Glaucoma is a group of eye diseases characterized by damage to the optic nerve usually due to excessively high intraocular pressure (IOP). This increased pressure within the eye, if untreated can lead to optic nerve damage resulting in progressive, permanent vision loss, starting with unnoticeable blind spots at the edges of the field of vision, progressing to tunnel vision, and then to blindness.
According to Dr.Asghar Hussain Naqvi Syed Ophthalmic surgeon and Glaucoma specialists at Aggarwal’s Eye Clinic Secunderabad, Glaucoma is a group of eye diseases characterised by damage to the optic nerve usually due to excessively high intraocular pressure (IOP) This increased pressure within the eye, if untreated can lead to optic nerve damage resulting in progressive, permanent vision loss, starting with unnoticeable blind spots at the edges of the field of vision, progressing to tunnel vision, and then to blindness.
Estimated to affect 12 million Indians and causes 12.8% of the blindness in the country. Prevalence of glaucoma is between 2% and 13% and is a leading cause of preventable blindness. The risk of glaucoma increases with age but can strike any age group, even newborn infants, and fetuses.
Glaucoma can be classified into two categories: open-angle glaucoma and narrow-angle glaucoma.
Glaucoma is also a secondary condition of over 60 widely diverse diseases and can also result from injury, inflammation, tumor, or in advanced cases of cataract or diabetes.
Causes and Symptoms
The cause of vision loss in all forms of glaucoma is optic nerve damage. There are many underlying causes and forms of glaucoma. Most causes of glaucoma are not known, but it is clear that a number of different processes are involved, and a malfunction in any one of them could cause glaucoma. The cause of optic nerve damage in normal-tension glaucoma is also unknown, but there is speculation that the optic nerves of these patients are susceptible to damage at lower pressures than what is usually considered to abnormally high. It is probable that most glaucoma is inherited.
Symptoms
At first, chronic open-angle glaucoma is without noticeable symptoms. The pressure build-up is gradual and there is no discomfort Moreover, the vision loss is too gradual to be noticed and each eye fills-in the image where its partner has a blind spot. However, if it is not treated, vision loss becomes evident, and the condition can be very painful.
On the other hand, acute closed-angle glaucoma is obvious from the beginning of an attack. The symptoms are blurred vision, severe pain, sensitivity to light, nausea, and halos around lights. This is an ocular emergency and needs to be treated immediately. Similarly, congenital glaucoma is evident at birth. Symptoms are big building eyes, cloudy corneas, excessive tearing, and sensitivity to light.
Treatment
When glaucoma is diagnosed, drugs, typically given as eye drops, are usually tried before surgery. Several classes of medications are effective at lowering IOP and thus preventing optic nerve damage in chronic and neonatal glaucoma.
There are several types of laser surgery used to treat glaucoma. Laser peripheral iridotomy makes an opening in the iris allowing the fluid to drain, argon laser trabeculoplasty is aimed at the fluid channel opening to help the drainage system function and laser cyclophotocoagulation is used to decrease the amount of fluid made.
Trabeculectomy is a microsurgery, also called “filtering surgery” has been used in many different types of glaucoma.
Recently, artificial drainage devices liked Ahmed Glaucoma Valve (AGV) and Express shunt have become popular.
Prevention
Because glaucoma may not initially result in symptoms, the best form of prevention is to have regular eye exams.
Patients with narrow angles should avoid certain medications (even over-the-counter medications, such as some cold or allergy medications). Any person who is glaucoma-susceptible (i.e. narrow angles and borderline IOPs) should read the warning labels on over-the-counter medicines. Steroids may also raise IOP, so patients may need to be monitored more frequently.
Not enough is known about underlying mechanisms of glaucoma to prevent the disease itself. However, prevention of optic nerve damage from glaucoma is essential and can be effectively accomplished when diagnosed and treated. As more is learned about the genes that cause glaucoma, it will become possible to test DNA and identify potential glaucoma victims, so they can be treated even before their IOP becomes elevated.