Which statement about intraocular pressure is true?

• A. The normal range is 10-21 mm Hg
• B. The normal range is 5-9 mm Hg
• C. The normal range is 22-30 mm Hg
• D. The normal range is 0-4 mm Hg

Answer: (A)

Intraocular pressure reflects the balance between aqueous humor production by the ciliary body and its drainage through the trabecular meshwork and other outflow routes. In most adults, the normal range is about 10-21 mm Hg, with the average around 15–16 mm Hg. Values below this range can indicate hypotony, which may occur after surgery or inflammation, while higher values raise concern for ocular hypertension or glaucoma, though diagnosing glaucoma also depends on optic nerve appearance and visual field testing rather than IOP alone. It’s also important to remember that some people can have glaucoma with normal IOP (normal tension glaucoma). So the statement that the normal range is 10-21 mm Hg is true, while the other ranges do not represent the typical normal range.