Eye

Cataract

# 1 prevalent disorder resulting in blindness, opaque clouding of the lens causing decreased vision, caused by injury, exposure to radiation, long-term use of steroids, or ey disease.

Glaucoma

# 2 prevalent disordergroup of diseases of the eye characterized by increased intraocular pressure that results in damage to the optic nerve, producing defects in vision

Astigmatism

(optics) defect in an optical system in which light rays from a single point fail to converge in a single focal point,

Rhodopsin

A visual pigment consisting of retinal and opsin. When it absorbs light, the retinal changes shape and dissociates from the opsin, after which it is converted back to its original form.

Conjuctivitis - pink eye

Acute inflammation of the conjuctiva (outermost layer of the eye and inner surface of the eyelid). Caused by allergic reaction or infection. S/S include redness, irritation, and watering. - pneumoccocci, staphylocccoco, hemophilus

Suspensory ligaments

Bands of collagen that connect the lens to the ciliary muscles(near sight relax), (far sight pull against lens)

Circular Smooth Muscle of Iris

Decreases pupil diameter, parasympathetic response, prevents light rays from entering on the periphery of the cornea and lens - looking at a near object the pupil constricts in order to prevent diverging light rays from hitting on the periphery of the retina, eye is becoming spherical

Radial Smooth Muscle

Increases pupil diameter, sympathetic response - looking at far object parallel light rays are entering the eye and the pupil will dilate, the eye is flattened

photopsin

Is the opsin in cones. There are 3 types of photopsin that have different sensitivities to different wavelengths of light.

Medial and Lateral Commissures

Location where the upper and lower eyelids meet medially and laterally.

Scotopic

Night vision; partial moon or starlight

Photopic

Referring to light intensities that are bright enough to stimulate the cone receptors and bright enough to "saturate" the rod receptors (that is, drive them to their maximum responses).

Accommodation Reflex

Reflex response associated with both somatomotor and parasympathetic components of CN III, resulting in constriction of the pupils, bulging of the lens (to allow for focusing at a near object), and medial deviation of the eyes, the overall effect of which is to allow an individual to correctly focus on an object when it is moved from a distant to a near position.

Optic Disc

Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of the eye because it contains only nerve fibers, no rods or cones, and is thus insensitive to light.

Rods

Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond.

Extrinsic eye muscles

Six muscles attach to the outer surface of the eye;Produce eye movements

Nyctalopia

Slow recovery of vision after flashes of bright light at night; an early symptom of vitamin A deficiency

Opsin

The protein part of the visual pigment molecule, to which the light-sensitive retinal molecule is attached.

Convergence

a binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object

Myopia/nearsightedness

a condition resulting from a refractive error in which light rays entering the eye are brought into focus in front of the retina, eyeball is too long or the refractive power is too great because the lens is too thick, can be fixed by concave lens that causes the light to diverge

Melanopsin

a photopigment present in ganglion cells in the retina whose axons transmit information to the CNS, the thalamus, and the olivary pretectal nuclei

Hyperopia/farsightedness

a refractive error in which light rays entering the eye are focused behind the retina because light rays cannot pass through the choroids layer and sclera, eyeball is too short or lens too thin, convex lens will fix by causing light to converge

Iris

a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

Strabismus

abnormal condition of squint or crossed eyes caused by the visual axes not meeting at the same point crossed eye.

Fovea Centralis

area consisting of a small depression in the retina containing cones and where vision is most acute

Scotomas

blind spots

Macula Lutea

central region of the retina responsible for central vision; yellow pigment provides its color, has many cones and no rods

Conjunctiva

clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids. Protects eyes from foreign bodies.

