Field of vision

Jihan Abdallah

1

The normal extent of field of vision

60°nasally.

50°superiorly

70°inferiorly .

90° temporally

2

VISUAL FIELD

• Visual sensitivity is greatest at the very center of the field and decreases toward the periphery.

• The part of environment where in a steadily fixating eye can detect visual stimulus.

• Photoreceptors and corresponding visual pathways upto the periphery of retina away from point of fixation.

• Reflects topographic sensitivity of various foci on retina and corresponding visual apparatus.

3

`Factors affecting field of vision1-Vision2-Refractive status3-Education , attentiveness, cooperation 4-real size of spots 5-distance from eye6-Duration of stimulus 7-Background illumination 8-Stimulus intensity9-Contrast 10-Colour11-Patient factors12-Light / dark adaptation

4

PHYSIOLOGICAL BLIND SPOT

Corresponding to optic nerve head

15 deg temporal to point of fixation

Span – 5 deg horizontal-- 7 deg vertical

Two thirds below the horizontal meridian

5

VISUAL FIELD DEFECTS

• 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.

• DEPRESSION : is an area of reduced sensitivity without a surrounding area of normal sensitivity

6

• Generalized depression(both peripheral and central contraction)

e g cataract

• Hemifield defect :

- Hemianopias

homonymous

heteronymous

• Altitudinal defect

7

• Central scotoma• Centrocaecal scotoma

• Arcuate scotomasSeidel scotomaparacentral scotomaBjerrum scotoma

• Nasal step• Ring – double arcuate• Barring of blind spot

8

EXAMINATION TEST

9

STATIC• The location, size and duration of stimulus is kept constant and the

luminance is gradually increased until seen.• Actual estimation of sensitivity of each point is THRESHOLD.

• SUPRA THRESHOLD stimulus used for screening.

-------------------------------------------------------------------------------IMPORTANT : one eye is tested at a time, other is occluded.

fixation of the patient has to be steady and is monitored throughout the test.---------------------------------------------------------------------------------

10

KINETIC

• 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).

11

Standard automated perimetry

HUMPHREY FIELD ANALYZER

• STATIC perimetry

• Measurement of threshold values

• Comparison to normative data

• Inbuilt program for analysis – diagnosis and progression

12

ADVANTAGES• Removal of examiner variability• More sensitive to subtle field defects

• Retests abnormal points automatically• Gives reliability parameters like

fixation monitoring Gaze trackingFalse positiveFalse negative

13

PROGRAMS / PATTERNS

30-2 – gold standard

24-2

10-2

MACULAR

14

MACULA PROGRAM :16 locations within the central 5°with 2° spacing. Each location is tested three times

15

Requirements

• Selection of adequate test

• Proper environment

• Comfortable sitting position

• Adequate size of pupil >3mm

• Adequate Near correction

• Proper explanation –

• Reassurance – not all points will be seen- test can be paused by keeping the response button

pressed

16

17

ZONE 1 : Patient data&Test data

Patient data

• Name, DOB, eye

• Vision, refraction,

• Pupil diameter

Test data

• Date and time

• Program and strategy

• Background illumination

• Test size, color, duration, interval

18

ZONE 2 : RELIABILITY

• Fixation monitor• Fixation target – central• Test duration

• Reliability indicesFixation losses <20 %Gaze tracking

False positives < 33%(trigger happy)

False negatives < 33 %

19

• Fixation loses= gaze monitor

Steadiness of gaze during test

Presenting stimuli to the blind spot.

20

• False positive

Stimulus with a sound.

If the sound alone is presented &the patient still responds.

False negative

Stimulus brighter than thershold.

21

ZONE 3 : GREY SCALE

• Based on actual threshold values at each location

• General identification

• Patient information

22

ZONE 4 :TOTAL DEVIATION PLOT

• Numerical plot – indicates by how much decibels in each point depressed compared to mean value in normal population of similar age

Generalized depression due to media opacities, refractive error, miosis affect appearance of a pattern

23

ZONE 5 : PATTERN DEVIATION PLOT

• calculated by adjustment for generalized depression or elevation of visual field

24

ZONE 6 : GLOBAL INDICESsingle numbers to denote whole field• MEAN DEVIATION : average loss of sensitivity

from normal age matched population.

• PATTERN STANDARD DEVIATION :is a measure of focal loss.

