The Ophthalmic Examination

Question 1

what are the components of the ophthalmic exam?

Answer 1

1. neuro-ophthalmic exam
   -pupillary light reflexes
   -palpebral reflexes
   -vision
   -ocular motility
2. exam proper:
   -orbits
   -eyelids
   -globe/all intraocular structures
3. ancillary test (ophthalmic minimum database)
   -schirmer tear test
   -fluorescein stain
   -intraocular pressure management

Question 2

describe general observations of the ophthalmic exam (7)

Answer 2

1. visual behavior: walking into walls? or able to navigate
2. across the room diagnosis: oh my god your eye is sticking out
3. asymmetries:
   -facial
   -orbital: globe position or size
4. eyelid position
5. ocular discharge
6. pupil size, shape, symmetry
7. overt opacities

Question 3

describe setting and equipment of optho exam

Answer 3

1. quiet room that can be made dark: or use blackout curtains in field
2. finoff transilluminator: for PLRs, retroillumination, basic light source, indirect fundic exam
3. slit beam: anterior chamber eval, lesion localization; focused light source (small dot or tiny rectangle); allows you to see junctions btwn different clear things
4. ophthalmoscope: light source with variable apertures, cobalt blue filter (use with fluorescein stain)
   -direct head
   -panophthalmoscope: type of direct but less magnification; can choose how projects light
5. indirect lens: indirect fundic exam
   -used with transilluminator or other light source; indirect ophthalmoscopy
   -variable magnification and filed of view
6. magnification: can use otoscope without attachment or loops, whatever works
7. schirmer tear test strips, fluorescin stain
8. tonometer
9. if large animal:
   -may need sedation
   -eyelid akinesia (auriculopalpebral block) to block motor function to CN VII (normally closes lids)
10. restraint!
    -eliminate ability to back up
    -MUST steadyhead/chin
    -sedation/anesthesia: often hinders exam except un very unruly or large animals; can cause 3rd eyelid elevation, ventral globe rotation, and even miosis

Question 4

what 2 drugs are used with ophthalmic exams?

Answer 4

proparicaine/tetracaine/lidocaine:
-topical anaesthetic: causes rapid, short acting ocular surface anesthesia
-facilitates ocular surface cytology and some procedures
-DIAGNOSTIC use only; NEVER therapeutic use!!! deadens nerve endings
-evaluate tear film quality and quantity BEFORE numbing the eye
-refrigerate

tropicamide ophthalmic solution (0.5 or 1%)
-parasympatholytic (anticholinergic) mydriatic
-causes rapid (15 min) and short acting (4-6 hours) pupil dilation for diagnostic use!
-allows more thorough lens and fundic exam
-evaluate PLRs and iris tissue BEFORE administration

Question 5

describe the pupillary light reflex

Answer 5

stimulus: light

receptor: retina (PRs)

afferent: optic n. (CN II)

interneuron: subcortical

efferent: occulomotor (CN III)

effector: iris sphincter muscle

response: constrict pupils; direct/consensual

crossover = consensual response (NONE IN BIRDS)

Question 6

describe the pathway of the pupillary light reflex

Answer 6

1. stimulus up optic nerve, crossesa t optic chiasm
2. decussation:
   -cats: 65%
   -dogs: 75%
   -horse: 80-90%
3. optic tract to pretectal nucleus to edinger westphal nucleus to parasympathetic fibers of CN III to iris sphincter muscle

Question 7

describe direct versus consensual PLR

Answer 7

direct: response in eye being stimulated; requires receptor (retina), afferent (2) and efferent (3) reflex arms, AND effectors (iris muscle/tissue) to be functioning and intact

indirect/consensual:
response in eye NOT being stimulated
-due to crossover of fibers at optic chiasm
-requires function and intact afferent pathway in stimulated eye and efferent pathway in non-stimulated eye

Question 8

is PLR a vision test?

Answer 8

NO! a blind eye could have a normal PLR and a sighted eye with severe iris atrophy may have a fixed and dilated pupil

may overlap with vision but does not test vision!

Question 9

describe important uses of PLR

Answer 9

1. assessing potential for return of vision
   -absent consensual PLR from affected eye to contralateral eye = low potential for restoration of vision (aggressive measures to save eye may not be indicated)
2. useful in cases of:
   -ruptured eye
   -glaucoma
   -lens luxation
   -cataract
   -proptosis
3. ALWAYS perform both direct and consensual PLR!!!

