terms Flashcards
aberrant regeneration
change in actions of muscles supplied by third nerve following traumatic/compressive 3rd nerve palsy (new nerve innervation)
ABSV
abnormal binocular single vision: form of BV occurs in absense of foveal fixation usually with abnormal retinal correspondence
Abnormal Retinal Correspondence
A binocular condition in which there is a change in a visual projection such that the fovea of the fixating eye has a common visual direction with an area other than the fovea of the deviating eye. The pairing of all retinal elements is similarly changed. It may occur when the eye is used for fixation.
absolute eccentric fixation
eccentric fixation in which the angle of eccentricity = objective angle of deviation
scotoma
loss of vision in part of visual field
accomodation
the ability of the eye to increase its dioptric power (the convexity of the crystalline lens) in order to obtain a clear image of a near object
accommodative convergence
one of the components of the eyes initiated by effort to overcome a blurred retinal image.
AC:A ratio
ratio of accommodative convergence in prism dioptres in relation to one dioptre of acomodation
accomodative facility
measure of how fast clarity is restored following a rapid change of focus
accommodative fatigue
inability to sustain sufficient accom over an extended period of time
accomodative inertia
difficulty in changing the accom state from one fixation distance to the other
accom insufficiency
amplitude of action is lower than would be expected for individuals’ refractive state and age
accom spasm
spasm of ciliary muscle resulting in nr and dis far points of accom becoming closer to eye than expected for patients age associated with psuedomyopia and conv spasm
adjustable suture
sutures can be readjusted within 24 hours
advancement
a surgical technique where the muscle insertion is moved forward from its original insertion thereby strengthening its action
afferent pupil defect
affected pupil does not constrict to direct light stimulation but reacts to consensual due to lesion in optic nerve
agnoist and antagonist
agonist = primary muscle
antagonist= EOM whose action opposes that of contracting muscle
altitudinal defect
involves 2 quadrants of either superior or inferior vf and seen in ischaemic optic neuropathies/ Resect the horizontal midline.
amplitude of accomodation
difference in dioptres between near and far points of accommodation between min and max amount of accommodation
amsler grid
chart used for assessing central visual fields
aniridia
absence of iris
anisocoria
difference in pupil size
anisokonia
difference in size/shape of retinal images of two eyes
anisometropia
difference in RE between two eyes
Anterior Positioning:
A surgical procedure where the insertion of the oblique muscle is moved more anteriorly.
Anticholinesterase
A drug that inhibits or inactivates the action of acetylcholinesterase.
Arcuate Scotoma:
Defect of the retinal fibres causing loss of vision in an arc shape from the optic disc to the nasal side of the fovea either above or below the mid line found in glaucoma.
Argyll Robertson Pupil:
Dissociation of light/near reflex in which the pupil responds normally to near but reacts slowly if at all to light.
In abberent regeneration in 3rd nerve palsy
Asthenopia:
The collective term for various ocular symptoms, including sore and aching eyes; blurred vision and ocular fatigue.
Ataxia
Impaired ability to co-ordinate movement.
mydriasis
pupil dilation
cycloplegia
paralyse the ciliary muscle
Augmented Recession:
Surgical procedure to further weaken a muscle action, ie. recession of tight conjunctiva or very large recession of muscle.
axial legnth
legnth of eyeball e.g. myoped have longer axial legnth
Bell’s Phenomenon:
Elevation of both eyes with divergence when the eyelids are closed.
Benedikt’s syndrome:
Lesion in the region of the red nucleus resulting to an ipsilateral third nerve palsy and contralateral hemitremor.
Bielschowsky Head Tilt Test:
The observation of change in vertical deviation when the head is tilted to the shoulder of the suspected superior oblique weakness. (differentiate between SO palsy and SR weakness in other eye)
Bifoveal Fixation:
Imaging of an object on both foveae at the same time.
Binocular Function:
The ability of the two eyes to co-ordinate binocularly either in free space e.g. using prisms
Binocular Single Vision:
The ability to use both eyes simultaneously so that each eye contributes to a common single perception; may be bifoveal or monofoveal.
Binocular Vision:
The ability to use both eyes simultaneously. This may be with normal or abnormal binocular single vision or with the appreciation of diplopia.
Blind Spot Mechanism (Swann’s Syndrome):
A compensatory mechanism whereby rays of light from the fixation area fall on the optic disc of the deviating eye and thus diplopia is avoided.
Botulinum Toxin (B.T.X.A.):
A neurotoxin produced by the anaerobic bacterium clostridium botulinum; used to paralyse extraocular muscles in the treatment of ocular motility disorders.
Brown’s Syndrome:
An ocular motility defect where the affected eye(s) does not elevate in adduction but has full depression in adduction. It can be congenital or acquired from injury to or defect of the superior oblique tendon or trochlea and has a positive forced duction test result. See `Click’ Brown’s Syndrome.
Cavernous Sinus Syndrome:
A lesion (e.g. tumour) in the cavernous sinus causing paresis of the ocular motor nerves and the first two divisions of the trigeminal nerve
Central Fixation:
The reception of the image of the fixation object by the fovea, the fixation object lying in the principal visual direction. Central fixation may be steady or unsteady.
Central Scotoma:
Only involves fixation. The scotoma is negative and depending on the severity of the lesion, it can be relative or absolute.
Cerebral Palsy:
A condition in which the control of the motor system is affected due to a lesion in the brain resulting from a birth injury or prenatal defect.
Chiasmal Lesion:
Damage to the optic nerve at the decussation above the dorsum sellae causing visual field defects, i.e. bitemporal hemianopias.
Chronic Progressive External Ophthalmoplegia (C.P.E.O.):
Progressive bilateral limitation of ocular motility accompanied by ptosis but usually without diplopia or pupil involvement.
`Click’ Brown’s Syndrome:
A variation of Brown’s Syndrome in which the superior oblique tendon intermittently passes through the trochlea leading to full elevation in adduction, a ‘click’ is felt by the patient when this happens. When the superior oblique tendon does not pass through the trochlea the classic features of Brown’s Syndrome result.
Clinical Governance:
A framework through which NHS organisations are accountable for continuously improving the quality of their services and safe-guarding the high standards of care by creating an environment in which excellence in clinical care will flourish.
Cogan’s Lid Twitch:
Transient eyelid retraction during refixation from down to straight ahead seen in Myasthenia Gravis.
Cogan’s Sign:
A tonic deviation of the eye occurring on forced eyelid closure and associated with lesions in the cerebral hemispheres.
Collier’s (Tucked Lid) Sign:
Unilateral or bilateral lid retraction due to a lesion in the midbrain, e.g. Parinaud’s Syndrome.
Coloboma:
A fissure or gap in the eyeball or one of its parts, e.g. iris.
Colour fields:
Often used for testing macular sensitivity, with red or green targets. The normal red field is between 5 and 7 degrees and the green field between 3 and 5 degrees from the central point of fixation. Conditions in which these fields may be performed include, patients taking hydroxychlorequine for arthritic conditions, compressive thyroid eye disease and optic neuritis.
Compensatory Head Posture:
A position of the head adopted in the interest of comfortable vision, which may consist of:-
a) chin elevation or depression
b) face turn to the right or left
c) head tilt to the right or left shoulder.
These components may exist together or singly.
