Book Call Girls in Kasavanahalli - 7001305949 with real photos and phone numbers
Visual Field presentation.nagla.ppt
1. Prof Dr Nagla Hassan, MD
Investigation Department.
Memorial institute for ophthalmic Research.
(MIOR)Egypt
2. What is the Field of Vision!!
• It is an island of
vision in a sea of
blindness
•The island has a
summit = highest
retinal sensitivity =
fixation point = Fovea
• It also has a trough
with retinal sensitivity
= zero = Blind spot (No
photoreceptors)
3.
4.
5. Because the image formed by the optics of
the eye is upside down, just as in a camera,
the image is reversed, thus the nasal retina
sees the objects in the temporal field and
vice versa. Points in the upper retina
corresponds to objects in the lower visual
field and vice versa.
6. Kinetic:
Moving the target from unseen area to seen area
Goldmann Perimetry
7.
8. Static:
Computerized testing for the best retinal
sensitivity in predetermined points in the field
(threshold) by changing the intensity of light ,The
stimuli typically consisted of projected white spots,
the size and the intensity of which can be adjusted.
Statistical analysis of the data in comparison to
normative data Automated Perimetry.
9. •Visual field defects detected after
substantial ganglion cell loss(40%)
•Time is according to test strategy
10. Perimetry testing fulfill important diagnostic
functions:
*Early detection of abnormalities because many ocular
and neurologic disorders are initially expressed as
sensitivity loss in the peripheral visual field, perimetry is
an important factor in identifying early signs of afferent
system dysfunction.
*Differential diagnosis as the pattern of visual field
deficits and comparison of patterns of visual field loss
between the two eyes also provide valuable differential
diagnostic information. Not only can this information be
helpful in defining the location of damage along the visual
pathways, it can also assist in identifying the specific type
of disease that has caused the damage.
11. *Monitoring progression and remissions the ability to
monitor a patient’s visual field over time is important for
verifying a working diagnosis, establishing whether a
condition is stable or progressive, and evaluating the
effectiveness of therapeutic interventions.
* Revealing hidden visual loss and perhaps the most
important role sub served by perimetry is the ability to
find afferent visual pathway loss that may not be apparent
to the patient.
Changes in foveal visual function are typically
symptomatic but peripheral vision loss, on the other hand,
can often go unnoticed, especially if it is gradual and
monocular
12. Mean deviation (M.D).
Short-term fluctuation (SF).
Corrected pattern deviation (CPSD).
Global Indices :
13.
14.
15. A measure of the overall height of the island
of vision as regards to the reference
population.
Negative number
-2 to -6 = Mild generalized depression
-6 to -12 = Moderate generalized depression
> -12 = Severe generalized depression
16. *p< (5%,2%, 1%,Or 0.5 % ): p< 2%’means that the
sensitivity of the patient at that test point is found
less than 2% of the time in the normal population
database.
17. The function of the Pattern Deviation plot is to
expose localized defects that may be masked by
either a generalized depression or an elevation
of the hill of vision. If, for example, cataract or
depresses the visual field almost all test points
may be abnormal enough to be represented by
very dark probability symbols in the total
deviation plot.
18. In addition to the primary points, there are six
other locations where the thresholding
procedure always is performed twice, yielding
a total of 10 preselected points at which the
test-retest difference is used to calculate the
measurement error, or short-term fluctuation
(SF).
19. *Indicators of test reliability (reliability indices).
*Threshold sensitivity measurements and
deviations of measured sensitivities from age
normal (MD) (Global indices).
* Description of the field defect through the
Corrected pattern standard deviation map.
27. Fixation losses: the number of times the
patient responded to the blind spot
stimulus presented.
False positive :the patient presses the
button which no stimulus is presented.
False negative :the patient fails to press
the response button when a visible
stimulus is presented.
28. PATIENT FACTORS
Automated perimetry is limited by the fact that
the outcome of a given examinationcan be
affected by a number of factors
Pupil size
Media opacities
The eyelashes and eyelids
Spectacle frame and ptosis
Fatigue effects
29.
30.
31.
32.
33.
34.
35.
36. Scotoma
Scotomata, contractions and depressions are further
characterized in terms of severity or depth.
Complete loss of function is termed an absolute defect.
All other deficits are labeled relative. Grading the depth
of relative defects is unsatisfactory.
The most common approach is to designate depth in
terms of deviation in decibels (dB) from average normal.
38. Scotomata
are (depression in sensitivity )-completely surrounded by areas with better
function.
Contractions
are deep dents that involve the field's periphery.
46. Glaucoma
What Are the Patterns of Visual Field
Loss?
• In the upper hemifield,, lying around the
fixation & much closer to the fovea than in the
lower hemifield (Paracentral scotoma).
• Nasal step represents a difference between
above and below horizontal line.
• Early (Bjerrum scotoma) , elongated along
nerve fiber (Seidel scotoma) then finally
arcaute scotoma.
• Arcuate scotma extended from blind spot .
47. •Ring scotma which is double upper and lower
arcuate scotoma.
• Small island of central vision.
48.
49.
50. The Glaucoma Hemifield Test (GHT)
Flags the field as being outside normal limits,
that is, the difference in sensitivity
between the superior and inferior fields
is greater than that found in an age matched
normal patient and reflects early
glaucomatous change.
79. When the grating on the left is alternated in
counterphase (black and white bars alternate
with each other) at a relatively rapid rate, the
grating on the right appears with twice the
spatial frequency of the original grating.
