Ocular hypertension (OHT) is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.
Current consensus in ophthalmology defines normal introcular pressure (IOP) as that between 10 mmHg and 21 mmHg. Elevated IOP is the most important risk factor for glaucoma, so those with ocular hypertension are frequently considered to have a greater chance of developing the condition.
Intraocular pressure can increase when a patient lies down. There is evidence that some glaucoma patients (e.g., normal tension glaucoma patients) with normal IOP while sitting or standing may have intraocular pressure that is elevated enough to cause problems when they are lying down.