Ординатура / Офтальмология / Английские материалы / Pickwell's Binocular Vision Anomalies 5th edition_Evans_2007

corresponding retinal points by the same object. This results in the

simultaneous appreciation of two images of one object. Diplopia of a

non-fixated target is physiological (see physiological diplopia) and of

Disjunctive eye movements See vergence. Synonym: disjugate eye

the heterophoria measured using a dissociation test.

Dissociated vertical deviation (divergence) (DVD) A condition in

which each eye, when covered, turns upwards (sursumduction) or

Dissociation test (diss. test) A test in which fusion is prevented by pre-

senting the two eyes with dissimilar or non-fusible objects.

Divergence (div.) A turning outwards of the eyes, typically to maintain fix-

ation upon an object as it moves away from the observer. An example of a

Divergence excess An exodeviation greater for distance vision than for

Divergence weakness An esodeviation greater for distance vision than

Donders squint An accommodative esotropia.

Duane’s retraction syndrome An ocular disorder consisting of retraction

of the globe, usually with narrowing of the palpebral aperture, in

attempted adduction, frequent abduction deficiency, with variable lim-

itation to adduction and upshoot and/or downshoot of the affected eye

Duction A consideration of the movement of one eye alone, e.g. abduc-

tion, adduction, depression, elevation. Sometimes, confusingly, the

term duction is used as a synonym for vergence.

Eccentric fixation (EF ) A monocular condition when the image of the

point of fixation is not formed on the foveola. This often occurs in stra-

bismic eyes and the angle of eccentric fixation is closely associated with

the visual acuity loss. The eccentrically fixating area is usually nasal to the

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foveola in esotropia but can be temporalward (paradoxical eccentric fixa-

rally, 45° nasally, 43° upwards and 50° downwards.

Fixation axis The line joining the object of regard to the centre of rota-

tion of the eye. A synonym is line of fixation.

Fixation disparity (FD) When both eyes are fixating a point that is seen

in binocular single vision, the eyes can be very slightly misaligned with-

out causing diplopia. This misalignment is called a fixation disparity

and usually occurs in the direction of the heterophoria, within Panum’s

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fusional areas.

clarity.

Fusion Sensory fusion is the neural process of synthesizing or integrat-

ing the monocular percepts into a single binocular percept. Motor

fusion refers to the act of moving the eyes to result in the object of

regard falling on corresponding retinal areas.

Fusional reserves The total fusional reserves are the maximum amount

by which the eyes can converge (positive fusional reserves) or diverge

(negative fusional reserves) while still maintaining binocular single

vision. Normally when the vergence changes the accommodation

changes by a linked amount. Relative fusional reserves are the amount

by which the vergence can change without changing the accommoda-

tion. Vertical fusional reserves can also be measured but are small.

Synonyms: vergence reserves, prism vergences.

Gaze palsy The inability to move the eyes conjugately, either laterally or

vertically, due to involvement of cortical or subcortical ocular motor

centres.

Global stereopsis The perception of depth in features that can only be

detected binocularly: they have no monocularly recognizable form.

Global stereopsis is tested with random dot stereograms, e.g. TNO test.

cf. local stereopsis.

Habitual angle of strabismus In a strabismic patient, the angle between

the two visual axes that is usually present during natural, everyday

viewing conditions.

Haidinger’s brushes An entoptic phenomenon that tags the projected

location of the centre of the macula and can be used in detecting and

treating eccentric fixation.

Haploscope The generic term for an instrument that presents separate

fields of view to the two eyes. There are many specially designed

haploscopes for clinical and experimental use, which allow con-

siderable manipulation of the fixation targets, accommodation and ver-

gence. Synoptophores and stereoscopes are examples of haploscopic

instruments.

Harmonious anomalous retinal correspondence (HARC) Synonym: har-

monious abnormal retinal correspondence. See retinal correspondence.

Hering’s law of equal innervation Nerve impulses stimulating an ago-

nist are equal to those stimulating its contralateral synergist.

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Herschel prism See rotary prism.

See heterophoria.

Lees screen An instrument used to quantify an incomitancy.

Line of sight Line joining the point of fixation to the centre of the entrance

Local stereopsis The perception of depth in features that can be seen

both monocularly and binocularly. Local stereopsis is tested with con-

toured stereograms (e.g. Titmus circles test). cf. global stereopsis.

