Normal intraocular pressure ranges between which values?

• A. 5 to 15 mm Hg
• B. 20 to 30 mm Hg
• C. 10 to 20 mm Hg
• D. 15 to 25 mm Hg

Answer: (C)

Intraocular pressure is the fluid pressure inside the eye, set by the balance between production of aqueous humor and its outflow. The normal range is typically about 10 to 20 mm Hg. This window is used because most healthy eyes function well within it, with optic nerves tolerating pressures here without damage. Pressures above roughly 21–25 mm Hg are considered elevated and may indicate ocular hypertension or glaucoma, especially if there are optic nerve changes or visual field loss. There can be small day-to-day and individual variations due to factors like corneal thickness, but a single reading outside this range is not by itself diagnostic. Therefore, 10 to 20 mm Hg best reflects normal intraocular pressure.