Confusion
The simultaneous appreciation of two superimposed images due to the stimulation of corresponding retinal points by two different images.
Congenital Saccadic Paresis:
An inability to execute voluntary saccades resulting in the subject thrusting the head to gain fixation and using the vestibulo-ocular reflex to maintain fixation as the head is moved slowly to the midline.
Conjugate Gaze Spasm:
The eyes are directed towards one side dependent on the site and nature of lesion.
Conjunctival Recession:
A surgical procedure to loosen the conjunctiva in order to enhance a weakening of the extraocular muscle.
Constant Esotropia: + Constant Exotropia:
The esotropia is present under all conditions. See also Esotropia with Accommodative Element and Without Accommodative Element + The exotropia is present under all conditions.
Contrast Sensitivity:
The ability of the eye to detect objects of varying contrast which can be tested using sinusoidal gratings of varying spatial frequency and varying luminance intensity.
Controlled Binocular Acuity (CBA):
The maximum visual acuity obtainable while maintaining binocular vision.
Convergence accommodation
Change in accommodation induced by convergence. Best demonstrated in open loop conditions, as in the closed loop situation relative negative accommodation will be used to maintain a clear image.
Convergence Excess Esotropia:
An intermittent esotropia with binocular single vision present at distance fixation but esotropia on accommodation for near fixation.
Convergence Insufficiency (C.I.):
The inability to obtain and/or maintain adequate binocular convergence without undue effort.
Convergence Retraction Nystagmus:
Nystagmus characterized when testing sustained upgaze or the optokinetic drum rotated downwards. Slow downward movements occur but upward movements are replaced by rapid convergent movements that may also retract the globe.
Convergence Spasm:
A condition in which there is excessive convergence. See also Accommodation Spasm.
Corneal Astigmatism:
Refractive error caused by the asymmetrical curvature of the cornea. It may be congenital or acquired from corneal disease.
Cortical Blindness:
A term applied to a severe defect of vision of both eyes as a result of a lesion of the visual cortex. Optic nerve and pupil reflexes may be normal.
Cover Test:
An objective dissociation test, in which each eye is covered in turn by an opaque occluder whilst the patient fixes a specified target in the required position, which detects manifest and/or latent deviations.
Cover Un-Cover Test:
Cover the eye and look at the same eye to see if it moves under the cover
Cover the eye and look at the other eye to see where it moves to (detects the squint in the other eye)
alternate cover = max dev angle
Cranial Nerve Palsy:
a decreased or complete loss of function of one or more cranial nerves. Cranial nerve palsies can be congenital or acquired.
Craniofacial Disorders (dysostosis):
A premature fusion of one or more of the sutures of the skull at a time when the brain is expanding which is caused by a failure in the development of the primitive mesoderm.
Crossed Fixation:
Patient uses right eye to fix in left field and left eye to fix in right field; seen in early onset esotropia, strabismus fixus and sixth nerve palsy. See also Tripartite Fixation.
Crowding Phenomenon (Separation difficulty):
The phenomenon in which a line of letters or symbols of the same size on a test type are identified less easily than single optotypes.
Cyclic Esotropia:
Normal binocular single vision alternates with large angle esotropia in rhythmic cycle.
Cyclic Exotropia:
Normal binocular single vision alternates with large angle exotropia in rhythmic cycle.
Cycloparesis:
Weakness of the ciliary muscle.
Cyclopentolate Hydrochloride (mydrilate):
A short acting mydriatic producing cycloplegia in 30 minutes (parasympatholytic).
Cyclophoria:
On dissociation the occluded eye wheel-rotates. See also incyclophoria; excyclophoria.
Cycloplegia:
Paralysis of the ciliary muscle resulting in loss of accommodation.
Cycloplegic:
A drug, e.g. atropine, which causes paralysis of the ciliary muscle and, therefore, loss of accommodation.
Cycloplegic Occlusion:
The reduction or blurring of vision of one eye by using a cycloplegic drug. e.g. atropine
Cycloplegic Refraction:
Objective refraction often retinoscopy whilst the accommodation of the eyes is paralysed .
Cyclotorsion
Rotation of the eye around its visual axis - see also incyclotorsion; excyclotorsion.
Cyclotropia:
One eye is wheel rotated so that the upper end of its vertical axis is nasal (incyclotropia) or temporal (excyclotropia) assessed objectively using fundus photographs.
Cyclovergence:
Range of incyclo and excyclo motor fusion.
Decreasing Velocity Exponential:
A term used to describe the slow phase in jerk nystagmus which has a decreasing velocity and which characterises latent nystagmus, manifest latent nystagmus and gaze evoked nystagmus.
Delayed Visual Maturation:
A condition where the appearance of the eye is normal, and the child does not respond to visual stimulus at a young age, but visual development occurs later than normal. This is the primary type of DVM, however, some classification systems include cases with an identifiable deficit in the eye or brain which result in slower visual development but may not reach normal levels.
Depression
Rotation of the eye downwards.
Depressor:
A muscle whose action is to turn the eyeball downwards.
Diabetic Ophthalmoplegia/ Ophthalmopathy:
Diabetic ophthalmopathy implicates complications of diabetes mellitus such as diabetic retinopathy, diabetic maculopathy, rubeosis of the iris, secondary glaucoma, complicated cataract, diabetic neuropathy of cerebral nerves supporting ocular muscles, diabetic neuropathy of optic nerves.
Diagnostic Occlusion:
Diagnostic occlusion to disrupt fusion in order to reveal the maximum deviation (30 mins for simulated by fusion in microtropia if d/nr angle increases, opp angle e.g. nr sim by fusion = after occ for 30 mins distance angle increases)
Dilate
To enlarge the pupillary aperture.
Dioptre:
A unit of measurement of the power of a lens equal to the inverse of the focal length in meters. A one dioptre lens brings parallel light in focus at one metre.
Direction of Nystagmus:
Defined by the direction of the fast phase or beat, although the pathological movement is the slow drift off fixation and the fast phase constitute the corrective movements.
Diplopia
The simultaneous appreciation of two images of one object. See also Pathological; Physiological; Homonymous; Heteronymous; Incongruous; Paradoxical
Direction of Nystagmus:
Defined by the direction of the fast phase or beat, although the pathological movement is the slow drift off fixation and the fast phase constitute the corrective movements.
Disjugate (disjunctive):
Movements of the two eyes in which the visual axes do not remain parallel but move in opposite relative directions. See also Convergence, Divergence.
Dislocated Lens:
The lens becomes dislocated into the vitreous or, rarely, into the anterior chamber because of an associated degeneration of the suspensory ligament of the lens.
Disorders of Accommodation:
See Accommodative Fatigue; Inertia; Spasm
Dissociated Nystagmus:
The movements of the two eyes are different.
Dissociated Vertical Deviation (Divergence) D.V.D.:
When the level of illumination received by either eye is reduced sufficiently that eye deviates progressively upwards, but reverts to its original position when the level of illumination returns to normally acceptable levels. It may sometimes be so asymmetrical as to be virtually unilateral and is associated with heterotropia usually of early onset or, rarely, with binocular single vision.
Distance Esotropia:
An intermittent esotropia where binocular single vision is present on near fixation and an esotropia on distance fixation.
Distance Exotropia:
An intermittent exotropia where there is binocular single vision on near fixation and exotropia (intermittent or constant) on distance fixation. See also True or Simulated Distance Exotropia.
