GLAUCOMA

‘The disease affects about eight million people in India. In the world, about 6.7 million people are totally blind. Fifty percent of the population in India are unaware about the disease in their
eyes and are in the process of becoming blind.’

Every eye has certain amount of intraocular pressure to maintain its structure and function. This is called as normal intraocular pressure, which ranges between 13 to 21 mm of mercury.
If there is rise of intraocular pressure which is not compatible with normal health and function of the eye, we call it glaucoma. Usually when the pressure exceeds 21 mm of mercury (Hg), we consider that the patient is glaucomatous but in some eyes, patient may suffer glaucomatous damage even at the pressure of 17-18mm of mercury. We term this condition as Normotensive glaucoma. In other words, pressure is a very important parameter to diagnose glaucoma but certain other factors may play a role to cause glaucomatous damage even if the pressure is within normal range.

There are following types of glaucomas:

1 Chronic Simple Glaucoma (Open Angle Glaucoma)
2 Acute Congestive Glaucoma (Angle closure or Narrow Angle Glaucoma)
3. Secondary Glaucomas: These are the glaucomas due to some other disease in the eye like uveitis, cataract, trauma, hemorrhage, tumour etc.
4. Steroid Glaucoma
5. Congenital Glaucoma. Glaucoma occurring in a newborn child.

Chronic Simple Glaucoma.

This is the commonest glaucoma occurring in ……..percent of persons. This glaucoma has a very incipient onset with practically no symptoms but has the potentiality to cause gradual and total irreparable blindness.

What Causes Rise Of IOP. Aqueous humour is constantly formed by the ciliary body. This aqueous travels to the anterior chamber, performs its function of nutrition and take away waste products and leaves the eyeball by traveling towards angle of anterior chamber and than through the trabecular spaces and out of the eyeball. This process of constant formation and drainage of aqueous maintains the intraocular pressure within the normal range i.e., 13 to 21mm Hg. In some patients, the trabecular spaces gradually become narrow and hence produces resistance to the outflow, thereby the intraocular pressure gradually rise which may quietly and slowly damage the structure and function of the eye.

Age Of Onset. This glaucoma usually occurs after the age of 35 years but may occur in young age also. With the age, the incidence of the disease increases and hence it becomes a significant aging problem. The incidence varies from country to country but in India, almost 3-4 percent of the population after the age of 40 suffer from this problem and out of this 50 percent of the patients are unaware of it and hence gradually become blind. The incidence in coloured races is more than in white races.
Hereditary. Most often this disease is hereditary and hence children with parents or grand parents having glaucoma, must get them examined at the age of 30 and 35 and thereafter every two years. The incidence is 15 times higher than general population.
The incidence is still higher if a sibling has the disease.

Risk Factors. Main risk factors are raised IOP, hereditary, myopic refractive error, diabetes, hypertension and advanced age. Myopic eyes have about 20 percent more chances of getting glaucoma and diabetes increases the incidence by about 10 percent.

Symptoms. Almost 30 percent of patients have no symptoms till the disease is quite advanced. Some patients may have mild blurring of vision or complain of simply watering in the eyes not responding to conventional drops, ocular discomfort or pain, visual fatigue or headache. Patients having normal distance vision may complain of defective near vision much before the common age of onset of presbyopia i. e., at the age of 35-38 years. Some patients with moderately advanced disease may have delayed dark adaptation or dusk blindness. Since the disease mostly affects the field of vision and hence quite a large number of patients do not visit ophthalmologist since their vision may continue to be almost 6/6 even with moderately advanced disease.
Some patients may complain of photophobia or seeing of coloured haloes.

Signs. Following are the signs of glaucoma
1 Raised IOP.
2Affection of field of vision
3 Pupillary reaction may become sluggish
4 Colour of pupil may become bluish-gray
5 Occasionally epiphora- watering of eyes

Diagnosis.

