Microtropia - Definition, Types and Shot Note

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.