The Eye, Motor System and Binocular Vision

The Eye

• The eye transforms light stimuli through refractive media and the retina.
• Retinal receptors convert light into physiochemical and electrical changes, transmitting impulses to the CNS, creating visual sensations like form, spatial relationships, and color.
• The motor system and central/peripheral nervous arrangements are sensory responses.
• Sensory aspects trigger motor responses, involving inner/outer eye muscles.
• The sensory system transmits information with no independent significance.

Motor System Tasks

• Field of Vision is the area where objects are perceived without eye or head movement, using confrontation test,
• Field of Fixation is the area where central fixation is possible by moving the eye, head is still
• Practical Field of Fixation is the field achieved by moving both eyes and head, as in casual seeing.
• Tasks bring images of interest onto the fovea.
• The motor system aligns the eyes to maintain single binocular vision.

Binocular Vision

• This refers to vision using both eyes.
• Coordination and integration of images from both eyes create a single binocular percept.
• Optics, motor skills, and neurologic processing are requirements.
• Functional eyes see similar parts of visual space with matching cortical images.
• Eyes must fixate images, and the oculomotor system must move eyes accurately.
• The binocular system fuses two percepts into a single image.

Pyramid of Binocular Vision

• The pyramid has integrative, motor and sensory steps
• Sensory function is fundamental for performance/efficiency.
• Motor activities align eyes during gaze.
• Integrative activities fuse images into one visual space.

Advantages of Binocular Vision

• Advantages include enhanced performance, spare eye, acuity, field of view and stereopsis.
• Suppressed images on disparate retinal areas don't fully disappear.

Essentials for Binocular Vision

• Healthy maculas and competent focusing are needed to form clear images.
• Normal EOMs must bring necessary, fine adjustments within the system.
• An efficient nervous mechanism must psychologically blend impressions.

Theories of Binocular Vision

• These theories include relative subjective visual directions, alternation, projection, motor, and isomorphism.

Relative Subjective Visual Directions

• Sensory binocular cooperation stems from correspondence and disparity.
• Retinal elements in one retina share visual direction with corresponding elements in the other retina.
• Binocular rivalry follows simultaneous stimulation by object points differing in character.
• Diplopia follows disparate elements being stimulated by one object point.
• Every retinal point has a partner in the fellow retina that it shares a common subjective visual direction with.

Alternation Theory

• Retinal points are represented separately, being available in consciousness by the same single unit.
• The conscious unit only receives a stimulus from one retinal unit at a time, excluding the other.

Projection Theory

• Objects are localized along a line, marking light's path from object to retina.
• Objects are localized at the intersection of two lines (one to each retina) in binocular fixation.

Motor Theories of Visual Orientation

• Awareness from muscle sense determine or produce spatial localization that are postural elements in visual localization including head and conjugate eye movements and convergence in binocular vision.

Theory of Isomorphism

• Neuroanatomic features bring excitations from two retinas into visual cortex proximity.
• Excitations from closer/farther objects than a fixation point come together with the resulting excitations.

Tests for Binocular Vision

• Tests encompass stereoscopic, bar reading, prism, Maddox rod, and hole-in-hand tests.
• Tests anatomically and physiologically assess collection and transmission to determine deficiencies.

Aiming the Two Eyes Incorrectly

• Incorrect alignment results in strabismus, amblyopia, suppression, diplopia, or anomalous correspondence.

Prerequisites for Single Binocular Vision

• Frontally placed eyes, partial optic nerve decussation, and a foveal region are needed.
• Coordinating neural mechanisms unify retinal images.

Morgan Requirements for Single Binocular Vision

• Accurate monocular fixation, simultaneous binocular vision, and integrated neuromuscular activity help.
• A sensory corresponding system is organized around foveas.
• Similarity and sensory unification of ocular images are also necessary.

Mechanics of Single Binocular Vision

• Uniocular fields must overlap, coinciding simultaneously on the fovea.
• Functionally related retinal points must coincide, leading to one perceptual impression.
• EOMs turn eyes so uniocular images fall on corresponding retinal points.

Stereoscopic Test

• Assess overall binocular function.

Bar Reading

• Patients with no suppression are still able to read through it.

Prism Test

• Assess eye alignment and vergence abilities.

Maddox Rod

• Evaluates phorias and tropias by dissociating vision.

Hole-in-the-Hand

• Demonstrates visual dominance.

Strabismus

• A misalignment of the eyes.

Amblyopia

• Reduced visual acuity in one or both eyes.

