Sense Organs (MD-302)

Stimulus

a signal to which an organism responds

Receptor

on or in a cell, a specific protein to whose shape fits that of a specific molecular messenger

Conjunctiva

Delicate membrane lining the eyelids and covering the eyeball

Pupil

the adjustable opening in the center of the eye through which light enters

Cornea

The clear tissue that covers the front of the eye

Sclera

outer protective layer of the eye; the portion seen on the anterior portion of the eyeball is referred to as the white of the eye

Choroid

middle, vascular layer of the eye, between the retina and the sclera

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

Ciliary Body

ring of tissue behind the peripheral iris that is composed of ciliary muscle and ciliary processes

Lens

the transparent structure behind the pupil that changes shape to help focus images on the retina

Fundus of the Eye

interior surface of the eye

Anterior Chamber

between cornea and iris

Aqueous Humor

the clear fluid filling the space in the front of the eyeball between the lens and the cornea.

Vitreous Chamber

the main interior portion of the eye, filled with vitreous humor

Vitreous Humor

jellylike substance found behind the lens in the posterior cavity of the eye that maintains its shape

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

Optic Nerve

the nerve that carries neural impulses from the eye to the brain

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.

Macula (Of the eye)

yellowish region on the retina lateral to and slightly below the optic disc

Fovea Centralis

tiny pit or depression in the retina that is the region of clearest vision

Optic Chiasm

the point in the brain where the visual field information from each eye "crosses over" to the appropriate side of the brain for processing

Visual Cerebral Cortex

occipital lobe

pathway of optic nerve

1. Retina
2. Optic Nerve
3. Optic Chiasm
4. Optic Tract
5. Thalamus
6. Visual Cerebral Cortex

Optic Tract

leads from optic chiasma to terminate in lateral geniculate body

Thalamus

located on top of the brainstem; it directs messages to the sensory receiving areas

Visual Fields

the area an individual can see when looking straight ahead

Accomodation

normal adjustment of the eye to focus on objects from far to near

Biconvex

consisting of two surfaces that are rounded, elevated, and curved evenly, like part of a sphere

Cone

Photoreceptor cell in the retina that transforms light energy into a nerve impulse. Cones are responsible for color and central vision.

Refraction

The bending of a wave as it passes at an angle from one medium to another

Rod

photoreceptor cell of the retina essential for vision in dim light and for peripheral vision

Aqueo

(ROOT) water

blepharo

(ROOT) eyelid

conjunctivo

root: conjunctiva

coro

(ROOT) pupil

corneo

(ROOT) cornea

cyclo

(ROOT) ciliary body

dacryo

(ROOT) tear, tear duct

iro

(ROOT) iris

irido

(ROOT) iris of the eye

kerato

(ROOT) cornea

lacrimo

(ROOT) tears

oculo

(ROOT) eye

ophthalmo

(ROOT) eye

opto

(ROOT) eye, vision

optico

(ROOT) eye, vision

palpebro

(ROOT) eyelid

papillo

(ROOT) optic disc

phaco

(ROOT) lens

phako

(ROOT) lens

pupillo

(ROOT) pupil

retino

(ROOT) retina

sclero

(ROOT) sclera

uveo

(ROOT) uvea

vitreo

(ROOT) glassy

amblyo

(ROOT) dull, dim

diplo

(ROOT) double

glauco

(ROOT) gray

mio

(ROOT) smaller, less

mydro

(ROOT) widen, enlarge

nycto

(ROOT) night

photo

(ROOT) light

presbyo

(ROOT) old age

scoto

(ROOT) darkness

xero

(ROOT) dry

-opia

(SUF) vision

-opsia

(SUF) vision

-tropia

(SUF) to turn

Astigmatism

An inability to produce a focused image on the fovea due to a cornea abnormality

Hyperopia

A condition in which visual images come to a focus behind the retina and vision is better for distant -- farsightedness.

Myopia

A condition in which images come to focus in front of the retina, resulting in vision better for close -- nearsightedness

my-

(PRE) close, shut

Presbyopia

impaired vision as a result of aging due to lose of elasticity on the lens

• Difficult for close objects

Blepharitis

inflammation of the eyelid

S+S of Blepharitis

• Scaling, Crusting, or Flaking of the eyelid margins
• Erythema of eyelid margin

Treatment for Blepharitis

Baby Shampoo

Cataract

A clouding of the lens, usually bilaterally

Most Common Cause for Curable Blindness

Cataracts

Nuclear Cataract

A cataract that forms on the central lens

Posterior Subcapsular Cataract

A cataract that involves the posterior lens

Senile Cataract

most common type. Consequence to the aging process

S+S of Cataract

• Frequent changing of glasses
• Visual Loss
• NO PAIN
• Blurred Vision
• Glare
• Myopia
• Lens Opacity

Chalazion

A slowly enlarging nodule of the eyelid due to inflammation of the glands

Meibomian Glands

oil glands found in the upper and lower edges of the eyelids that help lubricate the eye

Deep Chalazion

inflammation of the meibomian glands

zeis glands

oil glands opening into the follicles of the eyelashes

Superficial Chalazion

inflammation of the zeis glands

Diabetic Retinopathy

A condition in which the retina is changed due to diabetes

S+S of diabetic retinopathy

• Weak Retinal Vessels
• Microaneurysms of the Retina
• Neovascularization
• Hemorrhages
• Retinal Deposits
• Edema

Neovascularization

growth of abnormal new blood vessels

Managing Diabetic Retinopathy

• Maintain BS
• Eye Exams
• Laser Photocoagulation

Glaucoma

A condition caused by increased intraocular pressure, leading to blindness

Diagnosis for Glaucoma

tonometry

Tonometry

the measurement of intraocular pressure

open angle glaucoma

the most common form of glaucoma where pressure gradually increases leading to atrophy

Treatment for Glaucoma

• Medications
• Trabeculoplasty

Trabeculoplasty

procedure to treat open-angle glaucoma

Hordeolum (Stye)

A local and painful infection of the eyelid margin

External Hordeolum

A stye caused by infection of the eyelash follicle

Internal Hordeolum

A stye caused by infection of the meibomian glands