If your vision measures 20/20 and your eye pressure is normal, is glaucoma nothing to worry about? Not necessarily. Glaucoma is a leading cause of blindness in which the optic nerve is gradually damaged and the field of vision narrows. Because there are no clear symptoms in the early stages, many patients discover the disease only after it has progressed considerably.
On the 17th at 9 p.m., Dr. Na Jung-hwa, director of the Glaucoma Center at Hanil Eye Hospital, appears on SedailyTV's "Doctors Now" to explain why glaucoma can develop even with normal vision and normal eye pressure, along with early detection and treatment options. "Seeing well does not mean you do not have glaucoma," Na said. "What matters is catching it early, while there are no symptoms, and managing it consistently."
Glaucoma at 20/20 Vision, and Normal Pressure Is No Reassurance
Glaucoma damages the optic nerve that connects the eye to the brain, narrowing the field of vision. Even after nerve damage begins, patients feel almost no symptoms at first, and the loss typically starts in the peripheral rather than the central field. As a result, by the time symptoms become noticeable, the disease has often advanced significantly.
"You should not assume that normal vision means a normal optic nerve," Na said. Normal eye pressure is no cause for comfort either. In South Korea, normal-tension glaucoma — in which the disease develops even though pressure falls within the generally accepted normal range — is common.
The normal range is simply a statistical band derived from measuring large numbers of people, and falling within it does not mean everyone's optic nerve is safe.
"At the same pressure of 15 mmHg, one person's optic nerve may be healthy while another develops glaucomatous damage," Na said. "The average eye pressure among Koreans is about 14 mmHg, which is relatively low, and normal-tension glaucoma accounts for a large share of glaucoma cases in this country."
Regular Exams for Those Over 40, With Family History or Myopia
The main risk factors for glaucoma are elevated eye pressure, family history and myopia. Incidence also rises with age.
Findings vary by study, but some reports put the risk at more than twice as high when a parent has glaucoma and more than three times as high when a sibling does. The more severe the myopia, the more the structure of the eyeball and the area around the optic nerve change, which can leave the eye vulnerable to glaucoma.
Na advised regular optic nerve examinations for people aged 40 and over, those with a family history of glaucoma, those with myopia and those who have been told their eye pressure is high. A detailed workup is also needed for anyone whose health screening returns results such as "suspected glaucoma" or "increased cup-to-disc ratio."
Glaucoma is difficult to diagnose from vision and eye pressure alone. Doctors check the structure and thickness of the optic nerve through fundus examination and optical coherence tomography (OCT), then use visual field testing to determine where and how severely the field has been damaged. Eye pressure and the structure of the anterior chamber angle are examined as well for a comprehensive diagnosis.
Optic Nerves Rarely Recover, So Treatment Targets Eye Pressure
What matters most in glaucoma is that once the optic nerve is damaged, current medicine cannot bring it back. The goal of treatment is not to restore damaged nerve tissue but to prevent further damage and preserve the remaining optic nerve for as long as possible.
"Lowering eye pressure is the most firmly established way we have to slow the progression of glaucoma," Na said.
Treatment generally begins with pressure-lowering eye drops, which work either by reducing the production of aqueous humor inside the eye or by helping it drain out. Because glaucoma is a chronic condition, most cases require consistent management over the long term.
Laser treatment is also used, depending on the patient's condition. In selective laser trabeculoplasty (SLT), the most common such procedure, a laser is applied to the trabecular meshwork through which aqueous humor drains, improving outflow. For patients who experience side effects from medication or find it difficult to apply drops daily, SLT may be considered as a first-line treatment in some cases.
Surgery is considered when drops and laser treatment fail to lower pressure sufficiently. Such procedures reduce pressure by creating a new drainage channel for aqueous humor. Minimally invasive glaucoma surgery, which involves smaller incisions and an easier recovery, has also come into use in recent years.
Avoid Activities That Raise Eye Pressure, Such as Lifting Heavy Objects
There is no evidence that looking at a smartphone or computer screen in itself worsens glaucoma.
Lifting heavy objects or holding head-down positions such as a handstand, however, can temporarily raise eye pressure and is therefore inadvisable for glaucoma patients. Sleeping face-down can also elevate pressure, so patients with advanced disease or with markedly faster progression in one eye may want to review their sleeping position.
More important than lifestyle habits, though, is sticking with the prescribed treatment.
"Not every glaucoma patient goes blind," Na said. "Many patients lower their eye pressure, manage the condition consistently and preserve their vision into old age."
"In the early stages there are almost no symptoms, so patients do not feel any better after using their drops, and some stop treatment on their own," Na added. "The most important thing is to detect it early, not give up on treatment and keep managing it consistently to prevent as much further deterioration as possible."