Glaucoma, often called the silent thief of sight, is the leading cause of irreversible blindness. High pressure in the eyes damages the optic nerve. This causes peripheral vision to be lost (what you can see from the corners of your eye) and then a central idea to be affected (what you can see when you look straight ahead). Most people don’t notice symptoms until they experience vision loss.
Lowering high eye pressure is the only treatment that can prevent or stop glaucoma. Is it necessary to treat everyone with higher-than-normal eye pressure? Although a large, long-term study has provided some clues, it still needs to be completed.
Is glaucoma a common condition in people with high eye pressure?
Glaucoma is a condition that affects approximately three million Americans. Half of these people don’t know they have it. An ophthalmologist can do a comprehensive eye exam to determine if someone is suffering from glaucoma or is at risk of developing it. The long-running Ocular Hypertension Treatment Study (OHTS) has shown that some people with high eye pressure might not develop glaucoma. However, others may.
OHTS was launched in 1994 as a multicenter, randomized clinical trial. It continues to help us understand people with high eye pressure and their risk of developing glaucoma.
Researchers recruited a diverse group from the US, consisting of 1,636 people with ocular Hypertension. Participants were randomly assigned to the early eye pressure-lowering drops (medication) or close observation (control groups) to study glaucoma prevention.
The data showed that 4.4% had glaucoma after five years, while 9.5% of the controls developed it. This indicates that medicated eye drops can be used early to delay more than 50% of cases of glaucoma in patients with ocular Hypertension.
The control group received eye pressure-lowering medication in the later phases of the study. This was done to determine if starting medication later would still delay the onset of glaucoma. About 49% and 42% of the patients in the medication groups developed glaucoma after 20 years. The researchers could not compare the 20-year risks between the two groups because the study was not random.
Who participated in the study?
The study participants were a large proportion of Blacks (25%) which is significant because historically, minorities have been underrepresented in clinical trials. Other participants were predominantly white. The average age was 55. All participants had regular eye examinations, normal vision, and eye anatomy, known as the open angle. None had pre-existing glaucoma.
Is this new research changing your mind about when to start treating glaucoma?
The five-year data showed that Black people had a higher glaucoma incidence than other races. This apparent difference vanished when researchers adjusted for essential characteristics like age, cornea thickness, optic nerve cup size, and initial peripheral vision scores.
Glaucoma risk did not depend on eye pressure or race. It was a combination of examination findings. This information can help clinicians determine if a person suffering from ocular Hypertension is at high, moderate, or low risk of developing glaucoma. This information can help people determine when medicated drops should be used to slow or prevent vision loss.
What are the limitations to this long-term study of human behavior?
There are several limitations to the study:
- Trial participants are more likely to comply with appointments and medications than those who were not. This could make the real-world rate of glaucoma higher than what was observed with either group.
- OHTS was randomized for the first five years. However, both groups could be given eye pressure-lowering medication during later phases. Most participants used these medications 20 years later: 81% in the drug and 66% in the control groups. It isn’t easy to compare the long-term effects of each approach.
- Glaucoma detection has become easier with new diagnostic tests like ocular coherence and recently discovered risk factors like corneal hypersensitivity. Watchful waiting may be an option for those at lower risk of glaucoma if a combination of factors is used.
However, the study results do not apply to patients with glaucoma and other eye diseases.
What is the bottom line?
The 20-year follow-up data support decisions about preventive glaucoma treatment for ocular hypertension patients. This was based on additional exam findings. Glaucoma is more common in those with higher risk factors, such as higher eye pressures and older age, thinner corneas or larger optic nerve cups, and lower initial peripheral vision scores.
Ocular Hypertension can be prevented if you use eye pressure-lowering drops. A brief office procedure called selective laser trabeculoplasty may also help. Regular exams can help detect signs of glaucoma early if you have ocular Hypertension. Ocular Hypertension is a silent condition that can be difficult to detect. However, everyone who has it should have lifelong monitoring.
