Glaucoma is a chronic irreversible optic nerve disease due to many reasons, the most important risk factor of which is high intraocular pressure (IOP). 

It is the second cause of blindness in the western world and 50% of people suffering from it in the developed world are unaware of it.

We speak of glaucoma when we find that the optic nerve (which acts as a conductor of information from the eye to the brain) is affected. However, we talk about ocular hypertension when IOP alone is high, without any optical nerve defect. 

IOP is determined by the production of aqueous humour (the liquid responsible for the eye's tone) and the resistance and difficulty involved in its drainage. 

There is a wide variety of types of glaucoma although in general terms we can classify them according to their origin (primary and secondary) and angle width (open- or closed-angle). 

The majority of those affected do not usually show symptoms until the advanced stages of the diseases, when the eye damage is then significant.

This happens because of a loss of lateral vision, which the patient does not notice because the brain has the ability to compensate for the lost vision and fill in the blind spots by combining the images in both eyes to give a complete image. 

This is why it is called 'the silent thief' and early detection is crucial. 

• With an IOP (intraocular pressure) measurement
• With the visual field
• With an optical coherence tomography (OCT) 

Diagnosis is vitally important given that it is a chronic disease that hardly has any symptoms until it is at a very advanced stage, when the patient has tunnel vision. 

Glaucoma risk factors

• Ocular hypertension
• Over the age of 40
• Family history

Factors that may condition the progression of glaucoma

• High blood pressure or vascular diseases 
• Myopia
• Diabetes

The majority of treatments are aimed at increasing drainage and, in some case, reducing the production of aqueous humour. 

There are three main treatments, described herein from least to most invasive: 

Medical-drug treatment

• Hypotensive eyedrops
• Tablets

Outpatient laser treatment

• Laser iridotomy
• Trabeculoplasty
• Transscleral diode laser cyclophotocoagulation 

Surgery

• Microinvasive surgery (MIGS)
• Invasive surgery for more advanced cases 
• Filtering surgery (trabeculectomy and a non-penetrating sclerectomy
• Drainage devices (Ahmed and Baerveldt valves)

Early detection and timely treatment considerably improve the visual prognosis and prevent it progressing towards blindness.