Glaucoma

 

What is glaucoma?

 

 

Glaucoma is a potentially devastating group of eye diseases which is characterized by raised pressure inside the eye causing damage to the optic nerve. It is the second leading cause of blindness worldwide and has been known to be the "Silent Thief of Sight” because the symptoms are slow to present and many affected individuals do not know of the severity of their disease until it is too late.

The only known treatable risk factor associated with glaucoma is intraocular pressure. For the normal function of the eye, there has to be a ‘pressure’ which is a balance between fluid(not tears) production and fluid drainage within the eyeball. In glaucoma, there is pressure build up within the eye which causes damage to the optic nerve and irreversible vision loss.

Cross section of the eye showing the development of glaucoma

 

What causes glaucoma?

 

There is no known cause of glaucoma. However, there are many documented risk factors with intraocular pressure being the most common one. Other risk factors include:

Certain types of illnesses (like diabetes), prolonged use of certain medications (like steroids) and prolonged UV exposure are some of the other causes of cataract. Injury to the eye can also result in cataract formation.

  1. Persons over the age of 65 years BUT glaucoma can still occur at any age.
  2. Association with race – Asian (Orientals) are more prone to closed angle glaucoma whereas Afro-Carribeans are more prone to open angle glaucoma.
  3. People with diabetes have a higher risk of developing glaucoma.
  4. People who are short-sighted are more prone to open angle glaucoma whereas people who are far-sighted are more prone to closed angle glaucoma.
  5. Any serious eye injury can predispose to glaucoma sometimes many years after the initial injury.
  6. Use of certain types of medications (especially steroids) can cause glaucoma.
  7. Positive family history of glaucoma. In some families, the risk of developing glaucoma can be as high as 40% if a first degree relative (parent or sibling) has glaucoma.
 

Types of glaucoma

 

Open angle glaucoma – This type of glaucoma is the most common form and occurs when there is pressure build up within the eye even when there is no physical closure of the drainage angle.

Closed angle glaucoma – This type of glaucoma occurs when the drainage angle is narrow or closed and subsequent obstruction of fluid passage results in increased intraocular pressure.

Normal optic nerve head(left) and damaged optic nerve head from glaucoma (right)

 

The consequence of raised intraocular pressure is progressive damage to the optic nerve and subsequent loss of vision.

In the case of acute closed angle glaucoma, there can be a sudden onset of pain in the affected eye with associated headache, nausea and vomiting. Otherwise, in most instances, glaucoma gives no physical symptoms until a late stage when vision loss is significant.

 

Tunnel vision with end stage glaucoma (right)

 

Diagnosis and follow-up

 

Glaucoma is a chronic disease which means that individuals diagnosed with this disease will have to be treated for life in order to prevent blindness. Diagnosing an individual with glaucoma will have far-reaching consequences and impact on that person’s life and therefore, has to be done accurately and meticulously.

Comprehensive glaucoma screening involves quite a few tests, photos and scans which can seem "troublesome” to a lot of people but they are necessary to establish diagnosis.

  1. Measurement of intraocular pressure
  2. Measurement of thickness of cornea
  3. Assessment of drainage angle (gonioscopy)
  4. Imaging of optic nerve head
  5. Visual field assessment (check field of vision)
  6. Optic nerve head scan (check for structural damage)

Measuring intraocular pressure

Visual field assessment

 

Treatment of glaucoma

 

Glaucoma is a chronic disease and needs lifelong treatment! The aim of treatment is to control the disease and prevent blindness; therefore, it is vitally important to detect the disease early as any damage done cannot be reversed.

Eyedrops - After glaucoma has been diagnosed, the vast majority of the time, your ophthalmologist will start treatment with eyedrops. Eyedrops are used to lower the intraocular pressure and is required lifelong. There are many different types of eyedrops for glaucoma and they have different modes of action – some may be more effective in one individual compared to another.

Eyedrops for glaucoma have become very effective over the years. Sometimes when one drop is insufficient to control the pressure, different eyedrops may be used in combination. For even better convenience, pharmaceutical companies have also made fixed combinations of glaucoma eyedrops so that one bottle will contain 2 different types of medication.

 

Glaucoma eye drops

 
 

Laser treatment - Laser is used in many different ways to manage eye diseases and there is a role for laser treatment in glaucoma as well. Laser trabeculoplasty is used to treat open angle glaucoma whereas laser iridotomy is used to treat closed angle glaucoma. Laser treatment is not an operation per se as it is done in the office with the patient sitting up and does not hurt at all.

Laser treatment for glaucoma

 
 

Glaucoma is a chronic disease and needs lifelong treatment! The aim of treatment is to control the disease and prevent blindness; therefore, it is vitally important to detect the disease early as any damage done cannot be reversed.

Surgery - When all else fails, an operation would have to be done to lower the intraocular pressure. What is commonly done is a trabeculectomy which in effect creates an opening in the eye which allows drainage of fluid out of the eye in a controlled manner. In more advanced cases, a tube implant may be required to facilitate drainage of fluid.

Formation of a ‘bleb’ after trabeculectomy

Optonol Shunt - a metal tube implant

 

There are newer techniques of surgery which are collectively known as Microinvasive Glaucoma Surgery (MIGS) and these are designed to cause less trauma and allow quicker recovery after surgery. Currently they include the iStent and Trabectome which are approved for use in patients with mild to moderate glaucoma. As these are still relatively new, it remains to be seen if they will be widely embraced by ophthalmologists.

 

Treatment of glaucoma

 

The key to preventing blindness from glaucoma is early detection. Regular visits to your ophthalmologist will ensure that any evidence of glaucoma is detected at the earliest possible stage and treatment started appropriately. The following are recommended timelines for visits to your ophthalmologist for glaucoma screening:-

  1. Age 20-29 years
    - At least once during this period
    - Those with risk factors (eg. Family history, injury, diabetes, short sighted) should be seen every 3 to 5 years

  2. Age 30-39 years
    - At least twice during this period
    - Those with risk factors should be seen every 2 to 4 years

  3. Age 40-64 years – every 2 years

  4. Age 65 years or older – every year