eye

Question 1

how does sight work

Answer 1

Light passes through cornea, pupil, lens, and vitreous body to stimulate sensory receptors (rods and cones) on the retina.

Question 2

emmetropia

Answer 2

normal

Question 3

normal

Answer 3

emmetropia

Question 4

orbit

Answer 4

Cavity lined with fatty tissue that contains and cushions the eyeball.
Has several openings through which blood vessels and nerves pass.

Question 5

muscles

Answer 5

Six short muscles provide support and rotary movement of the eyeball.
Connect the eyeball to the orbital cavity.
Four muscles are straight (rectus) muscles and two are slanted (oblique) muscles.

Question 6

eyelids

Answer 6

Protect the eyeballs from intense light, foreign particles, and impact.
Edges have eyelashes and sebaceous glands, which secrete sebum into the eyelids.

Question 7

conjunctivia

Answer 7

Mucous membrane that lines the underside of the eyelid and anterior surface of the eyeball.
Protective covering for the exposed surface of the eyeball.

Question 8

lacrimal apparatus

Answer 8

Includes structures that produce, store, and remove the tears that cleanse and lubricate the eye.
Structures include: Lacrimal gland, ducts and canals.

Question 9

eyeball

Answer 9

organ of vision

composed of 3 sections

Question 10

eyeball- outer layer

Answer 10

Composed of the sclera and the cornea.
Posterior portion is the sclera (white)
Anterior portion is the cornea (transparent)

Question 11

sclera

Answer 11

White” of the eye

Question 12

cornea

Answer 12

Anterior transparent portion of the eye’s fibrous outer surface.
Surface is curved, allowing it to bend light rays to focus them on the retinal surface.

Question 13

eyeball- middle layer

Answer 13

Lies below the sclera.

Consists of: Choroid, Ciliary Body and Iris.

Question 14

choroid

Answer 14

Pigmented, vascular membrane.

Prevents internal reflection of light.

Question 15

ciliary body

Answer 15

Thickened part of the vascular membrane.
Iris is attached.
Part of the ciliary body governs the convexity (curve) of the lens.
Secretes the aqueous humor (nutrient fluids) that nourish the cornea, the lens and surrounding tissues.

Question 16

iris

Answer 16

Coloured membrane attached to the ciliary body.
Suspended between the lens and the cornea in the aqueous humor.
Circular opening in centre called the pupil.
Has 2 muscles which dilate or contract to regulate the amount of light admitted by the pupil

Question 17

eyeball- inner layer

Answer 17

Contains: Lens and Retina.

Question 18

lens

Answer 18

Colourless crystalline body.
Biconvex in shape
Enclosed in transparent capsule.
Suspended by ligaments just behind the iris.
Functions to sharpen the focus of light on the retina (called accommodation) by changing its shape.

Question 19

retina

Answer 19

Contains photoreceptive cells.
Translates light waves focused on its surface into nerve impulses.
Photosensitive cells are called rods and cones.
Absence of any rods or cones leads to blind spots in the field of vision.
Contains: Macula lutea and fovea centralis.

Question 20

mucula lutea

Answer 20

Small, yellow area of the retina.

Site where more than 6 million cone cells are grouped.

Question 21

fovea centralis

Answer 21

Tiny depression in the retina near the optic nerve.
Contains only cone cells.
Central focusing point within the eye.
Point of greatest visual acuity.

Question 22

rods

Answer 22

Function in dim light.
Provide low visual acuity (sharpness).
Do not respond to colour.

Question 23

cones

Answer 23

Active in bright light.
Have high visual acuity.
Respond to colour.

Question 24

errors of refraction (ametropia)

Answer 24

When light rays fail to focus sharply on the retina.
Due to: Defect in the lens, cornea, or the shape of the eyeball.
Includes: Myopia, astigmatism, hyperopia/hypermetropia and presbyopia.
Tx: Corrective lenses or LASIK surgery.

Question 25

myopia

Answer 25

nearsightedness Can see objects up close, but objects at a distance are not in proper focus. Image falls in front of the retina.

Question 26

Hyperopia/Hypermetropia

Answer 26

Farsightedness. Can see objects at a distance, but objects up close are not in proper focus. Image falls behind the retina.

