Glaucoma monitoring & Laser

What causes Glaucoma?

Let us explain with the simple example of a kitchen sink at your home.

There is a tap through which you can fill the sink, and there is a drain through which water can leave the sink. If the drain is blocked, water accumulates in the sink. Similarly, in your eye, there is an area which produces a clear fluid called the aqueous humour, which circulates inside the eye and provides oxygen and nourishment to the internal structures. Likewise, there is a small drainage channel through which all the waste products from inside the eye are drained. It is a sieve-like structure called the trabecular meshwork. In glaucoma, this passage or the drainage channel is blocked, either at its entrance or beyond. Unlike your kitchen sink, the eye is a closed structure, so excess water cannot overflow. This causes pressure in your eye to build up. This increased pressure causes damage to the optic nerve when it is called glaucoma. If it hasn’t caused damage yet, we call it Ocular Hypertension.
When the block is at the entrance it is called Narrow Angle Glaucoma or Angle Closure Glaucoma. When the blockage is not at the entrance, but beyond, somewhere inside, we call it Open Angle Glaucoma.

Types

Open angle glaucoma  is the most common form of the disease. There are no initial symptoms. It isn’t even evident until the optic nerve becomes damaged and peripheral (side) vision is lost through the slow build-up of pressure in the eyes.

Acute closed-angle glaucoma  happens more suddenly when blockage occurs in the normal flow of eye fluid between the iris and the lens. This type of glaucoma is a medical emergency and if not treated immediately, blindness could occur in one to two days. Acute closed-angle glaucoma symptoms include:

• Severe pain
• Nausea
• Vomiting
• Blurred vision
• Seeing a rainbow halo around lights

Chronic closed-angle glaucoma this type is similar to open-angle glaucoma, in that it progresses more slowly and can damage the optic nerve without prior symptoms.

Symptoms

Glaucoma can progress slowly and those who present with the disease may already have severe vision loss. Consequently, your best defence is to have regular eye exams and a glaucoma screening test, especially if you fall into a high-risk group.

Risks

Anyone can get glaucoma, but knowing the risk factors for the disease and being screened for it will give you a head start on detecting and treating the disease. Doing so is important because any vision lost in glaucoma patients cannot be regained. Unfortunately, everyone is at risk for developing glaucoma, but certain groups have a higher risk, including:

• All individuals who are over the age of 60
  Glaucoma is much more common among older people. You are six times more likely to get glaucoma if you are over 60 years old.
• Those with a family history of glaucoma 
  The most common type of glaucoma, primary open-angle glaucoma, has a hereditary link. If anyone your immediate family have glaucoma, you are at a much higher risk, about four to nine times, than the rest of the population.
• Diabetics or those with high blood pressure 
• Long term Steroid users
• People with high myopia (severe near-sightedness)
• Afro-carribean race
• Migraines or Raynaud’s Phenomenon
• Oral contraceptive medications
• Sleep apnea
• Previous eye injury
  Blunt injuries, usually sports related injuries with a ball hitting the eye, or injuries that penetrate the eye can damage the eye’s drainage system, leading to raised pressures and traumatic glaucoma.

Diagnosis

Diagnosing glaucoma is not always easy, and training and experience of your consultant goes a long way. Delayed diagnosis can cause irreversible loss of visual field or vision. Careful evaluation of the optic nerve continues to be essential for diagnosis and treatment. Using advanced technology like OCT Retinal Nerve Fibre layer Analysis and visual field tests every 6 months and careful examination of the optic nerve head by an experienced consultant can pick up early defects before it is too late.

Glaucoma management is not all about intraocular pressure but maintaining an adequate pressure to prevent optic nerve damage. The most important concern is protecting your sight.

Investigations

• Ophthalmoscopy
  This diagnostic procedure helps your consultant examine your optic nerve for any signs of glaucoma damage, and if present, to monitor any changes over a period of time. Eye drops may be used to dilate the pupil. Your consultant will then use a small high powered lens when you sit on the slitlamp to examine the shape and colour of the optic nerve and the ratio of the nerve fibres compared to the total size of the optic nerve, the cup:disc ratio, also called optic disc “cupping”.
• Perimetry
  Perimetry is a visual field test that produces a map of your field of vision. This test will help your consultant determine whether your vision has been affected by glaucoma. During this test, you will be asked to look straight ahead as a light spot is repeatedly presented in different areas of your peripheral vision. Damaged areas of the visual field can be identified this way.
  Ideally this test is repeated every 6 months, so that any damage can be picked up early.
• Gonioscopy
  This diagnostic test is used to determine whether the angle where the iris meets the cornea, called the irido-corneal angle, or just the angle, is open and wide or narrow and closed. During the exam, eye drops are used to numb the eye. A hand-held contact lens called a gonio lens is gently placed on the eye. This contact lens has a mirror that shows the consultant if the angle between the iris and cornea is closed and blocked (a possible sign of angle-closure or acute glaucoma) or wide and open (a possible sign of open-angle, chronic glaucoma). Also, other abnormalities like pigment in the angle, pseudoexfoliation etc can also be identified that can suggest other causes of glaucoma.
• Pachymetry
  Pachymetry is a simple, painless test to measure the thickness of your cornea — the clear window at the front of the eye. A probe called a pachymeter is gently placed on the front of the eye (the cornea) to measure its thickness. Pachymetry can help your diagnosis, because corneal thickness has the potential to influence eye pressure readings. With this measurement, your doctor can better understand your IOP reading and develop a treatment plan that is right for you. The procedure takes only about a minute to measure both eyes.
• Retinal Nerve Fibre Layer Analysis with OCT Scan
  This is one of the most advanced scanning technologies we offer to all glaucoma patients at Paragon Clinic. Not only is the test important, proper interpretation of the results by a highly trained glaucoma specialist is necessary to optimise you treatment.