Transcript Visual field defects

Visual field defects
• The Normal visual field is
defined as “Island of vision
surrounded by a sea of
blindness”
• The three dimensional concept
can be reduced to quantitative
values by plotting lines
(isopters) at various levels
around the island or by
measuring the height
(sensitivity) at different points
within the island of vision.
The normal extent of
field of vision
60°nasally.
 50°superiorly
 70°inferiorly .
 90° temporally
common causes of VF
defect
Central field loss occurs with:
• Optic neuropathy
• Macular degeneration
• Macular hole
• Cone dystrophies
• A number of rare conditions like
Best’s disease, Stargardt's
disease and achromatopsia.
Peripheral field loss occurs with:
• Retinitis pigmentosa
• Chorioretinitis
• Glaucoma
• Retinal detachment
• Leber's optic atrophy
Assessing for visual
field defects can be via
Screening tests …
confrontational visual field
testing
Amsler grid (assesses the
central 10° the visual field ) .
Quantitative measurements
using manual or automated
perimetry.
• Visual acuity tests the eye's
greatest power of resolution .
• visual field testing measures
the peripheral sensitivity.
Terms
• Visual field defect - a portion of
visual field missing. This may
be:
 central (e.g. optic disc or nerve
problem)
peripheral (along the visual
pathways from the optic chiasm
back).
• Scotoma - this is a type of visual
field defect. It is a defect
surrounded by normal visual field.
 Relative scotoma - an area where
objects of low luminance cannot
be seen but larger or brighter
ones can.
 Absolute scotoma - nothing can
be seen at all within that area.
• Hemianopia - binocular visual defect in
each eye's hemifield.
 Bitemporal hemianopia - the two
halves lost are on the outside of each
eye's peripheral vision, effectively
creating a central visual tunnel.
 Homonymous hemianopia - the two
halves lost are on the corresponding
area of visual field in both eyes, i.e.
either the left or the right half of the
visual field.
 Altitudinal hemianopia - refers to
the dividing line between loss and
sight being horizontal rather than
vertical, with visual loss either
above or below the line.
 Quadrantanopia - is an incomplete
hemianopia referring to a quarter
of the schematic 'pie' of visual
field loss.
 Sectoral defect - is also an
incomplete hemianopia
Static perimetry
 the most commonly used assessment .
 An 'on/off' light signal is presented
throughout the patient's potential
visual field and the patient clicks every
time they see the signal.
 can assess various amounts of the
visual field (10° to full field).
 sensitive tests but are difficult to
perform
 Humphries' (and to a lesser extent,
Henson's) machines are most
commonly used.
Kinetic perimetry
• This presents a moving stimulus
from a non-seeing area to a seeing
area.
• The most commonly used kinetic
test is Goldmann perimetry.
• It is repeated at various points
around the clock and a mark is made
as soon as the point is seen. These
points are then joined by a line (an
isoptre).
Goldmann perimeter
Lesions before the chiasm
• These will produce a field deficit in
the ipsilateral eye.
• Field defects from damage to the
optic nerve tend to be central,
asymmetrical and unilateral.
• Lesions just before the chiasm can
also produce a small defect in the
upper temporal field of the other eye
Lesions at the chiasm
• These classically produce a
bitemporal hemianopia.
 If they spread up from below, for
example, pituitary tumours, the
defect is worse in the upper field.
 If the tumour spreads down from
above , e.g. craniopharyngioma, the
lesion is worse in the lower
quadrants.
Lesions after the chiasm
• These produce homonymous field
defects.
• A lesion in the right optic tract
produces left visual field defect.
• Lesions in the main optic radiation
cause complete homonymous
hemianopia without macular sparing.
• Lesions in the temporal radiation
cause congruous upper quadrantic
homonymous hemianopia commonly
with macular sparing.
• Lesions in the parietal radiation (rare)
cause inferior quadrantic homonymous
hemianopia without macular sparing.
• Lesions in the anterior visual cortex
(common) produce a contralateral
homonymous hemianopia with macular
sparing .
• Lesions in the macular cortex produce
congruous homonymous macular
defect
• Lesions of the intermediate visual
cortex produce a homonymous arc
scotoma, with sparing of both macula
and periphery.
Occipital lobe lesions
• If both occipital lobes are injured
then the patient is in a state of
cortical blindness.
• some patients deny their blindness
and attempt to behave as if they
have vision. This state of denial of
cortical blindness is called Anton's
syndrome.
Influence of Glaucoma on
Visual Function
• The visual field defects that are
caused by loss of retinal nerve
fiber bundles are the most
common and familiar change,
the central vision is typically
one of the last region to be lost
Visual Field defects in
Glaucoma
Arcuate defect
Nasal step
Vertical step
Temporal sector defect
Advanced Glaucomatous
Field Defects
o Complete double arcuate
scotoma with extension to
peripheral limits in all areas
except temporally
o This results in a central island
and a temporal island of vision
in advanced glaucoma
Concentric contraction of
visual field
• Disease causing it :
1) Chronic progressive simple
glaucoma
( AOG & Chronic ACG )
2) Advanced retinitis
pigmentosa .
3) CRAO with cilioretinal
artery .
4) Post-papolloedemic optic
atrophy .
• Diagnostic for advanced case of glaucoma
Arcuate scotoma , Ronne nasal step &
concentric contraction of central field in
case of glaucoma