Distance Penalisation:
The use of the amblyopic eye for distance by using additional plus lenses in front of the fixing eye.
Divergence:
Simultaneous rotation of the eyes outwards.
Divergence Excess Exotropia:
See Distance Exotropia (divergence excess xop decompensated?)
Divergence Excess Type Exophoria:
Exophoria greater on distance fixation than near fixation.
Divergence Paralysis:
Inability to relax visual axes at distance, resulting in esotropia.
Divergence Weakness Type Esophoria:
Esophoria greater on distance fixation than near fixation.
Doll’s Head Manoeuvre:
A rapid, passive head rotation to elicit an initial proprioceptive contraversion deviation of the eyes followed by a prompt recentring.
Dorsal Midbrain Syndrome:
See Parinaud’s Syndrome
Double Depressor Palsy:
Limitation of downgaze without reference to a particular vertical muscle palsy.
Double Elevator Palsy:
A limitation of up gaze without reference to a specific muscle defect.
Downbeat Nystagmus:
Eyes drift up and beat down again, associated with a lesion in the posterior fossa near the cranio-cervical junction.
Down’s Syndrome:
A congenital abnormality with learning difficulties and characteristic facial features. May have myopia, strabismus and visual acuity problems.
Duane’s Retraction Syndrome:
A congenital condition of limitation of horizontal ocular movement with retraction of the globe and narrowing of the palpebral fissure on adduction.
Duction:
Rotary movement of ONLY one eye from the primary position, i.e. Adduction; Abduction; Supraduction; Infraduction; Incycloduction; Excycloduction. (version = both eyes moving simultaneously)
Infantile Esotropia:
Constant esotropia occurring before 6 months of age. With or without latent nystagmus, manifest latent nystagmus, dissociated vertical divergence, cyclotropia, abnormal head posture, limited ABduction.
Early Onset Esotropia:
Onset: 6 months to 2 years
Characteristics: N=D, Amblyopia common, Poor BSV prognosis, Dev may increase c time, Surgery often needed. check om no lateral incomitance and L + R is same size
Early Onset Nystagmus:
Oscillations in both eyes seen from early infancy of any waveform with increasing exponential slow phase.
Eccentric Fixation:
A uniocular condition in which there is fixation of an object by a point other than the fovea. This point adopts the principal visual direction. The degree of the eccentric fixation is defined by its distance from the fovea in degrees.
Eccentric Viewing:
A uniocular condition in which there is fixation of an object by a retinal point other than the fovea without change in the principal visual direction.
Ecchymosis
A bruise: an effusion of blood under the skin.
Ectopia Lentis:
Partial dislocation of the lens causing myopia and astigmatism.
Ectropion
A condition in which the lower lid margin falls away from the globe.
Electronic Health Record (EHR):
A longitudinal record of a patient’s health and healthcare from birth to death.
Electronic Patient Record (EPR):
Used as a replacement for separate files owned by different organisations and departments such as hospitals, GP’s, community services and laboratories.
Elevation
Rotation of the eye upwards.
Elevator
A muscle whose action is to turn the eyeball upwards.
Emmetropia:
A refractive state of the eye when parallel rays of light are brought to focus on the retina when the eye is at rest (not accommodating).
End Point Nystagmus:
Oscillatory eye movements which occur on extreme lateral gaze, with fast phase towards side of gaze.
Enophthalmos:
Posterior displacement of the eye.
Entropion:
A condition in which the lower lid margin turns in onto the globe.
Epicanthic Folds/Epicanthus
Skin folds between the medial canthi and the nose causing pseudostrabismus.
Epinephrine:
A drug which dilates the pupil (sympathomimetic).
Epiphora
An excessive flow of tears.
Epistaxis:
Bleeding from the nose.
Eserine (Physostigmine):
A drug used to constrict the pupil (anticholinesterase).
Esophoria
On dissociation of the two eyes the occluded eye deviates nasally.
Esotropia:
One or other eye deviates nasally when both eyes are open.
Esotropia Controlled by Refraction:
See Accommodative Esotropia
Esotropia Relating to Fixation Distance:
See Near Esotropia; Distance Esotropia
Esotropia Relating to Time:
See Cyclic Esotropia
Esterman Fields:
A visual field analysis carried out on the Humphrey visual field analyser in order to establish the extent of peripheral fields to meet D.V.L.A. standard.
Evidence Based Practice:
The conscientious explicit and judicious use of current best evidence when making decisions about individual patients.
Excyclophoria:
On dissociation the upper end of the vertical meridian rotates temporally.
Excyclotorsion:
1) Rotation of the eye around the anteroposterior axis so that the upper end of the vertical meridian rotates temporally. 2) A type of diplopia where a horizontal line tips down temporally associated with an incyclodeviation.
Excyclotropia (excyclodeviation):
The eyes are misaligned around the anteroposterior axis so that the disc appears above the macula due to weakness of the incyclorotating muscles [superior oblique, superior rectus].
Executive Bifocal Glasses:
The entire top portion of the lens is dedicated for distance use whilst the bottom portion is for reading. They offer a much wider reading area than other types of bifocal. See also Bifocal Glasses.
Exophoria:
On dissociation of the two eyes the occluded eye deviates temporally .
Exophthalmic Ophthalmoplegia:
A term used to describe protrusion of the eyeball, associated with defective action of certain of the ocular muscles due to thyroid dysfunction.
Exophthalmos:
Protrusion of the eyeball with upper lid retraction.
Exotropia
One or other eye deviates temporally when both eyes are open.
External Ophthalmoplegia:
Paralysis of all the extraocular muscles with the eye assuming the position of rest.
Extra Ocular Muscles (extrinsic):
The six extra ocular muscles that rotate the eyeball - superior rectus; inferior rectus; medial rectus; lateral rectus; superior oblique; inferior oblique.
Eye Strain:
See Asthenopia
Faden:
A surgical procedure where the muscle is stitched to the globe behind the insertion, to further weaken its action in its field of gaze.
False Localisation:
The incorrect uniocular subjective localisation of the fixation object.
False Negative Response:
There is no response despite the presence of previously seen stimuli.
False Positive Response:
A positive response is given despite the absence of stimuli.
Far Sight:
Hypermetropia; long-sighted.
Far Point of Accommodation:
The furthest point at which an object can be seen clearly.
Fascicular Lesion:
A lesion along the cranial nerve after the nucleus but before the nerve leaves the brainstem.
Fells Modification of Harado Ito Procedure:
A strengthening of the superior oblique by moving the anterior portion of the tendon anteriorly on the globe.
Field of Binocular Single Vision (Field of Binocular Fixation):
The extent to which binocular single vision is maintained by movement of the eyes whilst the head is kept still.
Field of Uniocular Fixation:
The extent to which each eye can maintain foveal fixation whilst the head is kept still.
Fixation Disparity:
A phenomenon which occurs in binocular single vision in which the image is seen singly despite a slight under or over convergence of the visual axes, provided the disparate retinal points are within Panum’s area. It generally increases if binocular single vision is under stress and can be demonstrated instrumentally when fusion occurs for identical features of two targets but any dissimilar features are displaced in the direction of the heterophoria.
Forced Duction Test:
A test used to determine the tone of the muscle by attempting to move the eye with forceps in different directions. It is termed positive when there is significant resistance to movement.
