What is Glaucoma?
It is a gradual progressive optic neuropathy which is often but not always associated with high intraocular pressure resulting in slow loss of peripheral vision.
It is a leading cause of blindness next only to cataract and is one of the top five disorders targeted by the World Health Organization.
What is the mechanism?
Aqueous humour, a fluid which is secreted by the ciliary body in the eye, normally circulates and egresses out of the eye through a complex meshwork present in the angle recess called the trabecular meshwork (TBM).
The flow of aqueous humour can be restricted at the pupil where the space between lens and iris is very small, at angle recess which is normally a narrow alcove or at the TBM which is like a fine sieve.
This results in build-up of fluid inside the eye and the pressure affects the delicate nerve head of the optic nerve resulting in constriction of the visual field.
What is Intraocular Pressure (IOP)?
Fluid pressure caused by aqueous humour inside the eye is called IOP.
What is normal IOP?
IOP is not a number; it is always expressed as a range. The normal range is between 10 to 20 mmHg
What are the types of Glaucoma?
There are 2 broad classifications of glaucoma
- Primary
- Secondary
Primary can be congenital, open angle or narrow angle.
Secondary can be open or narrow angle depending on many identifiable causes.
In the open angle variant the damage is in the TBM while in the angle closure variant the resistance is at the pupil followed by the narrowing of angle recesses.
What are the risk factors?
While IOP is the only modifiable risk factor, family history is also an important risk factor. One out of every five people with glaucoma has a close relative who has it.
What are the causes of secondary Glaucoma?
Trauma to the eye, certain drugs like steroids, medications that have anticholinergic properties like topiramate can precipitate glaucoma.
Certain retinal pathology itself can cause glaucoma like proliferative diabetic retinopathy.
A hyperopic patient with long sight is more prone to angle closure due to the small structure of the eye.
What are the symptoms of Glaucoma?
Most of the time one remains asymptomatic until significant damage is done.
In angle closure glaucoma there can be transient headaches.
In sudden angle closure attack, there may be eye pain, headache, nausea and vomiting. It is often mistaken for a migraine or GI emergency.
What eye tests does one need to undergo?
The tests help in justifying the diagnosis, in making decisions about the management, how effective the treatment has been and whether there has been any progression in the disease.
What are the treatment modalities?
Depending on the type and severity of glaucoma, there are various modalities of treatment from laser and topical medications to surgery. Treatment is tailored depending on the disease’s severity, patient’s age and quality of life.
Is it curable?
Glaucoma, by definition, is a progressive disease no matter what treatment is given. Treatment definitely slows down the progression and stabilises and prevents the visual loss. Hence, early diagnosis, awareness, regular check-ups and prompt treatment is a must to prevent visual loss.
