The adjustment of the eye for seeing at near distances, accomplished by changing the shape of the lens through action of the ciliary muscle, thus focusing a clear image on the retina.
A hereditary deficiency of melanin pigment in the retinal pigment epithelium, iris, and choroid.
Reduced visual acuity in the absence of sufficient eye or visual pathway disease to explain the level of vision.
A chart with vertical and horizontal lines used for testing the central visual field.
Congenital absence of the iris.
Unequal pupillary size.
Space filled with aqueous bounded anteriorly by the cornea and posteriorly by the iris.
Clear, watery fluid that fills the anterior and posterior chambers.
Eye fatigue from muscular, environmental, or psychological causes.
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.
Ability of the eyes to focus on one object and then to fuse two images into one.
Inflammation of the eyelids.
Drooping of the eyelid.
Involuntary spasm of the lids.
"Blank" area in the visual field, corresponding to the light rays that come to a focus on the optic nerve.
Blindness (Legally Blind):
In the United States, 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° in the better eye.
An opacity of the crystalline lens
Granulomatous inflammation of a meibomian gland.
The vascular middle coat between the retina and sclera.
Portion of the uveal tract between the iris and the choroid. It consists of ciliary processes and the ciliary muscle.
Congenital cleft due to the failure of some portion of the eye or ocular adnexa to complete growth.
Color blindness (deficiency):
Diminished ability to perceive differences in color.
Cones and rods:
Two kinds of retinal photo receptor cells. Cones are primarily involved in fine visual discrimination (optimal visual acuity) and color vision; rods with peripheral vision and vision in decreased illumination.
Mucous membrane that lines the posterior aspect of the eyelids and covers the anterior sclera.
Thin lenses that fit directly on the eye, usually on the cornea but sometimes on the sclera.
The process of directing the visual axes of the eyes to a near point.
Transparent portion of the outer coat of the eyeball forming the anterior wall of the anterior chamber.
A transparent biconvex structure suspended in the eyeball between the aqueous and the vitreous. Its function is to bring rays of light to a focus on the retina. Accommodation is produced by variations in the magnitude of this effect. (Usually called simply the lens.)
A drug that relaxes the ciliary muscle, paralyzing accommodation.
Infection of the lacrimal sac.
The ability to adjust to decreased illumination.
Unit of measurement of refractive power of lenses.
Diplopia (double vision):
Seeing one object as two.
Turning out of the eyelid.
Absence of refractive error.
Extensive intraocular infection.
A turning inward of the eyelid.
Complete surgical removal of the eyeball.
A manifest inward deviation of one eye.
Removal of the contents of the eyeball.
Abnormal protrusion of the eyeball.
An outward deviation of one eye.
A refractive error in which the focus of light rays from a distant object is behind the retina.
Field of vision:
The entire area that can be seen without shifting gaze.
Moving images in the visual field due to vitreous opacities.
1.5-mm-diameter zone of the central retina, characterized histologically by thinning of the outer nuclear layer.
The posterior portion of the eye visible through the pupil.
Combining the images received by the two eyes into one image.
Disease characterized by optic disc cupping and visual field loss, usually associated with elevated intraocular pressure.
A technique of examining the anterior chamber angle, utilizing a corneal contact lens.
Blindness in one-half of the field of vision of one or both eyes.
An acute, common bacterial infection of the eyelid.
Manifest upward deviation of one eye.
Blood in the anterior chamber.
Pus in the anterior chamber. anterior chamber.
Colored, annular membrane, suspended behind the cornea and immediately in front of the lens.
Ishihara color plates
A test for color vision based on the ability to see numbers in a series of pseudoisochromatic multicolored charts.
A test for near vision using lines of various sizes of type.
Inflammation of the cornea.
Cone-shaped deformity of the cornea.
An instrument for measuring the curvature of the cornea, used in fitting contact lenses and determination of intraocular lens power prior to cataract surgery.
The dilated area at the junction of the nasolacrimal duct and the canaliculi.
Laser in situ keratomileusis (LASIK):
Corneal excimer laser ablation under a stromal flap to treat refractive error.
Laser subepithelial keratomileusis (LASEK):
Corneal excimer laser ablation under an epithelial flap to treat refractive error.
An instrument for measuring the power of optical lenses.
Junction of the cornea and sclera.
5.5-6-mm-diameter area of central retina bounded by the temporal retinal vascular arcades. It is known to anatomists as the area centralis, to differentiate it from the macula lutea, and is defined as the part of the retina in which the ganglion cell layer is more than one cell thick.
A drug causing pupillary constriction.
A drug causing pupillary dilation.
A refractive error in which the focus for light rays from a distant object is anterior to the retina.
An involuntary rhythmic oscillation of the eyeball that may be horizontal, vertical, torsional, or mixed.
An instrument with a special illumination system for viewing the inner eye, particularly the retina and associated structures.
The nerve that carries visual impulses from the retina to the brain.
Infiltration of the cornea with blood vessels.
Swelling of the optic disks due to raised intracranial pressure.
Ability to perceive the presence and movement of objects outside of the direct line of vision.
Abnormal sensitivity to light.
Photorefractive keratectomy (PRK):
Surface corneal excimer laser ablation to treat refractive error.
Presbyopia ("old sight"):
Physiologically blurred near vision, commonly evident soon after age 40, due to reduction in the power of accommodation.
A wedge of transparent material that deviates light rays without changing their focus.
A triangular growth of tissue that extends from the conjunctiva over the cornea.
Drooping of the eyelid.
External orifices of the upper and lower canaliculi.
The round hole in the center of the iris that corresponds to the lens aperture in a camera.
(1) Deviation in the course of rays of light in passing from one transparent medium into another of different density. (2) Determination of refractive errors of the eye and correction by lenses.
Innermost coat of the eye, consisting of the sensory retina, which is composed of light-sensitive neural elements connecting to other neural cells, and the retinal pigment epithelium.
A separation of the neurosensory retina from the pigment epithelium and choroid.
The white part of the eye—a tough covering that, with the cornea, forms the external protective coat of the eye.
A blind or partially blind area in the visual field.
A combination light and microscope for examination of the eye, particularly allowing stereoscopic imaging.
Used for testing central visual acuity. It consists of lines of letters or numbers, graded in size according to the distance at which they can be discriminated by a normal eye.
Misalignment of the eyes.
An instrument for measuring intraocular pressure.
Uvea (uveal tract):
The iris, ciliary body, and choroid.
Inflammation of one or all portions of the uveal tract.
Measure of the optical resolution of the eye.
Surgical removal of the vitreous to clear vitreous hemorrhage, allow treatment of retinal detachment or retinal vascular disease, or treat intraocular infection or inflammation.
Transparent, colorless mass of soft, gelatinous material filling the eyeball behind the crystalline lens.
The numerous fine tissue strands that stretch from the ciliary processes to the crystalline lens equator (360°) and hold the lens in place.