Forced Generation Test:
A test to determine the function of a paralysed extra ocular muscle.
Form Deprivation:
A factor causing amblyopia due to an obstacle preventing a clear image at the fovea.
Fourth Nerve Palsy [4th/IV N. Palsy]:
Partial or complete loss of function of the superior oblique muscle.
Foville’s Syndrome:
Horizontal gaze palsy, fifth, seventh and eight nerve palsies, ipsilateral Horner’s syndrome
Frequency of Nystagmus:
The number of oscillations occurring per second.
Fresnel Lenses/Prisms:
Plastic prisms or lenses which can be adhered temporarily to spectacles.
Fully Accommodative Esotropia:
Esotropia in which normal binocular single vision is present for all distances when the hypermetropia is corrected.
Fully Accommodative Esotropia with Microtropia:
See Microtropia with Fully Accommodative Characteristics.
Functional:
1) A deviation which has the ability, at least potentially, for binocular single vision.
2) Patient shows signs or symptoms of a disorder but careful examination fails to reveal any evidence of structural or physiological abnormalities. There may be spiralling fields or improvement in visual acuity with plano lenses.
Functional Assessment:
The assessment of the behaviour of a person with low vision.
Functional Paralysis of Accommodation:
Inability to accommodate due to disordered states of mind or suffering from neurosis.
Fusion Range:
The range of convergence and divergence whilst maintaining binocular single vision.
Fusional Convergence:
One of the components of convergence initiated by disparity.
Imagine you have two eyes, and each eye sees things a little differently because they’re in slightly different positions on your face. Now, sometimes, these small differences are helpful because they help your brain figure out how far away things are.
So, “disparity” is just a fancy word for the difference between what each eye sees. When your brain compares these differences, it can tell if something is close, like your toy right in front of you, or far away, like a tree in the distance.
In simple terms, disparity is like a secret code that your eyes help your brain use to figure out how far things are from you. It’s like a little trick that helps you see the world in 3D!
Fusional Vergence:
The range of convergence and divergence of the eyes whilst maintaining clear binocular single vision. See also Negative and Positive Relative Fusional Vergence.
Gaze Evoked Nystagmus:
Nystagmus which is only present on eccentric gaze (looking in any other direction not straight ahead) with fast phase in the direction of fixation (one of your eyes moves quickly in the direction of where you’re trying to look), associated with neurological disease.
eccentric gaze
looking in any other direction rather than straight ahead
Gaze Palsy:
Partial or complete loss of conjugate gaze (px cant move both eyes at same time) which may affect horizontal or vertical versions (left, right, up or down)
General Fibrosis Syndrome:
A congenital, often familial developmental abnormality of the extraocular muscles and levator palpebral superioris. The features are bilateral ptosis and external ophthalmoplegia caused by fibrotic muscles.
Glissade:
A small corrective movement slower than a saccade, used to fixate an object after a hypo or hypermetric saccade.
Goldenhar’s Syndrome:
A syndrome characterised by preauricular skin tags, vertebral anomalies and hemifacial hypoplasia with microphthalmos and strabismus.
Grades of Binocular Vision:
These are the aspects of binocular function which indicate the degree of binocular vision present, i.e. simultaneous perception, fusion and stereopsis.
Gradenigo’s Syndrome:
Petrous apex otitis secondary to mastoiditis or suppurative otitis media causing a sudden onset sixth nerve palsy with facial pain.
Grave’s Disease:
-Systemic Condition: Graves’ disease is primarily an autoimmune disorder that affects the thyroid gland. It results in the overproduction of thyroid hormones (hyperthyroidism).
-Symptoms: Typical symptoms of Graves’ disease include weight loss, rapid heartbeat, anxiety, heat sensitivity, and an enlarged thyroid (goiter).
-Thyroid Involvement: Graves’ disease primarily affects the thyroid gland, leading to hormone imbalances.
Guillain-Barré Syndrome:
A viral syndrome followed by progressive motor weakness or paralysis and/or cranial nerve palsies.
Hangback/hang-loose Recession:
Hang-loose recessions: Muscle disinserted and reattached to its original insertion using extended sutures - WEAKENING
Harada-Ito Procedure:
A surgical procedure to the superior oblique to enhance the intorting action by moving the anterior portion of the tendon more anteriorly on the globe. See also Fells Modification.
Harmonious Abnormal Retinal Correspondence:
The angle of anomaly is equal to the objective angle.
(even though one eye isn’t looking perfectly straight, the brain somehow adjusts so that both eyes are working together to see the same thing as if they were both looking straight)
Hemianopia:
A hemianopia is a complete defect involving one half of the visual field. A heteronymous hemianopia involves opposite sides of the visual field. Lesions of the optic chiasm typically produce bitemporal heteronymous hemianopias. A homonymous hemianopia involves the same side of the visual field in each eye. Lesions of the retrochiasmal pathways typically produce homonymous hemianopias.
Hering’s Law:
A law of ocular motor innervation whenever an impulse for the performance of an eye movement is sent out, corresponding muscles of each eye receive equal innervations to contract or relax.
Herpes Zoster Ophthalmicus:
An infection of the trigeminal nerve due to herpes zoster virus producing neuralgic pain followed by vesicular reaction in the skin. May be associated with ocular nerve palsies.
Heteronymous (crossed) Diplopia:
Binocular diplopia associated with exotropia in which the image of the fixation object is received on the temporal area of the retina of the deviating eye and is projected nasally.
Heterophoria
Both visual axes are directed towards the fixation point but deviate on dissociation.
Heterotropia
A condition in which one or other visual axis is not directed towards the fixation point.
Hippus
A state of pupillary unrest with constant slight fluctuations without any change in illumination.
Homonymous (uncrossed) Diplopia:
Binocular diplopia associated with esotropia in which the image of the fixation object is received on the nasal area of the retina of the deviating eye and is projected temporally.
Horizontal Gaze Palsy:
Loss of horizontal saccades and/or pursuit in both eyes in lateral gaze.
Horner’s Syndrome
A lesion in the sympathetic pathway of the eye producing a miotic pupil, tonic accommodation, partial ptosis, loss of sweating on the same side of the face, hyperaemia of the conjunctiva.
Horopter
The locus of all points in space that are imaged on corresponding retinal points.
Hydrocephalus
Excess of cerebrospinal fluid causing pressure on the brain.
Hypermetric Saccades:
A fast eye movement which overshoots the target.
Hypermetropia
Refractive error where the principal focus of the eye is calculated to be behind the eye. May be axial, curvature or index.
Hyperphoria
On dissociation the occluded eye deviates upwards. May be one or both eyes. See also Alternating Hyper/Hypophoria
Hypertropia
One eye is deviated upwards when both eyes are open.
Hypoaccommodative Esotropia:
Convergence excess esotropia in which there is a remote near point of accommodation.
Hypometric Saccades:
A fast eye movement which undershoots the fixation target.
Hypophoria
On dissociation the occluded eye rotates downwards. May be one or both eyes.
Hypotropia
One eye is deviated downwards when both eyes are open.
Iatrogenic
A disorder resulting from treatment
Idiopathic
Without apparent cause.
Incomitant Strabismus:
Strabismus in which the angle of deviation differs depending upon the direction of gaze or according to which eye is fixing, associated with:
a) defective movement of the eye
b) asymmetrical
accommodative effort.
