Veterinary Ophthalmic Glossary

Front 1

accommodation

Back 1

adjustments in focal power of the eye necessary to maintain a clearly focused image on the retina
as an object moves closer to or farther from the eye; largely accomplished by changes in shape or position of the lens through action of the ciliary muscle. In some species (e.g., birds, fish) additional mechanisms are involved.

Front 2

adnexa (ocular)

Back 2

periocular structures,
consisting of orbit, orbital contents,
eyelids, nasolacrimal system, conjunctiva,
and third eyelid.

Front 3

agenesis

Back 3

failure of development of an
organ/tissue.

Front 4

albinism

Back 4

congenital and inherited absence
of melanin. In ocular structures, this is
most striking in the iris (which is pink)
and fundus (in which the choroid is
easily seen).

Front 5

alopecia

Back 5

absence of hair from an area
where it is normally found.

Front 6

amaurosis

Back 6

complete blindness without
overt ocular cause (cf. amblyopia).

Front 7

amblyopia

Back 7

reduced vision without overt
ocular cause (cf. amaurosis).

Front 8

angle-closure glaucoma

Back 8

glaucoma due to mechanical obstruction of the iridocorneal angle that prevents aqueous humor from reaching the trabecular meshwork. Also known as narrowangle or closed-angle glaucoma (cf. open-angle glaucoma).

Front 9

aniridia

Back 9

inherited congenital complete
absence of iris. Aniridia is extremely rare
because usually some iris root is present.
anisocoria disparity in pupil size between
the two eyes.

Front 10

ankyloblepharon

Back 10

fusion of the eyelid
margins; physiologic for the first 10 days
in puppies and kittens.

Front 11

anophthalmos/anophthalmia

Back 11

complete
absence of the eye. Anophthalmos is
extremely rare; usually some ocular
tissues are present; microphthalmos is
more common.

Front 12

anterior chamber

Back 12

space bounded
anteriorly by the cornea and posteriorly
by the iris and anterior lens. Contains
aqueous humor.

Front 13

anterior segment

Back 13

collective term for those parts of the eye anterior to the
vitreous; consisting of the lens, ciliary body, iris (and pupil), anterior chamber, cornea, anterior sclera, and conjunctiva (cf. posterior segment).

Front 14

anterior uveitis

Back 14

inflammation of the
ciliary body (cyclitis) and iris (iritis);
also called iridocyclitis.

Front 15

aphakia

Back 15

absence of the lens. Occurs
extremely rarely as an inherited condition;
extreme microphakia is more
likely.

Front 16

aphakic crescent

Back 16

crescent-shaped space
created between the equator of a dislocated
(luxated or subluxated) lens
and the dilated pupil. Pathognomonic
for lens dislocation.

Front 17

aqueous flare

Back 17

Tyndall effect seen when
a focal beam of light passes through
aqueous humor containing excessive
protein and/or cells (plasmoid aqueous).
Pathognomonic for disruption of the
blood-aqueous barrier.

Front 18

aqueous humor

Back 18

clear fluid made by the ciliary body epithelium; is released into the posterior chamber, fills the anterior chamber, and egresses through the iridocorneal angle. Responsible (in part) for meeting the metabolic needs
of the avascular lens and cornea.

Front 19

area centralis

Back 19

retinal region with high
density of cone photoreceptors and
ganglion cells that is lateral to the optic
nerve head in cats. Important for visual
acuity.

Front 20

asteroid hyalosis

Back 20

fixed opacities composed
of a calcium-lipid complex and
occurring in an otherwise normal
vitreous body. Relatively common
in older animals (cf. syneresis and
synchysis scintillans).

Front 21

astigmatism

Back 21

optical condition in which
light coming from a single point in the
environment is not focused to a single
point on the retina, usually owing to
irregularities in corneal curvature. In
regular astigmatism the cornea is
shaped more like a football than like part of a sphere and the resulting image is distorted but in a somewhat predictable fashion. In irregular
astigmatismthe cornea is very irregular and light is not uniformly brought into focus on the retina; usually due to corneal disease or injury.

