Who needs treatment for ocular hypertension?

Who needs treatment for ocular hypertension?

A long-term study explores risk factors for glaucoma and treatment options for people with high eye pressure.

Glaucoma is often described as the silent robber of sight, and is the most common cause of irreversible blindness in the world. Elevated pressure in the eye damages the optic nerve, first stealing peripheral vision (what you see in the corners of your eyes) and later damaging central vision (what you see when looking straight ahead). Usually, people do not notice any symptoms until vision loss occurs.

Lowering elevated intraocular pressure is the only known treatment to prevent or stop glaucoma. But does everyone with higher-than-normal eye pressure need treatment? A large, long-term study provides some evidence, although not yet a complete answer.

Does everyone with high eye pressure suffer from glaucoma?

In the United States, glaucoma affects an estimated 3 million people, half of whom do not know they have it. An ophthalmologist can perform a comprehensive eye exam to determine if a person has glaucoma or is at risk of developing it in the future due to high eye pressure (ocular hypertension). Research from a long-term study of treating ocular hypertension (OHTS) shows that some people with high eye pressure may never develop glaucoma, while others will.

Launched in 1994 as a multicenter, randomized clinical trial, OHTS continues to inform our understanding of people with high intraocular pressure, their risk of developing glaucoma, and whether they can take medications to prevent glaucoma.

The researchers enrolled a diverse group of 1,636 participants with ocular hypertension from 22 sites across the United States. For the Glaucoma Prevention Study, participants were randomly assigned to start early eye drops to lower intraocular pressure (drug group) or close monitoring (control group).

At five years, the data showed that 4.4% of participants developed glaucoma in the drug group, compared to 9.5% in the control group. This tells us that early use of medicated eye drops helps delay more than 50% of glaucoma cases in people with ocular hypertension.

During later stages of the study, the control group could receive medications to lower intraocular pressure to see if starting treatment later could delay glaucoma; she did. At 20 years, about 49% of those in the control group and 42% of the drug group developed glaucoma. However, because the study is no longer randomized, the researchers were unable to compare the 20-year risk reduction between the initial starting groups.

Who participated in the study?

A high proportion of study participants (25%) were black, which is significant because minorities have historically been underrepresented in clinical trials. Most of the other participants were white. Ages ranged from 40 to 80 years (median was 55 years). With the exception of ocular hypertension, all participants underwent normal eye examinations, normal vision, and an anatomy of the eye known as open angles. None of them had pre-existing glaucoma.

Has this research changed thinking about when to start glaucoma treatment?

At first glance, the five-year data indicated that black individuals had a higher incidence of glaucoma than people of other races. However, this apparent difference disappeared when the researchers controlled for important characteristics such as age, corneal thickness, a measure called optic nerve cup size, and initial peripheral vision test scores.

It turns out that the risk of glaucoma depends not only on eye pressure and race, but on a combination of test results. This information helps guide doctors in determining whether a person with ocular hypertension is at low, medium, or higher risk of developing glaucoma. Having such information can help people decide when to start using medicated eye drops to prevent vision loss or slow its progression.

What are the limitations of this long-term study?

The study has several limitations:

  • Typically, trial participants comply with medications and appointments better than non-participants, which could make real-world glaucoma rates higher than with either group in the study.
  • While the first five years of OHTS were randomly selected, during the later stages, both groups could receive medications to lower intraocular pressure. By the age of 20, most participants were using these drugs: about 81% in the drug group and 66% in the control group. This makes it difficult to compare the long-term effect of each starting approach.
  • The detection of glaucoma has improved over the years, with new diagnostic tests such as computed tomography of the eye and newly discovered risk factors such as slowing of the cornea. This may also support watchful waiting as a reasonable option for people at lower risk of developing glaucoma based on a combination of factors.

Of course, the study findings do not apply to those who already have glaucoma or other eye diseases, the anatomy of the eye known as narrow angles.

What is the bottom line?

Overall, 20 years of follow-up data support decisions about prophylactic glaucoma treatment for people with ocular hypertension based on a combination of additional test results. People with a greater number of risk factors — including higher eye pressure, older age, thinner corneas, larger optic nerve cups, and worse initial peripheral vision test scores — are more likely to develop glaucoma.

If you have ocular hypertension, especially with many other risk factors, eye drops that lower eye pressure can help prevent glaucoma. If you have ocular hypertension and fewer additional risk factors, you are likely to delay treatment if you have regular checkups for early signs of glaucoma. But because glaucoma is an often silent condition, anyone with ocular hypertension should have lifelong monitoring regardless of their treatment status.

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