Incyclophoria
On dissociation the upper end of the vertical meridian rotates nasally.
Incyclotorsion
i) Rotation of the eye around the antero posterior axis. ii) A type of diplopia where a horizontal line tips down nasally associated with an excyclodeviation.
Incyclotropia(incyclodeviation):
The eye is misaligned around the anteroposterior (Sagittal) axis so that the disc appears below the macula due to weakness of the excyclorotating muscles [inferior oblique; inferior rectus].
Infantile Glaucoma (Buphthalmos):
A congenital abnormality in the mesoderm between the iris root and the trabeculum which impedes access of aqueous to the trabeculum. This increases the intraocular pressure and enlarges the cornea.
Inferior Division Third Nerve Palsy:
Palsy of the inferior rectus, inferior oblique and medial rectus.
Inferior Oblique Muscle:
One of the extra-ocular muscles whose action results primarily in elevation of either eye but also in extorsion and abduction.
Inferior Rectus Muscle:
One of the extra-ocular muscles whose action results primarily in depression of either eye but also in extorsion and adduction
Internal Ophthalmoplegia:
Internal ophthalmoplegia is characterised by paresis of ciliary body with loss of power of accommodation and pupil dilatation because of lesions of ciliary ganglion.
Internuclear Ophthalmoplegia (I.N.O.):
A disorder of horizontal eye movement with impaired adduction on the side of the medial longitudinal fasciculus lesion and abducting nystagmus of the contralateral eye. Convergence may/may not be preserved.
Interpupillary Distance (I.P.D. or P.D.):
The distance between the two pupillary centres. The average for an adult is 60mm when the eyes are fixing in the distance.
Intractable Amblyopia:
Amblyopia which has not responded to treatment.
Intraocular Lens:
An acrylic lens inserted into the eye following cataract extraction.
Intrinsic Ocular Muscles:
The muscles inside the eye i.e. ciliary muscle, sphincter pupillae, dilator pupillae.
Inverse Knapp’s procedure:
A surgical procedure where the lateral and medical recti are transposed to the level of the inferior rectus insertion in order to improve depression.
Ipsilateral
Referring to the same side.
Iridodonesis
Tremulous wobbling of the iris
Isometropia
Equal refractive error in each eye.
Isopter
Positions of equal sensitivity plotted perpendicular to the limits of the expected visual field with kinetic perimetry.
Jensens
A surgical procedure to enhance abduction in which the lateral portions of the superior and inferior rectus are attached to the upper and lower portions of the lateral rectus using a nonabsorbable suture.
Jerk Nystagmus
Nystagmus with a fast and slow phase.
Kearns-Sayer Syndrome:
A chronic progressive external ophthalmoplegia due to deletions in mitochondrial D.N.A. associated with skeletal muscle weakness, heart block (cardiac conduction weakness) and hearing loss.
Keratometry
measure of the cornea to determine its curvature and therefore its power.
Kinetic Perimetry:
A mobile target of fixed luminosity is used with which visual field isopters are plotted through the free movement of the target in all directions.
Klippel-Feil Syndrome/Anomaly:
An abnormality of the cervical spine leading to a short neck and reduced movements and a low posterior hairline. May be associated with Duane’s Syndrome
Knapp’s Procedure:
A surgical procedure where the lateral and medial recti are transposed to the level of the superior rectus insertion in order to improve elevation.
Latent Nystagmus:
An involuntary rhythmical oscillation of both eyes which occurs when the stimulus to either eye is reduced. The fast phase is to the fixing, uncovered eye with decreasing velocity exponential slow phase.
Lenticular Astigmatism:
Refractive error caused by abnormal curvature of the posterior or anterior surface of the lens.
Lid-Lag
A condition occurring in thyroid eye disease where the upper lid does not follow the eye fully when changing fixation from up to downgaze. An area of white sclera will be exposed (von Graefe’s Sign).
Lid Retraction
Raised upper lid due to overaction of Müllers muscle. See also Collier’s Sign.
Light Deprivation:
A factor causing amblyopia due to an obstacle preventing the normal passage of light to the retina.
LogMAR
The logarithm of the minimum angle of resolution.
Loop Recession
A surgical procedure where the muscle is recessed and attached to the sclera with a non absorbable loop.
Low Vision
Any level of visual loss or impairment resulting in a level of disability even after treatment and/or standard refractive correction with visual acuity of less than 6/18 to light perception, or a visual field loss of less than 10 degrees from the point of fixation but with the ability to use vision for the planning and/or execution of a task.
Low Vision Aid:
Any piece of equipment used by a visually impaired person to enhance their vision. These aids may be optical or non-optical.
Macropsia
Objects are perceived as larger than their natural size.
Manifest Latent Nystagmus:
Manifest nystagmus of the latent nystagmus form, i.e. fast phase beats to fixing eye and decreasing velocity exponential slow phase.
Manifest Nystagmus
Nystagmus occurring with both eyes open, may be pendular or jerk.
Marcus Gunn Jaw Winking Phenomenon
A condition in which movement of the jaw results in a change in the lid position.
Marcus Gunn Pupil:
See Afferent Pupillary Defect
Mechanical Strabismus
A strabismus caused by obstruction to movement of the extraocular muscles.
Medical Exemptions:
A supply and administration mechanism. Exemptions to the Human Medicines Regulations (2012) are defined in law allowing specific listed medicines to be sold, supplied and/or administered to patients by a specific health professional group without the need for another appropriate prescribing or supply/administration mechanism. Exemptions are NOT a prescribing mechanism.
Meridional Amblyopia
Amblyopia which is the result of uncorrected astigmatism.
Microphthalmos
An abnormally small eye.
Microtropia
A small angle heterotropia (usually of 10 dioptres or less) in which a form of binocular single vision occurs.
Microtropia with Identity:
Occurs when there is absolute eccentric fixation, and the angle of anomaly equals the angle of eccentricity. A manifest deviation is not seen on cover test.
Microtropia without Identity:
A microtropia which is detected by a movement on cover test. May have central or non-absolute eccentric fixation.
For either form the retinal correspondence may be:-
1) abnormal retinal correspondence
2) normal retinal correspondence with central suppression and peripheral fusion.
Millard-Gubler Syndrome:
Sixth nerve palsy, ipsilateral seventh nerve palsy and contralateral hemiplegia.
Miller Fisher Syndrome:
A rare, acquired nerve disease that is considered to be a variant of Guillain-Barré syndrome, characterised by abnormal muscle coordination, paralysis of the eye muscles, and absence of the tendon reflexes.
Miosis
Constriction of the pupil
Mixed Anisometropia:
Refractive error in which one eye is myopic and the other eye is hypermetropic.
Mixed Astigmatism
Refractive error which is hypermetropic in one meridian and myopic in the other.
Moebius Syndrome:
A congenital syndrome with loss of abduction and facial weakness.
Motor Fusion:
The ability to maintain sensory fusion through a range of vergence, which may be horizontal, vertical or cyclovergence.
Muscle Sequelae:
Sequence of extra ocular muscle adaptation following muscle weakness or limitation. Relates to Hering’s and Sherrington’s laws of innervation.
Myasthenia Gravis
A disease of skeletal muscle acetylcholine receptors, characterised by increased fatiguability with use. May have ptosis and variable ocular motor paresis.