Front 22

Bergmeister’s papilla

Back 22

mass of glial
cells surrounding the hyaloid artery in
the center of the optic disc; pathologic
in most species; seen commonly in
ruminants.

Front 23

binocular vision

Back 23

the ability to use the
two eyes simultaneously to focus on
the same object. Fusion of these two
separate images by the brain allows for
stereopsis and a further improvement
in the ability to detect depth.

Front 24

blepharitis

Back 24

inflammation of the upper or
lower eyelids.

Front 25

blepharoplasty

Back 25

plastic surgery of the
eyelids.

Front 26

blepharospasm

Back 26

spasm of the orbicularis
oculi muscle resulting in eyelid closure.

Front 27

blood-aqueous barrier

Back 27

physiologic barrier
formed by the iris and ciliary body
vascular endothelium and the ciliary
epithelium that limits movement of
plasma components into the aqueous
humor. Part of the blood-ocular barrier.

Front 28

blood-ocular barrier

Back 28

physiologic barrier
formed by the vascular endothelium and
some intraocular epithelial tissues that
limits movement of plasma components
into the eye. Composed of the bloodaqueous
barrier anteriorly and the
blood-retinal barrier posteriorly.

Front 29

blood-retinal barrier

Back 29

physiologic barrier
formed by the retinal vascular endothelium
and the retinal pigment
epithelium that limits movement of
plasma components into the retina and
vitreous. Part of the blood-ocular
barrier.

Front 30

bulla

Back 30

a large fluid-filled vesicle or blister,
usually due to corneal edema.

Front 31

bullous keratopathy

Back 31

disease of the cornea
associated with bullae formation.

Front 32

buphthalmos/buphthalmia

Back 32

enlargement
of the eye due to glaucoma.

Front 33

canaliculus

Back 33

small epithelium-lined tube
at the inner aspect of the upper and
lower lids, leading from the nasolacrimal
punctum to the lacrimal sac (plural:
canaliculi).

Front 34

canthoplasty

Back 34

plastic surgery on the medial
or lateral canthus.

Front 35

canthotomy

Back 35

surgical incision of (usually
the lateral) canthus to improve surgical
visualization or access.

Front 36

canthus

Back 36

the angle at the medial and
lateral ends of the palpebral fissure
where the upper and lower eyelids join.

Front 37

caruncle

Back 37

a small piece of skin at the
medial canthus from which hairs often
protrude.

Front 38

cataract

Back 38

opacity of the lens and/or lens
capsule.

Front 39

central progressive retinal atrophy

Back 39

a group of disorders in which retinal degeneration is accompanied by numerous, small, pigmentlike foci over the tapetal fundus. The primary defect is in the retinal pigment epithelium, whereas in generalized progressive retinal atrophy (PRA) the defect is in the photoreceptors. Also known as retinal pigment epithelial dystrophy.

Front 40

chalazion

Back 40

lipogranuloma of a tarsal
(meibomian) gland due to impaction
of secretions and sometimes rupture
into the surrounding eyelid tissue.

Front 41

chemosis

Back 41

conjunctival edema.

Front 42

“cherry eye”

Back 42

lay term for prolapsed gland
of the third eyelid.

Front 43

chorioretinitis

Back 43

inflammation of the
choroid and retina in which choroiditis
is the dominant and presumed initiating
factor (cf. retinochoroiditis).

Front 44

choroid

Back 44

the posterior aspect of the uveal
tract immediately external to the retina;
responsible for nutrition of the outer
retinal layers.

Front 45

choroiditis

Back 45

inflammation of the choroid;
usually caused by or causing associated
retinitis, resulting in retinochoroiditis
and chorioretinitis, respectively.

Front 46

chronic immune-mediated keratoconjunctivitis
syndrome (CIKS)

Back 46

characteristic immune-mediated disease
of the cornea and conjunctiva of dogs
also known as chronic superficial
keratitis (CSK), pannus, and Uberreiter’s
syndrome

Front 47

chronic superficial keratitis (CSK)

Back 47

a general descriptive pathologic term that is sometimes used to describe a characteristic immune-mediated disease of the cornea and conjunctiva of dogs also known as pannus, chronic immunemediated keratoconjunctivitis syndrome (CIKS), and Uberreiter’s syndrome.

