WHAT IS GLAUCOMA?
Glaucoma is the name given to a set of different eye disorders which cause progressively increasing damage to the optic nerve, leading to progressive irreversible loss of visual field. The optic nerve connects and transmits visual signals from the eye to the brain. In most types of glaucoma, the pressure within the eye is higher than normal, and this high pressure directly damages the nerve. Not every eye with high pressures develops glaucoma, however, it is a known risk factor and people with high pressures therefore need regular eye examinations to rule out glaucoma. There is no specific level of eye pressure that definitely causes glaucoma or eliminates the risk of glaucoma. In some cases normal pressures can still lead to glaucoma. Advanced glaucoma can lead to blindness, hence its early diagnosis and treatment is imperative .
WHAT IS EYE PRESSURE ?
The cornea and the lens are special parts of the eyeball responsible for focusing and transmitting light. For this purpose they require to be crystal clear. Blood vessels, which normally supply nutrition to cells, are absent from these parts of the eyeball, as they will reduce their clarity. In order to supply nutrition to these sensitive parts, a special liquid, called the aqueous humour is produced in the eye. This liquid bathes the lens and back surface of the cornea, and then drains out of the eye through the ‘trabecular meshwork’, situated in the angle of the eye. When the normal outflow is blocked due to any cause, the pressure in the eye builds up, like a blocked sink. Eye pressures above the normal upper limit of 20 mmHg can lead to optic nerve damage – the mechanism for most types of glaucoma.
HOW DO YOU KNOW IF YOU HAVE GLAUCOMA?
Glaucoma being a silent thief of sight, rarely has any symptoms. Very often, patients come to us with complete loss of vision in one eye. Sometimes, in cases of closed-angle glaucoma, patients complain of headaches which are more in the evenings or in the dark. They may also complain of seeing coloured haloes (rainbows) of light when their eye pressure rises. In case of an attack of acute angle closure the patient may complain of severe headache, redness of the eyes, and sudden blurring of vision. This may be associated with nausea and vomiting, and can mimic an abdominal emergency. In India, ange closure accounts for nearly 40% of all cases of glaucoma, and these are the patients who progress to blindness very rapidly. Hence it is very important to diagnose these patients early, and prevent progression of the disease by treating it promptly.
Children with Congenital Glaucoma typically have large eyes, with photophobia and watering. If diagnosed and treated in time these are the eyes where early damage to the optic nerve may be reversed.
AM I AT RISK?
You are considered to be in a higher-than-normal risk category if you have any of the following:
1) High IOP
2) Age 40 years
3) Family history of glaucoma
4) History of eye injury
5) History of steroid use, topically / systemically
6) Are near-sighted (myopia, need minus powered spectacles)
Other risk factors, which can be detected only on examination, include:
1) High eye pressure
2) Thin corneas
3) Differences in the optic nerves of both eyes
If you have any of these risk factors, you need to consult you eye specialist. At Shobhana Eye Clinic we can determine your risk level and need for future check-up.
Glaucoma is diagnosed through a comprehensive eye examination. This includes:
1. Patient history – any specific symptoms, eye diseases, general health problems, family history and medication history.
2. Vision testing – although affected only in advanced glaucoma, it gives an indication about the visual function of the eye.
3. Eye pressure measurement (Tonometry) – high eye pressure is an important risk factor for glaucoma, and treatment is based mainly on reducing the eye pressure. We use the gold-standard Goldmann Applanation Tonometer as well as a state-of-the-art Non-Contact Tonometer for this purpose.
4. Corneal thickness measurement (Pachymetry) – to detect an additional risk factor for glaucoma, namely thin corneas.
5. Gonioscopy – a test to directly view the area of the eye (angle) from where the aqueous drains, and assess whether it is open or closed.
6. Comprehensive slit-lamp examination – to look at the various structures of the eye
7. Optic nerve head examination – which gives an idea about nerve damage due to glaucoma and comparison between the two eyes.
Other tests which are done and may require to be repeated are
1.Visual field testing (Perimetry) – to check if the field of vision has been affected by glaucoma. Usually the disease affects the peripheral vision first & later on may spread to affect the central part of the field. This test helps to confirm nerve damage by glaucoma and also is useful in monitoring whether the disease is under control. We use the Humphrey Perimeter for this purpose, preferred the world over.
2.Optical Coherence Tomography (OCT) – this test is useful in early or doubtful cases of glaucoma. It measures the microscopic thickness of the retinal nerve fibre layer and the ganglion cell complex (GCC), and provides a detailed 3-D image of the same. The test can confirm the presence or absence of glaucoma when other tests are uncertain. It is especially useful in detecting early glaucoma, sometimes even before Perimetry can detect the disease. We are equipped with the most advanced spectral-domain OCT- Cirrus 500 HD OCT by Carl Zeiss.
3.The Anterior Segment OCT – This is used to look at the status of the angle of the anterior chamber (the site of aqueous fluid drainage). It can also give us the exact angle measurements, the corneal thickness, and can be used post-operatively to assess the status of the Trabeculectomy bleb.
Presently, glaucoma treatment is aimed at reducing intraocular pressure whatever be the type of Glaucoma.
In an Angle closure glaucoma, one needs to start treatment with a Laser, followed by Medications / Surgery. Reduction in intra Ocular Pressure (IOP) can be achieved by medication (eye drops or tablets), laser, or surgery. It is important to remember that there is no cure for glaucoma, and that nerve damage that has already occurred cannot be reversed. In other words, vision that has been lost due to glaucoma cannot be regained; vision can only be retained.
1. Medications – there are a number of medications, which can either reduce the aqueous production or increase the aqueous outflow. They can be used either singly or in combination to get to the Target IOP. After starting treatment, your glaucoma specialist will call you back to confirm its efficacy and to look for any minor side effects.
2. Laser Peripheral Iridotomy (PI) – This is done with the help of a YAG Laser. This procedure helps in opening up a closed angle, the area in the eye from which the fluid drains by making a small hole in the iris (coloured part of the eye). Overcoming this block can automatically prevent eye pressure fluctuations in patients with this type of glaucoma and prevent an acute attack of angle closure from setting in.
3. Trabeculectomy – Trabeculectomy surgery is the gold standard in glaucoma surgery, and is primarily used in patients in whom the eye pressure cannot be controlled with medication. Here a new pathway is created for the aqueous to be able to drain out, thereby relieving hight eye pressure. To get better outcomes anti-fibrotic agents like Mitomycin-C are used.
There is no cure for glaucoma. Just like diabetes and hypertension, glaucoma is a lifelong disease, needing regular and lifelong treatment. Because the disease can worsen silently, regular checkups and repeated tests are essential to ensure stability.
Do not despair!
Glaucoma can be controlled, and patients can lead happy, healthy and productive lives if the disease is detected in time and monitored regularly.