Lec.4- Ocular Motility, Versions, Pursuits, Color Vision
Pursuits, versions, and ocular motility foundations
Eye movement overview
Six main types: visual fixation, vestibulo-ocular response (VOR), optokinetic nystagmus (OKN), saccades, pursuits, and vergences - VVVSOP
Today’s focus: pursuits, versions, NPC/saccades context, and NPC for NPC/vergence and saccades with NPC in NPC testing
Pursuits vs. saccades (and their kinship via muscles)
Pursuits: conjugate, smooth, slow eye movements; eyes move in the same direction (e.g., both to the right, both up)
Saccades: rapid, conjugate jumps to bring a new target onto the fovea
Both employ yoked muscles (Hering’s law): equal innervation to corresponding muscles in both eyes to move in the same direction
Hering’s law vs. Sherrington’s law
Hering’s law: yoked muscles in contralateral eyes receive equal innervation to move in the same direction
Sherrington’s law of reciprocal innervation: in each eye, one muscle is stimulated while its antagonist is inhibited during conjugate movement
Example: looking to the right
Right eye: lateral rectus stimulated; medial rectus inhibited (Shering)
Left eye: medial rectus stimulated; lateral rectus inhibited (yoked pairs coordinate to move both eyes right- Heringtons )
Six cardinal gaze positions and the cranial nerves involved
Six cardinal positions: up-right, right, down-right, down-left, left, up-left
Cranial nerves innervating extraocular muscles
CN III (oculomotor): medial rectus, superior rectus, inferior rectus, inferior oblique
CN IV (trochlear): superior oblique
CN VI (abducens): lateral rectus
Central control: occipital-parietal junction; cerebellum and vestibular nuclei assist with integration
Muscle insertions and actions (secondary/tertiary actions depend on insertion)
Rectus muscles insert anteriorly; obliques insert posteriorly
Primary actions in cardinal positions; secondary/tertiary actions depend on insertion and crossing midline
Examples of primary and secondary roles (in the context described):
Superior rectus: primary elevation; contributes to adduction via insertion geometry
Inferior rectus: primary depression; excyclotortion/contributes to abduction/adduction patterns
Superior oblique: primary depressor when eye adducted; contributes to intorsion (cyclotorsion)
Inferior oblique: primary elevator when eye adducted; contributes to extorsion
Key rule: rectus muscles mainly drive abduction/adduction; obliques contribute to cyclotorsion and rotation depending on gaze
Obliques = Opposite of what the name says
Recording and interpretation basics during versions/pursuits
Test both version (binocular movement across six gaze positions) and pursue smoothness simultaneously
Isolated deficits are described by which eye and which movement breaks down (e.g., “abduction deficit OD”)
If not full range of motion in a gaze, consider cranial nerve pathology, neuromuscular junction, or orbital restriction
If abnormal, you may proceed to ductions (monocular version tests). Ductions are monocular; versions are binocular
Observational vocabulary and recordings
Abduction/adduction terms abbreviated: ABduction/adduction; ADduction defined per eye and direction
Cyclotorsion: incyclotorsion vs excyclotorsion depending on rotation toward/away from nose
Practical testing notes (H pattern and variations)
H pattern is standard for testing six positions; other patterns exist (e.g., circular or full 60-minute arc approach) depending on neuro exam style
Purkinje reflexes: use transilluminator or penlight to observe reflections; maintain 75 cm distance for visibility; ensure lids are held appropriately to reveal reflections
Purkinje reflex rule: loss of reflex in one eye indicates a problem with that eye’s visibility or alignment in the test position
What constitutes a normal result in this testing domain
Normal: full range of motion and smooth pursuit across all six gazes
Abnormal pursuit: full range but jerky movement or endpoint nystagmus at endpoints
Document findings descriptively (e.g., “abduction deficit OS with preserved other movements”); avoid premature clinical diagnoses; consider differential until further tests
Head posture implications
Patients may adopt a compensatory head turn toward the good eye or away from diplopic field to reduce double vision
Assess head posture with patient’s head straightened; ensure not influenced by leg crossing or improper seating that might tilt the head
Saccades, OKN, VOR and related motion disorders
Saccades and OKN relationships
Saccades: fast conjugate jumps between targets; okn involves smooth pursuit and rapid resets when scenes move
OKN: slow phase followed by fast corrective phase; occurs when scene moves while viewer is stationary
VOR: stabilizes the image during head movement; compensates for head motion to keep gaze stable
Relevance to clinical testing
Saccades are used as part of basic eye movement evaluation; their speed and accuracy reflect neural control from cortex to brainstem
Abnormalities can indicate neuro-ophthalmic pathology or concussion-related deficits in motility and convergence
Near point vision and convergence testing (NPC) and vergence
Near Point of Convergence (NPC)
NPC: closest point at which a patient can maintain single binocular vision
Disjunctive (convergence) movement: eyes move toward the nose in opposite directions disjunctive movements include convergence/divergence
Vergence mechanisms
Fusional vergence: fusional disparity drives fusion; stereo depth depends on this.