Front 48

ciliary body

Back 48

part of the uveal tract
between the iris and the choroid; consists
of ciliary processes that produce aqueous
humor and the ciliary muscle responsible
for accommodation and iridocorneal
angle/trabecular meshwork opening.

Front 49

ciliary sulcus

Back 49

poorly defined transition
point between the posterior surface of
the iris and the anterior surface of the
ciliary body.

Front 50

closed-angle glaucoma

Back 50

glaucoma associated
with apposition of the peripheral
iris to the peripheral cornea (cf. openangle
glaucoma).

Front 51

collie eye anomaly

Back 51

inherited developmental
defect of collies and some other
breeds characterized by choroidal
hypoplasia, with or without colobomas,
and retinal detachment.

Front 52

coloboma

Back 52

congenital absence of any ocular tissue. Commonly affected tissues are eyelid, iris, choroid, and optic disc.
Usually present as a gap, hole, fissure, or notch-shaped defect. Sometimes differentiated into typical colobomas (defects lying in or near the 6 o’clock position within the eye and due to failed closure of the fetal fissure) and atypical colobomas (defects occurring in areas
other than the fetal fissure)

Front 53

cone

Back 53

retinal photoreceptor adapted for
vision in bright light, for color vision,
and for fine visual acuity.

Front 54

conjugate ocular movements

Back 54

movement of the eyes in the same fashion;
e.g., movement of both eyes to the
right, left, up, or down. These movements
are known as versions.

Front 55

conjunctiva

Back 55

mucus membrane lining the
posterior aspect of the upper and lower
eyelids (palpebral conjunctiva), both
surfaces of the third eyelid, and the
anterior sclera (bulbar conjunctiva).

Front 56

conjunctival follicles

Back 56

hypertrophy and coalescence of conjunctival lymphoid
tissue in response to conjunctival inflammation. Produces a characteristic cobblestone appearance on the conjunctival surfaces, especially within
the conjunctival fornix.

Front 57

conjunctival fornix

Back 57

region where the palpebral conjunctiva reflects to
become bulbar conjunctiva or to cover the anterior face of the third eyelid. There is also a secondary fornix
between the posterior aspect of the third eyelid and the globe. Also known as the conjunctival cul-de-sac.

Front 58

conjunctivorhinostomy

Back 58

surgical
creation of a communication between
the conjunctiva and the nasal cavity
performed to circumvent a dysfunctional
nasolacrimal system.

Front 59

corectopia

Back 59

displacement of the pupil
from its normal position.

Front 60

corneal degeneration

Back 60

unilateral or bilateral keratitis characterized by
corneal edema and subepithelial
deposition of lipid and/or mineral, and
often with corneal vascularization (cf.corneal dystrophy).

Front 61

corneal dystrophy

Back 61

progressive, bilateral,
approximately symmetrical hereditary
corneal disease unassociated with
inflammation; may affect the epithelium,
stroma, or endothelium (cf. corneal
degeneration).

Front 62

corneal erosion

Back 62

loss of corneal epithelium.
Distinguished from corneal ulcers
by connotation, erosions being superficial
(sometimes not even all epithelial
layers) and typically recurrent.

Front 63

corneal graft

Back 63

surgical placement of a
section of donor cornea to replace a
diseased region of host cornea (cf.
keratoplasty).

Front 64

corneal reflex

Back 64

closure of the eyelids
induced by light touching of the cornea
with a few wisps of cotton teased off a
cotton-tipped applicator.

Front 65

corneal sequestrum

Back 65

enigmatic condition unique to the cat cornea in which
a (usually axial) region of stroma becomes amber to black, undergoes degeneration, and may be slowly
extruded by the surrounding normal cornea while eliciting a marked foreign body reaction. Corneal ulceration mayor may not be present. Also known as
feline keratitis nigrum, corneal necrosis, and corneal mummification.

Front 66

corneal ulcer

Back 66

a break in continuity of
corneal epithelium with or without loss
of corneal stroma. Also known as
ulcerative keratitis (cf. corneal
erosion).

