Who needs treatment for ocular hypertension?

Long-term study explores glaucoma risk factors and treatment options for people with ocular hypertension.

Often described as the silent thief of sight, glaucoma is the most common cause of irreversible blindness worldwide. High pressure in the eye damages the optic nerve, first stealing peripheral vision (what you see at 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 high eye pressure is the only treatment known to prevent or halt glaucoma. But should everyone with higher than normal eye pressure be treated? A large long-term study provides some clues, but not yet a complete answer.

Do all people with ocular hypertension develop glaucoma?

In the United States, glaucoma affects approximately three million people, half of whom are unaware they have it. An eye doctor 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 pressure in the eye (ocular hypertension). Research from the long-running Ocular Hypertension Treatment Study (OHTS) shows that some people with ocular hypertension may never develop glaucoma, while others will.

Initiated in 1994 as a multicenter randomized clinical trial, the OHTS continues to inform our understanding of people with ocular hypertension, their risk of developing glaucoma, and their ability to take medication to prevent glaucoma.

The researchers recruited a diverse group of 1,636 participants with ocular hypertension from 22 sites across the United States. To study glaucoma prevention, participants were randomly assigned to start either early eye pressure-lowering eye drops (medication group) or close observation (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.

In later phases of the study, the control group might receive eye pressure-reducing drugs to see if starting the drugs later might further delay glaucoma; it made. By age 20, about 49% of people in the control group and 42% of those in the drug group developed glaucoma. However, because the study was no longer randomized, the researchers were unable to compare the 20-year risk reduction between the original starting groups.

Who participated in the study?

A high proportion of study participants (25%) were black, which is important because minorities have historically been underrepresented in clinical trials. The other participants were predominantly white. The ages ranged from 40 to 80 (the average was 55). Except for ocular hypertension, all participants had normal eye exams, normal vision, and ocular anatomy known as open angles. None had pre-existing glaucoma.

Has this research changed the way of thinking about when to start treating glaucoma?

At first glance, the five-year data suggested that black people had a higher rate 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 measurement called optic nerve cup size, and baseline peripheral vision test results.

It turned out that the risk of glaucoma didn’t just depend on eye pressure and race, but on a combination of test results. This information helps clinicians determine whether someone with ocular hypertension is at low, medium, or high risk of developing glaucoma. Having such information could 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:

  • Trial participants generally adhere better to medications and appointments than those who don’t, which could make real-world glaucoma rates higher than what happened with either the other of the study groups.
  • While the first five years of OHTS were randomized, in later phases both groups could receive medication to lower eye pressure. By age 20, most participants were using these drugs: about 81% in the drug group and 66% in the control group. It is therefore difficult to compare the long-term effect of each starting approach.
  • Detection of glaucoma has improved over the years, with new diagnostic tests such as ocular coherence tomography and recently discovered risk factors such as corneal hysteresis. This may further support watchful waiting as a reasonable option for people at low risk for glaucoma based on a combination of factors.

And, of course, the study results don’t apply to those who already have glaucoma or other eye conditions, and the eye anatomy known as narrow angles.

What’s the bottom line?

Overall, the 20-year follow-up data supports making decisions about glaucoma preventive treatment for people with ocular hypertension based on a combination of additional test results. People with a higher number of risk factors — including higher eye pressures, older age, thinner corneas, larger optic nerve cup sizes, and lower initial peripheral vision test results — are more likely to develop glaucoma.

If you have high blood pressure in the eye, especially in combination with several other risk factors, eye pressure-reducing eye drops may help prevent glaucoma. If you have ocular hypertension and fewer additional risk factors, you can probably 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 treatment status.

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