DVD

Differential diagnosis of Dissociated vertical deviation

1. Differential diagnosis Of DVD

2. Diagnosis of DVD Easier to see when patient fixates a distance target (greater at distance ) Either eye elevates when fellow eye is fixating. Elevation is followed by extorsion and refixation is followed by intorsion . The vertical angle of dissociated deviation is somewhat less in abduction than in adduction. Latent nystagmus occurs in approximately half the patients with DVD.

3. Contd … It is often found in association with infantile esotropia and less often with accommodative acquired esotropia, exotropia and heterotropia of sensory origin. Head tilt towards fixating eye. Likely to develop poor BSV.

4. DVD Vs overaction of IO In DVD covered eye becomes elevated in abduction, primary position and adduction. Conversly , with the overaction of IO muscles each eye becomes elevated primarily in adduction but never in abduction unless there is coexisting contracture of ipsilateral SR muscle.

5. Contd … When a patient with overacting IO muscle fixates with involved eye in field of action (elevation and adduction) the contralateral SR will under act. Conversely in patients with DVD who are tested in same manner under action of contralateral yoke muscle doesn’t occur.

6. Contd.. Refixation movement in overaction of IO is rapid- 20 to 400°/s Refixation movement is slow in DVD- 10 to 200°/s Tonic incycloduction in IO overaction when takes refixation is so rapid that it cannot be appreciated. While, in DVD excyclotorsion on elevation and on refixation intorsion can easily be observed.

7. Contd … Both A and V patterns can be seen in DVD, however A pattern are more common and this can differentiate DVD from IO over action where V pattern would be expected. Latent nystagmus is usually present in DVD but absent in IO over action Belchowsky darkening wedge test is positive in DVD and negetive in IO over action.

8. Belchowsky darkening wedge test The principle is to gradually reduce the amount of light entering the eye. A graded wedge was originally used but a neutral filter density bar is preferred nowadays. The patient fixates a light and the non fixating eye is occluded, hence the eye behind the occluder will elevate. .

9. As the density of neutral filter is gradually increased before the fixating eye, the eye under cover will be seen to move down possibly below the midline As the filter density is reduced the eye under cover will progressively elevate again.

10. DVD associated with comitant cyclovertical anomalies. When associated with comitant or paretic cyclovertical anomalies the diagnosis of DVD is more difficult. When evaluating such patients one must take into account the starting position of each eye before the cover is applied. For instance, if a right hypertropia is associated with a DVD, the right eye will become further elevated under the cover And the fellow left hypo tropic eye will move upward the same amount but may only reach the midline, since it began its movement from depressed position.

11. Red glass test Red glass yields peculiar result in DVD. Regardless of whether the red filter is placed before the right or left eye the patient describes a red image below a white image. This contrasts with patients with a true vertical deviation. In true hypertropia the second (red) image is seen above or below the primary image depending on whether the red filter is place before hypo or hyper deviated eyes.

12. DVD and SO overaction The SO muscles formerly were implicated as a possible cause of DVD. However the report of A pattern exotropia, SO overaction and DVD made this hypothesis unpopular. Recent studies have resurrected this theory based on the fact that the eye elevates and undergoes excyclotorsion in DVD. A hypo functioning SO muscle could explain both findings.

13. Management The initial management consideration for a patient with DVD is the prognosis for establishing normal binocular vision. If the prognosis for establishing BSV is good , the management strategy is based on the characteristics of associated horizontal strabismus. If the prognosis is poor, the treatment is directed towards addressing concerns about cosmesis.

14. The sequential strategy Its general treatment strategy is to avoid those viewing conditions that produce temporary abnormal innervations And to enhance those conditions that prevents the manifestation of DVD

15. The sequential strategy Prescribe the appropriate lens correction for far and near Determine the dissociated horizontal and vertical deviations at far and at near. (Note which eye has larger hyperdeviations ) Prescribe associated viewing Active Vision Therapy to establish peripheral sensory fusion without vertical prism or prism target separation.(Avoid dissociation and darkening of eyes)

16. 4. Prescribe minimum vertical prism resulting in stable sensory fusion if primary component. 5. Prescribe AVT to improve motor fusion range. Note vertical need for sensory fusion if primary component is present. 6. Prescribe the vertical prism or the most frequently encountered vertical prisms that results in stable central sensory fusion at the orthoposition . 7. Establish efficient binocular vision in open space at all distances

17. Prism Therapy Prisms should not be given until such time that a primary component is identified Measuring the objective angle under associated viewing conditions ( eg. Major amblyoscope ) can give more reliable results.

18. Occlusion Therapy Occlusion may be needed to eliminate sensory anomalies such as suppression, amblyopia and AC. Note- Covering one eye may result in larger and more varialble hyperdeviations when patch is removed.

19. Active vision therapy In orthoptic procedures for constant strabismus DVDs are best approached by first ignoring the vertical condition Anti suppression procedures are prescribed with the goals to achieve normal sensory fusion. Some DVD patient progress to efficient binocular vision showing no vertical deviation when associated . While some may show an accompanying primary vertical requiring prism therapy to maintain efficient binocular fusion.

20. Case presentation A 7 yrs old girl presented with fair cosmesis. History: The parents were concerned about her school performance. They complained of an eye turn inward and outward were present at times. Onset was unknown, but thought it was from infancy. No previous exam.

21. Refractive status Cycloplegic RE +3.00-1.00*180 20/20 LE +3.00-1.00*180 20/20 Deviation With correction a constant BET of 10Pd with LE preferred for fixation.Verticals were estimated to be 12 pd right hyper(RH) and 8 pd left hyper (LH).DVD increased in size with prolonged occlusion.

22. Associated condition No amblyopia and steady fixation RE and LE. Intermittent suppression and sensory fusion of peripheral targets and constant suppression of central or foveal targets at distance. Normal correspondence andno stereopsis with or without BO or vertical prism. Plan Rx RE +2.00-1.oo*180 5BO LE +2.00-1.00*180 5BO

23. Vision therapy -Stereoscope with large peripheral targets. Blinking and pointing to break suppression Sensorimotor stimulation at distance and vectograms (vertical prisms added if needed). Tritated BO prisms prisms as fusional divergence increased.

24. Results: Suppression lessened and sensory fusion was stabilized with AVT. Efficient binocular viewing at all conditions

25. Surgery Surgical procedures preferred by various authors are Recession of superior combined with resection of inferior rectus muscle. Resection of inferior recti Retroequatorial myopexy ( posterior fixation ) of superior recti combined with or without a recession of these muscles. Unconventionally large recessions(5 to 10 mm) of superior recti. Anterior displacement of inferior oblique insertion which may be combined with superior rectus recession.

26. Summary The overaction of IO may look like DVD or vice verca . So meticulous observation or other tests (if required) are performed to make the diagnosis. DVD should not be chased with vertical prisms. The key is to establish normal sensory fusion first . After sensory fusion occurs the presence of primary vertical component either comitant or non comitant is often clearly evidenced.