Localization Perception of the direction of an object in space with

respect to either the eye (oculocentric localization) or the self (egocen-

Magnocellular visual system The sensory visual system can be subclassi-

fied into pathways, two of which are the parvocellular and magnocellular

pathways, named after the type of ganglion cell. The magnocellular path-

way detects movement and gross structures, which may then be exam-

ined in more detail by the parvocellular system. Synonym: transient

Major amblyoscope See synoptophore.

Maxwell’s spot An entoptic phenomenon that can be used in the assess-

Mental effort A method of orthoptic treatment based on the wilful pro-

or 10

difficult or impossible to detect by cover testing. A microtropia with

identity occurs when the angles of the deviation, anomaly and eccentric

Middle third technique A method of exploring the functions of accom-

modation and convergence. It is used to determine whether a het-

erophoria is likely to be compensated, and can be used as an aid to

prescribing prisms. The original middle third technique, proposed by

Percival, was later modified by Sheard. See Sheard’s criterion,

Monofixational heterophoria See Parks’ monofixational syndrome.

Morphoscopic visual acuity (Morph. VA)

ing a row of letters (cf. angular visual acuity when viewing isolated sin-

gle letters). The morphoscopic visual acuity is normally slightly worse

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(much worse in strabismus) than the angular visual acuity, because of

Oculorotatory muscles

See extraocular muscles.

Ophthalmoplegia Paralysis of the extraocular muscles. Ophthalmoplegia

can be external, referring to one or more of the extraocular muscles (if the

levator palpebrae are involved this is usually called ocular myopathy),

internal, referring to the muscles of the iris and ciliary muscle, or total (all

the muscles, including the levator palpebrae).

Opsoclonus A type of

ocular flutter in which the saccades are

multidirectional.

Optic nerve hypoplasia Underdevelopment of the optic nerve. In

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severe cases, there will be a small optic disc and poor acuity. In subtle

Parks’ monofixational syndrome The appearance, during cover testing,

of an esophoria superimposed upon a microtropia.

Parks’ three-step test A test for determining which of the vertical

extraocular muscles is paretic.

Parvocellular visual system The sensory visual system can be subclassi-

fied into pathways, two of which are the parvocellular and magnocel-

lular pathways, named after the type of ganglion cell. The parvocellular

system is responsible for the detailed analysis of an object. Synonym:

sustained visual system.

Passive position The position that the eyes adopt when they fixate at a

given distance without any stimulus to achieve fusion, e.g. during a dis-

sociation test.

Past pointing The inability to accurately point to a fixated object; com-

monly seen in eccentric fixation and recent-onset strabismus.

Penalization A method of treating amblyopia and eccentric fixation

in which the vision of the non-amblyopic eye is reduced (e.g. by topical

drugs, optical overcorrection) to compel the amblyopic eye to fixate.

Percival’s criterion For a heterophoria to be asymptomatic, the point of

fixation should lie within the middle third of the vergence range (meas-

ured between break, diplopia, points).

Phi movement The illusion of movement created when one object dis-

appears and an identical object appears in a neighbouring region of the

same plane. A similar phenomenon can result in the subjective impres-

sion of movement during the alternate cover test. Bennett & Rabbetts

(1989, p 177) argued that the term should not be used for binocular

vision, because the physiological mechanism was different from the sim-

ple movement illusion to which the term usually refers.

Phoria See heterophoria.

Physiological diplopia Diplopia that exists during normal binocular

single vision. It is the appreciation that a near object appears double

when a distant object is fixated, and vice versa. The diplopia is crossed

(heteronymous) when the more distant of the two objects is fixated and

uncrossed (homonymous) when the nearer is fixated.

Pleoptics A method of treating amblyopia (usually severe) using bright

lights to dazzle the eccentrically fixating area.

Polyopia Appreciation of a number of images of a single object.

Position of anatomical rest The position that the eyes take up when

they are completely devoid of tonus, as in death.

Primary angle of deviation The angle of deviation when the non-

paretic eye is fixating.

Primary position The direction of gaze when both eyes fixate an object

at infinity, on the midline, at eye level.