Front 67

corpora nigra

Back 67

irregular cystic dilations
on the pupillary margin of the iris in
large herbivores. Most notable dorsally
but typically also present ventrally.
Also known as granula iridica.

Front 68

cortical blindness

Back 68

blindness caused by a
lesion in the visual (occipital) cortex

Front 69

cotton-wool spots

Back 69

fluffy white opacities
within the nerve fiber layer of the retina
due to edema secondary to microinfarcts.
Seen as an early change with
systemic hypertension

Front 70

cyclitic membrane

Back 70

organized fibrinous exudate and, subsequently, a fibro-
vascular membrane extending from the
ciliary body over the posterior lens
capsule as a result of uveitis.

Front 71

cyclitis

Back 71

inflammation of the ciliary body;
usually seen with iritis and therefore
termed iridocyclitis (or anterior uveitis).

Front 72

cyclocryotherapy

Back 72

cryodestruction of the
ciliary body epithelium by application
of a cryoprobe to the overlying sclera
to reduce the rate of aqueous humor
formation and lower intraocular pressure
for the treatment of glaucoma (cf.
cyclophotoablation).

Front 73

cyclodialysis

Back 73

surgical procedure for
glaucoma to establish a communication
between the anterior chamber
and the suprachoroidal space.

Front 74

cyclodiathermy

Back 74

procedure for glaucoma
to destroy a portion of the ciliary body
by diathermy and reduce the quantity
of aqueous humor produced.

Front 75

cyclophotoablation

Back 75

destruction of the ciliary body epithelium by application
of a laser probe to the overlying sclera to reduce the rate of aqueous humor formation and lower intraocular pressure for the treatment of glaucoma (cf.
cyclocryotherapy).

Front 76

cycloplegia

Back 76

paralysis of the ciliary
muscle induced to reduce pain due to
ciliary spasm associated with anterior
uveitis.

Front 77

dacryoadenitis

Back 77

inflammation of the
lacrimal glands (orbital or third eyelid).

Front 78

dacryocystitis

Back 78

inflammation of the
lacrimal sac.

Front 79

dacryocystorhinography

Back 79

use of contrast
material for radiographic studies of the
nasolacrimal drainage system.

Front 80

dacryocystorhinostomy

Back 80

surgical
procedure to construct an alternate
nasolacrimal drainage system into the
nasal sinuses.

Front 81

dark adaptation

Back 81

biochemical and neurologic
process by which the eye
becomes more sensitive to light during
a period in darkness.

Front 82

dazzle reflex

Back 82

subcortical reflex in which
a rapid eye blink is elicited by a bright
light shone into an eye.

Front 83

decussation

Back 83

crossing of nerve fibers or
tracts from one side of the nervous
system to the opposite side, for example
as occurs at the optic chiasm.

Front 84

denervation hypersensitivity

Back 84

increased
sensitivity to neural effector substance
that follows postganglionic interruption
of the nerve supply of organs innervated
by the autonomic nervous system.

Front 85

dermoid

Back 85

a congenital tumor consisting
of skin and its appendages.

Front 86

descemetocele

Back 86

deep corneal ulcer characterized
by sufficient stromal loss
that there is exposure of Descemet’s
membrane.

Front 87

Descemet’s membrane

Back 87

the basement membrane of the corneal endothelium.
diopter unit of measurement of the refractive power of lenses, equal to the reciprocal of the focal length of the
lens expressed in meters.

Front 88

diplopia

Back 88

the perception of one object as
two images (“double vision”).

Front 89

distichiasis

Back 89

condition in which a single
cilium emerges from one or more
meibomian (tarsal) gland orifices (cf.
districhiasis, ectopic cilia, and
trichiasis).

Front 90

districhiasis

Back 90

condition in which multiple
cilia emerge from one meibomian
(tarsal) gland orifice (cf. distichiasis,
ectopic cilia, and trichiasis).

Front 91

drainage angle

Back 91

traditional outflow pathway by which aqueous tumor exits the eye. It is bounded anteriorly by the peripheral cornea, posteriorly by the iris and ciliary muscles, internally by the pectinate ligaments, and externally by the sclera. The trabecular meshwork
and ciliary cleft are contained within the iridocorneal angle. In some cases this term is used to refer to the geometric angle between the anterior surface of
the iris and cornea (synonyms: filtration angle, iridocorneal angle).

