Glaucoma: Diagnosis and Treatment

By Eyecare NG

Glaucoma is a group of eye diseases that progressively damage the optic nerve and can lead to permanent loss of vision. It is not curable and any vision loss due to the disease is irreversible. If detected early, it can be managed to ensure no further loss of vision occurs. 

Diagnosis

Most cases of glaucoma do not show signs and symptoms early. Hence, regular screening and at least an annual eye examination are important for early diagnosis.

Diagnosis involves carrying out some or all of the following tests and procedures:

  • Visual acuity test to check how well you can identify letters or figures on a standard chart positioned at a distance in front of you.
  • Measurement of your eye pressure using an instrument known as tonometer: To ensure that the pressure measurement is accurate, the doctor may measure the thickness of your cornea and then adjust the reading of the tonometer based on the thickness of your cornea. This is because the corneal thickness can affect the reading of the tonometer. Thick cornea tends to exaggerate the eye pressure while thin cornea tends to underestimate the eye pressure.
  • Examination of the external structures of your eyes for abnormalities using a penlight or a slit lamp bimicroscope.
  • An assessment of the filtration angle using a goniolens and a slit lamp biomicroscope (a procedure known as gonioscopy). This determines whether the filtration angle is wide open, narrow or completely closed.
  • Examination of the retina and optic nerve with an ophthalmoscope
  • A visual field test (perimetry) to assess your peripheral vision and determine whether or not vision loss has started taking place.
  • Ocular coherence tomography to identify some early damages that are not yet visible to the eye or are not obvious on visual field test result.  Your doctor may recommend this test if you have risk factors for glaucoma or show signs of glaucoma that are not confirmed by other tests. This results of this test can help the doctor make a definite diagnosis.

Treatment of glaucoma

There are various treatment options for glaucoma. These include the use of medications, surgery and drainage devices. These treatment options may be combined depending on your condition.

Medications

Glaucoma is frequently treated with eye drops.  There are several classes of eye drops with varying mechanisms for reducing eye pressure. Some increase the drainage of aqueous humour, some reduce the production of aqueous humour while other combine both mechanisms to reduce eye pressure. On rare occasions, eye drops may be combined with tablets.

Surgery

Surgery is usually done for the treatment of angle closure glaucoma or in cases where medications do not sufficiently lower the intraocular pressure in other types of glaucoma. Surgery types include laser surgery and the conventional surgery. In laser surgery, known as trabeculoplasty, a laser beam is used to create a hole in the iris allowing more outflow of aqueous humour. The conventional glaucoma surgery called trabeculectomy involves the creation of a new channel through which aqueous humour can flow out.

Insertion of drainage devices

The use of drainage devices is usually the last option in glaucoma management. They are inserted into the eye under the conjunctiva with the tube positioned into the anterior chamber of the eye. They have been used to successful lower eye pressure in cases where surgery failed.