OPT505 Lecture 10: Visual Fields Overview

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Questions and Answers

What does the term 'hill of vision' refer to in the context of visual fields?

The area that denotes the boundary of normal visual perception

The maximum extent of vision in both eyes combined

The overlapping areas of monocular fields in both eyes

The graphical representation of visual field sensitivity (correct)

Which of the following is NOT a main method of perimetry?

Kinetic perimetry

Static perimetry

Dynamic perimetry (correct)

Confrontation perimetry

What is the typical vertical extent of a normal monocular visual field?

160°

140°

120° (correct)

100°

Why is it crucial to evaluate the reliability of visual field data?

To confirm the accuracy and validity of the assessment Signup and view all the answers

What might a loss of field in the superior temporal quadrant suggest?

Pathology affecting the posterior occipital cortex Signup and view all the answers

Which of the following can potentially lead to errors during visual field assessment?

Inadequate patient instructions Signup and view all the answers

What does the term 'monocular field' specifically reference?

The area seen by each eye independently Signup and view all the answers

Which of the following is NOT a typical application for visual field testing?

Determining the optimal eye correction prescription Signup and view all the answers

What is the primary reason there is no vision in the blind spot?

There are no photoreceptors in this area. Signup and view all the answers

How does the representation of the visual field in the striate cortex differ for the macula compared to the peripheral vision?

The macula has a magnified area of representation. Signup and view all the answers

What characterizes the fast threshold strategy compared to the full threshold test?

It utilizes a single crossing of the threshold. Signup and view all the answers

What does the term 'retinotopic mapping' refer to?

The mapping of adjacent points in the visual field onto adjacent points in the cortex. Signup and view all the answers

Which statement best describes the staircase method?

It provides a faster method than measuring true thresholds. Signup and view all the answers

What effect does a visual field defect have on the identification of lesions in the visual pathway?

It can help locate the lesion along the pathway. Signup and view all the answers

In a supra-threshold test, how is the stimulus presented to the patient?

Slightly brighter than the estimated sensitivity. Signup and view all the answers

What percentage of the cortex is informed by the central 30 degrees of vision?

83% Signup and view all the answers

What is the main advantage of using the fast threshold strategy over the full threshold test?

It measures the threshold at a faster rate despite larger errors. Signup and view all the answers

Which of the following is NOT true about monocular vision?

It is solely responsible for depth perception. Signup and view all the answers

What is the initial stimulus selection process for the fast threshold strategy?

It uses the anticipated age value of the patient. Signup and view all the answers

When observing a field plot with a blind spot, where is it located?

On the temporal side of the retina. Signup and view all the answers

What happens to the congruence of visual field defects as the pathway progresses towards the occipital cortex?

They become more congruous. Signup and view all the answers

What characteristic of pre-chiasmal lesions is typically observed?

Monocular and ipsilateral involvement is common. Signup and view all the answers

What type of visual field defect is typical for chiasmal lesions?

Binocular and heteronymous, usually bi-temporal. Signup and view all the answers

What is a common outcome from lesions affecting the optic nerve?

Reduced visual acuity and possible colour vision impairment. Signup and view all the answers

Which statement best describes the defects associated with postchiasmatic lesions?

Congruity of visual field defects tends to increase. Signup and view all the answers

What would you most likely observe in the optic nerves of someone with a pre-chiasmal lesion?

Normal appearance if the pathology is behind the globe. Signup and view all the answers

Which of the following conditions is typically associated with chiasmal lesions?

Pituitary adenoma. Signup and view all the answers

What visual field defect pattern would typically present if there is a compressive lesion at the optic chiasm?

Bi-temporal hemianopia with possible junctional scotoma. Signup and view all the answers

What is the expected effect on the pupils when damage occurs in the optic pathway?

Relative afferent pupillary defect (RAPD) is common. Signup and view all the answers

What characteristic is associated with a post-chiasm visual defect?

Defect is homonymous Signup and view all the answers

Which statement accurately describes cortical visual defects?