Front 92

dyscoria

Back 92

abnormally shaped pupil (adj.
dyscoric).

Front 93

dystrophy

Back 93

noninflammatory, developmental,
nutritional, or metabolic
abnormality.

Front 94

ectasia

Back 94

dilation or expansion; may be
toward the observer (e.g., corneal
ectasia) or away from the observer (e.g.,
posterior scleral ectasia).

Front 95

ectopia

Back 95

displacement or malposition,
especially congenital (adj. ectopic).

Front 96

ectopic cilia

Back 96

hair/cilia protruding through
palpebral conjunctiva. The cilia usually
abrade the cornea, causing pain and
ulceration.

Front 97

ectropion

Back 97

an eversion or rolling out of
the eyelid.

Front 98

ectropion uvea

Back 98

eversion of the posterior
iris epithelium around the pupillary
margin and into the anterior chamber;
usually associated with anterior uveitis
(cf. entropion uvea).

Front 99

electroretinogram (ERG)

Back 99

a graphic
record of the action potential that follows
stimulation of the retina by light.

Front 100

emmetropia

Back 100

condition in which no refractive error is present within the eye such that a distant point of lightis properly focused onto the retina when the eye is “at rest” (i.e., not
accommodating).

Front 101

endophthalmitis

Back 101

inflammation of the
intraocular contents, excluding the
corneoscleral tunic (cf. panophthalmitis).

Front 102

enophthalmos

Back 102

abnormal recession of
the eye within the orbit (cf.
exophthalmos).

Front 103

entropion

Back 103

an introversion or rolling in of
the eyelid.

Front 104

entropion uvea

Back 104

posterior rolling (or
inversion) of the pupillary margin into
the posterior chamber; usually associated
with anterior uveitis (cf. ectropion
uvea).

Front 105

epiphora

Back 105

overflow of tears due to
impaired drainage, excessive production,
or both.

Front 106

episcleritis

Back 106

inflammation of the connective
tissue immediately exterior to
the sclera.

Front 107

equine recurrent uveitis (ERU)

Back 107

recurrent
inflammation of the anterior and/or
posterior uvea in horses; the cause is
unknown (older terms include “periodic
ophthalmia” and “moon blindness”).

Front 108

esotropia

Back 108

form of strabismus in which
there is convergent deviation of one
eye toward the midline while the other
fixates normally (cf. exotropia).

Front 109

euryblepharon

Back 109

horizontally enlarged
palpebral fissure due to excessive
eyelid length (also known as macropalpebral
fissure).

Front 110

evisceration

Back 110

surgical removal of the
intraocular contents, with retention of
the corneoscleral tunic and placement
of a prosthesis within the corneoscleral
shell.

Front 111

exenteration (orbital)

Back 111

surgical removal
of all the orbital tissues, including
the eye and its nervous, vascular, and
muscular connections.

Front 112

exophthalmos

Back 112

abnormal protrusion of the eye from the orbit (cf. enophthalmos). May be pulsatile when associated with an orbital arteriovenous fistula. exotropia form

Front 113

exotropia

Back 113

form of strabismus in which
there is divergent or lateral deviation
of one eye while the other fixates
normally (cf. esotropia).

Front 114

fascia bulbi

Back 114

connective tissue sheath
encircling the globe posterior to the
limbus (also known as Tenon’s capsule).

Front 115

filtration angle

Back 115

traditional outflow pathway by which aqueous humor exits theeye. It is bounded anteriorly by the
peripheral cornea, posteriorly by the iris and ciliary muscles, internally by the pectinate ligaments, and
externally by the sclera. The trabecular meshwork and ciliary cleft are contained within the iridocorneal angle. In some cases this term is used to refer to the geometric angle between the anterior surface of the iris and cornea (synonyms: drainage angle; iridocorneal angle).

Front 116

fluorescein angiography

Back 116

serial photography of the ocular fundus after intravenous administration of fluorescein solution. Used to characterize vascular disease of the retina, choroid,
and optic nerve head.

Front 117

fovea

Back 117

retinal region of high visual acuity
in primates and birds.

