Glaucoma

What is glaucoma?

Glaucoma is a group of diseases that damage the eye’s optic nerve. Damage to the optic nerve is usually, but not always associated with increase in eye pressure. It can result in vision loss and blindness. With early detection and treatment, one can often protect one’s eyes against serious vision loss.

How does the optic nerve get damaged by glaucoma?

Eye pressure is a major risk factor for optic nerve damage. In the front of the eye is a space called the anterior chamber, a clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the angle where the cornea and iris meet. When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye Due to the build-up of fluid in the eye; the eye pressure rises and damages the nerve of the eye. Sometimes the damage may occur with normal eye pressure called normal tension glaucoma or low-tension glaucoma.

What are the types of glaucoma?

Primary Glaucoma

There are 2 types of Primary glaucoma:

Open angle glaucoma – when the drainage angle is open but the fluid passes slowly through it
Angle closure glaucoma – when the drainage passage is narrow and prevents outflow of fluid.

In this type of glaucoma patient may have a sudden increase in eye pressure. Symptoms include severe pain and nausea, as well as redness of the eye and blurred vision. If one has these symptoms, one needs to seek treatment immediately. This is a medical emergency, and needs to be treated promptly with medicines and laser or there can be permanent visual loss.
However, all angle closure glaucoma cases do not present with an acute attack but may give intermittent rise of eye pressure with serious damage to the optic nerve. In Asian and Indian eyes, incidence of this glaucoma is very high and usually more aggressive.

Secondary glaucoma

It can be due to inflammation in the eye, medical conditions like diabetes which can lead to new blood vessels formation and lead to neo-vascular glaucoma.

Can children be born with glaucoma?

Children are born with a defect in the angle of the eye that slows the normal drainage of fluid. These children usually have obvious symptoms, such as cloudy eyes, sensitivity to light, and excessive tearing. Conventional surgery typically is the suggested treatment, because medicines are not effective and can cause more serious side effects in infants and be difficult to administer. Surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.

What are the symptoms of glaucoma?

Glaucoma is called the ‘silent killer’ or the ‘thief of light’ because it is usually asymptomatic. However, in certain cases, there could be dull headache or peri-ocular pain, halos. Initially, the vision may not be affected. It can develop in one or both eyes.

Without treatment, people with glaucoma slowly lose their peripheral vision and gradually only a tunnel vision remains.

Damage to the optic nerve caused due to glaucoma is irreversible and permanent.

Are there conditions that increase the risk of glaucoma?

Family history of glaucoma
Myopia or short-sightedness
Diabetes
History of trauma to the eye
Age

How is glaucoma diagnosed and evaluated?

Glaucoma is detected through a comprehensive eye exam that includes the following:

Visual acuity test: This eye chart test measures how well one sees at various distances. Eye is numbed with local anaesthetic drop and following tests are done:

Tonometry is the measurement of pressure inside the eye by using an instrument called a tonometer. There are different tonometers but the gold-standard method of measuring eye pressure is with applanation tonometer.

Pachymetry is the measurement of the thickness of the cornea with the help of an ultrasonic wave instrument. It helps to assess the accuracy of the eye pressure reading.

Gonioscopy to assess the drainage passage of the eye and the angle structures.

Dilated eye exam. Pupils are dilated with drops and with the help of special magnifying lens the optic nerve and retina are assessed for signs of damage. Vision is blurred for a few hours after the test.

If glaucoma is suspected, further tests for imaging of the optic nerve and visual field test are ordered.

How is glaucoma treated?

Medicines like timolol, betoxolol, dorsolamide, latanoprost in the form of drops to reduce the pressure have to be used regularly as advised. Regular follow-ups are required. Tablets are advised temporarily if eye pressure is very high.

Laser therapy may also be advised in certain cases. They are outpatient procedures and the patient can get back to their normal life immediately after the treatment. The following types of laser therapies are advised as per the type of glaucoma:

Peripheral laser iridotomy (PI) for angle closure glaucomas
Argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT) for open angle glaucoma.

In certain cases, trabeculectomy (surgery) which helps to lower the eye pressure in 60-80% cases may be required. After surgery, regular follow up is necessary.