- Range over which change of sensitivity at all the points has occurred, along with probability

-compensates for effect of generalized depression or elevation of field on mean deviation value

local defects affect PSD > MD

25

ZONE 7 : GLAUCOMA HEMIFIELD TEST

• Comparison of 5 corresponding of points in superior hemifield with mirror images in inferior hemifield

as glaucomatous change is:

Vertically asymetrical.

26

OUTSIDE NORMAL LIMITSall cluster pairs differ @ p < 1% OR1 cluster pair differs @ p < 0.5%

BORDERLINEhemifields differ @ p < 3%

GENERAL REDUCTION OF SENSITIVITYoverall field depressed @ p < 0.5%

ABNORMAL HIGH SENSITIVITYoverall field elevated( best 15 % points)

WITHIN NORMAL LIMITS

27

ARTEFACTS

RIM ARTEFACTSPTOSISMEDIA OPACITIES

• MIOSIS

• Refractive error• High power plus and minus lenses

28

high

29High false negative score

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.

30

Peripheral field loss occurs with:

• Retinitis pigmentosa

• Chorioretinitis

• Glaucoma

• Retinal detachment

• Leber's optic atrophy

31

Focal field defects in optic neuropathies

• Central scotoma

Demyelination

Toxic and nutritional

Leber hereditary optic neuropathy

Compression

32

Focal field defects in optic neuropathies

• Enlarged blind spotPapilloedemaCongenital anomalies• Respecting horizontal meridianAnterior ischaemic optic neuropathyGlaucomaDisc drusin• Upper temporal defects not respecting

vertical meridianTilted discs.

33

Field defects in MS

• Diffuse depression of sensitivity.

• Altitudinal / arcuate defects.

• Focal centrocecal scotomas

• Focal defects with generalized depression.

34

Visual field defects in psoriasis

• Central scotoma ,non specific paracentralrelative visual field defects

• probably induced by toxic posterior optic neuropathy.

• The scotoma incompletely resolved after cessation of Methotrexate (MTX) therapy.

35

Visual field defects in diabetic retinopathy

• Foveal thresholds were unaffected in the diabetic patients but there is significant reductions in visual field sensitivity.

36

Nutritional optic neuropathy

• Field defects

Bilateral relatively symmetrical centrocaecalscotomas

The margins of the defects are difficult to define with a white target but easier using red target.

37

Lesions before the chiasm

• These will produce a field deficit in the ipsilateraleye.

• 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

39

Lesions at the chiasm

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.

Chiasmal tumor

• Visual loss may precede optic atrophy.

• Pupils usually react sluggishly to light.

• Afferent pupillary defect is usually present.

• Visual fields are abnormal.

41

Pituitary adenomas a bitemporalhemianopsia.

42

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.

44

• 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.

46right superior quadranopsia

47

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.

• Markedly decreased vision and visual field in both eyes (sometimes no light perception).

• With normal pupillary responses.

• Bilateral occipital lobe infarctions.

• Checkerboard Visual Field Defect: Bilateral quadranopsia caused by two separate lesions one above the calcarine fissure on one side of the brain and one below on the opposite side can produce a checkerboard pattern. This can occur from two simultaneous events or events separated in time.

49

• A congruent visual field defect presents with the same exact shape in the field of both eyes.

• Visual fields that are different in shape are considered incongruent.

• More incongruent fields may point towards lesion of the optic tracts

• while congruent defects point more towards the visual cortex of the occipital lobe.

50

Pupillary reflexes

• Pontine hge pinpoint pupil

• Midbrain lesiondilated fixed pupil.

• Dorsal tectal lesionslight -near dissociation.

51

Light-near dissociation

• Compressive lesion as pinealoma

• involves the dorsal pupillomotor fibers

• Sparing ventral fibers concerning with near reaction.

52

Differential Diagnosis of “Light-Near” Dissociation

• Bilateral optic neuropathy or severe retinopathy: Reduced visual acuity with normal pupil size.

• Adie (tonic) pupil: Unilateral or bilateral irregularly dilated pupil that constricts slowly and unevenly to light. Normal vision. Adie (Tonic) Pupil.

• Dorsal midbrain (Parinaud) syndrome: Bilateral, normal to large pupils. Accompanied by convergence retraction nystagmus and supranuclearupgaze palsy. Adie (Tonic) Pupil and “Convergence-retraction” in Nystagmus.

53

THANK YOU

54