The Parks-Bielschowsky three-step test is a diagnostic tool developed to identify the paretic muscle causing acquired hypertropia, particularly useful for diagnosing superior oblique palsies. The test consists of three steps, focusing on determining which eye is hypertropic and how the condition changes with gaze and head tilt. It is unreliable in cases with multiple paretic muscles or restrictive strabismus.

1. Parks-Bielschowsky -3
step test
Sudama kharbind

2. Bielchowsky park-3 step
• It was first described by Bielschowsky in 1935 and later popularized by
Marshall M. Parks.
• It is a diagnostic test used to identify which muscle is paretic in the case of an
acquired hypertropia.
• The three-step test, also known as the Parks-Bielschowsky three-step test or the
Parks-Helveston three-step test.
• This test is most useful in diagnosing superior oblique palsies in clinical practice

3. Bielschowsky park-3
• It is designed for the diagnosis of a single paretic vertical muscle and is
unreliable when there are multiple paretic muscles or in restrictive strabismus
• Performed in three step.
• Aim-To diagnose which cyclovertical muscle is paralyzed/palsied.

4. Bielschowsky's head tilt test
• Step 1: Determine which eye is hypertropic in primary position.
Step 2: Determine whether the hypertropia increases on right or left gaze.
Step 3: Determine whether the hypertropia increases on right or left head tilt.

5. Eg: Right hypertropia increase left gaze and
right head tilt

6. Step 1. Which eye is hypertropic?
• In the patient in Figure 1, the right eye is hypertropic (RHT). When trying to isolate
which muscle is paretic in a right hypertropia, it must be either one of the depressors
of the right eye or one of the elevators of the left eye. Therefore, we have deduced
from step 1 that the paretic muscle must be one of the following cyclovertical muscles:
• Right superior oblique
• Right inferior rectus
• Left inferior oblique
• Left superior rectus

7. Step 2. Does the hypertropia increase in
right gaze or left gaze?
• Hypertropia increases in left gaze
• Understanding cyclovertical muscle field of action is crucial
• Isolating prime mover muscles in cardinal positions
• Paretic muscle elevates left eye or depresses right eye in left gaze
• Right superior oblique and left superior rectus meet criteria for paretic
muscles

8. Step 3. Does the hypertropia increase in
right head tilt or left head tilt?
• Final step in determining paretic muscle
• Right hypertropia worse in left gaze
• Deviation increases on right head tilt, decreases on left
• Implicates right superior oblique as paretic
• Right superior oblique and rectus work together
• Paretic superior oblique causes right eye elevation
• Otolith system adjusts eyes during head tilt
• Right eye moves upward due to paresis
• Right hypertropia decreases significantly in left tilt
• Positive three-step test for right superior oblique palsy

9. What are the condition in which parks-3 step
test is inapplicable?
1. Multiple cyclovertical muscle palsies
2. Restrictive squint (Eg. Thyroid ophthalmopathy, Duane’s retraction
syndrome, Brown syndrome, Orbital fracture with muscle entrapment)
3. Dissociated vertical deviation (DVD)
4. Squint resurgery
5. Skew deviation
6. Mysthenia gravis

10. Thank you