Diag Tests for Strabismus 1390 2011
Transcript of Diag Tests for Strabismus 1390 2011
Diagnostic Techniques forStrabismus
Ramin Sahebghalam M.DOculoplastic and Strabismus Fellowship
2011
Tests of Ocular Alignment
Cover tests. Corneal light reflex
tests. Dissimilar image tests. Dissimilar target tests.
Tests of Ocular Alignment
Eye movement capability. Image formation and perception. Foveal fixation in each eye. Attention. Cooperation.
Cover Testsprerequisites
Cover-uncover test, Alternate cover test, Prism and cover test. Prism and cover–uncover test, Prism under cover test.
Cover Tests
Cover Uncover TestPrism and Cover Test
An absence of movement of an eye when the other eye is covered occurring in both eyes, means that the patient does not have a heterotropia
It does not differentiate between orthophoria and heterophoria.
Cover-Uncover Test
Alternate Cover TestAlternate Prism and Cover Test
The patient's right eye is covered while fixating a series of distant accommodative targets.
After 2 to 3seconds, the right eye is uncovered , cover rapidly is moved to the other side and left eye is covered.
The patient whose eye moves on alternate cover has either a heterophoria or heterotropia.
Differentiation between the two requires the cover–uncover test.
Alternate Cover Test
A temporal horizontal shift is esophoria or esotropia,
A nasal shift is exophoria or exotropia, The movement of the eye downward is
hyperphoria or hypertropia . If both eyes make movements downward, it
is called dissociated vertical deviation.
Alternate Cover test
Is used to measure the size of DVD, Base down prism is place on the eye, Cover is place in front of prism, Prism power is increased until no movement
of the eye can be seen after removing the cover.
Prism Under Cover Test
Hirschberg, Krimsky and Modified Krimsky, Bruckner, Major amblyoscope.
Light Reflex Tests
A light reflected in the deviated eye:
Nearer the pupillary center than the margin: 5°,
At pupillary margin : 15°, Midway between pupillary margin and
limbus it is 25°, At the limbus it is 45° to 60°, and beyond
the limbus it is 60° to 80°.
Hirschberg Method
Each 1-mm deviation of light reflex represents 7° or 15 Δ of deviation.
Brodie’s rule: 1 mm=21 Δ (using flash photographs with millimeter rulers included for standardization, Brodie estimated a Hirschberg ratio of 21 prism diopters/mm, this angle correlates highly with that derived from alternate prism and cover testing).
Hirschberg Method
Hirschberg Method
Traditional: center the displaced light reflex by putting appropriate prism over deviated eye.
Modified: hold the prism over fixating eye (easier to read).
Krimsky Method
The Krimsky test is especially useful in: Younger patients, Patients unable to maintain concentration for
prolonged prism and alternate cover testing, Patients with diminished central fixation in
one or both eyes.
Krimsky Test
Krimsky Method
Dissimilar image tests are based on the patient's response to diplopia created by 2 dissimilar images.
Maddox rod test, Double Maddox rod test, Red glass test.
Dissimilar Image Tests
Are based on the patient's response to the dissimilar images created by each eye viewing a different target; the deviation is measured first with one eye fixating and then with the other.
Lancaster red-green projection test, Hess screen test, Major amblyoscope test.
Dissimilar Target Tests
Torsional strabismus occurs when the eye is abnormally rotated about the visual axis.
Malfunction of the vertical rectus and oblique muscles is responsible.
Evaluation of torsion is mandatory in vertical strabismus, whether or not the patient complains of torsional diplopia.
Evaluation of Ocular Torsion
Evaluation of torsion is not possible with external landmarks.
While the actual axis of rotation is close to visual axis, it is easier for most examiners to visualize the fovea moving relative to the optic nerve.
Evaluation of Ocular Torsion
Primary oblique muscle overaction (most common).
Secondary oblique muscle overaction ( most common :S.O paralysis).
Restrictive processes involving cyclovertical muscles:
1. Thyroid ophthalmopathy2. Brown syndrome,3. Blowout fracture4. Local myotoxicity (retro or peribulbar injections) Orbital displacement (plagiocephaly)
Evaluation of Ocular TorsionEtiology
Plagiocephaly
Anatomic (objective) torsion refers to anatomic rotation of eye.
Subjective torsion refers to the patient’s perception of rotation.
Comparison of anatomic and subjective torsion can help determine the time of onset of cyclovertical strabismus.
Evaluation of Ocular Torsion
Fundus Photography (most accurate), Blind spot mapping, Indirect Ophthalmoscopy (easiest).
Measuring Objective Ocular Torsion
Measuring Objective TorsionIndirect Ophthalmoscopy
Grading system for estimating abnormal torsion
Measuring Objective Ocular Torsion
X
Easily performed Quick Quantitative
Measuring Subjective TorsionDouble maddox rod test
Measuring Subjective TorsionDouble maddox rod test
Provides a diagrammatic representation of horizontal, vertical and torsional strabismus in 9 diagnostic positions of gaze.
Measuring Subjective TorsionLancaster red-green test
Measuring Subjective Torsion Lancaster red-green test
Method: Patient is seated 1 meter from screen with
head straight, wearing anaglyphic goggles. Room darkened. Examiner projects the red streak obliquely
on the center of scale ( primary position).
