What is it?
Glaucoma is a progressive neurodegenerative disease that preferentially occurs at the optic nerve papilla, but evolves to affect all structures of the optic pathways.
Axons and glial structures of the papilla and retrobulbar optic tract are affected in the process; on examination of the ocular fundus, the papilla may show more or less marked excavation. Early functional disorders are diagnosable only by perimetry (paracentral arciform scotomas); at a more advanced stage there is decreased visual acuity.
These dysfunctions, together with morphologically recognizable changes, constitute ” glaucoma damage.”
The result of this is damage that corresponds to the loss of some of the nerve fibres as they exit the eyeball through the optic papilla to form the optic nerve.
Types of Glaucoma
- open angle glaucoma
- angle-closure glaucoma
- normal pressure glaucoma
- congenital glaucoma (present at birth)
- secondary glaucoma
All these forms, although different, have as a common end result progressive and irreversible damage to the optic nerve.
The effect of glaucoma is a progressive reduction of the visual field, starting from the most peripheral areas and affecting, in the most advanced stage, the central part of the visual field itself.
Scotomas (blind areas) are only perceived by the patient at a late stage when the optic nerve damage is already advanced. For this reason, glaucoma is also called the ‘silent thief of sight’. This is why it is essential that all patients over the age of 40 have their eye pressure checked at least every two years. Glaucoma is also affected by hereditary aspects, which is why it is advisable to have an earlier and more frequent check-up in family members of people with glaucoma.
Ocular pressure is determined by the liquid that fills the eye: aqueous humour. The aqueous humour also enables the eye to maintain its more or less spherical shape. This is continuously being produced but at the same time must also be eliminated. An imbalance in this dynamic can lead to increased intra-ocular fluids and at the same time increased pressure.
There are various instruments called tonometers for measuring tone. The most common ones require the use of an anaesthetic eye drops as they have to be in contact with the eye even if only for a few moments.
There is also the so-called ‘blowing’ tonometer, which does not require the use of drugs.
In both the former and the latter case, it is a quick and absolutely painless and non-traumatic examination, which one can undergo with extreme peace of mind.
In the case of open-angle glaucoma, it is the ineffectiveness of the aqueous humour outflow system, known as the trabecularis, that leads to increased pressure. In rarer cases, there may be overproduction.
In the case of angle-closure glaucoma, it is the internal structure of the eye that causes an anatomical alteration of the outflow system, which narrows, thus reducing the passage of aqueous humour to be eliminated.
In the case of normal pressure glaucoma, one consideration must be made: not all of us are equally sensitive to pressure variations. Most likely, glaucoma patients with normal pressure are so sensitive to intraocular pressure that they show the typical signs of glaucoma even if the tone is measured normally. Conversely, there are people who, despite manifesting an above-normal tone for years, never develop glaucoma.
Damage to the optic nerve caused by glaucoma is irreversible. What one can do is to plan with one’s ophthalmologist scheduled measurements of eye tone and to keep pressure under control with numerous eye drops capable of lowering eye pressure within the normal range. If, as is sometimes the case, medication is insufficient, laser or surgical treatments can be used to improve the outflow of the aqueous humour.
As glaucoma is a neurodegenerative disease, it shares some characteristics with other neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and others.
The common characteristics of these diseases are:
- death by apoptosis of specific neuronal populations (retinal ganglion cells in glaucoma)
- transynaptic degeneration (which leads to alterations in glaucoma along the entire optic pathway)
- the progression of the disease over time
NEUROPROTECTION represents one more opportunity to intervene on GLAUCOMA.
The purposes of neuroprotection are:
1) prevent retinal ganglion cell death 2) repair or regenerate degenerating neuronal cells 3) slow down disease progression.