They may exhibit macula sparing. Signup and view all the answers

What type of hemianopia is typically associated with a pituitary tumor?

Bitemporal hemianopia Signup and view all the answers

Which of the following is a common cause of post-chiasm visual defects?

Stroke Signup and view all the answers

What is true about the pupil light reflex in cases of optic nerve lesions?

It is mediated by retinal ganglion cells. Signup and view all the answers

What phenomenon describes the relative sensitivity of vision at various locations in the visual field?

Hill of Vision Signup and view all the answers

Which of these statements accurately reflects the nature of a quadrantinopia?

It can occur due to lesions of radiations. Signup and view all the answers

What does 'macula sparing' refer to in the context of cortical defects?

Central vision remains intact despite other defects. Signup and view all the answers

What is a primary disadvantage of kinetic perimetry as described?

It needs an experienced examiner for accurate results. Signup and view all the answers

In static automated perimetry, how are results typically recorded?

In decibels (dB). Signup and view all the answers

Which parameter indicates the smallest, dimmest intensity in the grading system?

01a Signup and view all the answers

What is one advantage of kinetic perimetry?

Rapid and typically accurate with deep defects. Signup and view all the answers

How is a visual field result recorded when it is not full?

Drawing a cross and shading areas not seen. Signup and view all the answers

What is the purpose of the frequency of seeing curve in perimetry?

To determine a light intensity that is detected 50% of the time. Signup and view all the answers

Which technique in kinetic perimetry involves comparing the examiner's visual field with that of the patient?

Gross perimetry. Signup and view all the answers

What distinguishes static automated perimetry from kinetic perimetry?

The fixed location of the stimulus. Signup and view all the answers

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OPT505 Lecture 10: Introduction to Visual Fields

The lecture is on visual fields, and is given by Ellie Livings.
The presentation outlines the concepts of visual fields.

Intended Learning Outcomes

Students will learn the terminology for describing visual fields and concepts like the "hill of vision."
Students will apply knowledge of ocular anatomy and the visual pathway.
Students will interpret visual field defects and identify potential lesion locations.
Students will compare different perimetry techniques and visual field programs.
Students will learn how to reduce visual field assessment errors.
Students will interpret visual field plots and determine their reliability.

Fields: Overview

Visual field is the area you can see, either with one eye (monocular) or two eyes (binocular).
Visual fields are normally discussed monocularly unless in special cases.
Visual field integrity reflects the overall health of the visual system.
Testing is used for screening, diagnosis, localizing visual loss, and determining functional vision.

The Normal Field: Extent

Normal monocular fields overlap.
Normal visual fields include about 120° vertically and 160° horizontally.
Blind spots are located temporally in field plots.

The Normal Field: The Blind Spot

Blind spot is the area of the field occupied by the optic nerve.
There's no vision in the blind spot.
The blind spot is a useful landmark on visual field plots and is located temporally.

Visual Pathway

Visual field defects help pinpoint lesions within the visual pathway.
The visual pathway begins in the retina and progresses through the optic nerve, optic tract, lateral geniculate nucleus (LGN), optic radiations, and ends at the primary visual cortex.
Visual pathway defects can occur along any segment of that pathway.

Visual Pathway: Chiasm

Nasal fibers from each eye cross at the optic chiasm.
Fibers from the left and right visual fields project to the same side of the brain.
Fibers from the temporal side do not cross at the optic chiasm.

Visual Pathway: Topographic Organization in Striate Cortex

Adjacent points in the visual field are mapped adjacently in the striate cortex, showing a one-to-one relationship
The macula has more cortical representation in the striate cortex.
Information about a central 30 degrees of vision occupies around 83% of the cortex.

What does this mean for the retinal fibres?

Retinal fibre organization along the visual pathway impacts resulting visual field defects.
Lesions affect visual field differently depending on their location.
Examples of lesions and resulting visual defects in the visual field are mentioned.