Question 27

presbyopia

Answer 27

Form of farsightedness. Can see objects at a distance, but objects up close are not in proper focus. Caused by inability of the lens to accommodate because of loss of elasticity. Occurs between ages 40-45-years (aging process). Image falls behind the retina.

Question 28

astigmatism

Answer 28

Cornea or lens has a defective curve. | This curvature causes light rays to diffuse over a large area of the retina, rather than being sharply focused.

Question 29

LASIK Surgery

Answer 29

Laser-assisted in situ keratomileusis surgery. Procedure permanently changes the shape of the cornea. procedure: Small incision is made to the cornea to produce a flap. Flap is lifted while a laser reshapes the underlying corneal tissue. Flap is replaced. Surgery lasts about 15 minutes.

Question 30

cataracts

Answer 30

Opacities that form on the lens and impair vision. Opacities produced by protein that slowly builds up over time until vision is lost. Types: Age-related and congenital. Tx: Removal of the clouded lens and replacement with an artificial, bendable intraocular lens (IOL).

Question 31

glaucoma

Answer 31

Characterized by increased intraocular pressure caused by: Overproduction of the aqueous humor. Failure of aqueous humor to drain from the eye due to blockage. Leads to atrophy of the optic nerve. Most easily prevented cause of blindness.

Question 32

acute vs chronic glaucoma

Answer 32

Acute Glaucoma: Rapid onset of symptoms. Includes: Pain, redness of the eye, feeling of pressure, blurred vision, decreased visual acuity, moderately dilated and nonreactive pupil. Without tx, blindness in 3-5 days. Chronic Glaucoma: Insidious (gradual) and usually not recognized until too late. Includes: Mild aching, loss of peripheral visions, seeing halos around lights, and difficulty with night vision.

Question 33

prevention and treatment of glaucoma

Answer 33

Prevention: Regular eye examinations. Easily diagnosis. treatment Drugs to reduce the production of aqueous humor. Eye drops to aid in the outflow. Surgery to create an opening for circulation of fluid.

Question 34

strabismus (Heterotropia or tropia)

Answer 34

One eye is misaligned with the other Eyes do not focus simultaneously when viewing an object. Misalignment can be in any direction: Esotropia (inward). Exotropia (outward). Up, down, or any combination of these. Amblyopia (lazy eye) – Vision is suppressed in the “lazy” eye and child only uses “good” eye. Left untreated, blindness in the “lazy” eye results.

Question 35

treatment of strabismus

Answer 35

``` Early detection. Must be treated by the age of 6 years. Eye patches. Eye exercises. Corrective lenses. Surgery. ```

Question 36

muscular degeneration

Answer 36

Deterioration of the macula (the most sensitive portion of the retina). Leads to loss of central visual field. Leading cause of vision loss in North America. Rarely leads to total blindness. Causes: Toxic effects of some drugs, and age-related. Two types: Wet and dry. Wet: Small blood vessels form under the macula and leak destroying visual cells. Dry: Small, yellowish deposits develop on the macula and interfere with central vision.

Question 37

treatment of macular degeneration

Answer 37

Depends on type and severity. | Laser surgery

Question 38

conjunctivitis (pink eye)

Answer 38

Inflammation of the conjunctiva. Produces a red or pink eye; pain, swelling, and discharge. Causes: Secondary to viral, Chlamydial, bacterial, or fungal infections; or allergy. Tx: Depends on the cause. Antibiotics, antifungals, antihistamines.

Question 39

blepharitis

Answer 39

Inflammation of the eyelids. Caused by excess secretions of the sebaceous glands. Produces greasy scales and sticky, crusted eyelids; leads to itching and burning sensations. Tx: Daily cleansing of the eyelids.

Question 40

retinal detachment

Answer 40

Characterized by the separation of the retina from the choroid layer of the eyeball. Due to: Aging, hypertension, diabetes, trauma, and other systemic diseases. Symptoms: Seeing floating spots, flashes of light, and gradual vision loss. Tx: Limiting eye movements with a patch, bed rest, sedation, appropriate positioning of head. Laser beam can repair simple tears. Surgery.

Question 41

surgical removal of the eye ball

Answer 41

enucleation

Question 42

nystagmus

Answer 42

condition of rapid, involuntary, rhythmic movements of the eyeball

Question 43

structure that prevents internal reflection of light

Answer 43

choriod

Question 44

function of retina

Answer 44

translate light waves into nerve impulses