 One study found a conversion rate of 18% within 5 years, meaning less than 1 in 5 people with an elevated intraocular pressure will develop glaucomatous visual field loss over that period of time.It is a matter of debate whether every person with an elevated intraocular pressure should receive glaucoma therapy; currently most ophthalmologists favor treatment of people with additional risk factors.Open-angle glaucoma accounts for 90% of glaucoma cases in the United States.