Describing the Defect

Visual field defects can be described based on their relationships to the horizontal and vertical midline.
Common defect classifications are quadrantanopia, hemianopia, altitudinal defects, and scotomas.
Comparison between the left and right visual fields are important for understanding the extent and location of a defect

Pre-chiasmal

Visual problems in the pre-chiasmal segment, such as optic nerve disorders, glaucoma or trauma, lead to ipsilateral and monocular defects.
Pupil function may be affected as part of the defect (e.g., afferent pupillary defect)

Chiasmal

Visual problems in the chiasmal segment, like tumors at or near the crossing point, may result in binocular defects.
Defects often involve both temporal visual fields (bitemporal hemianopsia).

Post-chiasmal

Visual problems after the optic chiasm lead to a defect on the same side of both visual fields.
Visual defects respect the vertical midline and are typically more congruent.
Lesions can be stroke or tumor.

Pupilomotor fibres (mid-brain connections)

Pupil light reflex is mediated by retinal ganglion cells projecting directly to the pretectum.
Lesions in the optic nerve, chiasm, or tract cause loss of both visual perception and pupil light response.

Lesions along the visual pathway

Visual pathway lesions affect visual field assessment according to their location.
Visual deficits can be detected at any stage in the visual pathway, including prechiasmatic (before the optic chiasm), chiasmatic (at the optic chiasm), and postchiasmatic (after the optic chiasm).

Mapping the Field: Kinetic and Static Perimetry

Kinetic perimetry maps visual field sensitivity using moving stimuli.
Static perimetry uses stationary stimuli at various intensities to chart the visual field.

Kinetic perimetry: Types

Bjerrum screen, Octopus 900, Goldmann bowl perimeter machines are commonly used machines (hardware) for kinetic perimetry tests with their specific uses and benefits in clinical practice.

Kinetic perimetry: Goldmann

The Goldmann visual field test is the most common manual kinetic perimetry instrument.
It uses calibrated stimuli on a bowl-shaped perimeter with variable intensity and size.
Data interpretation is logarithmic and expressed as degrees or decibels.

Kinetic perimetry: Used when

Used for suspected neurological visual field defects, especially large areas of absolute loss, and previous findings of unrepeatable tests.

Mapping the field: Kinetic perimetry

Gross or confrontation visual fields tests are a type of kinetic perimetry test.
This test involves comparing a patient's visual field with the examiner's own.

Static Automated perimetry

Automated visual field testing uses programmed visual stimuli (usually light) presented at various points in the visual field.
Results can be quantified in decibels (dB).
Common methods include SITA.

Frequency of seeing curve

The frequency of seeing curve plots the proportion of times a target is seen at different light intensities.
50% of the time is used to define a threshold.

Full threshold

Full threshold tests (e.g., Humphrey visual field analyser) precisely measure the smallest stimulus (light) intensity to produce a successful response (detection).

Staircase method

Staircase method is a specific technique used in threshold estimations in visual-field testing.
It has particular properties for increasing and decreasing intensities.

Supra-threshold Test

Supra-threshold testing evaluates a larger section of the visual field than standard threshold tests.
By measuring the sensitivity to higher light intensities, this technique pinpoints the shape of the hill of vision.

Background learning

The normal visual field, various instruments and strategies are detailed to provide a comprehensive background of the subject matter for study.

Factors influencing visual field measurements

Visual field measurement is influenced by patient performance, stimulus type and the testing environment.
Patient and testing factors are provided for the evaluation.

How bright is the light, how sensitive is the retina?

Light intensity used in visual field testing is measured using apostilbs as the absolute units of light intensity to assess retinal sensitivity.
Logarithmic scales (e.g., decibels with a scale of 0-40dB) are used to measure the intensity.

Mapping the field

The shape and features of the visual field are analysed through different techniques with varying advantages and disadvantages.

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Description

Explore the key concepts of visual fields in this informative lecture by Ellie Livings. Students will learn important terminology, apply their knowledge of ocular anatomy, and interpret visual field defects. Prepare to enhance your understanding of visual fields.