Ocular deviations can be classified as heterophorias or heterotropias. Heterophorias are latent deviations that are suppressed by fusion, while heterotropias are manifest deviations. Specific types of heterophorias include esophoria, exophoria, hyperphoria, and hypophoria. It is important to record the size of any deviation in prism diopters and the distance at which the test was performed. Heterotropias can be incomitant, meaning the deviation varies with gaze direction, or concomitant, where the deviation remains constant. Incomitant strabismus is often paralytic in origin while concomitant may have an accommodative element.

1. Ocular Deviations

2. Heterophoria A deviation kept latent by the fusion reflex

3. Heterotropia A manifest deviation of the eyes Strabismus Squint “ cock eyed”

4. Heterophoria Orthophoria: the visual axes remain in alignment when fusion is prevented Esophoria: the visual axes converge from alignment when fusion is prevented Exophoria: the visual axes diverge from alignment when fusion is prevented

5. Clinical Records It is not necessary to specify the eye as a phoria is “shared” Record the size in ∆ Record the distance the test was performed Distance 5SOP Near 2XOP

6. Esophoria

7. Heterophoria Orthophoria: the visual axes remain in alignment when fusion is prevented Hyperphoria: one line of sight is higher than the other when fusion is prevented Hypophoria: one line of sight is lower than the other when fusion is prevented

8. Vertical Phorias A right hyperphoria is the same as a left hypophoria It is important to specify the eye

9. Clinical Records It is necessary to specify the eye in vertical phorias Record the size in ∆ Record the distance the test was performed Distance 5RHyperphoria Near 2L/R

10. Rotations Excyclophoria: upper poles of the corneas deviate outwards when fusion is prevented Incyclophoria: upper poles of the corneas deviate inwards when fusion is prevented

11. Cyclodeviations

12. Physiological Exophoria At near it is usual for the phoria to be relatively more divergent than the distance phoria Accommodative lag gives less drive through AC/A Small XOP common at near

13. Aetiology Static or Anatomical Kinetic or Accommodative Neurogenic Innervational

14. Vergence system Convergence insufficiency Convergence Excess Divergence insufficiency Divergence excess

15. Convergence Insufficiency Distance 3XOP Near 12XOP Breaks from XOP to XOT Orthoptic therapy helps

16. Convergence Excess Distance Rx typically hyperopic Distance 4SOP Near 18SOP High AC/A ratio Can be controlled with Rx

17. Convergence Excess

18. Divergence Excess Distance 15XOP Distance Intermittant XOT Near 5XOP Patient not aware when Strabismus present Responds to orthoptic therapy

19. Divergence Excess

20. Divergence Insufficiency Distance 8SOP Near 2XOP

21. Heterotropia Incomitant Concomitant

22. Incomitant Strabismus The angle of deviation varies with direction of gaze Paralytic in origin Angle of squint largest when eyes turned in direction of affected muscle Assessment of ocular motility essential Often need to be referred

23. Incomitant Squint

24. Abnormal Head Posture

25. Concomitant Strabismus Angle of deviation is constant for all directions of gaze May be intermittant Often an accommodative element (Donder’s squint) Alternating strabismus Congenital Childhood

26. Heterotropia Esotropia: the visual axes converge from alignment Exotropia: the visual axes diverge from alignment

27. Esotropia

28. Accommodative Esotropia

29. Accommodative Esotropia

30. Alternating Esotropia

31. Exotropia

32. Exotropia

33. Clinical Records It is necessary to specify the eye in strabismus Record the size in ∆ Record the distance the test was performed Distance 5RSOT Near 2LXOT Alt D & N, prefers R fix

34. Heterotropia Hypertropia: one line of sight is higher than the other Hypotropia: one line of sight is lower than the other

35. Hypertropia

36. Hypotropia

37. Clinical Records It is necessary to specify the eye in strabismus Record the size in ∆ Record the distance the test was performed Distance 15RHyperT Near 10LHypoT Alt D & N, prefers R fix

38. Clinical Tests Cover test Ocular motility Additional tests as required

39. Summary Phoria or Tropia? Tropia: incomitant or concomitant? Incomitant: Old or New? Work in a systematic manner