Week 12: Perimetry Flashcards
What is a visual field and perimetry?
The area of space perceived by the eyes sensitivity to light. Perimetry = plotting the sensitivity of this area in space
What are the boundaries of the Monocular visual field?
○ 60 degrees superiorly
○ 70 degrees inferiorly
○ 60 degrees nasally
○ 100 degrees temporally
Binocular horizontal field is approximately 120 degrees wide
Describe the Hill of vision
The Hill of Vision is a 3D sensitivity profile across the visual field. Its also known as the Traquair’s Island. The topography of the island is dynamic, varies with retinal adaptation.
What are isopters?
They are areas of equal sensitivity.
What are the best condition to do visual fields test and why?
Scotopic conditions are best to start the test. They allow the stimuli to be the brightest. Under mesopic conditions, the slope of decreased sensitivity towards the periphery is much more gentle than photopic conditions. Comparison of visual fields must be made under standardised conditions of retinal adaptation.
How does pathology effect the hill of vision?
Pathology can cause lower sensitivity which results in a low hill of vision.
What is the relationship between sensitivity and threshold?
Sensitivity = 1/threshold
What affect threshold testing in Automated Perimetry?
Background photopic luminance
Pupil size
Clear ocular media
Test conditions – stimulus size, duration of exposure etc
What is the purpose of threshold testing in Automated Perimetry?
What law does it utilise?
- Mapping the boundaries of the field
- measure the sensitivity of the eye in detecting a stimulus in different regions of the visual field
Weber’s Law: ∆L/L = C
List some reasons for visual fields assessed?
- Detection of pathology
- Evaluation of disease status
- Monitoring of disease progression
- Determination of efficacy of treatment
- Visual ability testing
- driving, visual impairment assessment, MBS for blepharoplasty
- Visual ability testing
What are some common types of Perimetry?
Kinetic Perimetry - Confrontation
Static Perimetry
- amsler grid
- automated perimetry
What are some less common Perimetry tests?
What psychophysical method do they use?
Subjective Techniques
○ Short wavelength automated perimetry (SWAP)
○ Frequency doubling Technology perimetry (FDT)
○ Flicker perimetry
○ Motion perimetry
○ High Pass resolution perimetry
Objective Techniques
○ Multifocal Visual Evoked potentials (mfVEP)
- Multifocal Electro-retinography (mfERG)
Staircase Method
How does a Automated Perimetry Test measure sensitivy?
- Stimuli are randomly shown at fixed locations with background constant photopic luminance of (31.5asb) for HFA
- Brightness is increased/decreased until required number of threshold reversals completed by patient
- Assess monocular visual function outside the fovea
What do the numbers of the visual field test mean? e.g. 24 - 2
The first number is the degrees from fixation
The second number is the num
