Diseases of the eye can steal more than sight. Without good eyesight, the world literally becomes duller and less enjoyable.
Our vision guides all our action — studying, working, movement, and practically everything humans do. One can live with most vision impairments; put on a pair of glasses (or contact lenses) and your eyesight is back to normal. For extreme cases of imperfect eyesight, LASIK surgery is an option. Someone developing a cataract with age could get it operated on and regain normal eyesight. But there is one disease that causes irreversible blindness, without the patient realising — glaucoma.
One of the leading causes of blindness in India and worldwide, glaucoma is rightly called the silent thief of sight, because it develops slowly, symptoms remaining highly unnoticeable, until the disease has progressed to some vision loss.
Understanding the human eye
The front of our eyes is nourished and protected by a fluid (aqueous humor), which is constantly generated anew and flown in and out of the eye through a drainage system, made of tubes and angles. The light entering our eyes activates the big bunch of tiny nerves at the back of our eyeballs (the optic nerve) which in turn sends the signal to the brain, forming an image of the things in our view, helping us see.
What is glaucoma?
Glaucoma is an eye disease in which the optic nerve gets damaged. Blind spots are created in patients’ field of vision as nerves begin to die. This typically causes ‘tunnel vision’, or loss of sight from the periphery of the field of vision. As the disease progresses, the field of vision becomes narrower, leading to complete blindness, if left untreated.
Glaucoma is caused by a rise in fluid pressure inside the eye (IOP or intraocular pressure) that damages the optic nerve.
Diabetes, hypertension, eye injury and age can lead to increased IOP. Importantly, there are genetic factors that could put a person at risk of glaucoma even at a young age.
Types of glaucoma
Depending on the reason for increase in the pressure inside the eye, glaucoma is categorised as:
Primary open angle glaucoma: The most common form of glaucoma, in this case, the eye’s drainage canals get clogged, obstructing fluid flow and building up pressure inside the eye.
Primary angle closure glaucoma: In this, the angle in most areas between the iris and cornea gets closed, thus reducing the drainage of the fluid, building up IOP. Angle closure glaucoma may set in with symptoms like severe pain in the eye or forehead, headache, redness, and nausea.
Normal tension glaucoma: In several cases, the IOP may be within normal range, but the patient might develop blind spots in their vision.
Secondary glaucoma: Certain diseases like diabetes, hypertension, or migraine may lead to glaucoma too. Long-term use of steroid medications and refractive errors are risk factors.
Congenital and juvenile forms of glaucoma are also known with children born with the disease or developing it at an early age.
Prevention and treatment
The value of early testing and detection in the prevention of glaucoma cannot be overemphasised. Getting an eye checkup done regularly is the only way to prevent glaucoma, because the eye doctor would assess peripheral vision, IOP (tonometry), optic nerve health (ophthalmoscopy and optical coherence tomography), drainage angle (gonioscopy), and any visual impairments to determine the health of the patients’ eyes, catching symptoms early on. There is no single confirmatory test for glaucoma; the diagnosis is based on the combined results. If glaucoma runs in your family, a genetic test could reveal the severity and onset age of the disease. Genetic tests help get you an early risk assessment and diagnosis, informing your family planning decisions and giving doctors a chance to design more effective treatment regimens.
Treating glaucoma means preventing the damage from spreading further than it already is. Vision that is already lost cannot be restored. It is importat that blurry vision, eye pain, headaches and other vision problems be examined without delay. Eye drops and laser surgeries are the first line of treatment to bring IOP within normal range. When these fail, a surgical solution such as trabeculectomy is employed.
Since glaucoma is a lifelong condition, prescribed eye drops need to be taken daily forever. So, prevention is the only real ‘cure’.
(The author is a science communicator and life science researcher.)