Intraocular pressure (IOP) is the fluid pressure inside the eye. The front half of the eye is filled with a clear fluid known as the “aqueous humor”. This fluid is continuously produced and constantly flows in and within the eye, maintaining normal pressure inside the eye. If there is either reduced drainage or excessive production of this fluid, the pressure in the eye will increase. This increased eye pressure if left untreated can damage the eye (optic) nerve leading to glaucoma and can cause irreversible vision loss.
Dr.Sathi, please tell us, what is ‘Glaucoma’?
Glaucoma is a disease of the nerve of vision (optic nerve) caused by increased pressure in the eye. Glaucoma is the leading cause of IRREVERSIBLE blindness worldwide. In India alone, it affects around 12 million people. The sight loss caused by glaucoma is progressive and, unlike cataract, is irreversible. Fortunately, early diagnosis and treatment can prevent blindness.
How does this happen?
The inside of the eye contains a fluid, which is being produced and drained out of the eye constantly, flowing through a sieve like structure situated at the angle between the transparent cornea and the brown colored iris. When the drainage mechanism becomes ineffective, the pressure in the eye (intra-ocular pressure) increases leading to optic nerve damage.
Who is at risk of developing glaucoma?
Those above 40 years of age, family history of glaucoma, on long term steroids, those with diabetes or hypertension, short sight (myopia), history of injury to the eye.
What are the symptoms of Glaucoma?
Is it associated with pain or redness or decreased vision? Glaucoma is a silent disease, which cannot be seen or felt in the initial stages. Small defects in the vision go unnoticed by the patient and hence the disease will go on progressing as the patient remains unaware of the problem. In the later stages, when the side (peripheral) field of vision is severely affected, i.e from sides, up and below, the patient becomes aware of the problem. In several cases, patients can even lose the vision in one eye completely without realizing it.
What are the different types of glaucoma?
Open angle glaucoma, in which the drainage angles are open but the sieve like meshwork through which the eye fluid has to drain, is clogged.
Closed angle glaucoma, in which, the angle itself is closed, preventing fluid drainage.
Secondary glaucoma, which occurs due to some other disease or treatment in the eye.
Can a person have glaucoma even if the eye pressure is normal?
Yes, some people have nerve damage despite a normal eye pressure. This is called Normal Tension Glaucoma.
What are narrow angles? How does this cause Glaucoma?
The angle is the structure inside the eye which acts as a drainage area for the fluid inside the eye. If this area is narrow, then the fluid does not leave the eye easily which can increase the pressure in the eye. These eyes are more predisposed to develop angle closure glaucoma at a later date. A simple laser procedure could widen the narrow angles, reducing the risk of getting glaucoma. Also, sometimes these narrow angles may get fully closed, leading to a sudden increase in eye pressure and severe eye pain. This is called acute angle closure attack, which needs emergency
How is Glaucoma detected?
What is the procedure in the clinic? At your visit to the clinic, you will be subjected to a detailed eye examination after enquiring about your eye related complaints and general health conditions. Specific examination with Applanation tonometry Gonioscopy and a detailed Optic Nerve examination will be conducted in cases where there is an increased risk or suspicion for Glaucoma. The disease is then confirmed with photographs of the optic nerve head, Visual field test – to map the field of vision and extent of damage in each eye, NFL analysis to calculate the retinal nerve fiber layer thickness and assess its loss in glaucoma and Pachymetry and ORA ,which measure corneal thickness and corneal hysteresis respectively.