What is a normal intraocular pressure and which device is used to measure it?

What is a normal intraocular pressure and which device is used to measure it?

• A. 22 mm Hg, measured by tonometry
• B. 40 mm Hg, measured by ophthalmoscopy
• C. 10 mm Hg, measured by tonometry
• D. 28 mm Hg, measured by slit-lamp

Answer: (A)

Intraocular pressure is measured in millimeters of mercury (mm Hg), with a typical normal range of about 10–21 mm Hg. The instrument used to measure it is tonometry, which directly assesses ocular pressure. The option that pairs tonometry with a value around the upper end of normal (22 mm Hg) reflects the correct measurement method and a plausible normal-to-borderline reading, making it the best choice. Ophthalmoscopy looks at the retina and optic nerve and does not measure pressure; a slit-lamp is an exam setup that may host a tonometer, but the actual pressure measurement is done with tonometry; a much higher value (40 mm Hg) would be clearly abnormal, while a much lower value (10 mm Hg) is at the lower end of normal.

Intraocular pressure is measured in millimeters of mercury (mm Hg), with a typical normal range of about 10–21 mm Hg. The instrument used to measure it is tonometry, which directly assesses ocular pressure. The option that pairs tonometry with a value around the upper end of normal (22 mm Hg) reflects the correct measurement method and a plausible normal-to-borderline reading, making it the best choice. Ophthalmoscopy looks at the retina and optic nerve and does not measure pressure; a slit-lamp is an exam setup that may host a tonometer, but the actual pressure measurement is done with tonometry; a much higher value (40 mm Hg) would be clearly abnormal, while a much lower value (10 mm Hg) is at the lower end of normal.