In glaucoma the field of vision decreases gradually, due to various factors.Often the patient does not realize the problem till the later Stages of the disease. Since it usually causes blindness without any symptoms, glaucoma has been called the 'Silent Thief of Sight'. It is the second most common cause of irreversible blindness worldwide.

Internally, our eyes constantly produce a clear fluid called aqueous humor, which bathes and nourishes different regions of the eye. The aqueous normally drains out of the eye through a 'drainage canal' located in the 'angle' of the eye. In persons with glaucoma, the fluid does not drain out as freely as it should, thus increasing the pressure inside the eye, known as intraocular pressure (IOP). Raised IOP damages the optic disc (that part of the optic nerve that is inside the eye is called the optic disc).

There are mainly two mechanisms for raised IOP in the eye:

In open angle glaucoma, the outflow pathway is open, but an increase in resistance to the outflow within the pathway (the trabecular meshwork) causes a rise in the IOP. This type develops gradually and the symptoms may not be obvious till the damage has occurred. The patient may lose peripheral vision, leaving only central or 'tunnel' vision. This occurs more among people above 45 years of age.

In angle closure glaucoma the outflow pathway itself is narrow, which causes raised pressure. In the acute cases, the symptoms are dramatic and may include severe pain in the eye, headache, nausea, reduced vision, and seeing rainbow coloured rings around lights. The more common variety of angle closure glaucoma is chronic angle closure. This behaves similar to open angle glaucoma but here, the 'drainage' canal is closed by the iris.

Another type is developmental glaucoma, which may be further divided into congenital glaucoma (present since birth) and juvenile glaucoma (occurs in children and young adults).

Glaucoma or high IOP may also be secondary and occur due to other causes such as the use of steroid drops without prescription. Such drops should never be used without monitoring the intraocular pressure.

RISK FACTORS FOR GLAUCOMA

• Increasing Age
• Positive Family History in first degree relatives
• Refractive Error- Myopia, Hypermetropia
• Uncontrolled Diabetes and Hypertension can cause Neovascular Glaucoma
• Vascular Factors like Migraine, Raynaud's phenomenon
• Prolonged Steroid Use in any form, from topical eye drops to nasal sprays, skin ointments and oral tablets.
• Acute trauma may cause bleeding inside the eye called Hyphema which raises the IOP
• Prior history of eye trauma may have caused damage to the outflow pathway leading to a specific type of glaucoma called Angle Recession Glaucoma.
• Obstructive Sleep Apnea/ Snoring

Since glaucoma detection in the early stages is mostly incidental, we recommend regular screening for all patients over the age of 40 years, in a similar fashion to screening for diabetes or hypertension. During routine screening we will check the IOP (either through Non contact Tonometry or Applanation tonometer), examine the angles (using a gonioscope) and check the optic disc for any features of glaucoma damage.

If any suspicion of glaucoma is present, we will further investigate with the means of an

1. Automated Perimeter (to test the visual field),
2. OCT (Optical Coherence Tomography) - to check the thickness of the optic disc
3. Pachymeter - to check the central corneal thickness

Glaucoma is a multifactorial disease, which like Diabetes and Hypertension cannot be cured, but only managed with various therapeutic options available now. As the damage caused by glaucoma is irreversible, the need for lifelong compliance and regular follow ups cannot be stressed enough to prevent further progression of the disease.

Medical Management: Glaucoma in the early stages or milder varieties of glaucoma can be managed with the help of eye drops that reduce the IOP by various mechanisms.

LASER procedures are indicated in the closed mechanism of glaucoma. Using laser we create an alternative pathway for the aqueous to drain out called peripheral laser iridotomy.

Surgical Management: In patients with uncontrolled glaucoma, or intolerance to medication, various surgical options are available to manage the IOP. The gold standard treatment is Trabeculectomy, in which we create a controlled fistula (or filter) for the aqueous to drain out. Newer surgical option include shunts (a tube is inserted into the anterior chamber through which aqueous drains out into a footplate sutured to the back portion of the eye), and Minimally Invasive Glaucoma Surgeries (the point of resistance at the outflow pathway is addressed here)

1. Tonometry instrumentation like Goldmann Applanation Tonometer, Perkins tonometer, and Non Contact Tonometer – To measure the intraocular pressure.
2. Humphrey Field Analyser/ Perimeter for visual field examination.
3. Fundus Photography for optic disc documentation by color and Red free photographs.
4. Optic disc imaging and Retinal nerve fiber layer analysis by optical coherence tomography (OCT).
5. Nd- Yag Laser facility for Yag Laser Iridotomy.
6. Glaucoma Surgeries like Trabeculectomy and combined procedure of Cataract Surgery and Trabeculectomy.
7. Cyclodestructive procedures like Cyclocryopexy and Trans scleral cyclo photocoagulation.
8. Glaucoma Drainage Device like AGV implantation.
9. Minimally Invasive Glaucoma Surgeries like iStent, KDB (kahook dual blade), BANG(Bent ab-interno needle Goniotomy)