Question 10

describe vision/menace response/cotton ball tracking

Answer 10

1. stimulus: motion

receptor: retina (PRs) but requires anterior media to be clear

afferent: optic nerve

interneuron: cortical/cerebellum

efferent: facial nerve!!!!!

effector: orbicularis oculi muscle!!!!!!!

response: blink, retract globe

LEARNED response! not reflex; not present in young animals
-cats and some dogs ignore so
use cotton ball tracking

Question 11

describe blink reflexes

Answer 11

stimulus: touch cornea/skin

receptor: touch

afferent: CN V (opth/maxillary branch)

interneuron: subcortical

efferent: CN VII

effector: orbicularis oculi muscle assuming lack of mechanical reflex

Question 12

describe dazzle reflex

Answer 12

stimulus: BRIGHT light

receptor: retina (PRs)

afferent: optic nerve

interneuron: subcorticcal

efferent: facial nerve

effector: orbicularis oculi muscle

response: blink, retract globe

Question 13

describe vestibulo-cochlear/Doll’s eye reflex

Answer 13

1. involuntary ocular movements induced by turning head slowly from side to side
2. fast phase IN DIRECTION. OF head movement
3. assesses: CN III, IV, VI

Question 14

describe how to evaluate extraocular muscles

Answer 14

1. restrain patient’s head and lead eye through positions of gaze; check physiologic nystagmus as well
2. lack of normal movement may be associated with neurologic disease or mechanically restrictive orbital disease

Question 15

describe exam proper of adnexa

Answer 15

1. eyelids, conjunctiva, nasolacrimal system
2. examine with diffuse and focal light and magnification
3. look for the obvious/overt abnormalities or changes: squinting, drooping, lacerations, masses
4. then look more closely for:
   -eyelash abnormalities
   -in turning or rollout of eyelid margins (entropion/ectropion)
   -subtle masses
   -foreign bodies, lacerations
5. assess NL puncta esp if ocular discharge and NLD function
6. 3rd eyelid:
   -variably pigmented, can cause look of red eye
   -assess: naked eye with good light source +/- magnification; retropulse globe to eval palpebral surface
   -topical anesthetic and manual retraction to eval bulbar aspect
   -look for prolapsed gland (cherry eye), cartilage abnormalities, masses

Question 16

describe anterior segment exam proper

Answer 16

1. cornea, anterior chamber, iris/pupil, and lens
2. use
   -retroillumination: using light source arms distance away, generate eye shine (deer in head lights) to backlight all structures between back of eye and you!
   -very useful for detecting subtle abnormalities!! but does not tell you where it is, just know it between you and back of eye

-diffuse illumination

-transillumination: observe light as it passes through transparent and translucent ocular structures (for looking at cysts)

+/- magnification

3. then use a focused slit beam or small circle of light and an oblique convergent viewing axis to create an optic cross section of the eye (purkinje images) bc bunch of clear things staked on top of each other; allows lesion localization

Question 17

describe purkinje images for lesion localization

Answer 17

create optic cross section with light and highlight transition of tissues/structures; tells where lesion is!!!

slit beam creates 5 optical cross sections:
1. tear film/cornea

2. black anterior chamber
3. anterior lens capsule/front of lens
4. smokey lens
5. posterior lens capsule/back of lens

Question 18

describe axis of rotation for lesion localization

Answer 18

center axis of rotation of eye is center of the lens;

lesions anterior to the center of the lens move in the same direction as front of eye;

lesions posterior to center of lens move in opposite direction of eye

Question 19

describe object overlay for lesion localization

Answer 19

know which structures live behind which (anatomy!)

Question 20

what are 9 opacities/colors to look for in the cornea?

Answer 20

1. edema
2. blood vessels (blood)
3. deposit (lipid or mineral)
4. pigment- melanin
5. infiltrate (WBC or neoplasia)
6. scar
7. foreign bodies
8. iris adhesion (synechia) or prolapse
9. stromal loss/loss of substance

cornea should be moist/shiny, smooth and clear!