Mydriasis
Dilation of pupil
Mydriatic
A drug which dilates the pupil.
Myectomy
Removal of a portion of a muscle.
Myopathy
A primary disease of the muscle, causing it to underact.
Myopia
refractive error where parallel rays of light come to a focus in front of the retina when the eye is at rest.
Myositis
Inflammation of a muscle.
Myotomy
Incision into the muscle which has a weakening effect.
Near Penalisation:
The use of the amblyopic eye for near by using a cycloplegia in the better eye and adding a convex lens up to 3 dioptres to the amblyopic eye.
Near sightedness
Myopia
Near Esotropia:
An intermittent esotropia where there is binocular single vision on distance fixation and esotropia at near even when the accommodation is relieved.
Near Exotropia:
An intermittent exotropia where there is binocular single vision on distance fixation and exotropia at near (intermittent or constant).
Near Point of Accommodation:
The nearest point at which an object can be seen clearly.
Near Point of Convergence:
The nearest point at which binocular convergence can be achieved.
Near Synkinesis
Association between convergence accommodation and pupil reflexes.
Negative Fusional Range/Vergence:
Motor fusion maintained with base in prisms or with the eye diverging.
Negative Relative Convergence:
Exerting less convergence in association with required accommodation.
Neuropathy
A disorder affecting the structure and function of the nervous system.
Neutral Density Filter:
Filter which reduces the intensity of all wave lengths equally (usually Kodak Wratten filter 90, ND2 and ND 0.50), used in diagnosing organic amblyopia.
Neutral Zone of Nystagmus:
Position of the eyes in which the direction of the nystagmus reverses.
Night Blindness:
Inability to see in the dark, may be associated with Retinitis Pigmentosa.
Night Blindness:
Inability to see in the dark, may be associated with Retinitis Pigmentosa.
Normal Binocular Single Vision:
Occurs with bifoveal fixation and normal retinal correspondence in everyday sight.
Normal Retinal Correspondence:
A binocular condition in which the fovea and areas on the nasal and temporal side of one retina correspond to and have a common visual direction with the fovea and temporal and nasal areas of the retina of the other eye.
Null Position of Nystagmus:
Position of the eyes in which the intensity (amplitude x frequency) of nystagmus is least.
Nystagmus
Involuntary oscillations of the eyeball.
Nystagmus Block Syndrome:
Unilateral constant esotropia associated with a face turn towards the side of the fixing eye in order to maintain the eye in an adducted position thereby lessening or eliminating the oscillations of nystagmus.
Objective Angle:
The angle of misalignment of the visual axes as measured by the observer.
Occlusion
The reduction or elimination of retinal image in order to prevent or reduce visual stimulation.
Occlusion Amblyopia:
Reduced vision in the eye being occluded due to prolonged treatment.
Ocular Bobbing:
Intermittent rapid downward deviation with slow drift up, usually associated with pontine dysfunction.
Ocular Dominance:
A preferred eye used for monocular tasks and relied upon more than the other eye in binocular vision.
Ocular Dysmetria:
Eyes overshoot and oscillate to take up fixation (associated with cerebellar disease). See also hypometric; hypermetric saccades
Ocular Myasthenia:
A disease of the ocular muscles due to a defect in the acetylcholine receptors with no electro evidence of systemic involvement.
Ocular Myoclonus:
Rhythmic oscillatory eye movements which persist during sleep and which may be associated with oscillation of non-ocular muscles.
One + a Half Syndrome:
Combined lesions of paramedian pontine reticular formation and medial longitudinal fasciculus producing an I.N.O. and horizontal gaze palsy to one side.
Optic Nerve Hypoplasia:
Small grey optic disc surrounded by a yellow halo of hypopigmentation, can cause reduced vision and pupillary reflexes with possible visual field defects.
Optokinetic Nystagmus:
Normal oscillatory eye movements which occur with movement of the visual environment.
Optotype
Letter, symbol or picture used to test visual acuity.
Orbital Apex Syndrome:
Abnormal eye movement caused by a lesion in the apex of the orbit.
Orthophoria
Both visual axes are directed towards the fixation point and do not deviate on dissociation.
Oscillopsia:
An illusion of oscillatory movement of the environment experienced in patients with acquired nystagmus.
Oscillopsia
An illusion of oscillatory movement of the environment experienced in patients with acquired nystagmus.
Overaction
Excessive action of a muscle caused by increased innervation as a consequence of palsy or limitation to the ipsilateral antagonist or contralateral synergist.
Palpebral fissure:
The distance/gap between the upper and lower lids.
Palsy
Partial or complete loss of function of a muscle.
Panoramic Vision:
The awareness of an enlarged field of vision due to the separation of visual fields occurring in exotropia.
Panum’s Area:
The area surrounding corresponding retinal points within which disparity of correspondence may occur whilst maintaining binocular single vision.
Panum’s Space:
A band around the horopter in space within which object points give rise to binocular single vision.
Paracentral scotoma:
This involves an area of visual field away from fixation and tends to be elongated circumferentially along the course of the optic nerve fibres within the central 30 degrees. It may be seen in glaucoma or lesions affecting the optic disc such as papilloedema.
Parafoveal Fixation:
Fixation of an object in the area adjacent to the fovea.
Paralysis of Accommodation:
Total or partial loss of accommodation due to paralysis of the ciliary muscle.
Paramacular Fixation:
Fixation of an object in an area adjacent to the macula.
Parasympatholytic
Drugs that block the action of the parasympathetic system causing mydriasis and cycloplegia.
Parasympathomimetic
Drugs that constrict the pupils.
Paresis
Partial paralysis or defective action in a muscle.
Parinaud’s Syndrome (Dorsal Midbrain Syndrome):
A lesion in the dorsal midbrain causing loss of upgaze; convergence retraction nystagmus; and Collier’s Sign.
Partial Dissociation:
Reduction of fusional stimuli, using e.g. filters; lenses; septum.
Partial Sight:
Substantially and permanently handicapped by defective vision caused by congenital defect, illness or injury.
Partially Accommodative:
Term used to describe a constant esotropia with an accommodative element.
Pathological Diplopia:
Double vision caused by misalignment of the eyes, can be monocular or binocular.
Penalisation
The treatment of amblyopia and/or eccentric fixation by optical reduction of form vision of the non-amblyopic eye at one or all fixation distances. The effect may be achieved by the alteration of the spectacle correction and/or use of a cycloplegic drug, or neutral density filters. see also near penalisation, distance penalisation.
Pendular Nystagmus:
A type of nystagmus which can be congenital or acquired and which resembles a sinusoidal oscillation.
Perimeter
Equipment used to assess visual fields.
Periodic Alternating Nystagmus:
Horizontal jerk nystagmus that periodically reverses direction, can be congenital or acquired, mainly reported in cerebellar disorders.
Peripheral Fixation:
Eccentric fixation in the peripheral area of the retina, it may be steady or unsteady.
Photophobia
An intolerance of light.
Physiological Diplopia:
A type of diplopia which exists in the presence of binocular single vision. It consists of the appreciation that a near object appears double when a distance object is fixated (heteronymous or crossed diplopia) and a distant object appears double when a near object is fixated (homonymous or uncrossed diplopia).
