Terms Related to the Eye
By:
Dr. Najam Iqbal Choudhery
Senior Registrar
Ophthalmology Dept.
KEMU & Mayo Hospital
Accommodation:
The adjustment of the eye for seeing at different distances, accomplished by
changing the shape of the lens through action of the ciliary muscle, thus
focusing a clear image on the retina.
Albinism: A hereditary
deficiency of pigment in the retinal pigment epithelium, iris, and choroid.
Amblyopia: Reduced visual
acuity (uncorrectable with lenses) in the absence of detectable anatomic defect
in the eye or visual pathways.
Aniridia: Congenital absence
of the iris.
Anisocoria: Unequal pupillary
size.
Anophthalmos: Absence of a true eyeball.
Anterior chamber: Space filled with
aqueous bounded anteriorly by the cornea and posteriorly by the iris.
Aphakia:
Absence of the crystalline lens.
Aqueous: Clear, watery fluid
that fills the anterior and posterior chambers.
Astigmatism: Refractive error
that prevents the light rays from coming to a point focus on the retina because
of different degrees of refraction in the various meridians of the cornea or
crystalline lens.
Binocular vision: Ability of the eyes
to focus on one object and then to fuse two images into one
Bitot's spots: Keratinization of
the bulbar conjunctiva near the limbus, resulting in a raised spot—a feature of
vitamin A deficiency.
Blepharitis: Inflammation of the eyelids (lid
margin).
Blepharospasm: Involuntary spasm
of the lids.
Blind spot: "Blank"
area in the visual field, corresponding to the light rays that come to a focus
on the optic nerve.
Blindness:
In the USA, the usual definition of blindness is corrected visual acuity of 20/200 or less in the better eye, or a visual
field of no more than 20 degrees in the
better eye.
Buphthalmos: Large eyeball in
infantile glaucoma.
Canaliculus:
Small tear drainage tube in inner aspect of upper and lower lids leading from
the puncta to the common canaliculus and then to the tear sac.
Canthus:
The angle at either end of the eyelid aperture; specified as outer and inner.
Cataract: Opacity of the
crystalline lens.
Chalazion:
Chronic Granulomatous inflammation of a meibomian gland.
Coloboma:
Congenital cleft due to the failure of some portion of the eye or ocular adnexa
to complete growth.
Color blindness: Diminished ability
to perceive differences in color.
Dacryocystitis: Infection of the
lacrimal sac.
Dacryocystorhinostomy:
A procedure by which a communication is made between the nasolacrimal duct and
the nasal cavity to relieve an obstruction in the nasolacrimal duct, or sac.
Diplopia: Seeing one object
as two.
Ectropion: Turning out of the
eyelid margin.
Emmetropia: Absence of
refractive error.
Endophthalmitis:
Extensive intraocular infection sparing the outer coat of eye ball
Entropion:
A turning inward of the eyelid margin.
Enucleation:
Complete surgical removal of the eyeball.
Epiphora:
Tearing due to blockage of tear drainage passage.
Esotropia:
A manifest inward deviation of the eyes.
Exenteration:
Removal of the entire contents of the orbit, including the eyeball and lids.
Exophthalmos:
Abnormal protrusion of the eyeball.
Exotropia:
A manifest outward deviation of the eyes.
Evisceration:
Removal of the contents of the eyeball.
Fornix:
The junction of the palpebral and bulbar conjunctiva.
Glaucoma:
Disease characterized by abnormally increased intraocular pressure, optic
atrophy, and loss of visual field.
Hordeolum, external (sty): Infection of the glands of Moll
or Zeis.(acute Staphylococcal infection)
Hordeolum, internal: Meibomian
gland infection.(acute Staphylococcal infection)
Hyperopia, hypermetropia (farsightedness):
A refractive error in which the focus of light rays from a distant object is
behind the retina provided accommodation is at rest.
Hyphema:
Blood in the anterior chamber.
Hypopyon:
Pus in the anterior chamber.
Hypotony: Abnormally soft eye
from any cause.
Keratic precipitate (KP):
Accumulation of inflammatory cells on the posterior cornea in uveitis.
Keratitis: Inflammation of the
cornea.
Leukoma:
Dense corneal opacity due to any cause.
Limbus: Junction of the
cornea and sclera.
Macula:
Moderately dense corneal opacity due to any cause.
Myopia
(nearsightedness): A refractive error in which the focus
for light rays from a distant object is anterior to the retina provided
accommodation is at rest.
Nebula:
Slight corneal opacity due to any cause.
Nystagmus: An involuntary,
rapid movement of the eyeball that may be horizontal, vertical, rotatory, or
mixed.
Orbital cellulitis: Inflammation
of the tissues surrounding the eye.
Panophthalmitis: Inflammation of the
entire eyeball.
Papilledema:
Swelling of the optic disk due to raised intracranial pressure.
Papillitis: Optic nerve head
ischemia or inflammation that is ophthalmoscopically visible.
Peripheral vision: Ability to perceive
the presence, motion, or color of objects outside of the direct line of vision.
Phlyctenule: Localized
lymphocytic infiltration of the conjunctiva.
Photophobia: Abnormal
sensitivity to light.
Phthisis bulbi:
Atrophy of the eyeball with blindness and decreased intraocular pressure, due
to end-stage intraocular disease.
Poliosis:
Depigmentation of the eyelashes.
Posteriorchamber: Space filled with
aqueous anterior to the lens and posterior to the iris.
Presbyopia
("old sight"): Physiologically blurred near vision,
commonly evident soon after age 40, due
to reduction in the power of accommodation.
Pseudophakia:
Presence of an artificial intraocular lens implant following cataract
extraction.
Pterygium:
A triangular degenerative growth of conjunctiva that encroaches cornea.
Ptosis: Drooping of the upper
eyelid.
Pupil: The round hole in
the center of the iris that corresponds to the lens aperture in a camera.
Sclera: "The white
part of the eye--a tough covering that, with the cornea, forms the external
protective coat of the eye.
Scotoma: A blind or
partially blind area in the visual field.
Staphyloma: A thinned part of
the coat of the eye, causing protrusion of uveal tissue.
Strabismus (heterotropia, tropia):
A manifest deviation of the eyes.( Squint ).
Sty: See Hordeolum, external.
Symblepharon:
Adhesions between the bulbar and palpebral conjunctiva.
Synechia:
Adhesion of the iris to cornea (anterior synechia) or lens (posterior
synechia).
Tarsorrhaphy:
A surgical procedure by which the upper and lower lid margins are united.
Trabeculectomy: The
preferred first-line procedure for surgically creating an additional aqueous
drainage channel in the treatment of glaucoma.
Trichiasis:
Inversion and rubbing of previously normal eyelashes against the globe.
Uvea (uveal tract): The iris,
ciliary body, and choroid.
Uveitis: Inflammation of one
or all portions of the uveal tract.
Visual acuity: Measure of the
acuteness of vision; the finest of detail that the eye can distinguish.
Vitiligo: Localized patchy
decrease or absence of pigment on the skin.
Vitreous: Transparent, colorless
mass of soft, gelatinous material filling the eyeball behind the crystalline
lens.
Zonule: The numerous fine
tissue strands that stretch from the ciliary processes to the crystalline lens
equator (360 degrees) and hold the lens
in place.