Lecture 3: Eyes Flashcards
Learning Objectives
Learn the structure and function of the external and internal components of the eyes
Learn the methods of examination of vision and external eye
Differentiate between normal and abnormal findings of the eye and vision
Record the assessment accurately
Abbreviations of eyes
OD (oculus dexter) right eye
OS (oculus sinister) left eye
OU (oculus uterque) bilateral eyes
External Eye Anatomy:
Eyelids
Protective mechanisms
Lids
Eyelashes
When lids closed, margins approximate
When lids open upper lid covers part of iris
External Eye Anatomy:
Canthus
Corners of the eye
-Lateral and Medial
Upslanting Palperbral Fissure
normal: horizontal line from lateral to medial canthus
abnormal: upslanted eyes
External Eye Anatomy
Conjunctiva
Conjunctiva
- Transparent protective covering
- Mucous membrane
pink eye: viral infection that is treated like bacterial
External Eye Anatomy:
Lacrimal Gland
Upper outer corner
Drain at puncta
Secretes tears
Provide constant irrigation to keep conjunctiva and cornea lubricated
Internal Anatomy:
Outer Layer
Middle Layer
Inner Layer
Outer layer: fibrous sclera
Middle layer: vascular choroid
Ciliary body and iris
Pupil
Lens
Anterior chamber
Inner layer: nervous retina
Transparent vitreous body
Optic disc
Retinal vessels
Macula
Internal Anatomy: Outer Layer
- sclera
- cornea
Sclera:
tough, protective, white covering
Continuous anteriorly with cornea
Cornea:
Covers iris and pupil
part of refracting media of eye
Very sensitive to touch
Internal Anatomy:
Middle Layer
- choroid
Choroid:
darkly pigmented
- prevents light from reflecting internally
heavily vascularized to deliver blood to retina
- Anteriorly is continuous with ciliary body and iris
need special equipment to examine but can see hypertension or brain tumors on occasion
Internal Anatomy:
Middle Layer
- ciliary body
- iris
- pupil
Ciliary body
Alters curvature of lens
Iris:
Contract pupil:
- in bright light
- to accommodate for near vision
Pupil: round
CN III
- Parasympathetic (“breed and feed”):: causes constriction of pupil
- Sympathetic (fight or flight) dilates pupil and elevates eyelid
Internal eye Anatomy: middle layer
- lens
Lens:
- biconvex disc located just posterior to pupil
- Transparent
- Refracts to keep a viewed object in focus on retina
- *Thickness controlled by ciliary body
- lens more spherical to focus on near objects
- flattens for far objects
Internal Anatomy:
Inner Layer
Retina
Retina: visual receptor
Changes light waves into nerve impulses
Retinal structures:
(optic disc
retinal vessels
general background
Macula)
Optic Disc- fibers from the retina converge to form the optic nerve
The inner layer cannot be seen with the naked eye. You need to use an opthalmoscope
This is an advanced practice skill
Extraocular Muscles (EOMs)
CN 3, 4, 6 : All 3 work together for conjugate movement of the eye or movement of both eyes in the same direction to maintain binocular gaze.
