Understanding Visual Fields

Presented on Friday 2 November 2007

The Visual Pathway and Methods to measure Visual Fields

Dr Jennifer Skillen, Specialist Orthoptist, NHS Fife

What are Visual Fields?

The Visul Fields are a measure of the area from which you are able to perceive visual signals, when your eyes are in a stationary position and looking straight ahead.

visual fields

Normal Adult dimensions
50-60 deg superiorly
70-75 deg inferiorly
60 deg nasally
90-100 deg temporally

Central and Peripheral components

Division of Labour - Central Field

Peripheral Field

Schematic of the Retina

schematic of retina

Why measure fields?

What are we looking for?

Relative field defect/scotoma - a light target can be seen but only when it is made brighter or larger (that is, reduced sensitivity).

Absolute defect/scotoma - No response to a stimulus regardless of brightness or size (definitive absence of processing from this area).

Perimetry - measure of the visual field

Two ways to measure the visual field.

Similarities are

Differences are

Normal development of visual field

Goldmann Perimetry - Kinetic testing

goldmann perimetry

goldmann

Humphrey -Static Perimetry

humphrey sttic perimetry

Sample field plots - static

sample field plots

Testing in Children under 10 - Goldmann

child Golmann test

Example of a normal Peripheral field in 10 year old

normal peripheral field

Confrontation

What are we measuring?

The visual pathway

visual pathway

Retinal Representation of Visual World – horizontal perspective

horizontal perspective

Vertical perspective

The visual pathway

visual pathway

Different patterns of field loss

1. Central or peripheral
2. Ocular level
3. Brain Level
a) Early visual pathway
b) Late in the visual pathway

The visual pathway

visual pathway

Field Loss relates to Anatomy of the Visual Pathway

Optic Nerve involvement

optic nerve involvement

Optic Nerve Field Defects -retinal

optic nerve defects

Optic nerve defects

optic nerve defects

graphic

Post Chiasm Lesion Optic Tract

Post Chiasm Lesion Optic Tract

Post Chiasm Lesion Optic Tract

Optic Radiations

optic radiations

Optic Radiations – Clear Segregation Superior and Inferior retinal signals

retinal signals

Temporal involvement-Myers Loop

Myers Loop involvement

myers loop involvement

Extensive damage to optic radiations

damage to optic radiations

Inferior defect – quadrantopia damage to the superior fibres passing through parietal lobe – affecting peripheral and central area of field.

Visual Cortex

Homonymous Hemianopia

homonymous hemianopia

Left side of brain – occipital lobe.

Visual Cortex

Lesion affecting both visual lobes will be devastating to vision – result in cortical blindness.

2 separate blood supplies to occipital cortex

2 separate blood supplies

Two main types of Occipital Lesions

posterior Posterior Cerebral Artery

middle Middle Cerebral Artery

 

Pointers when reviewing fields

Pointers

Visual Field

Common behaviors observed in children with field defects

Field Projection Summary

whole system

Adding insult to injury

Attention and Visual Neglect

Visual Attention Network

The prognosis for rehab of field defects which exist in addition to attentional difficulties is much poorer and their visual experience different to children with isolated field defects.