- written by Dr Arun Kumar

Glaucoma is a disorder of the eye characterised by damage to the optic nerve (nerve responsible for vision). Though in many cases it is due to the increased pressure in the eye, some individuals can develop glaucoma even with normal eye pressure.
Regular eye checkup is necessary for correct diagnosis of eye symptoms

Glaucoma is the second leading cause of blindness in the world, according to the World Health Organisation. In India at least 12 million people are affected and nearly 1.2 million people are blind due to glaucoma.

What is the main cause of Glaucoma?

Aqueous humor is a clear watery fluid that flows inside of the eyes. The production and drainage of this fluid maintains the pressure inside stable. If the outflow of aqueous humor doesn't work properly either due to overproduction or pathology in the drainage system, fluid builds up. This increases pressure inside the eyes, damaging the optic nerve.  It is a progressive disease, which is manifested initially as visual field loss and ultimately can lead to irreversible blindness if left untreated.

The following groups are at higher risk of developing glaucoma,

  • Family history of glaucoma
  • Elderly people of age 40 and above
  • Injury to the eye - glaucoma can develop immediately after the trauma or years later
  • High eye pressure (Intraocular pressure - IOP)
  • Having high refractive error of eyes
  • Systemic diseases like diabetes and hypertension
  • Long term use of steroid medicines

Types of glaucoma and its symptoms:

All glaucomas are characterised by progressive optic neuropathy resulting in a specific pattern of irreversible visual field defects with characteristic optic disc appearance. This is due to the death of retinal ganglion cells (RGCs).

  1. Primary open angle glaucoma (POAG):

This is the most common type of glaucoma. In this the eye’s drainage canals becomes clogged over time causing increase in the internal eye pressure. Most people with open angle glaucoma present as a chronic disease and do not have any early symptoms. Initially the loss of vision is only peripheral (side) vision. As the optic nerve is more damaged, there is  progressive vision loss till only the central vision is left resulting in tunnel vision (as if looking through the end of a narrow tunnel).

Tunnel vision
This is how a patient with tunnel vision views the environment

2. Primary angle closure glaucoma (PACG):

Also called Narrow angle glaucoma, this type of glaucoma presents acutely. In this the angle between iris and cornea becomes too narrow resulting in blockage of the drainage canal and the eye pressure raises very quickly. This is called an acute attack and requires immediate medical attention.

Signs of acute angle closure glaucoma attack:

  1. Sudden blurring of vision
  2. Pain in the eyes
  3. Headache
  4. Nausea and vomiting
  5. Seeing rainbow-coloured rings (halos) around lights

In some people this also develops slowly as a chronic angle closure glaucoma with no initial symptoms, patients know it when there’s an acute attack or when the damage is severe.

3. Normal tension glaucoma:

In this type, people have eye pressure within the normal range, but show signs of optic nerve damage and blind spots in their field of vision. The exact cause of normal tension glaucoma is not known. This is also called normal-pressure or low-tension glaucoma.

4. Secondary and Congenital glaucoma:

Secondary glaucomas result from predisposing conditions like eye injury, inflammation (uveitis), use of certain drugs and advanced cases of cataract or diabetes. Congenital glaucomas present in babies born with defective development of the eye's drainage canal in their prenatal period. It may present at birth or develop in the first few years of life.

5. Pigmentary glaucoma:  

In this, the pigment granules from your iris (the colored part of the eye) break into the clear fluid produced inside the eye. These granules build up in the drainage canals and slowly clog them, causing elevated eye pressure.

Glaucoma Diagnosis:

A regular comprehensive eye checkup can help detect glaucoma in its early stages, before significant damage occurs. This is important in preventing loss of vision or to delay its progress. A complete eye examination by your Ophthalmologist will include the following:

  • Slit-lamp & Dilated eye examination
  • Tonometry - to measure your eye pressure
  • Visual acuity tests - to check for vision loss
  • Visual field tests (perimetry) -  to check changes in peripheral (side) vision
  • Pachymetry - to measure corneal thickness
  • Gonioscopy - to measure the angle between iris and cornea
  • To look for changes in optic nerve using optical coherence tomography (OCT)

Other specialised tests like confocal laser scanning ophthalmoscope and scanning laser polarimetry are available for early detection.

opthalmology is more than just an eye check up

Management of glaucoma:

  1. Medical Management - In most cases of glaucoma, medical management is the first line of treatment. This includes eye drops and oral tablets. They act either by reducing the amount of aqueous humor in the eyes or increase its outflow through the drainage angle.
  2. Laser therapy - Laser treatment is used in glaucoma to help the drainage of aqueous from your eyes. For lowering the intraocular pressure procedures known as Trabeculoplasty and Iridotomy are done in patients with POAG & PACG respectively.
  3. Surgical Management - Invasive procedures like surgery helps achieve better eye pressure control faster than laser therapy or medical management. However, it does not improve the lost visual function. Depending on the specific type and severity of glaucoma, your doctor may choose the treatment modality which suits best for you.
Early detection  and appropriate management is the best way to prevent irreversible vision loss due to glaucoma. Knowing your risk factors, regular screening will help in early detection. Once diagnosed, regular treatment and followup will help preserve your quality of vision.

written by DR. ARUN KUMAR

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