Prism A type of lens that deviates light in one direction without bring-

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ing it to a focus. A prism is wedge-shaped (or made up of wedge-shaped

Prism dioptre ( ) A prism of power 1 prism dioptre will deviate parallel

rays of light by a distance of 1 cm on a flat surface at a distance of 1 m

from the prism. 1

Prism reflection test

Prism vergences See fusional reserves.

Ptosis A drooping of the upper eyelid resulting in a narrowing of the

palpebral fissure.

Pursuit A type of eye movement where the eyes follow smoothly a rela-

tively slowly moving target. If the target moves too quickly then the eyes

start making saccadic movements to ‘catch up’ with the target.

Random dot stereograms A stereogram in which the eye sees an array

of small characters or dots containing no recognizable shape or con-

tours. Some characters are displaced and, although this is monocularly

imperceptible, this facilitates global stereopsis.

Range of fusion See fusional reserves.

Recession A surgical procedure to weaken the action of a muscle by

moving its insertion nearer to the origin of the muscle.

Recidivism A relapse (usually relapsing into crime). In amblyopia treat-

ment, recidivism is used to describe a relapse of acuity following appar-

ently successful treatment.

Refraction The process of measuring the refractive error of the eyes.

Refractive error (Rx) The power of lenses needed to correct any anom-

alies of the refractive state of the eye.

Relative fusional convergence/divergence See fusional reserves.

Relative vergences See fusional reserves.

Resection A surgical procedure to increase the action of a muscle by

excising a portion of a muscle and thus shortening it.

Retinal correspondence The concept that retinal points (or areas) in

similar positions in the two eyes give rise to a common visual direction

to images falling on them. When the two visual axes are perfectly

aligned an object falling on a certain point on the retina of one eye will

always fall on the same corresponding point on the retina of the other

eye. In fact, a point on the retina of one eye innately corresponds with

an area (Panum’s area) on the retina of the other eye. This is normal

retinal correspondence (NRC). If the visual axes become significantly

misaligned (strabismus) then an object will no longer be imaged on

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corresponding retinal points. These innately non-corresponding retinal

points may become associated with one another through a cortical

adaptation, resulting in anomalous (abnormal) retinal correspon-

dence (ARC). Nearly always, this is harmonious anomalous retinal

correspondence (HARC), when the angle between the abnormally cor-

responding points and innately corresponding points is equal to the

habitual angle of the strabismus so that diplopia and suppression can be

prevented. Unharmonious anomalous retinal correspondence (UARC)

describes the rare condition where the angle between the abnormally

corresponding points and innately corresponding points is not equal to

the habitual angle of the strabismus. Usually, UARC is an artefact result-

ing from using tests that interfere with normal viewing conditions.

UARC can also result from a second strabismus developing ‘on top of’

an initial strabismus, sometimes following surgery.

Retinal rivalry A condition that occurs when dissimilar images fall on

corresponding retinal areas and the subject perceives an unstable per-

ception comprising of alternation and occasional mixing of the monoc-

ular images.

Retinoscopy An objective method of measuring the refractive error of

the eye by neutralizing (with lenses) light reflected back from the

retina.

Risley prism See rotary prism.

Rotary prism A type of prismatic lens the power of which can be

smoothly altered. Synonyms: Risley prism (UK), Crétès prism (France),

Herschel prism (Germany).

Saccade A rapid conjugate movement of the eyes to fixate a point of

interest.

Scobee’s three-step test A method for determining which of the vertical

extraocular muscles is palsied.

Scotoma An area of partial or complete blindness surrounded by normal

or relatively normal visual field.

Secondary angle of deviation In incomitant deviations, the angle of

deviation when the paretic eye is fixating.

Sensory fusion See fusion.

Sensory fusion disruption syndrome A condition in which a patient, in

a haploscopic device or with prisms, can achieve superimposition of

each eye’s image (cf. horror fusionis) but cannot achieve sensory fusion.

Separation difficulties See crowding phenomenon.

Sheard’s criterion States that, for a heterophoria to be compensated,

the opposing fusional reserve (to blur point) should be at least double

the heterophoria.

Sherrington’s law of reciprocal innervation The contraction of a mus-

cle is accompanied by simultaneous and proportional relaxation of its

antagonist. Sherrington’s law applies to the muscles of one eye.

SILO Acronym for Small In, Large Out (cf. SOLI). It refers to the percep-

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tion that some people experience when horizontal prisms are introduced