Introduction  

Open-angle glaucoma is an eye disorder that causes optic nerve damage. It occurs even with the drainage angle wide open as should be. It accounts for more than 90% of all glaucoma cases. It is also said to be the leading cause of blindness.

The eye produces a fluid known as the aqueous humor. In a healthy eye, the production level and drainage of the fluid is usually balanced. The fluid drains through a channel referred to as the trabecular meshwork before entering the bloodstream. The meshwork is located in the anterior chamber angle. Despite the drainage angle being fully open in this condition, the fluid drains slowly. As a result, the intraocular pressure inside the eye increases and causes optic nerve damage.

Sub-Types

  • Primary open-angle glaucoma (POAG)
  • Congenital glaucoma
  • Secondary glaucoma
  • Normal tension glaucoma 
  • Pseudoexfoliation glaucoma
  • Pigmentary glaucoma
     

Causes and Risk Factors

The causes of open-angle glaucoma are based on the type of the disease. These include:

  • Primary open-angle glaucoma - Due to slow aqueous humor flow, the intraocular pressure (IOP) increases and causes optic nerve damage. The slow draining is said to be associated with aging of the draining canals.
  • Secondary glaucoma - Similar to primary open-angle glaucoma, the IOP increases in this type of glaucoma. However, the cause of the disease is usually other medical conditions such as tumors, cataracts, or diabetes among others.
  • Pigmentary glaucoma - In this case, the drainage canals are usually clogged by pigments shed off from the iris. This causes slow draining and eventual build up of internal pressure.
  • Pseudoexfoliation glaucoma - This occurs in the event excess material is produced for internal structures and then shed off. The material blocks the canals, again slowing the drainage.
  • Congenital glaucoma - It occurs in newborns who either inherit the condition or whose eye drainage system develops abnormally. 
  • Normal tension glaucoma - It can also be referred to as low-tension or normal-pressure glaucoma. It differs from all the rest in that, deterioration of the optic nerve occurs when there is normal IOP level. It is believed to be occur due to poor flow of blood to the optic nerve.

Risk factors include:

  • Being over 40 years of age
  • The African-american or Hispanic descent
  • Medical conditions such as tumors, eye infections, cataracts, or diabetes
  • Family history of the disease
     

Signs & Symptoms

There are no onset symptoms in open-angle glaucoma. However, with time, one may begin to lose peripheral (side) vision. It is usually the first sign of the disorder. Other symptoms may include sudden eye pains and headaches.

Diagnosis

The diagnosis is aimed at checking the IOP levels as well as testing for side vision. The eye exams may include the following:

  • Dilated eye exam
  • Tonometry
  • Visual field test
     

Treatment 

Treatment focuses on lowering the internal eye pressure and preventing loss of vision.

Medical Treatment

Eye drops and pills are the most common. They may include carbonic anhydrase inhibitors, beta blockers and alpha-agonists. They work by either slowing the rate of production of the aqueous fluid or increasing the rate of drainage.

Surgical Treatment

Surgical options include the following:

  • Laser trabeculoplasty - This helps to drain the aqueous humor out of the eye. It may present side effects such as inflammation.
  • Trabeculectomy - This is an alternative to the laser surgery. A small piece of tissue is removed in the eye to create a new channel for drainage.
     

Alternative Treatment

Although rarely, a number of complementary therapies have been used in treatment of open-angle glaucoma. These include medical marijuana which is said to lower eye pressure when used for a few hours.  Others may also go for Acupuncture, which is an ancient chinese treatment method that could aid in reducing the intraocular pressure. Besides these, there are also dietary supplements such as Mitrogenol and citicoline which work to lower the pressure.

Prognosis/Long-term outlook

If left untreated, blindness can easily occur. However, open-angle glaucoma can be managed and the progress slowed down with treatment.

Prevention/Follow Up

It is important to have regular eye tests to check for glaucoma. Those above 40 should especially visit an eye care professional as frequently as possible.
Doctors also recommend an active lifestyle as a preventive measure for any type of glaucoma. Those already diagnosed with the condition are required to go for exams until the IOP is controlled.