Binocular eye movements

what are eye movements in which both eyes move in the same direction called

versions

what are all the version movements and which direction do they point

• Dextroversion (rightwards)

• Laevoversion (leftwards)

• Sursumversion (upwards)

• Deosursumversion (downwards)

• Dextrocycloversion (top of the eyes moves to the right)

• Laevocycloversion (top of the eyes moves to the left

Binocular eye movements in which both eyes move in the opposite direction (disconjugate) are called

vergences

what are all the vergence movements and which direction do they point

• Convergence (eyes move inwards)

• Divergence (eyes move outwards)

• R supravergence (RE upwards = LE downwards)

• R infravergence (RE downwards = LE upwards)

• Incyclovergence (eyes roll inwards towards nose)

• Excyclovergence (eyes roll outwards away from nose

what is Herings law of equal innervation

movement of one eye is accompanied by a movement of the other eye of equal amplitude and velocity, either in the same or opposite directions

what are the 4 Maddox classifications of vergence

1. tonic

2. disparity

3. accommodative

4. proximal

what is a tonic vergence

the amount of vergence present when no other cues to vergence are available. This is the baseline or resting vergence position of the eyes, present even in the absence of any specific visual stimuli.

what is accomodative vergence

This is the vergence response driven by the need to focus on a target at different distances, as the eyes converge or diverge to maintain a clear image

what is disparity vergence

vergence component that is induced by retinal disparity. • Vergence eye movements are made to ensure that the two fovea coincide

what is proximal vergence

evoked by stimuli that give the impression of being nearer or further. This vergence is stimulated by cues related to the perceived distance or nearness of a target, such as the size of the target or the presence of other objects in the scene

how many degrees is equivalent to 1 prism dioptre

0.57

what factors affect alignment of both eyes

• Anatomical factors.

• The basic tonus of the extraocular muscles.

• The eyes’ accommodative power and

• The fusion reflex (the presence of a fusion

  stimulus

what is hetrophoria

• latent deviation of the eyes.

• Which means it occurs, if present, when the stimulus to fusion is removed.

• The uncovered eye does not move

• when the occluder is removed the eye will return to its original position

when a cover is placed in front of one eye, the covered eye will deviate: the eye movements are called …

• Not move – orthophoria

• Inwards – esophoria

• Outwards – exophoria

• Upwards – hyperphoria

• Downwards – hypophoria

what is a tropia

• manifest deviation of the eyes.

• In this position the eyes are turned all the time).

• when occluded the eyes dont move

what are the types of tropia and what directions do they moves

• Outwards – esotropia

• Inwards – exotropia

• Upwards – hypotropia

• Downwards – hypertropia

what are the methods of measuring a heterophoria

• Maddox Rod

• Maddox Wing

• Von Graefe

• Know normal values of H and V heterophoria in population

what is the method for horizontal phoria - maddox rod

• The horizontal Maddox rod is used to measure horizontal phoria.

• The patient looks at a spot of light (usually at a distance).

• Orthophoria: The spot and line intersect.

• Heterophoria: The spot and line appear apart.

• Prism is used to align the two and measure the size of the phoria.

what is the method for esophoria - maddox rod

• A Maddox rod is placed in front of the patient's right eye (RE).

• The patient reports seeing a 4Δ esophoria.

• The red line appears to the "right" of the light spot due to the horizontal deviation.

Maddox Wing - Measurement of Phoria at Near

• Used to measure phoria at near.

• The device has a septum to dissociate the eyes.

• There are 3 scales: horizontal, vertical, and cyclophoria.

• Each scale has numbers and directions (e.g., eso, exo, hypo, hyper).

• One eye sees the scale, the other sees the "arrow.

Maddox Wing - Procedure

• The patient holds the Maddox Wing in place.

• The patient reports if they can see both the scale and the arrow.

• The number where the arrow points is recorded as the size and direction of the heterophoria.

Von Graefe Method - Fusion and Dissociation

• Fusion is broken using prism, causing dissociation and diplopia.

• Horizontal phoria is measured with about 6 prism diopters (Δ), base down (BD) or base up (BU).

• The patient sees 2 images (one above the other), misaligned if heterophoria is present.

• The amount of prism required to align the images equals the phoria.

what are Normal Findings for Heterophoria

• Horizontal Phoria:

  • Distance: 1 exo (SD ±2) prism diopter.

  • Near: 3 exo (SD ±3) prism diopter.

• Vertical Phoria:

  • Orthophoria (no vertical deviation).

define vergence

simultaneous movement of the pupils of the eyes towards or away from one another during focusing

how to calculate AC/A ratio using the gradient method

change in phoria in dipoters / change in accommodation in diopters

what does the Ac/A ratio represent

the amount of convergence in prism diopters that is induced per diopter of accommodation

how to measure AC/A ratio using the calculated method

what does an AC/A ratio with converge excess suggest ( higher than 6:1 )

can suggest that the patient converges too much when they accommodate, leading to esophoria or excessive near vergence

what does an AC/A with a convergence insufficiency ( lower than 3:1) suggest

may suggest the patient has difficulty converging their eyes for near tasks

which conditions does AC/A ratios help solve

esophoria and exophoria

what is the worth 4 dot test

test assesses how well the eyes can align and fuse two images. The patient is shown a set of four dots with different colors, and the examiner can evaluate the patient's ability to fuse the images together (i.e., no double vision)

what is a synoptophore (or Stereopter)

a device that presents two images to each eye, and the patient is asked to align them. The examiner can then adjust the images to measure how well the eyes can converge or diverge.