A disease that affects the optic nerve, glaucoma is the third most common cause of blindness in the country. Approximately, 11.2 million people aged 40 years and older have glaucoma in India but only 10% of them know they have it. The numbers can be more, as experts say 90% of cases go undetected.
A disease caused by an increase in pressure in the eyes, it is asymptomatic and hence called the ‘silent killer of vision’. Though those over 40 are at risk and need regular checkups, only 2% of the urban population is aware of the disease. Many have heard about hypertension, but are unaware that high pressure in the eyes can damage the optical nerves.
“Aqueous humor, a clear fluid inside the eye, is normally secreted and continuously drained via microscopic outlets in the eye. Blockage in these channels leads to fluid accumulation within the eye and this eventually raises the normal intraocular pressure (IOP). This will cause optic nerve damage. Such type of glaucoma can occur without any pre-existing eye disease,” says Dr S Soundari, Regional Head-Clinical Services, Dr Agarwals Eye Hospital, Chennai.
During annual checkups, doctors check the pressure in the eye to determine if the patient is at risk. Normally, IOP should be 15-21mmHg, if it goes above 21 mmHg it is considered abnormal. “We have to first see why the pressure is elevated and check the optic nerve and other parts. If they are normal, then that person can be put on continuous monitoring,” says Dr M R Chitra, director, the Regional Institute of Ophthalmology and Government Ophthalmic Hospital, Chennai.
Though it is asymptomatic in rare cases, if the pressure in the eye is very high people might see rings (halos) around light, and feel pain, headache, nausea and other symptoms. “There are two main types of glaucoma - primary and secondary. The latter is caused due to complications like injury and diabetes. The use of steroids also can cause secondary glaucoma. This is important as in India people use steroids indiscriminately. There is also congenital glaucoma,” said Dr Ronnie George, director (the glaucoma department), at Sankara Nethralaya Hospital, Chennai, and director of research, Medical Research Foundation.
There will be a reduction of the field of vision if the optic nerve is affected and finally, the vision will be like looking through a tube. “If that too is not controlled, it results in complete vision loss. Since it starts with damaging the peripheral vision, most people don’t realize they have a problem,” Ronnie adds.
Glaucoma is common in adults in the age group of 40-50 years. “It is important for those in their 40s and above to get regular eye check-up once every year. If the pressure is high, vision loss can happen within months. Otherwise, it can take nine to ten years,” said Dr Ronnie. “Many patients are aware of blood pressure but many do not know that there is eye pressure. So, people who come to the hospital are checked for eye pressure and if any abnormality is detected they will be followed up,” said Dr Chitra.
Treatment depends on the type of glaucoma and it is mostly controlled by administering drops and surgery, say doctors. There are several surgical management techniques for glaucoma including minimally invasive glaucoma surgery.
“This is the latest innovation in glaucoma management which is safer and less invasive alternative to conventional glaucoma treatment. The advantages include faster recovery time and minimal disruption of eye tissues. This is useful in case future interventions are needed,” said Dr Soundari. Other surgical management includes trabeculectomy, a filtering surgery, where an alternate drainage pathway is created to lower the eye pressure. “In this procedure, a piece of drainage angle tissue is removed to create an opening to allow the fluid to drain out of the eye bypassing the clogged channels,” she adds.
“There are also glaucoma drainage devices. These devices have shown successful IOP control in complicated glaucomas like neovascular glaucoma, uveitic glaucoma and previously failed trabeculectomy,” says Soundari. The aim of treatments is to reduce eye pressure to a target level that will prevent damage to the optic nerve. “The choice of treatment, depending on the type and severity of glaucoma, includes medication, laser therapy and surgical intervention,” she adds. In addition to conventional methods of detection, doctors and researchers are also studying the possibilities of using AI and genetics for early detection.
“Other methods being studied include assessing genetic risk factors at birth and whether we can tell which patient can develop glaucoma. We are also doing a study on the kind of biochemical changes that happen in glaucoma and looking at how to improve surgical outcomes,” Dr Ronnie adds. Awareness about glaucoma is very poor in India, say doctors.
“Years back, we did a survey and found that only 2.5% of urban and 1% of rural population have heard about it,” said Ronnie. Glaucoma is the most common cause of irreversible blindness in India and the second most common cause globally. In India 10% of glaucoma patients have blindness. “Enlarged eyeballs in children is also a sign of glaucoma and immediate surgery should be done. Any delay will cause vision loss,” adds Dr Ronnie.