It it is estimated that around a million people are affected by it in Italy, but there is evidence that unfortunately only half of those affected are aware of it. Around 500 thousand Italians are at risk of becoming blind, but are either unaware of it and/or have no symptoms. Blindness or a significant reduction in sight and the field of vision can be prevented, as long as the disease is treated in time. We discuss the issue with Doctor Salvatore Giglio, Head of the Ophthalmology Department at the Istituto Clinico San Siro, a Gruppo San Donato facility, and with Doctor Giovanni Bolzoni, an ophthalmologist in the same department.
What causes an increase in intraocular pressure?
“There is a fluid inside the eyeball, known as the aqueous humour, which has various functions for the health of the eye. In a normal eye, it is produced and reabsorbed in the same amount. A simple example would be to compare the eye to a tank with both a constantly running tap and an open drainage tube. If there is a reduction in drainage compared to production, it will cause an increase in pressure inside the tank, exactly as happens inside the eye. With the passing of time, high pressure causes damage to the nerve fibres that conduct light signals and damages the optic nerve, compromising the field of vision and subsequently also central visual acuity. If the optic nerve is damaged by high pressure within the eyeball, it results first in the loss of peripheral vision and then the loss of central vision, because the fibres forming it no longer conduct the images generated by the retina to the brain”.
What is the damage to visual acuity and the field of vision?
“What we see around us is called the field of vision. The central part is sharper while the peripheral part is less detailed and this allows us to orient ourselves in space without any problem. The macula, that is, the central vision cells, send high resolution images to the brain via the optic nerve (along with the nerve fibres that lead from the retina, ed.), while those of peripheral vision sends less focused images. If high pressure within the eyeball damages the optic nerve, first peripheral vision is damaged, and then central vision, because the fibres forming it no longer conduct the images generated by the retina to the brain. Tragically, the damage is irreparable: it starts slowly in the field of peripheral vision, gradually working its way to the centre until it leaves a small central zone of clear vision, just like when we travel through a tunnel and see its end from afar. Hence this kind of vision is known as tunnel vision”.
Are there different types of glaucoma?
“Glaucoma can occur in both an acute or chronic form. Chronic open angle glaucoma is the most common form of glaucoma, progressing slowly and without symptoms. The disease is not noticed until it is at an advanced stage and the damage is irreversible. If for some reason the drainage channels should suddenly close, with a consequent rapid increase in intraocular pressure, accompanied by blurred vision, nausea, vomiting and headache, acute closed angle glaucoma occurs. This describes an acute attack of glaucoma which, if not treated swiftly, can cause serious, irreversible damage, to the point of losing the sight”.
Is it a hereditary disease?
“There are predisposing factors linked to a reduced depth of the anterior chamber, the space between the cornea and the iris, usually associated with long-sightedness and also possible with a cataract that has become so advanced that it pushes the iris forward, reducing the available space and blocking the angle, the area where drainage occurs. There are also other forms of glaucoma, such as a congenital form in which a child exhibits symptoms such as intolerance to light, excessive watering of the eye and blepharospasm (the child keeps their eyes partially closed and finds it difficult to try and open them, ed.). In these cases, a check by a specialist is necessary. There is also a secondary form associated with diabetes and retinal thrombosis, with the use of certain medications such as the prolonged use of cortisone, or with haemorrhages, cancers or inflammatory forms”.
How is it diagnosed?
“For glaucoma to be accurately diagnosed a full sight test is required, carried out by an optician who will check:
• Eye pressure, using a Goldmann tonometer, a pneumotonometer or the Icare method;
• Appearance of the optic nerve head, or papilla, a test that can easily be carried out by a specialist ophthalmologist with an ophthalmoscope;
• Condition of the field of vision, a test that uses computerised perimetry to determine the level of damage to the optic nerve and detect any increase in eye pressure or any anomalies in a matter of minutes. These tests are simple and non-invasive and, with the right equipment, can provide a correct diagnosis. An additional test which is useful for the correct classification of the disease is corneal pachymetry, thanks to which the thickness of the cornea can be measured non-invasively in a matter of seconds. In normal conditions, eye pressure varies between 10 and 20 mmHg (millimetres of mercury); if eye pressure reaches around 20 and the cornea is thin (500 microns), then there is a danger of glaucomatous damage, while if the cornea is thick (600 microns), the risk is lower. Optical coherence tomography (OCT) is also an important diagnostic tool: it is a completely non-invasive, fast, accurate test, which allows the thickness of the optic papilla nerve fibres to be measured, quantitatively highlighting reported damage to the field of vision. In the event of further diagnostic doubt, there are more sophisticated tests using more complex technology that can reveal the state of damage that is already present and assess the progression of the disease; besides OCT these include scanning laser polarimetry (SLP) and confocal laser scanning (CLS)”.
What does treatment involve?
“Treatment can be conservative or surgical: the former is mainly based on the use of eye drops that act on the various factors causing the disease, particularly on reducing the production of the aqueous humour, while others act to increase its drainage. A new category of drugs works through neuroprotection, which is to say they are aimed at protecting the nerve fibres from ischemic attack and programmed cell death. Surgery is resorted to when conservative treatment has failed or for those cases which, despite early diagnosis, proper treatment and the patient's correct following of treatment, are nonetheless deteriorating. Surgery consists of reducing the pressure by creating aqueous humour drainage channels”.
Following treatment is essential! A failure to carefully follow treatment leads to steady deterioration and ultimately blindness. In the event of doubt or side effects, always consult your regular ophthalmologist without ever stopping treatment of your own accord.
Translation: TDR Translation Company
Editing: Arianna Derossi