Ocular motility and the H-test: ductions, versions and the nine positions of gaze
Quick answer
The H-test examines eye movements by asking the patient to follow a target in an H shape through the six cardinal positions of gaze. In each of those positions one muscle of each eye is the main mover, so an eye that lags in a position points to weakness of the muscle that works best there. Versions are movements of both eyes together, ductions are movements of one eye with the other covered, and vergences move the eyes in opposite directions. Adding straight up, straight down and primary position gives the nine positions of gaze, which also reveal A and V patterns.
Open the simulatorDuctions, versions and vergences
| Movement | What moves | Examples |
|---|---|---|
| Duction | One eye, with the other covered | Abduction, adduction, elevation (supraduction), depression (infraduction) |
| Version | Both eyes in the same direction | Dextroversion (right gaze), levoversion (left gaze), supraversion, infraversion |
| Vergence | Both eyes in opposite directions | Convergence, divergence |
How to perform the H-test
- Sit about 50 cm in front of the patient and hold a target, such as a pen tip, at eye level. Ask the patient to keep the head still and follow the target with the eyes only.
- Move the target slowly to the patient's right, then up and down; bring it back through the center, then to the left and up and down, tracing a letter H.
- In each position, watch both eyes for underaction or overaction, and ask whether the patient sees double and where the double vision is greatest.
- Add straight up and straight down to complete the nine positions of gaze, and check convergence to a near target.
- If a version looks limited, test the ductions of each eye with the other eye covered to confirm which eye and which direction are affected.
Which muscle is tested in each cardinal position?
In each cardinal position one muscle of each eye is the main mover. These pairs are called yoke muscles.
| Gaze position | Right eye | Left eye |
|---|---|---|
| Right | Lateral rectus | Medial rectus |
| Left | Medial rectus | Lateral rectus |
| Up and right | Superior rectus | Inferior oblique |
| Down and right | Inferior rectus | Superior oblique |
| Up and left | Inferior oblique | Superior rectus |
| Down and left | Superior oblique | Inferior rectus |
Actions of the extraocular muscles
| Muscle | Primary action | Secondary | Tertiary | Nerve |
|---|---|---|---|---|
| Medial rectus | Adduction | — | — | III |
| Lateral rectus | Abduction | — | — | VI |
| Superior rectus | Elevation | Intorsion | Adduction | III |
| Inferior rectus | Depression | Extorsion | Adduction | III |
| Superior oblique | Intorsion | Depression | Abduction | IV |
| Inferior oblique | Extorsion | Elevation | Abduction | III |
The extraocular muscle anatomy guide explains why these actions change with the direction of gaze.
Hering's and Sherrington's laws
- Hering's law of equal innervation: yoke muscles receive equal innervation during a version. This is why, in a paralytic strabismus, the deviation is larger when the paretic eye fixates (secondary deviation) than when the healthy eye fixates (primary deviation).
- Sherrington's law of reciprocal innervation: when a muscle contracts, its direct antagonist in the same eye relaxes by a matching amount.
What abnormal findings suggest
- Limited abduction with an esotropia that increases on gaze to that side: a sixth nerve palsy — or Duane retraction syndrome if the globe retracts and the lid fissure narrows on adduction.
- Limited elevation in adduction: Brown syndrome (a restricted superior oblique tendon) or an inferior oblique palsy.
- An eye that shoots up in adduction: inferior oblique overaction, often with a superior oblique palsy or childhood esotropia.
- Slow or limited adduction on side gaze with nystagmus of the abducting fellow eye: internuclear ophthalmoplegia.
- Neither eye can look to one side: a horizontal gaze palsy.
Practice it on the virtual patient
- Open the normal exam, choose the H-test tool and trace the six cardinal positions to learn what full versions look like.
- Switch to a right sixth nerve palsy and find the gaze direction where the eyes separate most.
- Compare with Duane retraction syndrome and Brown syndrome.
- Open the 3D anatomy view to see each muscle's pull in the nine gaze positions.
Frequently asked questions
What are the six cardinal positions of gaze?
The six cardinal positions are right, left, up and right, down and right, up and left, and down and left. In each one, one muscle of each eye is the main mover, so together they test all twelve extraocular muscles.
What is the difference between ductions and versions?
A duction is the movement of one eye alone, tested with the other eye covered. A version is a movement of both eyes together in the same direction.
Why test nine positions of gaze instead of only the H?
The H pattern never asks the patient to look straight up or straight down, so it can miss A and V patterns and purely vertical problems. Adding up, down and primary position gives the nine diagnostic positions of gaze.
What are primary and secondary deviations?
In a paralytic strabismus, the primary deviation is measured with the healthy eye fixating and the secondary deviation with the paretic eye fixating. Because of Hering's law, the secondary deviation is larger.
Related guides
- Extraocular muscles: anatomy, actions and nerve supply Origins, insertions, actions and nerve supply of the six eye muscles — and why actions change with gaze.
- Third, fourth and sixth cranial nerve palsies and the three-step test Recognize each ocular motor palsy, run the three-step test and spot the red flags.
- Internuclear ophthalmoplegia (INO), one-and-a-half syndrome and gaze palsies Localize INO, one-and-a-half syndrome, gaze palsies and Parinaud syndrome from eye movements.