Which of the following is used to assess visual acuity?

Haryana CHO - 2022

Applied Physiology

Easy

Appeared in: Haryana CHO - 2022

Explanation

The Snellen chart is the standardized, most common tool for measuring a patient's distance visual acuity.
The test involves reading rows of letters of progressively smaller size from a distance of 20 feet (6 meters).
Visual acuity is recorded as a fraction (e.g., 20/20), where the first number is the distance from the chart and the second is the distance from which a person with normal vision could read the same line.
It is a fundamental test to screen for refractive errors like myopia (nearsightedness) and hyperopia (farsightedness).

Option A: A slit lamp is a binocular microscope used for detailed, magnified examination of the anterior eye structures (e.g., cornea, iris, lens). It assesses eye health, not visual acuity.
Option C: A Wood's light uses ultraviolet (UV) light to detect certain fungal or bacterial infections and, in ophthalmology, to highlight corneal abrasions after applying fluorescein dye.
Option D: Gonioscopy is a specialized examination to visualize the iridocorneal angle (the eye's drainage system). It does not measure visual acuity.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Assessment of Visual Acuity as background academic context rather than a clinical decision trigger.
Routine visual acuity testing with a Snellen chart is a fundamental nursing assessment to screen for vision problems, especially in school health, occupational health, and primary care settings.
A decline in visual acuity can be an early sign of serious eye conditions such as cataracts, macular degeneration, or diabetic retinopathy, necessitating a prompt referral to an ophthalmologist.
What if? If a patient cannot read even the largest letter on the Snellen chart from 20 feet, the nurse should next assess their ability to count fingers (CF), detect hand motion (HM), or perceive light (LP), and document the finding accordingly.

How to Approach the Question

First, identify the key concept in the question stem, which is the method to 'assess visual acuity'.
Recall the definition of visual acuity: the ability to see details clearly at a distance.
Systematically review each option and recall its primary function in an ophthalmic context.
Snellen's Chart is specifically designed to test distance vision by having the patient read standardized letters from 20 feet away.
Eliminate the other options by identifying their distinct purposes: Slit lamp (magnified structural exam), Wood's light (fluorescence for abrasions/infections), and Gonioscopy (examining the eye's drainage angle for glaucoma).
Conclude that the Snellen chart is the only tool listed whose primary function is to assess visual acuity.

Concept Tested & Keywords

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