Humans require conjugate movement
Requires both muscles and nerves
CN III: Oculomotor nerve
innervates all the rest: the superior, inferior, and medial rectus and the inferior oblique muscles
CN IV: Trochlear nerve
superior oblique muscle
CN VI: Abducens nerve
lateral rectus muscle
Pupillary Light Reflex
The retina detects the brightness of light
Pupils respond by constricting
Direct light reflex:
Pupil constricts when exposed to bright light
Consensual light reflex
simultaneous constriction
The sensory afferent CN II optic nerve carries the message in
The motor efferent CN III oculomotor nerve carries the message out
Visual Reflexes: Accommodation
adaptation of eye for near vision
- Ciliary muscles contract
- Increases curvature of lens
- Pupils constrict
Tested by:
Convergence
Pupillary constriction
Subjective Data
Vision difficulty: decreased acuity, blurring, blind spots
Pain
Redness, swelling
Infections in the past
Watering
Discharge
- Color
(purluent: bacterial or watery)
History of ocular problems
Surgery
Allergies
Glaucoma
Cataracts
Macular Degeneration
Family History
Medications: for eyes and others
Use of glasses or contact lenses
Physical Assessment Equipment
Equipment needed:
Snellen eye chart
Handheld visual screener
Opaque card or occluder
Penlight
Ophthalmoscope
Snellen Chart
Lines of letters arranged in decreasing size
20 feet from chart
Use opaque card to shield one eye at a time during test
Check vision with glasses/contact lenses ON
= Remove only reading glasses
= Client can miss 2 letters per line
Testing Peripheral Vision
Confrontation:
Confrontation
Cover eye opposite yours
Position at eye level of tester, about 2 feet away
Slowly advance wiggling finger
Gross test
Assumes acuity of tester
Extraocular Muscle Function
Corneal Light Reflex
Corneal Light Reflex
Also known as Hirschberg test
- shine light toward eyes from 12 inches, while they stare straight ahead
- The reflection of the light should be seen same “clock location” in each eye
If you look at this picture you see the reflection of light, in the two corneas, at the same exact spot or symmetrical, about clock position 12
Extraocular Muscle Function:
cover/uncover test
Have patient stare at distant object
Cover one eye with a card
then uncover
Normal: no moving
When weaker eye is covered- it will drift to a relaxed position
Once the eye is uncovered, it will quickly move back to reestablish fixation
The uncovered eye is weaker- when the stronger eye is covered, the weaker eye moves to refocus
Abnormalities of the Pupil:
Ansiocoria
pupils of unequal size, could be normal or abnormal
- Greater in bright light compared with dim light, cause could be trauma
- Greater in dim light compared with bright light, cause could be Horner syndrome, caused by paralysis of the cervical sympathetic nerves
EOR Myopia
Nearsightnedness:
- Can clearly see close objects, but distant objects are blurry
- Light rays focus in front of the retina
*clear near vision
*blurry distance vision
Causes:
Globe is too long
Cornea is too curved
EOR Hyperopia
Farsightedness:
- Difficulty focusing on small print
- Light focuses behind the retina
*blurry vision up close
*clear vision far away
Causes:
- Globe is too short
- Cornea is too flat in relation to the length of the eye
EOR Presbyopia
Lens stiffens with age
- becomes less flexible and unable to accommodate to near
- ability to focus on small print becomes difficult
Presbyopia will happen to 100% of the population sometime during midlife
EOR Presbyopia
Lens stiffens with age
- becomes less flexible and unable to accommodate to near
- ability to focus on small print becomes difficult
Presbyopia will happen to 100% of the population sometime during midlife
EOR Astigmatism
When the cornea is shaped more like a football than a basketball, it causes distortion and blurry vision as light enters the eye
Instead of one focus point, there are multiple focus points when light enter the eye
Exophthalmos
“Protruding Eyes”
Forward displacement of the eyeballs and widened palpebral fissures
Upper lid rests well above the limbus (border between the cornea and sclera and white sclera is visible
Associated with thyroid disease with hyperthyroidism or an overactive thyroid
Forward displacement and widened palpebral fissures (the distance and shape between the two corners of the opening of the eye)
Ectropion
Outwardly turned lower lid
The lower lid is loose and rolls out.
Puncta cannot siphon tears effectively, so excess tearing results.
Eyes feel dry and itchy because tears do not drain correctly.
Ectropion
Outwardly turned lower lid
The lower lid is loose and rolls out.
Puncta cannot siphon tears effectively, so excess tearing results.
Eyes feel dry and itchy because tears do not drain correctly.
Entropion
Inwardly turned lower eyelid
Lower lid rolls in because of spasm of lids or scar tissue contracting.
Constant rubbing of lashes may irritate the cornea
The person feels a “foreign body” sensation
Periorbital Edema
Upper and lower lids are swollen and puffy.
Lid tissues are loosely connected so excess fluid is easily apparent.
Occurs with:
Crying
CHF
Renal failure
Allergies
Hypothyroidism
