Ocular Hypertension

Pressure and the nerve

Eye pressure is a risk factor for glaucoma in the way blood pressure is a risk factor for stroke: higher is riskier, but many people with high readings never come to harm and some with normal readings do. What defines glaucoma is damage to the optic nerve. Ocular hypertension is the state of having the risk factor without the damage, and the purpose of managing it is to make sure damage never begins.

Assessing your risk

A large clinical trial identified the factors that predict which patients with ocular hypertension will develop glaucoma, and they are measured at the evaluation:

• The level of pressure: risk rises steeply above the mid-twenties
• Corneal thickness: a thin cornea both under-reads pressure and independently raises risk
• Age
• The appearance of the optic nerve, particularly a large cup
• Any early change on visual field testing
• Family history, race, diabetes and high myopia

These are combined into an estimate of your five-year risk, which guides the decision.

Treat or monitor?

Patients at low risk are monitored, with pressure, OCT and visual fields repeated every six to twelve months, and treated only if the nerve or field changes. Patients at higher risk (with pressures in the high twenties or above, thin corneas or a suspicious nerve) are offered treatment now, because the trial showed that lowering pressure halves the rate of conversion to glaucoma. Treatment is the same as for glaucoma: drops, or selective laser trabeculoplasty for patients who prefer to avoid them. The choice is discussed openly, including the option of watching carefully.

What monitoring involves

Each visit repeats the pressure measurement and, at intervals, OCT of the nerve fiber layer and a visual field. OCT is the most sensitive early warning: thinning of the nerve fiber layer beyond age-related change is the signal to begin or step up treatment before any vision is affected. Baseline scans at the first visit are what every later scan is compared against.