Accommodative vergence: accommodation drives convergence (accommodative convergence)
Proximal vergence: convergence due to awareness that a target is near
NPC testing protocol and targets
Preferred accommodative target: a small, detailed target (e.g., 20/30 letters) used at ~40 cm with appropriate illumination
Alternative accommodative targets: transilluminator with near target; use discrimination of single vs double (break) and recovery after break
Recording endpoints: break point (when image doubles) and recovery point (when single again)
Typical norms for accommodative target: break ≤ 5 cm and recovery ≤ 7 cm (for clinical accommodative NPC)
Penlight NPC norms: break ≤ 7 cm and recovery ≤ 10 cm (more tolerant due to less accommodative demand)
Testing considerations and documentation
If no break occurs before bridge of the nose (TTN: to-the-nose), it's still considered a normal or near-normal endpoint depending on test type
If the patient reports double at or before a break, document diplopia and break point; note if suppression occurs and which eye suppresses
Use break/recovery measurements to assess convergence reserve and potential insufficiency; plan further testing if deficits persist
Practical testing notes
Test with glasses on, have lighting adequate, and ensure the patient sees the accommodative target clearly
Document whether suppression occurs, whether the patient reports diplopia, and which eye leads in convergence (dominant eye considerations are discussed later)
Stereopsis, monocular cues, and binocular testing
Stereopsis basics
Stereopsis is depth perception arising from binocular disparity between the two retinas
Simultaneous perception occurs early; true depth perception (stereopsis) develops around 3–5 months; simultaneous perception can appear by 1–3 months
Suppression can mask stereopsis in certain strabismus conditions; global stereopsis requires true binocular alignment; constant strabismus often eliminates stereopsis, intermittent strabismus may retain some
Monocular cues can still aid depth perception if stereopsis is absent
Monocular cues for depth perception
Relative size: smaller objects appear farther away
Interposition (occlusion): closer objects occlude farther ones
Linear perspective: parallel lines converge at a distance (vanishing point)
Aerial perspective: distant objects have reduced contrast and saturation
Light and shade: shading conveys depth
Parallax: closer objects move relative to farther objects when you move your head
Stereopsis tests (local vs global)
Randot (Randot Circles) and Randot shapes: polarized stereograms
Local stereopsis: fine depth discriminations; can reach ~20 seconds of arc
Global stereopsis: more challenging, requires true binocular fusion; tests like Randot circles and shapes
Testing setup: patient wears polarized glasses; testing distance ~40 cm; ensure proper illumination and avoid monocular cues
Testing protocol: begin with simple targets, progress to more complex; evaluate suppression and whether both eyes are contributing
Interpretation: ability to perceive depth indicates binocular fusion; failure may indicate constant strabismus or suppression; intermittent strabismus may still yield stereopsis depending on fixation and alignment
Other key stereopsis tests and concepts
The anomaloscope and macular/perception-based tests (e.g., anomaloscope, Landolt-C-based tests) help quantify color and depth perception in some contexts; discussed later in color testing section
Randot testing specifics and scoring
Randot Circle test (local stereo): assesses depth of two circles; scores reflect depth perception at given arcmin
Randot Shapes: polarised shapes; higher-order global stereo may involve more complex perception tasks
Scoring examples mentioned: 500 seconds of arc and 250 seconds of arc for global stereopsis; local stereo can be as fine as 20 seconds of arc
Suppression considerations: if suppression is present, certain stimuli may still be perceived by one eye; documentation should reflect suppression status and stereo results accordingly
Color vision testing: congenital vs acquired, tests, and interpretation
Why color vision testing matters
Baseline screening for new patients; essential for professions requiring color discrimination (e.g., police, aviation, military, etc.)
