Temple of Healing

VOLUME 1 , ISSUE 5, SEPTEMBER-OCTOBER, 2018

COVER STORY

Glaucoma-The Sneak thief of vision

BY DR. ANUJ SHARMA, HEAD OF DEPARTMENT, SSSIHMS, PRASANTHIGRAM


Glaucoma is the second most common cause of blindness in the world after cataract accounting for up to 8% of total blindness. Glaucoma is a complicated disease in which damage to the optic nerve leads to progressive, irreversible vision loss. This disease affects about 60 million (6 crore) worldwide. In India , glaucoma is the leading cause of irreversible blindness with at least 12 million (1.2 crore) people affected and nearly 1.2 million (12 lakh) people blind from the disease. More than 90 percent of cases of glaucoma remain undiagnosed in the community. According to WHO the challenge posed by Glaucoma is more severe because unlike cataract, the blindness caused by Glaucoma is irreversible.

How does Glaucoma occur?

Glaucoma is often associated with increased pressure within the eye. Eye pressure, referred to as Intra Ocular pressure (IOP), is determined by the balance of formation and drainage of a fluid called ‘aqueous’ that fills the front of the eye. Elevated pressure is often the result of blockage or a decrease in drainage from the eye, causing aqueous to build up. Fluid pressure builds up over time and in turn leads to damage to the optic nerve fibers.

Signs of Glaucoma and its diagnosis:

Glaucoma is known as the ‘silent thief’ and there are typically no early warning signs or painful symptoms related to its onset. This disease causes slow loss of peripheral vision which may result in ‘tunnel vision’. If left untreated, it may result in complete blindness. One must visit the Eye doctor (Ophthalmologist) if one experiences:

  • Fall in vision, seeing colored halos around light sources
  • Pain in and around the eye

The Ophthalmologist will then conduct a comprehensive eye examination including the following:

  • Intraocular Pressure – IOP - (By Applanation)
  • Gonioscopy- To assess the angle of eye (open or closed)
  • Disc evaluation using 78/90D (Most important)
  • Pachymetry (for determining Corneal thickness)
  • Phasing (Diurnal variation of IOP)
  • Structural evaluation- OCT (RNFL, GCC)
  • Functional evaluation- Visual Field evaluation (Gold standard)


Schematic Diagram of how aqueous circulates in the eye. If this flow is blocked then the aqueous keeps forming without exiting because of which pressure in the eye builds and damages the optic nerve.

Photo Courtesy. National Eye Institute. https://www.nei.nih.gov/. Modified to show the direction of pressure.

Types

Like every disease it is also divided into various types for the ease of understanding and management.

Open Angle (based on gosnioscopy)

  1. Primary open angle glaucoma
  2. Primary angle closure glaucoma (More common in Asian population)

Closed Angle (based on gonioscopy)

  1. Secondary open angle glaucoma
  2. Secondary angle closure glaucoma

Childhood glaucoma

  1. Primary childhood glaucoma
  2. Secondary childhood glaucoma
  • Low Tension Galucoma (IOP is in normal range, disc is Galucomatous)

Here Primary refers to Glaucoma with no known cause, while the secondary Glaucoma refers to Glaucoma with a known cause.

NORMAL VISION

INITIAL STAGE OF GLAUCOMA

SEVERE GLAUCOMA (Tunnel Vision)

Treatment

Unfortunately, Glaucoma is an irreversible disease, and currently the only modifiable risk factor is the Intraocular Pressure. Therefore, treatment for glaucoma is aimed at reducing intraocular pressure (IOP). The three mainstays of therapy are:

1. Medications, in the form of eye drops.

2. Laser therapy - Nd-Yag laser for peripheral iridotomy or selective laser trabeculoplasty.

3. Surgery - Conventional, Implants, Micro Invasive Glaucoma Surgery.

People with more risk of developing glaucoma include people who are:

• Over 40 years of age;

• Have family members who have glaucoma;

• Are of African or Hispanic heritage;

• Are of Asian heritage (Asians are at increased risk of angle closure glaucoma and Japanese are at increased risk of low-tension glaucoma);

• Have high eye pressure;

• Are farsighted or nearsighted;

• Have had an eye injury;

• Have corneas that are thin in the center; or

• Have diabetes, migraines, high blood pressure, poor blood circulation or other Health problems affecting the whole body.

People with more than one of these risk factors have an even higher risk of glaucoma.

Screening for Glaucoma for All:

Due to the progressive and irreversible nature of the disease, early diagnosis and treatment are very important. The American Academy of Ophthalmology (AAO) recommends a baseline comprehensive eye exam at the age of 40, followed by eye exams every 2 years until the age of 65 when annual exams are then recommended. This comprehensive eye exam includes visual acuity testing, intraocular pressure measurement, gonioscopy and dilation. Those identified as higher risk based on their findings may be subject to functional tests (Visual field evaluation), structural tests (optic nerve imaging like OCT etc), and corneal thickness measurements (Pachymetry).


~ “I opened two gifts this morning. They were my eyes.” ~