Measuring Subjective Torsion
Lancaster red-green test
Method: The streak is rotated upon patients
command to be seen vertical. The patient is asked to place the green
streak in the same place as the red streak. The actual location of projected streaks is
manually recorded.
Measuring Subjective Torsion
Lancaster red-green test
Method: Test repeated in 9 diagnostic positions of
gaze. Examiner and the patient change
flashlights and repeat the test.
Measuring subjective torsionLancaster red-green test
Interpretation: The Lancaster red-green test is interpreted as
if the two streaks are direct projections from the foveas:
Left side of the plot indicates the left gaze and the right , right gaze.
If the red streak is rotated clockwise, the right eye is extorted, if the red streak is upper, the right eye is upper. If the red streak is on the right, there is exotropia and vice versa.
Measuring subjective torsion
Lancaster red-green test
Measuring Subjective Torsion
Lancaster red-green test
Recent onset V pattern ET , right hypertropia and subjective extorsion.
Measuring Subjective Torsion
Lancaster red-green test
Old V pattern ET & right hypertropia ,no subjective torsion
The examiner can read the amount of subjective deviation directly from the screen.
If this degree is equal to formerly measured objective deviation (measured in cover-uncover test, then NRC is present.
If the two amounts are not equal, ARC is present
Superimposition of both targets on zero shows harmonious ARC.
Measuring Subjective Torsion
Lancaster red-green test
Possible in children who can count to five. If the visual acuity can be determined, so
can the Worth 4 dot response. The test is performed with ordinary room
illumination to provide the usual peripheral vision clues.
Results should be reported as suppression or fusion.
Best at detection of suppression.
Worth 4 Dot Test
Distant Worth 4 dot test. Near Worth 4 dot test.
Worth 4 Dot Test
3° macular scotoma : Far W4DT: no fusion @ 6 m fusion begins @ 2.5 m Near W4DT: no fusion @ 2m fusion begins @ 0.66 m
Worth 4 Dot TestMonofixation syndrome
When NRC: In both far and near tests: ET: Homonymous diplopia (5 dots) XT: Heteronymous diplopia (5 dots)
Worth 4 Dot Test Strabismic patients who acquire deviation of 10Δ or more after having developed normal binocular vision reflexes
When ARC: Sees 4 dots Test must be done @ near
5° suppression scotoma in ET (40 cm) >5 ° suppression scotoma in XT
Worth 4 dot test Strabismic patients who acquire deviation of 10Δ or more after having developed normal binocular vision reflexes
Forced ductions, Active force generation, Saccadic velocity.
Special Motor Tests
This test places obilque muscles on maximum stretch by simultaneously retroplacing, torting and rotating the globe.
Forced duction of rectus muscle are best done by pulling the eye forward to put these muscles on maximum stretch.
Exaggerated Traction Testforced duction for oblique muscles
One handed exaggerated traction test for the superior oblique muscle right eye
EF
NASAL
TEMPORAL
Intraoperative assessment of completeness of an oblique muscle weakening procedure is the most useful application of this test.
The test must be done before and after oblique tenotomy and disinsertion.
The test can confirm the diagnosis of oblique muscle overaction.
Exaggerated Traction Testforced duction for oblique muscles
Applications
Deciding over tuck or recess in SO paresis. Differentiation of IO paresis and Brown. The test helps differentiate hyperdeviation
causes: inferior oblique overaction, DVD, rectus contracture.
Exaggerated Traction Testforced duction for oblique muscles
Applications
Is investigated in adult patients with constant starabismus.( a study on 424 patients by Kushner B.J, Archive of Ophthalmo,vol 120, Nov 2002)
Prism Testing for Prediction of Postoperative Diplopia
Patient wears appropriate correction. Patent fixes to an accommodative Snellen
optotype near to his vision threshold in better eye.
Neutralize the deviation by placing prisms over the deviating eye and ask the patient if he sees double.
Then remove the first prism and introduce increasing rotary or bar prisms, begin with 0 and overcorrect the deviation by 5 to 10 .
Prism Testing for Prediction of Postoperative Diplopia
Method
If the patient sees double in any of the former stages, then he/she is asked about type of diplopia:
Cross or uncross ? Sharp, or shadowy ghost images? What is the distance between the two
images?
Prism Testing for Prediction of Postoperative Diplopia
Method
Does not see double in any test :no risk. A shadowy ghost image in far periphery :
(ARC):very low risk of temporary or constant post- op diplopia.
Intense and close together:a little risk. Unable to subjectively localize the second
image (lost or confused localization):
Prism Testing for Prediction of Postoperative Diplopia
what the patient my see:
9% of all adult patient with constant strabismus undergoing surgery will develop post op diplopia.
0.8% of such patients will develop constant diplopia.
Prism Testing for Prediction of Postoperative Diplopia
28% of patients with positive pre-op prism test will develop temporary post op diplopia.
2% of such patients will develop permanent post-op diplopia.
Prism Testing for Prediction of Postoperative Diplopia
Temporary post-op diplopia
Permanent post-op diplopia
Sensitivity 100% 100%
Specificity 73% 67%
Positive predictive value
28% 2%
Negative predictive value
100% 100%
Predictive Values of the Test