Glaucoma, which is frequently called “the silent thief of sight,” is the most common global cause of permanent blindness. The optic nerve is harmed by high intraocular pressure, which first impairs peripheral vision (what you see out of the corners of your eyes) and then central vision (what you see when looking straight ahead). Most of the time, symptoms are unnoticed until vision loss occurs.
Glaucoma can only currently be treated by reducing elevated ocular pressure. But is treatment necessary for everyone who has elevated ocular pressure? A significant long-term study offers some hints but not yet an entire solution.
Does glaucoma always result from elevated eye pressure?
An estimated three million Americans are thought to be affected by glaucoma, and half of them are unaware of their condition. To find out if someone has glaucoma or is at risk for getting it in the future due to excessive eye pressure, an ophthalmologist can do a thorough eye exam (ocular hypertension). Some patients with high eye pressure may never develop glaucoma, while others will, according to research from the long-running Ocular Hypertension Treatment Study (OHTS).
We continue to learn more about persons with high ocular pressure, their risk of developing glaucoma, and if they can take drugs to prevent glaucoma thanks to the multicenter, randomised clinical trial known as OHTS, which was started in 1994.
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A heterogeneous group of 1,636 ocular hypertension patients from 22 sites across the US were enlisted by the researchers. Participants were randomised to begin early pressure-lowering eye drops (medication group) or close observation for the purpose of studying glaucoma prevention (control group).
In the pharmaceutical group, 4.4% of patients had glaucoma at five years, versus 9.5% in the control group. This indicates that early usage of prescription eye drops helps persons with ocular hypertension delay more than 50% of glaucoma cases.
To test whether commencing treatment later could still delay glaucoma, further study stages allowed the control group to receive ocular pressure-lowering drugs; it did. At age 20, glaucoma affected 42% of those using medication and 49% of those in the control group. The researchers were unable to assess the 20-year risk decrease between the initial starting groups, however, because the study was no longer randomised.
Who participated in the research?
Black people made up a sizable section of the study population (25%) which is significant because historically minorities have been underrepresented in clinical trials. Most of the other participants were white. Ages ranged from forty to eighty (the average was 55). All subjects had normal eye exams, normal vision, and open angle eyes, with the exception of those who had ocular hypertension. None of them had glaucoma at the time.
Has this research altered opinions on when to begin glaucoma treatment?
The five-year data first seemed to indicate that Black people had a higher rate of glaucoma than those of other races. When the researchers took into account crucial factors like age, corneal thickness, a measurement known as optic nerve cup size, and initial peripheral vision test results, the apparent difference vanished.
It turned out that a combination of exam results, rather than just ocular pressure and race, determined glaucoma risk. With the aid of this information, practitioners can more effectively determine if a patient with ocular hypertension has a low, medium, or high risk of developing glaucoma. Such knowledge could assist people in deciding when to start using prescription eye drops to stop vision loss or stop its progression.
What are the shortcoming of this extensive study?
The study contains a number of restrictions:
- Trial participants typically adhere to their medication and appointment schedules better than non-participants, which may lead to real-world glaucoma rates that are higher than those observed in either research group.
- While the initial five years of the OHTS were randomised, later phases allowed for the administration of ocular pressure-lowering drugs to both groups. By the age of 20, the majority of participants—roughly 81% in the pharmaceutical group and 66% in the control group—were taking these drugs. Because of this, evaluating the long-term impact of each initial strategy is challenging.
- With the development of novel diagnostic procedures like ocular coherence tomography and risk indicators like corneal hysteresis, glaucoma detection has become more accurate over time. This may strengthen the case for cautious waiting as a viable choice for those with decreased glaucoma risk due to a number of reasons.
Of course, people who already have glaucoma or other eye disorders, as well as those who have the eye architecture known as narrow angles, are not affected by the study’s findings.
What’s the verdict?
Overall, the results of the 20-year follow-up study support the use of a combination of additional exam results to guide decisions about preventative glaucoma therapy for persons with ocular hypertension. Higher ocular pressures, older age, thinner corneas, larger optic nerve cup diameters, and worse first peripheral vision test results are among the risk factors that increase a person’s likelihood of developing glaucoma.
Eye drops that lower eye pressure can help prevent glaucoma in people who have ocular hypertension, especially when it is present in combination with numerous other risk factors. If you get regular exams to look for early signs of glaucoma, you may be able to put off treatment if you have ocular hypertension and few other risk factors. Any person with ocular hypertension, regardless of whether they are receiving therapy, should have lifelong monitoring because glaucoma is an illness that frequently goes unnoticed.
