Different types of glaucoma 

Primary open angle glaucoma

The most common and chronic type of glaucoma – open-angle glaucoma – doesn't have symptoms. Without any early warning signs, this condition can develop slowly over several years without the patient experiencing any loss of sight. 

The majority of people who have open-angle glaucoma do not notice any changes in vision until they lose peripheral vision. Most patients with this type of glaucoma can even maintain the sharpness of vision or visual acuity until the later stages of the disease. By the time most patients notice vision loss, the disease has already advanced quite far. 

Neovascular glaucoma

Neovascular glaucoma is a condition that causes very high eye pressure and regular headaches. It is a secondary type of glaucoma where abnormal blood vessels grow over the drainage system. 

The development of these abnormal drainage-angle vessels and iris vessels can occur whenever an individual is dealing with the more severe type of diabetic eye disease known as proliferative diabetic retinopathy. These abnormal vessels can also result from vascular occlusions in the eye, like central retinal vein occlusion. 

Although there are other, less common types of neovascular glaucoma, they all involve the growth of abnormal vessels. Eventually, the drainage angle is completely covered and the IOP climbs excessively high. 

Angle-closure glaucoma

Angle-closure glaucoma is another condition that causes extremely high eye pressure and subsequent headaches. 

With an angle-closure glaucoma attack, the IOP increases gradually until the angle for drainage is entirely closed. This causes the pressure in the eye to spike more rapidly. Your patients may experience nausea, pain, blurred vision, and headaches.

Before an angle-closure glaucoma attack, the patient with narrow angles may experience closure of the angle from time to time for various reasons:

• Entering a dark room 
• Excitement or stress
• Taking certain drugs such as antidepressants and antihistamines
  

If the episode doesn't develop into a full attack and the angle-closure resolves, the symptoms will typically resolve. 

Causes of glaucoma

Most cases of glaucoma are caused by a build-up of pressure in the eye when fluid is unable to drain properly. This increase in pressure damages the nerve that connects the eye to the brain (optic nerve).

While it's unclear why this happens, certain factors can increase the risk.

• Age – glaucoma becomes more common as you get older
• Ethnicity – people of African, Caribbean or Asian origin are at a higher risk
• Family history of glaucoma 
• Other medical conditions – such as short-sightedness, long-sightedness and diabetes

Diagnosing and treating glaucoma 

Early diagnosis and treatment of glaucoma can help prevent a patient’s vision from worsening.If a patient references chronic headaches, it's vital you check the eyes as a potential source of the pain. Having regular dilated eye exams helps to catch glaucoma and start treatment as soon as possible – this is particularly important for those with diabetes. Depending on the type of glaucoma will determine the treatment plan.

Once a diagnosis has been made treatment may include:

• Eyedrops – to reduce the pressure 
• Laser treatment – to open up the blocked drainage tubes or reduce the production of fluid in your eyes
• Surgery – to improve the drainage of fluid

Several drugs – including antihistamines and other over the counter medicines – have been known to cause untreated glaucoma to worsen. So becareful when prescribing over the counter drugs.