Suppression

• The brain ignores input from one eye.

Diplopia

• Double vision.

Anomalous Correspondence

• Retinal points associate in an abnormal way.

Binocular Vision Sequence

• It depends on sensory, motor and spatial/temporal mechanisms coupled with psychological and psychophysiological aspects.

Anatomical Basis for Binocular Vision

• Rods and cones, ganglion cells, bipolar cells construct a series of neurons in visual process.
• In periphery there is motion in the night and day while the center we have acuity.

Visual Centers

• Brain areas process eye movements including the striate area (17) and parastriate/peristriate areas (19, 18).

Striate Area (#17)

• It is for perceptions like color, direction, form, and three-dimensional impression as well as blinking reflex.
• Blinks per minute - 12-15
• Lagophthalmos - inability to close eyes

Parastriate (#19) and Peristriate Area (#18)

• Centers serve as visuo-psychic or visual memory centers, surrounding #17.

Frontal Lobes

• They are for eye movement, especially saccadic and pursuit
• It is located to front, especially key in emergencies.

Occipital Lobe

• It is the location of where fusion, accommodation and voluntary eye movements to outside of central vision starts, also responsible for maintenance of fixation on a point

Contralateral Frontal Motor Cortex

• Upper portion stimulation leads to downward deviation.
• Lower portion leads to upward component deviation.

Pontine Region

• It serves as a center for conjugate lateral gaze (steady fixation).

Subcortical Center

• It is for vertical eye movements.

Corresponding Points and the Optic Chiasm

• We use the fovea as our primary visual direction and it is used for reference. Central vision applies in this
• Eyes normally center foveas on the same locus in space.
• Foveas are represented by corresponding cortical retinal points.

Binocularity in Visual Cortex

• LGN neuron inputs conclude in the striate cortex. Conditions involving binocular response in visual:
• Identical orientations
• Stimulating receptive fields' similar regions
• Binocular summation

Visual-Evoked Potential: (VEP)

• It objects information for binocular processing in visual cortex.
• VEP helps find issues inside brain in which its related with amblyopia

Binocular Vision Disorders

• These disorders, which can result in amblyopia, commonly surface during infancy
• Visual cortex facilitates fusion and single binocular vision. All information from the optic tract ends up in the LGN. Integration then starts

Four Major Types of Disparity-Tuned Cortical Neurons

Tuned Excitatory Cells

• Nerve cells here are tuned for spot on locations and they are on the horopter which the limit of our vision
• They do not well when there's crossed or uncrossed discrepancies. The former means the object falls in front whereas the latter, behind.

Tuned Inhibitory Cells

• Nerve cells which react in a inhibitory manner while at horopter.
• The said cells were no inhibited to whichever type of disparity
• As vergence drifts, the said stimulus helps maintain fusion as it returns to normal position

Near Cells

• As presented targets get closer when the target is nearer than the horopter, they increases rate of firing.

Far Cells

• These cells respond by any forms of uncrossed disparities or of distance targets, or of distances larger than the fixation point

Extraocular Muscles

• These muscles are the Medial Rectus, Lateral Rectus, Superior Rectus and Inferior Rectus muscles, Superior Oblique and Inferior Oblique.
• Center of Rotation (COR) occurs when all axes of rotation cross and lies behind the corneal vertex (Myopia is high while Hyperopia, low.)
• All obliques cause eyes to abduct while all rectos cause eyes to adduct, except the lateral which causes ablation movement.

Blood Supply

• The ophthalmic artery is lateral in the superior rectus, lps, and superior oblique
• The ophthalmic artery is medial in the inferior rectus, medial rectus and inferior oblique

Actions of the Eyes

• Primary-main action, Secondary-supporting action, Tertiary-supportive action

Park's Three Step Method

• Which eye shows hyperdeviation? Does hyperdeviation increases in the Right or Left gaze? Does one observe increase in the Right or Left hyperdeviation head tilt?

Fundamental Laws of Ocular Motility

• Includes Donder’s Law, Listing’s Law, Sherrington’s Law of Reciprocal Innervation and Law of Motor Correspondence/Hering’s Law.

Donders Law

• Meridian cannot be repeated or duplicated, is a given a fixed point
• Can also not interpret torsion

Listing’s Law

• Imaginary lines connecting physical and subjective space and connect by a visual axis

Sherrington’s Law

• Aka Unequal Innervation
• Contracting sends equally inhibitory pulses to antagonists that help release or lengthen

Innervation Law/Hering’s Law

• Pulses send for performance are equally sent for each muscles in eye movement

KINETICS

• Revolves with movement and side direction
• The (X, Y and Z AXIS) (Horizontal. Vertical and adduction )

Movement

• Movements include saccadic, fixation, and pursuit.
• High frequency tremors are minute eye jerks.
• Slow drifts entail coordinated shifting.

