Optometry Visual Field Testing Overview

Questions and Answers

What unit of measurement is used for luminance in perimetry?

Candelas

Apostilbs (correct)

Lumens

Decibels

A zero decibel (0 dB) is the dimmest stimulus on all perimeters.

False

What does WANDER stand for in the context of visual field report interpretation?

WHAT WAS DONE

The standard test area for central vision in visual field testing is _____ degrees.

30 Signup and view all the answers

Match the following strategies used in visual field testing with their descriptions:

Full Threshold strategy = Methodical testing for full sensitivity Screening strategy = Quick assessment of visual field Fast test strategy = Quick test using SITA FAST Top strategy = Testing based on Octopus methodology Signup and view all the answers

What is the acceptable threshold for fixation loss in a visual field test?

33% or less Signup and view all the answers

Fixation loss can be accurately assessed even when the blind spot is enlarged.

False Signup and view all the answers

What do we call the number of times a patient responds to an audible click when no target stimulus is presented?

False positive Signup and view all the answers

Short-term fluctuation in visual field examination is measured in _____ between readings.

dB Signup and view all the answers

Match the following terms with their definitions:

Fixation Loss = The number of times a patient sees a target in the blind spot False Positive = Response to an audible signal when no visual stimulus is present Short-term Fluctuation = Variance in threshold responses within a single examination Long-term Fluctuation = Fluctuation of measured thresholds between different examinations Signup and view all the answers

Study Notes

Visual Field Testing Overview

Visual field testing evaluates pathological eye conditions, particularly those affecting retinal function.
Modern perimeters generate complex printouts that require careful interpretation.

Importance of Knowledge in Optometry

Knowledge is equated with sight in optometry, emphasizing the importance of understanding visual field data.

Apostilbs and Decibels

Luminance in perimetry is measured in apostilbs, an absolute unit.
Decibels (dB) measure sensitivity on a relative scale and vary by device; 0 dB signals the brightest stimulus.

WANDER Interpretation Scheme

WANDER aids in systematically interpreting visual field reports:
- What was done?: Identify test area and strategy.
  - Test areas: 10°, 24°, 30°, 60°.
  - Strategies: Full Threshold, Screening, Fast Test (e.g., SITA FAST, Top).
- Fixation Loss: Measures patient’s engagement with the test. Should be less than 33% for reliability.
- False Positive: Indicates when a patient responds to an audible cue rather than visual stimuli.
- Short-term Fluctuation: Normal range is 1-2 dB; >2 dB suggests poor reliability.

Evaluating Normal vs. Abnormal Fields

Assess the field's normality by analyzing gray scale and numerical values.
Gray Scale: Provides a visual impression but is not fully reliable due to limited test points.
Numerical Values: Reflect retinal sensitivity relative to age. The normal decay rate of sensitivity is 0.5 to 1.0 dB per decade.

Total and Pattern Deviations

Total Deviation: Compares patient's retinal sensitivity to age-corrected norms.
Pattern Deviation: Adjusts measured thresholds based on generalized changes to assess localized defects.
Pattern Deviation Probability (PDP): Visualizes deviations beyond expected norms for age.

Global Indices for Interpretation

Developed by perimeter manufacturers to aid clinicians in interpreting results:
- Mean Deviation (MD).
- Pattern Standard Deviation (PSD).
- Corrected Pattern Standard Deviation (CPSD).
- Short-Term Fluctuation (SF).

Clinical Significance of Mean and Pattern Deviations

Mean Deviation: Represents the overall height of the visual field.
Pattern Standard Deviation: Reflects the shape of the field.
Thresholds:
- Normal MD and PSD indicate an intact visual field.
- Abnormal findings can suggest generalized depression or localized defects, with specific thresholds indicating severity of depression.

Summary of Findings Interpretation Table

MD and PSD combinations help determine field health:
- Normal MD and PSD: Normal visual field.
- Abnormal MD with normal PSD: Generalized depression; no focal defects.
- Normal MD with abnormal PSD: Localized defects present.
- Abnormal MD and PSD: Severe localized defects.

These notes encapsulate key concepts and procedures related to visual field testing that are crucial for understanding and interpreting results in optometry.

Description

This quiz explores the essential aspects of visual field testing in optometry, focusing on interpreting complex printouts generated by modern perimeters. It covers the significance of luminance measurements in apostilbs and decibels, and the WANDER interpretation scheme to ensure accurate assessments of visual field data.