Intraocular pressure is monitored by?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2018

Explanation

A tonometer is the specific medical instrument designed to measure intraocular pressure (IOP).
The procedure of measuring IOP with a tonometer is called tonometry.
Tonometry is a crucial diagnostic test for screening and managing glaucoma, a condition characterized by high IOP that can damage the optic nerve.
The normal range for intraocular pressure is generally considered to be between 10 and 21 millimeters of mercury (mmHg).
As shown in the image, common types include the Goldmann applanation tonometer (gold standard), the Schiotz indentation tonometer, and the non-contact (air-puff) tonometer.

Option B: The oculomotor nerve is the third cranial nerve (CN III). It controls eye muscles and pupil constriction; it is part of the nervous system, not a measurement device.
Option C: A manometer is a general term for an instrument that measures fluid pressure. While a tonometer is a specialized type of manometer, 'tonometer' is the precise and correct term for measuring eye pressure.
Option D: A perimeter is an instrument used to measure a patient's visual field. It helps detect blind spots (scotomas), which is important in monitoring glaucoma progression, but it does not measure the pressure inside the eye.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Measurement of Intraocular Pressure (IOP) as background academic context rather than a clinical decision trigger.
Nurses play a key role in educating patients before tonometry, instructing them to avoid squeezing their eyelids, holding their breath, or performing a Valsalva maneuver, as these actions can falsely elevate the IOP reading.
Accurate IOP measurement is fundamental for the early detection and management of glaucoma, a leading cause of irreversible blindness worldwide. Routine screening is vital, especially for high-risk populations.
What if? If a patient presents with a suspected corneal abrasion or infection, contact tonometry (like Goldmann or Schiotz) is contraindicated to avoid further trauma or spreading infection. In such cases, a non-contact tonometer may be used cautiously, or the measurement may be deferred.

How to Approach the Question

First, identify the core concept of the question, which is the measurement of 'intraocular pressure'.
This is a factual recall question that requires knowledge of medical terminology and diagnostic equipment.
Scan the options to find the specific instrument used for this purpose.
Recall or deduce that 'tono-' is a prefix related to pressure or tension, and 'meter' means to measure. This points directly to 'Tonometer'.
Differentiate the function of the tonometer from the other options: Oculomotor (nerve), Manometer (general pressure device), and Perimeter (visual field tester).

Concept Tested & Keywords

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E6 Nursing Brunner Adult Health 3SA Vol 2 Part 1 p. 86-88

E6 Physiology Guyton 4SAE Part 3 p. 146-148

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