Front 118

fundus (ocular)

Back 118

the posterior portion of
the eye visible through an ophthalmoscope,
composed of the sclera,
choroid, retina, and optic nerve head.

Front 119

glands of Moll

Back 119

apocrine glands of the
upper and lower eyelid margins.

Front 120

glands of Zeis

Back 120

sebaceous glands of the
upper and lower eyelid margins.

Front 121

glaucoma

Back 121

ocular disease that may produce a syndrome of findings but that in domestic animals is uniformly characterized by increased intraocular pressure with resulting damage to the optic nerve. Categorized as primary glaucoma (occurring without preexisting ocular disease in an otherwise apparently healthy eye) or secondary
glaucoma (glaucoma attributable to
another ocular abnormality, such as lens
luxation, intraocular tumor, anterior
uveitis).

Front 122

granular iridica

Back 122

irregular cystic dilations
on the pupillary margin of the iris in
large herbivores. Most notable dorsally
but typically also present ventrally.
Also known as corpora nigra.

Front 123

Haab’s striae

Back 123

linear gray-blue opacities deep within the cornea caused by fractures or stretching of Descemet’s membrane and development of fibrosisand edema within the crack. Pathognomonic for glaucoma in most
species; however, their significance in horses is not understood. Also called striate keratopathy.

Front 124

haws syndrome

Back 124

bilateral condition in
cats characterized by protrusion of the
third eyelids without detectable cause.

Front 125

hemeralopia

Back 125

visual impairment/ blindness
in bright light (“day blindness”).

Front 126

hemianopia

Back 126

blindness involving one
half of the visual field.

Front 127

heterochromia iridis

Back 127

condition in which
the iris is not of uniform color or in
which the right and left irides of one
animal differ in color from each other.

Front 128

hippus

Back 128

spasmodic dilation and contraction
of the pupil independent of stimulation
with light.

Front 129

hordeolum

Back 129

localized, purulent infection of a gland of the eyelid. May be external (infection of the glands of Moll or
Zeis; also known as stye) or internal (infection of the meibomian [tarsal] glands).

Front 130

Horner’s syndrome

Back 130

set of ocular signs
due to sympathetic denervation. May
include miosis, ptosis, enophthalmos,
and protrusion of the third eyelid.

Front 131

hyalitis

Back 131

evidence of inflammation (usually white blood cells, inflammatory proteins/ debris, etc.) within the vitreous body; reflects inflammation of the surrounding tissues (ciliary body, retina, and choroid) rather than primary inflammation of the vitreous body itself (cf. aqueous flare).

Front 132

hyperopia (hypermetropia)

Back 132

refractive state of the eye in which the parallel
rays of light would come to focus
behind the retina if not intercepted by
it (“farsightedness”). (See also myopia.)

Front 133

hypertropia

Back 133

deviation of the eyes in
which one eye is higher than the other.

Front 134

hyphema

Back 134

blood in the anterior chamber.

Front 135

hypopyon

Back 135

white blood cells in the
anterior chamber.

Front 136

hypotony

Back 136

reduced intraocular pressure.

Front 137

intumescent lens

Back 137

a swollen or enlarged
lens.

Front 138

ipsilateral

Back 138

situated on or pertaining to
the same side.

Front 139

iridencleisis

Back 139

surgical procedure for glaucoma in which an incision is made at the limbus and the iris is incarcerated into the wound to create a filtering wick between the anterior chamber and the subconjunctival space. Performed rarely in domestic animals owing to the excessive inflammatory response in these species.

Front 140

iridocorneal angle

Back 140

traditional outflow pathway by which aqueous humor
exits the eye. It is bounded anteriorly by the eripheral cornea, posteriorly by the iris and ciliary muscles, internally by the pectinate ligaments, and externally by the sclera. The trabecular meshwork and ciliary cleft are contained within the iridocorneal angle. In some cases this term is used to refer to the geometric angle between the anterior surface of the iris and cornea (synonyms: filtration angle; drainage angle).

Front 141

iridocyclitis

Back 141

inflammation of the iris
(iritis) and ciliary body (cyclitis). Also
called anterior uveitis.