Physiological Nystagmus:
Normal oscillatory eye movements. See also End Point Nystagmus; Optokinetic Nystagmus; Caloric Nystagmus.
Pilocarpine
A parasympathomimetic cholinergic drug used to constrict the pupil.
Positive Fusional Range/ Vergence:
Motor fusion maintained with base out prisms or with the eyes converging.
Positive Relative Convergence:
Exerting more convergence in association with required accommodation.
Posterior Fixation Suture:
Faden
Post-Operative Diplopia Test:
Diagnostic test normally carried out in patients requesting strabismus surgery. The angle of deviation is corrected and overcorrected with prisms and the patient investigated for appreciation of diplopia.
Presbyopia:
The loss of accommodation with age.
Primary Angle of Deviation:
The deviation when fixing with the unaffected eye in paralytic incomitant strabismus.
Primary Esotropia:
The convergent deviation constitutes the initial defect.
Primary Exotropia:
The divergent deviation constitutes the initial defect.
Principal Visual Direction:
The line of projection in subjective space of images stimulating the fovea or eccentric point used for fixation.
Prism:
A wedge-shaped refracting media which deflects traversing rays of light towards the base.
Prism Dioptre:
A unit of measurement of the strength of a prism. A prism of one dioptre displaces the image of the object through one cm for each metre of distance between the object and the prism.
Progressive Supranuclear Palsy (Steele Richardson Syndrome):
Impairment of vertical saccades caused by a degeneration of the brainstem reticular formation. It may lead to complete ophthalmoplegia.
Projection:
The subjective interpretation of the direction of an object.
Proprioceptively Elicited Eye Movement:
Movement of the eyes which result when the head is turned forcibly right, left, up or down or tilted to right or left (see also Doll’s Head Manoeuvre).
Proptosis
Protrusion of one or both eyeballs.
Proximal Accommodation:
Change in accommodation induced by the awareness of nearness of the object perceived.
Proximal Convergence:
One of the components of convergence initiated by the nearness of an object.
Pseudo Myopia:
A condition of excessive accommodation inducing artificial myopia. May be associated with controlling an intermittent exotropia or decompensating exophoria. See also Accommodative Spasm.
Pseudo von-Graefe Sign:
Elevation of the upper lid on downgaze associated with third Nerve palsy, with aberrent regeneration.
Pseudophakia:
The presence of an intraocular lens replacing the crystalline lens.
Pseudostrabismus
The appearance of a deviation, often due to epicanthus or facial asymmetry.
Ptosis:
Drooping of the upper eyelid, may be partial or complete.
Quadrantanopia:
This is a complete defect involving a quadrant of each visual field. Heteronymous quadrantanopia involves opposite sides of the visual field and either superior or inferior quadrants. Homonymous quadrantanopias involve the same side of the visual field in each eye and either superior or inferior quadrants. These may be produced by temporal, parietal or occipital lobe lesions.
Range of Accommodation:
The linear distance between the near and far points of accommodation.
Readvancement
A surgical procedure where a previously recessed muscle is advanced to its original insertion.
Recession
A surgical procedure which weakens the action of the muscle by moving the insertion towards the origin.
Refraction:
The process within the optical system that brings light into focus on the retina involving the curvature of the cornea, the refractive power of the lens and the axial length of the eye. A refractive error exists if these components do not balance.
Refractive Amblyopia:
Amblyopia caused by a refractive error. See also anisometropic, ametropic and meridional amblyopia.
Refractive Error:
An imbalance in the optical system of the eye which may be hypermetropia, myopic or astigmatic.
Refractive Polyopia:
More than two images of an object are perceived. It may be caused by opacities or irregularities of the refractive media.
Relative Afferent Pupil Defect (RAPD):
An indication of damage to the visual system which is greater on one side than the other. The pupils constrict less when a light is directed into the affected eye than they do when the same light is directed into the normal (or less affected) eye. The presence of an RAPD usually indicates damage to the retina or optic nerve that results in diminished light impulses being transmitted from the eye to the brain on the affected side.
Residual Esotropia:
Esotropia remaining after surgery for original esotropia.
Residual Exotropia:
Exotropia after surgery for original exotropia.
Resting State of Accommodation:
See Tonic Accommodation
Restriction (Eye Movement):
A term to describe abnormal ocular rotation where the movement does not improve fully when testing ductions and is often associated with mechanical aetiology. (ductions = versions)
Retinal Correspondence:
Retinal areas of each eye have the same visual direction during binocular vision.
Retinal Detachment:
A break in the integrity of the retina which allows fluid from the vitreous to pass into the subretinal space.
Retinal Incongruity:
A phenomenon found under test conditions in which images are seen by each eye simultaneously, but cannot be superimposed or related to each other.
Retinal Rivalry:
Occurs in binocular vision when non-fusible images are presented to corresponding retinal points. The images are alternately suppressed, “shimmer” or form a changing mosaic.
Retinopathy of Prematurity (R.O.P.):
A retinal pathology associated with premature birth varying in severity from incomplete vascularisation of the retina to total retinal detachment.
Saccade:
Rapid conjugate eye movements under both volitional and reflex control. Voluntary includes willed refixations and those in response to command. Reflex include saccades in the direction of a new stimulus and usually are accompanied by head movement in the same direction.
Saccadic Intrusions:
Unintended saccades away from fixation, not necessarily followed by a return movement.
Scotoma:
An area of partial or complete blindness surrounded by normal or relatively normal visual field. See also Relative, Absolute, Central, paracentral and cecocentral Scotoma.
Secondary Angle of Deviation:
The deviation when fixing with the affected eye in paralytic incomitant strabismus.
Secondary Eso/Exotropia:
Eso/Exotropia which follows loss or impairment of vision.
See Saw Nystagmus:
One eye elevates and intorts whilst the other eye depresses and extorts. Associated with pituitary tumours, head trauma or midbrain infarction.
Sensory Fusion:
The ability to perceive two similar images, one formed on each retina, and interpret them as one.
Sherrington’s Law:
A law of reciprocal innervation: whenever an agonist receives an impulse to contract, an equivalent inhibitory impulse is sent to its antagonist which relaxes.
Short Sight:
See Myopia
Simple Astigmatism:
Refractive error in which one meridian is emmetropic and the other ametropic.
Simulated Distance (Divergence Excess) Exotropia:
The near angle of deviation increases/near exophoria becomes exotropia with:
1) prolonged disruption of fusion;
2) elimination of accommodation;
Simultaneous Perception:
The ability to perceive simultaneously two images, one formed on each retina.
Single Opto-Type Visual Acuity:
Visual acuity tested using isolated symbols.
Sixth Nerve Palsy [6th/VIth N. Palsy]:
Partial or complete loss of function of the lateral rectus muscle.
Skew Deviation:
A hypertropia caused by prenuclear input which may be concomitant or may alternate. It is differentiated from a vertical muscle palsy by the co-existence of other signs of central neurologic dysfunction.
Smooth Pursuit Movement:
Conjugate, smooth, slow movement of one or both eyes to maintain fixation on a moving object.
Stereoacuity/Stereoscopic Acuity:
An angular measurement of the minimum resolvable binocular disparity necessary for the appreciation of stereopsis.
Stereoscopic Vision / Stereopsis:
The perception of relative depth of objects on the basis of binocular disparity.
