Definition, Types, etiology, clinical features and clinical techniques for differentiation

1. Microtropia
Evaluation and Management
KAPIL GAUTAM
Institute Of Medicine, MMC, KTM, Nepal

2. Introduction
• A small angle usually less than 6-8 PD in
angle,inconspicuous strabismus
• Not usually detected by cover test either
because the deviation is too small or because
the angle of ARC and EF coincide with the angle
of deviation
• Also known as Monofixation syndrome,Retinal
slip,Retinal flicker,Minisquint,Fusion
disparity,fixation disparity etc

4. Types of Microtropia
(Based on fixation pattern,By Lang)
• Type I-central fixation
• Type II-eccentric fixation without identity
• Type III-eccentric fixation with identity,eg
angle of anomaly is same as the
ecentricity of fixation,no movement seen in
cover test.

5. Etiology of Microtropia
• Residual deviation after the treatment of
larger strabismus
• Uncorrected anisometropia
• Foveal scotoma due to any lesion
• Hereditary
• Amblyopia

6. Clinical features of Microtropia
• Relative scotoma of fovea(3-5 degree)
• Mild amblyopia with harmonious ARC
• Unequal visual acuity with anisometropia
• Parafoveal eccentric fixation
• Presence of sensory and motor fusion with
good peripheral fusional range
• Lower level of stereoacuity(commonly
3000 secs of arc)

7. • Small angle or fully adapted deviation
• Absence of bifoveolar fusion
• Eye does not move on cover test if the
angle of the eccentricity of the fixation is
same as the angle of strabismus
• A very small cover test movement may be
seen if degree of EF is less than the angle
of strabismus

8. Investigations of Microtropia
• Visual acuity and refraction
• Cover test
• Four prism diopter test-no vergence movement
on putting 4PD BO on affetced eye,reverse
occur if placed in normal eye
• Amsler charts-scotoma
• Bagolini striated lens test- a foveal suppression
scotoma with a gap in the center
• Worth’s four dot test,stereopsis test.
• Binocular perimetry etc.

9. 4D BASE-OUT PRISM TEST

10. Diagnostic method
• BAGOLINI STRIATED GLASSES
TEST
– Pair of glasses positioned such that the
streak seen by the right eye is at 135°
and the streak seen by the left eye is at
45°
– Microtropia
• The gap around the fixation light, projected
onto a grid, indicates a scotoma of 3° to 5

11. Diagnostic method
• STEREOACUITY
TESTS
– Normal: betwn 14 and
40 seconds of arc
– Microtropia - between
60 and 3000 seconds
of arc
Titmus Stereotest.

12. Symptoms of microtropia
• Uniocular reading difficulties due to
suppression scotoma
• Uniocular blurring of vision
• Left hand letters or words disappeared
when LE microtropic,similar for RE
• Difficulty in judging depth.

13. Management of Microtropia
• Proper refractive correction with glasses
• In young children who are visually immature(6
years or younger)part time occlusion therapy for
few months.Afterwards microtropia may
disappear.Follow up is necessary to check
fixation pattern of eyes
• For older children and adults-need not to be
treated since they have comfortable and nearly
normal BSV with good peripheral fusional
amplitudes.