Verifying the Distance Between the Visual Acuity (VA) Chart, Mirror, and Patient

Topic Overview

Proper distance between the VA chart, mirror, and patient is essential for accurate visual acuity testing. The total viewing distance should equal approximately 20 feet (or 6 meters).

This guide outlines how to verify the setup using a simple measuring process.

Materials Needed

• Measuring tape (capable of measuring at least 20 feet or 6 meters)

Step-by-Step Instructions

Step 1: Understand the Goal

• The total optical distance from the VA chart to the patient should equal 20 feet (6 meters).

• This distance is achieved through the combination of:

  • Distance from the VA chart to the mirror

  • Distance from the mirror to the patient’s seat (exam chair)

  • Example: 14 ft + 6 ft = 20 ft OR 11 ft + 9 ft = 20 ft

Step 2: Measure Distance from VA Chart to Mirror

1. Place the measuring tape at the surface of the VA chart.

2. Extend the measuring tape to the surface of the mirror.

3. Record this measurement.

Step 3: Measure Distance from Mirror to Exam Chair

1. Place the measuring tape at the surface of the mirror.

2. Extend the measuring tape to where the patient's eyes would be when seated in the exam chair.

3. Record this measurement.

Step 4: Calculate Total Distance

1. Add the two measurements:

   • (VA chart to mirror) + (Mirror to exam chair) = Total Distance

2. The total should be as close to 20 ft (6 meters) as possible.

Step 5: Adjust Exam Chair (If Needed)

• If the total distance is not close to 20 ft:

  • Move the exam chair forward or backward as needed to achieve proper distance.

• Note that larger exam lanes provide more flexibility (example: extra space behind the chair), while smaller lanes may have tighter configurations.

Key Notes

• The space may look or feel different depending on room size but should still achieve the 20 ft distance.

• Example configurations:

  • Large Room: 14 ft + 6 ft + 4 ft behind the chair

  • Small Room : 11 ft + 9 ft (no extra space behind chair)

Final Verification

• Once adjusted, repeat the measurement to confirm the total distance is approximately 20 ft.

• If time is limited or assistance is needed, another team member can help verify.