ALPHABET PATTERNS

1. ALPHABET PATTERNS

2. V or A patterns may occur when the relative contributions of the superior rectus and inferior oblique to elevation , or of the inferior rectus and superior oblique to depression , are abnormal , resulting in abnormal balance of their horizontal vectors in up- and down-gaze . They can also be caused by anomalies in the position of the rectus muscle pulleys leading to abnormal lines of action of the muscles .

3. They are assessed by measuring horizontal deviations in the primary position , up-gaze and down-gaze and may occur regardless of whether a deviation is concomitant or incomitant .

4. V PATTERN V pattern is significant when difference between up-gaze and down-gaze ≥ 15 ∆ , allowing for a small physiological variation between up-gaze and down-gaze . Causes • Inferior oblique over action associated with fourth nerve palsy . • Superior oblique under action with subsequent inferior oblique over action which is seen in infantile esotropia as well as other childhood esotropias . The eyes are often straight in up-gaze with a marked esotropia in down-gaze .

5. Superior rectus under action . • Brown syndrome . • Craniofacial anomalies which are associated with shallow orbits and down-slanting palpebral fissures . Treatment Treatment involves inferior oblique weakening or superior oblique strengthening when oblique dysfunction is present .

6. Without oblique muscle dysfunction treatmet is as follows : 1- V pattern esotropia : can be treated by bilateral medial rectus recessions and down transposition of the tendons . 2- V pattern exotropia : can be treated by bilateral lateral rectus recessions and upward transposition of the tendons .

10. A PATTERN A pattern is significant if the difference between up-gaze and down-gaze is ≥ 10∆. In a binocular patient it may cause problems with reading . Causes • Primary superior oblique over action ,which is usually associated with exodeviation in the primary position of gaze . • Inferior oblique under action/ palsy with subsequent superior oblique over action .

11. Inferior rectus under action . Treatment Patients with oblique dysfunction are treated by superior oblique posterior tenotomy . Treatment of cases without oblique muscle dysfunction is treated as follows : 1- A pattern esotropia is treated by bilateral medial rectus recessions and upward transposition of the tendons .

12. 2- A pattern exotropia is treated by bilateral lateral rectus recessions and downward transposition of the tendons .

16. PARALYTIC SQUINT Third nerve palsy Diagnosis 1- signs of a left third nerve palsy : - Weakness of the levator causing profound ptosis , due to which there is often no diplopia . • Unopposed action of the lateral rectus causing the eye to be abducted in the primary position . • The intact superior oblique muscle causes intorsion of the eye at rest , which increases on attempted down gaze .

17. Normal abduction because the lateral rectus is intact . • Weakness of the medial rectus limiting adduction . • Weakness of the superior rectus limiting elevation . • Weakness of inferior rectus limiting depression . • Parasympathetic palsy causing a dilated pupil associated with defective accommodation . • Partial involvement will produce milder degrees of ophthalmoplegia .

19. Treatment 1- non-surgical treatment options include the use of Fresnel prisms if the angle of deviation is small , uniocular occlusion to avoid diplopia ( if ptosis is partial or recovering ) and botulinum toxin injection into the uninvolved lateral rectus muscle to prevent its contracture before the deviation improves or stabilizes .

20. 2- surgical treatment , as with other ocular motor nerve palsies , should be contemplated only after all spontaneous improvement has ceased . This is usually not earlier than 6 months from the date of onset .

21. FOURTH NERVE PALSY Diagnosis Acute onset of vertical diplopia in the absence of ptosis , combined with a characteristic head posture , strongly suggests 4th nerve disease . 1- signs of a left 4th nerve palsy : • Left hypertropia ( left over right ) in the primary position when the uninvolved right eye is fixating due to the weakness of the left superior oblique . • Left limitation in depression in adduction due to the superior oblique weakness .

22. Excyclotorsion . • Diplopia which is vertical , torsional and worse on looking down . • The left hypertropia increases on right gaze due to the left inferior oblique overaction . 2- abnormal head posture is adopted to avoid diplopia • To intort the eye ( alleviate excyclotorsion ) there is contralateral head tilt . • To alleviate the inability to depress the eye in adduction , the face is turned to the right and the chin is depressed .

23. 3- bilateral involvement should always be suspected until proved otherwise : • Right hypertropia in left gaze , left hypertropia in right gaze . • Greater than 10° of cyclodeviation on double Maddox rod test . • V pattern esotropia . • Bilaterally positive Bielschowsky test .

24. SPECIAL TESTS Parks three-step test is very useful in the diagnosis of fourth nerve palsy and is performed as follows : A- first step. Assess which eye is hypertropic in the primary position . Left hypertropia may be caused by weakness of one of the following four muscles : one of the depressors of the left eye ( superior oblique or inferior rectus ) or one of the elevators of the right eye ( superior rectus or inferior oblique ) . In a fourth nerve palsy the involved eye is higher .

25. B- step two . Determine whether the left hypertropia is greater in right gaze or left gaze . Increase on right gaze implicates either the right inferior rectus or left inferior oblique . Increase on left gaze implicates either the right superior oblique or left superior rectus ( in fourth nerve palsy the deviation is Worse On Opposite Gaze – WOOG ).

26. C- step three .the Bielschowsky head tilt test ( isolates the paretic muscle ). With the patient fixating a straight ahead target at 3 meters, the head is tilted to the right and then to the left . Increase of left hypertropia on left head tilt implicates the left superior oblique and increase of left hypertropia on right head tilt implicates the right inferior rectus . ( in fourth nerve palsy the deviation is Better On Opposite Tilt – BOOT )

28. Double Maddox rod test • Red and green Maddox rods , with the cylinders vertical , are placed one in front of either eye . • Each eye will therefore perceive a more or less horizontal line of light . • In the presence of cyclodeviation , the line perceived by the paretic eye will be tilted and therefore distinct from that of the other eye . • One Maddox rod is then rotated till fusion ( superimposition ) of the line is achieved .

29. The amount of rotation can be measured in degrees and indicates the extent of cyclodeviation . • Unilateral fourth nerve palsy is characterized by less than 10° of cyclodeviation whilst bilateral fourths may have greater than 20° of cyclodeviation. This can also be measured with a synoptophore .

30. Sixth nerve palsy Diagnosis 1- signs of left 6th nerve palsy • Left esotropia in the primary position due to unopposed action of the left medial rectus. • Esotropia is characteristically worse for a distant target and less or absent for near fixation . • Marked limitation of left abduction due to weakness of the left lateral rectus . • Normal left adduction .

31. 2- compensatory face turn into the field of action of the paralyzed muscle ( i.e. to the left ) to minimize diplopia , so that the eyes do not need to look towards the field of action of the paralyzed muscle ( i.e. to the left ).