Pursuit Movements

• These consist of slow movements, from one point to another, occurring in a reading style.
• Vergence causes movement and disconjugaitnes which creates fusion that can cause movement that is usually involuntary

Monocular Rotations

• Only involves movement of one eye
• strabismic patient (better to use; emphasizes that the the eye a problem).

Conjugate

• When two sight lines move by an equal movement the eye or eye that helps fixate those point

Versions

• Movements are yoke synergisms that lead together

Vergence

• Movements lead to direction in a reverse format
• Can lead to convergence or divergence

Classifications

• Includes vertical. lateral and torsional movements.

Primary position

• Is what causes us to experience either pure horizontal, or pure vertical movements.

Basic Kinematics

• Rotation around a center point or (Vertical or Horizontal ).
• The Axes on the other hand are (Transitively and Rotarily )

Versions are:

• Simultaneous with a movement for either of them.
• Eye movements can either up, or down both lead to both of that

Classifications

• To what eyes movements will be linked.
• Can either be in (Lateral and Vertical movements)

Versions

• Parallel with conjugate are just equal with actions are to follow that particular point

Innervation

• Leads with our muscle memory
• Can easily direct our actions

Vergence

• Movement occurs and results with an opening or separation point with either

Movement

• In either horizontal, or vertical formats
• Always be sure a action can direct a direction when their linked

Development of Binocular Vision

• At birth, no synchronization exists between the eyes, existing as separate sensory tools instead,
• Retina is already in place in early phase however, the musculature and corresponding oculomotor areas are still early

Binocular Period

• Starts at ~ three months
• Vision changes to that of a visual stimulus.

Sensitive Development

• Is critical time (three months), where there is a limited, best use for the process of visuals
• If they do not properly stimulated, disorders will happen due to low activity

Visual Skills

• VA in the area usually is for light detection first, than temporal resolution and motion all this before color follows after a period of time

Accommodation

• Is slow but accurate given months to accomplish this.

Viewing and Response

• Begins at approx., one month with fully given months there there comes full convergence

Stereopsis

• Has a long period to properly evolve with that of movement with visual stimulus before the person tracks object with ability at three and half moths

If There are:

• If issues happens with abnormal view point (amblyopia) which leads too a visual process to lack information thus
• If there is, strabismus also one requires treatment, that said strabismus history requires intervention

Visual Traits (or thoughts):

• Empiricism: we have to make sure that there is full improvement because things need to be shown and done, if we have it as Nativism not everything is needed.

ViewPoint in under:

• Four Months: we like faces, large angle, as Kappa, small acumen or resolution, wide refraction, asymetrcal vision

Visual direction has what two?

• Angular and size to its form, both a object needs that to be seen

Angularly

• One sight with the passing at each point between pupil or going on to space all direction exist with the specific line.

Retinas

• All are located to have equal areas and this makes the system work when working to their full potential

Oculocentric vs Egocentric

• Head is same no eyes when it comes to eyes and heads direction when you move its relative to both

Retinomotor and Iso values

• Iso meaning equal
• the test you can use with that is (High or Scarsburge) with what value

Retinas

• This process then creates correspondence which allows visual ability for common or relative values to determine it this means you can see with relative or similar object view points

Abnormal Vision

• There are cases that the LGN is bad in a particular direction, if those is a eccentric point (non/ bad sight).
• The basics for vision (angular size, spatial relation or both); and how and when the brain combines all this that in short is a process

What LGN does?

• Terminate inputs and the binocular process is needed to connect with each eye to bring to the light and this should have similar features (Stimulus that is) because that is to stimulate the process to function at best or with a purpose.

Donders Law

• That line you see is the only spot point at you and allows at angle to rotate

Vergence & Version are key to what (what causes direction)?

• Innervations with how you feel. So both are equally important for helping to understand each their actions
• You can preform motor and fusional skills for the eye that helps a alignment to be stable, with proper actions.
• This just a break down of all those steps from now

What and/or what point to that particular locus on retina what

• The key elements here Angular and how its position will make us relate what its that object.

With the elements to make with two?

• They are the Retinomotor and or also (Stimulus and or Spacial).