Help diagnose color vision defects that might impact daily life or occupational safety
Distinguish congenital color vision deficiency from acquired defects due to pathology (e.g., macular disease, optic neuropathies)
Types of color vision defects
Congenital color vision defects (inherited): present from birth; stable; bilateral; often affect all fields of view
Monochromats: one cone type; essentially color blind with reduced acuity; extremely rare
Dichromats: two cone types missing one cone type; three main categories:
Protanopia: absence of red cones
Deuteranopia: absence of green cones
Tritanopia: absence of blue cones (rare)
Prevalence: red-green defects most common in men; about 8% of men have red-green deficiency; often X-linked (more common in males)
Anomalous trichromats (trichromats with shifted cone sensitivity)
Protanomaly (reduced red cone sensitivity)
Deuteranomaly (reduced green cone sensitivity)
Tritanomaly (reduced blue cone sensitivity)
These are milder than dichromats and are more common than true dichromats; overall more prevalent in men for red-green types
Congenital vs acquired color vision defects
Congenital: present since birth; usually bilateral and diffuse; often detected during childhood; stable
Acquired: due to ocular disease or systemic disease (e.g., cataract, macular disease, glaucoma, optic neuropathies); often asymmetric and can affect one eye or a portion of the visual field; may improve after treatment (e.g., cataract extraction) or progress with disease
Tests for color vision
Ishihara plates: red-green color deficiency screening; standard in many clinics
Abbreviated vs full tests available; first demonstration plate (plate 12) checks comprehension, not color vision per se
Hardy-Rand-Rittler (HRR) plates: tests red-green and blue-yellow; better for diagnosing both red-green and blue-yellow defects; includes demonstration plates and diagnostic plates
D-15 and 100 Hue tests: arrange colors in sequence; diagnose order of hues to determine color deficiency pattern; less common for screening, more for pattern assessment
Anomaloscope: clinical gold standard for precise red-green color vision testing; patient adjusts color mixture to match reference; determines type and severity of color vision deficiency
Other specialized tests: anomaloscope use beyond congenital defects; HRR and Ishihara for baseline; pseudoisochromatic tests, etc.
Testing conditions and interpretation
Lighting: color vision testing requires daylight-equivalent illumination (sea daylight). Many lab lamps do not meet this; use daylight-equivalent bulbs to avoid misinterpretation
Distance and glasses: testing distance typically 75 cm; wear corrective lenses as needed
Record-keeping: documentation includes which eye tested, results for screening plates, and diagnostic plates; note suppression and binocular status when applicable
Norms and cutoffs (as discussed)
Ishihara: screening red-green; abbreviated test may have 2,200 or better threshold as an eligibility factor for full testing; abnormal results require HRR or diagnostic Ishihara plates
HRR: tests red-green and blue-yellow; diagnostic plates help classify protan vs. deutan and mild/medium/severe defects; blue-yellow subset may be tested if red-green is normal and vice versa
D-15 / 100 Hue: pattern analysis to distinguish type and severity; used for more nuanced color naming and pattern recognition rather than straightforward screening
Diagnostic interpretation framework
Dichromats vs anomalous trichromats: HRR and Ishihara help identify whether the patient is protan/deutan/tritan type and whether the defect is dichromatic or anomalous
HRR can separate red-green and blue-yellow; provides more information about the specific defect than Ishihara alone
The diagnostic plates provide the pattern to classify type; the scoring often emphasizes the number or pattern of errors
Practical and clinical notes from the session
Color vision testing can be used for occupational screening and disease monitoring (pathology-acquired defects)
HRR sometimes preferred due to its broader testing scope (red-green and blue-yellow), though Ishihara remains widely used
Lighting and distance standards are important for valid results; some clinics still apply older standards; be aware of current recommendations in your program
Some clinicians still value color vision testing (e.g., for patients on certain medications like Plaquenil) even if newer standards emphasize optic coherence tomography (OCT); local practice may vary
Summary terms and concepts
Monochromats: one cone type; color vision absent
Dichromats: two cone types; major categories are protanopia, deuteranopia, tritanopia
Protanomaly, Deuteranomaly, Tritanomaly: anomalous trichromats with shifted sensitivity; varying severity
Red-green defects: most common, X-linked; prevalence higher in men
Blue-yellow defects: less common; separate diagnostic pathways (HRR and/or specialized tests)
Acquired color defects: due to disease or treatment; patterns may reflect pathology and may be unilateral/asymmetric
Testing conditions: daylight lighting, proper distance, correct refractive correction
Ocular dominance and dominant-eye testing
Ocular dominance concept
Tendency to prefer one eye over the other when viewing; two-thirds of people are right-eye dominant; about one-third left-eye dominant