Lacrimal apparatus

consists of the lacrimal gland and the ducts that drain excess lacrimal secretions into the nasal cavity

Macular degeneration

degeneration of the cells of the macula lutea which results in blurred vision and can cause blindness

Superior Oblique

depresses eye and turns it laterally - IV abducens

Inferior Rectus

depresses eye and turns it medially - III oculomotor

Retinene

derivative of vitamin A in photopigment

Inferior Oblique

elevates eye and turns it laterally - III oculomotor

Superior Rectus

elevates eye and turns it medially - III oculomotor

Palpebrae

eyelids

Presbyopia

farsightedness resulting from a reduced ability to focus caused by loss of elasticity of the crystalline lens of the ciliary muscle with age, lose the ability to bulge or become spherical

Lacrimal Caruncle

fleshy elevation at the medial commissure; produces a whitish oily secretion

Sty

inflammation of one ciliary gland or a small tarsal oil gland

Lacrimal Glands

located on the underside of the upper eyelid just above the outer corner of each eye; secretes lacrimal fluid (tears)

Posterior Segment

makes up two thirds of the eyeball behind the lens - is lined with the retina and filled with vitreous gel

Ciliary Glands

modified sweat glands between the eyelashes

Tarsal Glands

modified sebaceous glands associated with the eyelid edges

Medial Rectus

moves eye medially - III oculomotor

Lateral Rectus

moves eyeball laterally - IV abducens

Conjunctiva

mucous membrane lining the eyelids and covering the anterior portion of the sclera

Photoreceptor neuron layer

next to the choroids layers, have both rods and cones

Ganglion Neurons layer

next to the vitreous body, second order neurons - can detect light intensity through sensory pigment melanopsin

Emmetropic/Emmetropia

of or relating to the normal condition of the eye in which visual images are in clear focus on the retina

Sclera Venous Sinus

opening found at the junction of the cornea and sclera that drains aqueous humor back into the blood stream

Floaters

particles of cellular debris that float in the vitreous fluid and cast shadows on the retina

Fovea Centralis

pinpoint depression in the center of the macula lutea that is the site of sharpest vision consisting of the highest number of cones

Amblyopia

reduced vision in one eye caused by disuse or misuse associated with strabismus, unequal refractive errors, or otherwise impaired vision; also called lazy eye

Cones

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Detect fine detail and give rise to color sensations.

Ciliary Body

ring of muscle behind the peripheral iris that controls the power of the lens

Bipolar Neurons layer

second major layer of retina, first order neurons

Colorblind

sharks are this, A disorder of vision caused by a sex linked recessive trait - a single group of color receptive cones is missing from the retina

Ciliary Muscle

smooth muscle portion of the ciliary body, which contracts and the choroids forward towards the lens to assist in near-vision capability. It releases the tension on the lens and the suspensory ligaments, the lens shortens, and becomes spherical, the thicker the lens the more light rays will be bent to be brought to focus on the retina (near sight contract) (far sight relax)

Vitreous humor

soft, jelly-like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball

Lacrimal Puncta

tear duct, Blinking spreads the tears downward and across the eyeball to the medial commissure, where they enter the paired lacrimal canaliculi via two tiny openings called __________, visible as tiny red dots on the meidal margin of each eyelid.

Ishihara Color

test for color blindness

Smellen Acuity

test for sharpness of vision

Refraction of Light Rays

the bending or deflection of light rays as they pass through the various media of the eye that include the conjuctiva, cornea, aqueous humor, lens, and vitreous body

Vitreous Body

the clear colorless transparent jelly that fills the posterior chamber of the eyeball

Retina

the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

Aqueous humor

the lipid fluid within the eyeball between the cornea and the lens

Optic Nerve

the nerve that carries neural impulses from the eye to the brain; where the axons leave the retina

Uvea

the part of the eye that contains the iris and ciliary body and choroid

Anterior cavity

those parts of the eye in the front of and including the lens, orbit, extraocular muscles, and eyelid, containing the watery fluid called aqueous humor

Sclera

tough, fibrous, white outer coat extending from the cornea to the optic nerve

Cornea

transparent anterior portion of the outer covering of the eye

Lens

transparent structure behind the pupil that bends and focuses light rays on the retina

Cornea

transparent, anterior part of the eyeball covering the iris, pupil, and anterior chamber that functions to refract (bend) light to focus a visual image

Choroid

vascular layer beneath the sclera that provides nourishment to the outer portion of the retina containing dark pigment that prevents light scatter

Aqueous humor

watery liquid secreted at the ciliary body that fills the anterior chamber of the eye and provides nourishment for the cornea, iris, and lens

Normal Refraction

when an object is 20 feet or more, the light rays reflected from the object are nearly parallel to one another. the parallel light rays are then bent sufficiently to fall exactly on the fovea centralis