Stimulus Deprivation Amblyopia:
Amblyopia which is the result of lack of adequate visual stimulus in early life.
Strabismic Amblyopia:
Amblyopia which is the result of manifest strabismus.
Strabismus Fixus:
A marked esotropia which can be congenital or acquired with fibrosis and contracture of both medial rectus muscles resulting in adduction of both eyes.
Subjective:
Response from the patient or subject.
Subjective Angle:
The angle between the visual direction of the retinal element in each eye receiving images of the fixation object. It is shown by the subjective separation of diplopia in heterotropia or dissociated heterophoria.
Superimposition:
The simultaneous perception of the two images formed on corresponding areas, with the projection of these images to the same position in space. This may occur whether the correspondence is normal or abnormal. If fusion is absent two similar images are seen as separate but superimposed and no fusion range is demonstrable.
Superior Oblique Muscle:
One of the extraocular muscles whose action results primarily in elevation of either eye but also in intorsion and abduction.
Superior Oblique Myokymia:
Monocular intermittent rapid fine vertical and torsional movement accompanied by vertical and torsional diplopia and oscillopsia. Best seen with ophthalmoscope.
Superior Rectus Muscle:
One of the extraocular muscles whose action results primarily in elevation of either eye but also in intorsion and adduction.
Suppression:
The mental inhibition of visual sensations on one eye in favour of the other eye, when both eyes are open. This may occur in binocular single vision and in manifest strabismus. It may vary in area and density. A defined area is known as suppression scotoma.
Supranuclear Palsy:
A lesion in the pathway for eye control above the level of the nucleus resulting in gaze palsies.
Syndrome:
A collection of clinical signs and/or co-existence of conditions.
Sympatholytic
Drugs that block the action of the sympathetic system.
Sympathomimetic:
Drugs that dilate the pupils.
Synergists:
Contralateral muscles which normally work together.
Synoptophore (Major Amblyoscope):
Equipment which can be used to assess the angle of deviation and binocular potential at a theoretical distance fixation.
Tenectomy:
A surgical procedure which removes a portion of the tendon thereby weakening its action (usually the superior oblique).
Tenotomy:
A surgical procedure which cuts into the tendon thereby weakening its action (usually the superior oblique).
Third Nerve Palsy [3rd/III. N. Palsy]:
Partial or complete loss of function of the superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris, constrictor pupillae and ciliary muscle (muscles supplied by the third nerve). The involvement of the combination of muscles may be partial or complete; superior or inferior division; internal or external.
Thyroid Eye Disease (T.E.D.):
Eye signs associated with thyroid dysfunction: e.g. lid retraction, lid lag, proptosis, restricted eye movements, oedema.
Tolosa-Hunt Syndrome:
A rare syndrome with unilateral ocular nerve palsy, ipsilateral periorbital or hemicranial pain, pupillomotor dysfunction and sensory loss along the first and second division of the trigeminal nerve.
Tonic Accommodation:
The level of accommodation under stimulus free conditions.
Tonic Convergence:
Passive state of vergence of the eyes in the absence of a stimulus, maintained by the tonus of the extraocular muscles.
Total Penalisation:
The use of the amblyopic eye for all distances by using a strong convex lens to the better eye with or without cycloplegia.
Toxic Amblyopia:
Amblyopia caused by toxins, e.g. alcohol, tobacco.
Transposition
1) A surgical procedure which moves the insertion of the muscle to alter its action, eg. vertical transposition of horizontal recti for A or V pattern; Knapp procedure; Jensen’s; Hummelschiem’s, etc.
2) conversion of the prescription of a spherical/cylindical lens from a plus cylinder form to a minus cylinder form or vice versa.
Tropicamide (Mydriacyl):
A short acting cycloplegic drug (parasympatholytic).
True Distance (Divergence Excess) Exotropia:
Exotropia (intermittent or constant) on distance fixation with binocular single vision on near fixation under all testing conditions.
Tuck (Plication):
A surgical procedure which shortens the tendon and thereby strengthens its action (usually performed on superior oblique).
Typoscope:
A non-optical low vision aid made from dark (usually black) card with a central or paracentral aperture of varying size. This is used to reduce confusion from print and enhance tracking and reading skills of patients who experience difficulties locating sections of print on a page.
Underaction (Eye Movement):
Reduced ocular rotation which improves on testing ductions, often associated with neurogenic palsy.
Unharmonious abnormal retinal correspondence:
The angle of anomaly is less than the angle of deviation.
Uniocular Nystagmus:
When present in the primary position, nystagmus in one eye is due to spasmus nutans; monocular visual deprivation; superior oblique myokymia or multiple sclerosis. If present in eccentric gaze this may be the consequence of internuclear ophthalmoplegia; restrictive syndromes or superior oblique myokymia.
Upbeat Nystagmus:
Eyes drift down and beat up again, associated with lesions of anterior vermis or cerebellum or medulla.
V Pattern:
Relative divergence on elevation of the eyes and relative convergence on depression of the eyes.
Vergence:
Disjugate fast or slow eye movements. See also Fusional Vergence
Vernier Acuity:
The ability to detect nonalignment of two lines usually horizontal alignment of two vertical lines.
Version:
Movement of the two eyes in the same direction, i.e. lateroversion; dextroversion; laevoversion; direct elevation.
Vertical Gaze Palsy:
A lesion in the vertical gaze pathway causing defective saccade and pursuit vertically.
Vertical Nystagmus:
Type of acquired nystagmus in which the direction is determined by the fast phase. See also upbeat; downbeat nystagmus.
Vestibular Ocular Reflex:
A mechanism to maintain clear vision during rotation of the head and stimulated by the angular acceleration sensors of the labyrinthine semicircular canals (see Doll’s Head Manoeuvre).
Visual Agnosia:
Lesions in visual association areas which do not cause true blindness but a form of mind blindness in which objects remain meaningless.
Visual Direction:
The line of projection in subjective space associated with a given retinal point.
Visual Evoked Response/Potential:
Recording of electrical activity at the occipital cortex that results from light flashes or repeating patterns stimulating the retina.
Visual Field:
Extent of peripheral visual function without movement of the eye.
Visual Field Assessment:
An assessment of the field of vision, extending nasally, temporally, superior and inferior, which determines the boundaries of the visual field and ensures a full field within the documented boundaries.
Visual Field Defect:
A departure from the normal shape of the hill of vision which may be localised or a general depression of the whole field.
Visual Halos:
Coloured rings of light seen around a light source. May be caused by e.g. corneal oedema resulting from closed angle glaucoma.
Visual Handicap:
A disadvantage for an individual, resulting from a visual impairment or a visual disability that limits or prevents the fulfilment of a role that is normal for that individual.
Von Graefe Sign:
Elevation of the upper lid on downgaze of the eye associated with thyroid eye disease.
Wandering Fixation:
A uniocular condition in which the fovea has lost its functional superiority and no one retinal element is used for fixation.
With the Rule (Astigmatism):
Astigmatism in which the refractive power of the vertical meridian is the greatest.
X Pattern:
Relative divergence of the eyes on elevation and depression.
Y Pattern:
Relative divergence of the eyes on elevation.
Yoke Muscle:
See Synergist.
Yokoyama Procedure:
Surgery to join superior rectus and lateral rectus muscle when globe dislocation occurs in association with high myopia.