Diagnosing of glaucoma is not always easy. The doctors have to weigh various factors in labeling a patient as glaucomatous since unnecessary use of antiglaucoma drugs may have some adverse effects in some patients and missing the diagnosis may definitely be very harmful. Hence, it is vital that borderline cases of glaucoma is fully examined and investigated by an expert before confirming the diagnosis. Recording of intraocular pressure alone is not sufficient since patient with IOP of 25 mm may not be glaucomatous but a patient with only 14 mm may be suffering glaucomatous damage. And hence almost 30 percent of patients may require services of an expert glaucomologist who has well equipped clinic.


Diagnosis is mostly based on following:

1.Symptoms and Risk factors. As stated above.
2 Tonometry. Recording of IOP
This is the most important test carried out with the help of instruments like Schiotz Tonometer, Goldmann Applanation Tonometer or Non- Contact Tonometer. Later two techniques are more precise.
3.Fundus Examination or Ophthalmoscopy
With the help of Ophthalmoscope, we examine the Retina and the Optic Disc to evaluate effect of raised intraocular pressure on these structures.
Due to increased pressure, a cup in the central part of Optic disc becomes enlarged and the disc colour becomes pale. This results in affection of the fields. Larger the cup or pallor of the disc, more the irreversible damage to the eye. Recently introduced more sophisticated Scanning Laser Ophthalmoscope can pick-up the changes in the retina and optic disc much earlier.
It is said that by the time coventional ophthalmoscopy appreciate the changes in the disc, lot of damage has already occurred to the field of vision.
3.Perimetry. Process of recording the field is called Perimetry.It is a special test that produces map of the complete field of vision. Very early glaucoma can be picked up by this test, more so when a sophisticated Computerized Automated Perimetry is used.
Goldmann Perimeter is moderately reliable manual perimeter but it takes lot of time and hence the cooperation of the patient is difficult.
Computerized Automated Permeters are far more relable and rapid and their results can be stored in the compuer and compared when repeat procedure is done. In these procedures, lights of varying intensities are flashed automatically by a computer around a bowel shaped area and the patient is asked to press a button when he sees the light. This way a definite record of area of field of vision which is partially or totally affected is obtained.
The procedure is more vital for diagnosis. specially in eyes where is pressure is just on the borderline. Recording of field is also essential to evaluate the result of therapy.
Automated Computerized Perimetry is the latest and very precise method to record the fields. Such a record shall distinctly show as to how much field of vision is totally lost and how much area is partly affected.
4.Gonioscopy. Procedure of examination of Angle of Anterior Chamber is called Gonioscopy and is very helpful to precisely pinpoint the type and cause of glaucoma.

It is done with the help of Goldmann Gonio Contact lens.

In recent years still more advanced and sophisticated tests like Confocal Scanning Laser Tomography, Scanning Laser Polarimetry and Optical Cohrens Tomography have emerged which may pickup glaucomatous damage at a very early stage but these are extremely costly and sparsely available.

Prevention. We cannot prevent glaucoma but what we can prevent is the blindness if we are aware of this disease and the risk factors.
Glauco patient under an expert shall rarely become blind if he religiously follows doctors instruction as regards frequency of therapr and regular checkup.

How is glaucoma treated

Medical therapy is aimed to control the intraocular pressure and worsening of visual fields. Medical therapy only controls the disease but does not cure it and hence medications has to be instilled very regularly at prescribed time. Any carelessness even for a day is harmful to the patient.
Basically there are three types of drugs:
1. Drugs which decreases the formation of aqueous
2. Drugs which increases the outflow of aqueous through the trabecular meshwork or Uveo- scleral channels.
3. Drugs which do both.
In modern times , with the advancement of therapy, the doctors have various options to control IOP by utilizing specific drug in a specific person and use of single or multiple drugs.
The principle of treatment is ‘ to use least amount of medication that produces the best results with the fewest side effects.’
Evaluating all factors , the doctor prescribes a drug which can effectively reduce the IOP.At times by trial and error, the doctor finds out a single or multiple drugs which can achieves ‘ target IOP’ i.e. an intraocular pressure which is going to be safe for that particular person.
Patient must help the doctor by giving a correct family history