence, are reduced to eye soreness, photophobia, myopia and other visual disturbances (for example, astigmatism). Diagnosis is performed by traditional ophthalmological techniques (tonometry, elastometry, perimetry), as well as molecular genetic analyses. Treatment of this disease is carried out surgically, conservative therapy is justified only in the case of mild forms or in preparation for surgery.
Juvenile open angle glaucoma (primary open–angle glaucoma) is an ophthalmological disease, most often having a genetic nature and accompanied by a violation of the outflow of watery moisture from the anterior chamber of the eye with its morphologically unchanged angles. This form of increased intraocular pressure is the most common in people aged less than 35 years, according to some data, it occurs in 1 person per 10-15 thousand of the population, men suffer twice as often as women. It is not possible to more accurately determine the occurrence of juvenile open angle glaucoma for the reason that in some cases this condition has been asymptomatic for many years and is sometimes detected only in old age, which leads to an erroneous definition of pathology as senile glaucoma.
Moreover, in some individuals, the presence of genetic defects does not provoke the development of obvious juvenile open angle glaucoma, but is manifested only by an asymptomatic increase in intraocular pressure throughout life. Nevertheless, this form of glaucoma is still potentially dangerous, as it can begin to progress spontaneously and, if left untreated, cause a sharp deterioration in vision or even blindness for only 4-7 years. Modern genetics identifies several genes responsible for the development of this disease, their mutations are almost always inherited by an autosomal recessive mechanism.
Unlike other forms of congenital glaucoma – infantile and especially early – juvenile open angle glaucoma is almost always a genetically determined condition and cannot be caused by intrauterine lesions of the fetus. At the moment, several genes have been identified whose defects lead to this disease. Most often, in juvenile open angle glaucoma, mutations of the CYP1B1 gene, which is located on the 2nd chromosome, are detected. The product of its expression is a special protein – cytochrome P4501B1, which participates in the metabolism of signaling molecules that are responsible for the formation of the trabecular network of the eye. Defects in this gene cause disruption of the cytochrome, resulting in abnormal development of the tissues of the organs of vision, subsequently, among other things, leading to juvenile open angle glaucoma. Currently, geneticists are trying to determine which CYP1B1 mutations (more than 50 are known) cause an increase in intraocular pressure in adolescence.
The second most common cause of open–angle juvenile glaucoma is defects in the MYOC gene – it is located on the 1st chromosome and encodes the structure of the myocillin protein. Expression of this gene occurs mainly in the organs of vision, myocillin, like cytochrome P4501B1, participates in the formation of the trabecular network. In addition to juvenile open angle glaucoma, MYOC mutations can cause a similar disease in adults and the elderly. Defects in both CYP1B1 and MYOC are inherited by an autosomal recessive mechanism. The pathogenesis of the development of glaucoma in these genetic conditions has no characteristic features – as a result of increased intraocular pressure, a gradual compression of the main structures of the eye (cornea, optic nerve disc, retina) occurs. This becomes the cause of their damage – corneal opacity and retinal dystrophy gradually develop, optic nerve atrophy may occur. The combination of these processes in the absence of treatment can eventually lead to irreversible blindness.
Unlike other forms of hereditary glaucoma, in this condition, no ophthalmic symptoms are usually detected in the first years of a child’s life. The onset of juvenile open angle glaucoma usually occurs in adolescence, but sometimes it is first diagnosed in adults. Most researchers in the field of ophthalmology associate this with a long asymptomatic course of the initial stage of the disease. One of the first manifestations of the pathology is increased fatigue of vision, which turns into soreness and a feeling of bursting in the eyes, accompanied by headaches. Similar symptoms in juvenile open angle glaucoma can persist for several years without pronounced signs of progression.
In the future, visual disturbances join the above–mentioned manifestations – complaints may arise about the presence of “halos” around light sources and bright objects, “flies” in front of the eyes, turbidity. In many cases, open–angle juvenile glaucoma at this stage is combined with myopia (myopia), less often with astigmatism or strabismus. The absence of any therapeutic measures leads to a gradual narrowing of the field of vision along the periphery (peripheral scotoma) and a decrease in the ability to dark adaptation. In advanced cases, juvenile open angle glaucoma, like other forms of chronic increase in intraocular pressure, causes blindness due to retinal detachment or optic nerve atrophy.
Diagnosis and treatment
Diagnosis of juvenile open angle glaucoma is performed using ophthalmological examinations (examination of the anterior chamber and fundus, measurement of intraocular pressure), as well as molecular genetic analyses. An ophthalmologist during examination reveals an increase in the horizontal size of the cornea and an increase in intraocular pressure. At the same time, a single measurement of the indicator does not give grounds for an unambiguous definition of open–angle juvenile glaucoma – several repeated measurements are needed over several weeks to confirm a persistent increase in intraocular pressure. A significant amount of information important for diagnostics can be given by various functional load tests – water–drinking, pilocarpine, Krasnov’s test.
With advanced forms of juvenile open angle glaucoma, patients will have a narrowing of the visual field (the presence of “blind spots” on the periphery), as well as changes in the fundus. The latter include the excavation of the optic nerve disc and thinning of the retina, in some cases its ruptures and associated areas of regmatogenic detachment are detected. At any stage of the disease, a geneticist can make a molecular genetic diagnosis of this disease by sequencing the CYP1B1 and MYOC genes. The reason for such a study may be a burdened hereditary history of the patient – cases of early glaucoma in his relatives.
Treatment of juvenile open angle glaucoma can be both conservative and surgical, but most specialists regard the second option as the most reliable way to eliminate this condition. The use of medications (drops based on pilocarpine, epinephrine or clonidine) is allowed as part of preoperative therapy or if there are contraindications to surgery. The essence of the operation is reduced to the formation of more passable paths for the outflow of watery moisture, which leads to a decrease in intraocular pressure. In recent years, minimally invasive laser techniques for the elimination have been gaining popularity.
Prognosis and prevention
Relative to other hereditary forms of glaucoma, the prognosis of this disease is more favorable. Firstly, it is characterized by less pronounced manifestations and progresses slowly, which gives more time for its diagnosis and subsequent treatment. Secondly, the development begins at the conscious age of the child, when he is already able to inform adults about the subjective manifestations of this pathology, which also contributes to its timely detection. Cases of blindness due to this condition are quite rare and are recorded only with prolonged neglect of symptoms or refusal of treatment for one reason or another. Prevention of primary juvenile open angle glaucoma is possible only with prenatal or genetic diagnosis in the first years of a child’s life, which is reasonable to do if relatives have such a condition.