visual fields

describe the normal visual field

inferiors 75 degrees

superiorly 60 degrees

nasally 60 degrees

temporal 100 degrees

monocular fields overall to give 120 degree stereoscopic zone

what types of perimetry are there

static and kinetic

what is static perimetry

uses a stimulus of increasing intensity to determine threshold at a particular location on the retina generating sensitivity plot

what is kinetic perimetry

constant sized target brought towards central fixation and where just noticed used as a threshold relating to size

what types of static perimetry are there

full threshold, screening, estermann, ambler is gross static method

name types kinetic perimetry

gross perimetry

when should you conduct visual field assessment

px new to practise

drivers

risk factors eg FHG

signs and symptoms

what testing distance is the Henson 9000 at

25cm

what output results do visual fields include

total deviation

pattern deviation

what is total deviation

deviation individual points vs age matched normal

what is pattern deviation

modified plot showing localised defects by removing the effect of overall shifts in sensitivity

what reliability indices are there

false positives

false negatives

fixation losses

hemifield test

what percentages of these indices makes these percentages unreliable

false positives>15%

false negatives>30%

fixation losses>20%

describe how to do estermann fields

1. both eyes opening driving glasses

2. advise px that fixation light mat move and to follow the light if so

what counts as acceptable loss for estermann

scattered single missed points

single cluster of up to 3 adjoining points

what counts as unacceptable visual field loss

cluster of 4 or more adjoining missed points up to and including 20 degrees form fixation and any sep missed points within central 20 degrees area

any central loss that is an extension hemianopia and quadrantanopia size greater than 3 missed points

describe the amsler chart and how to use it

10cm by 10cm at 28cm. each square is 5mm wide corresponding to 1 degree

monocularly with reading glasses in good light

what amsler chart is used if someone has optic neuritis

red variant

what amsler is used if someone cannot see the fixation target

use amsler 2, with diagonal lines included

what is the red amsler useful for

detecting early adverse drug reactions at the macula eg hydorxycholoruqine maculoapthy

draw and label the visual pathway

what lesion causes left homonymous hemianopia

lesion in right optic tract or LGN

what causes pie in the sky defect

lesion in Meyers loop of the optic radiation

what is a bitemporal hemianopia caused by

lesion at optic chiasm, pituitary adenoma

what can cause left homonymous hemianopia with macular sparing

lesiosn in occipital lobe. dual blood supply by MCA and PCA spared macula

what causes left inferior homonymous hemianopia

damage t superior fibres of optic radiations in parietal lobe

what causes monocle defect

retinal or optic centre problems