Why dominance matters
Relevance for monovision or multifocal contact lens prescriptions; dominant eye often the near or far eye in monovision setups; influences binocular balancing strategies
For profession-specific decisions (e.g., targeting, aiming tasks), knowing the dominant eye helps in planning tasks
How to determine ocular dominance (two quick methods shared)
Hand-triangle method: form a small triangle with hands and align with a distant target; close one eye, then the other to see which eye maintains the target visible in the triangle; the dominant eye keeps the target aligned when the other eye is closed
Occluder method: hold an occluder and cover one eye at a time to see if the target stays centered; the eye that maintains alignment when either eye is used is dominant
Practical notes
A dominant-eye assessment helps in planning prescriptions and management for monovision or depth-perception demands
Cross-dominance (e.g., left-eye dominance with right-handed bias) does not reliably improve performance in many sports (e.g., cricket data cited); do not rely on dominance alone for performance claims
Dominance testing can be done quickly in clinic; the results can inform treatment planning and patient education
Practical tips and integration with clinical practice
General testing tips throughout the session
Maintain Purkinje reflex visibility during pursuits/versions testing; misalignment reduces reflex visibility and affects accuracy
Watch for scleral show and ensure correct eye alignment during lateral/eccentric gaze movements; adjust distance and head position accordingly
Ensure patient head is straight and stable; avoid postural cues (crossed legs, tilt) that can confound measurements
Document not just whether movements are full/smooth, but also whether the movement is normal, full with end-gaze nystagmus, or incomplete (e.g., AB duction deficit) with affected gaze direction
In cases of diplopia, determine whether it is binocular or monocular by cover test and subsequent checks
When to pursue additional testing
Abduction/adduction deficits or other motility issues may require ductions, forced ductions, cover tests, or neuroimaging depending on the clinical context
Diplopia that does not resolve with covering one eye (binocular diplopia) is suggestive of a motility or alignment issue; monocular diplopia is more often refractive or corneal/ocular surface related
If a patient demonstrates a persistent deficit, consider cranial nerve pathology, neuromuscular junction issues, or orbital restrictions; plan for further testing as appropriate
Quick recap of key numbers and guidelines (LaTeX-friendly)
Acuity notation relationships
Snellen fraction
Geometric/size calculations
Letter size relation to MARR:
Pinhole rules (clinical teaching vs. lab context)
Pinhole if: acuity is 20/40 or worse in any relevant condition; if any one of the tested conditions is 20/30 or better, do not pinhole
NPC norms (accommodative target)
Break: ≤ 5 cm; Recovery: ≤ 7 cm (accommodative target)
Penlight NPC: Break ≤ 7 cm; Recovery ≤ 10 cm (less demanding)
Depth perception and stereopsis
Local stereopsis: as good as ~20 seconds of arc (Randot Circles/Shapes local targets)
Global stereopsis: around 250–500 seconds of arc (Randot Circles/Shapes; broader tests)
Color vision testing standards
Ishihara: red-green screening (abbreviated vs full plates; demonstration plates separate)
HRR: red-green + blue-yellow screening; diagnostic plates differentiate protan vs deutan and mild/medium/severe defects
Anomaloscope: gold standard for precise red-green typing; used to quantify type and severity of deficiency
Lighting: daylight-equivalent illumination (sea daylight) is recommended for valid results
Common patterns in recording
Document direction of movement deficits (e.g., ABduction deficit OD)
Record the exact gaze positions where deficits occur; note if end-point nystagmus is present
Capture any compensatory head posture during testing (head turns, tilts)
Quick glossary (for quick study)
Pursuits: smooth, conjugate eye movements in a direction
Versions: binocular eye movements that include both eyes moving in the same direction; includes pursuits in practice
Ductions: monocular versions (one eye) used in some tests
Vergences: disjunctive eye movements (convergence/divergence)
Hering’s law: yoked muscles receive equal innervation in both eyes
Sherrington’s law: reciprocal innervation within the same eye
NPC: near point of convergence; break and recovery points used to assess convergence and accommodative demand
Stereopsis: depth perception arising from binocular disparity; subdivided into local vs global tests
Monocular cues: depth cues available even with one eye (size, occlusion, perspective, shading, parallax)
Dichromats: two-cone types; protanopia, deuteranopia, tritanopia
Anomalous trichromats: shifted cone sensitivity (protanomaly, deuteranomaly, tritanomaly)
Anomaloscope: color-matching instrument to quantify color vision deficiency
Purkinje reflex: brightness reflections used in motility testing
If you’d like, I can format this into a printable study guide or tailor it to a specific exam outline (e.g., board-style questions, short answer prompts, or fill-in-the-blank practice). I can also add a condensed quick-reference sheet with the key normal values and common abnormal patterns for rapid review.