Question 21

describe corneal ulcers

Answer 21

1. visualize with naked eye or closer examination
2. use fluorescein stain; then assess for presence of
   -infiltrate
   -malacia/melting
   -depth: superficial, stromal, descemetocele
   -degree of uveitis
   -vascularization

Question 22

describe how to exam the anterior chamber

Answer 22

1. retroillumination
2. diffuse and transillumination
3. focused (slit beam)
4. compare to other eye

should be black, quiet with no
aqueous flare,
no hypopyon: settled out WBCs
no fibrin,
no blood/hyphema: settled out RBCs
no cysts,
uniform and symmetric depth

Question 23

describe iris/pupil exam

Answer 23

should have uniform texture and pupil shape

iris:
-color change: normal variation or pathology?
-texture change: mass/thickening
-hemorrhage: harder to see in bron eye dogs
-denesis: shimmering or shaking of iris or lens due to loose zonules

pupil:
-abnormal movement
-ansiocoria (different pupils each eye), dyscoria (abnormal pupil shape), synechia
-atrophy

Question 24

describe exam of the lens

Answer 24

like cornea and anterior chamber

1. retroillumination to backlight subtle opacities
2. diffuse and transillumination
3. focused slit beam to determine depth within lens
4. axis of rotation

look for:
1. cataract: true opacity of the lens
-problem
2. nuclear sclerosis: age related densening of the lens
-differentiate from cataract by age (starts at 6; visible by 9 or 10)
-clinically insignificant and normal age change
3. alterations in size (uncommon)
4. alterations in position: luxation or subluxation (in sublux see aphakic crescent)
-all lux occur from failure of zonules!!

Question 25

describe exam of the posterior segment

Answer 25

1. includes vitreous and fundus (composite image of retina and optic nerve, choroid, +/- sclera) -fundus= what you see when you look at the back of the eye; varies based on opacity!! 2. maximize via pharmacologic mydriasis with short acting topical ophthalmic anticholinergic agent (tropicamide) -also facilitates and benefits thorough lens eval -DONT do if IOP elevated 3. use direct ophthalmoscopy to exam fundus; must be VERY close to patient -has different spot sized to match pupil size

Question 26

describe direct ophthalmoscopy

Answer 26

1. image is upright and true to right and left (up is up, down is down, it makes sense)- good! 2. image is highly magnified in small eyes: not great for mice or even in dogs and cats bc is too magnified for a screening tool (like going straight to 100x on a microscope and trying to find something) 3. small field of view

Question 27

describe mononuclear indirect ophthalmoscopy

Answer 27

also for fundus exam! use and indirect lens and a light source; farther away than direct (arms distance away) starting point: retroillumination for tapetal reflex to line up then drop lens in and start indirect exam magnification and field of view vary with eye size and power of lens = useful fundus screening in dogs and cats! (higher dioptic power = lower magnification = larger field of view) can add binocular view to add depth perception (use both eyes) and free hand IMAGE IS UPSIDE DOWN AND BACKWARDS

Question 28

compare and contract direct versus indirect ophthalmoscopy

Answer 28

direct: pros: easy to use, real upright image, high mag, readily available equipment, useful for closer exam of optic nerve and/or lesions cons: shorter working distance, monocular view, small filed of view = poor screening tool indirect: pros: lower mag (varies with size of eye and lens (lower diopter = higher mag), longer working distance, depth perception when binocular, larger field of view so better screening tool and more context cons: requires practice to master, inverted and reversed image

Question 29

describe fundic exam (4); more to come in later lectures

Answer 29

look for 1. optic nerve head: colors, borders, size, shape 2. retinal vasculature: congestion, tortuosity, hermorrhage, attenuation 3. tapetum (PART OF CHOROID NOT FUNDUS): hypo or hyper reflectivity 4. non-tapetum: infiltrate, scars lots of normal variation!!

Question 30

describe exam of the orbit

Answer 30

1. assess symmetry of orbits and eyes (position, size, mvmt) by visual inspection -buphthalmos (cow eyed, enlargement due to glaucoma) -microphthalmus (congenitally small) -phthisis bulbi (small shrunken eyeball following inflammation) -exophthalmus (protrusion) -enophthalmos (recession into orbit) strabismus (deviation of eye) 2. +/- manual palpation (retropulsion) -not with deep ulcers and not necessary in most cases anyways -only if have some suspicion of orbital disease 3. additional exam generally only if issue present- more later

Question 31

describe the schirmer tear test

Answer 31

1. measures aqueous (water) component of tear film produced in response to irritating corneal stimulus -STT I (technically): measures basal and reflex tears 2. perform prior to instillation of any liquids (topical anesthesia) 3. avoid touching end of strip! 4. place in inferio-lateral lid; remove and read after 60 sec 4. normal values: -greater than or equal to 15mm in dogs, 10 mm in cats (variable in cats due to sympathetic tone; can have a schirmer of zero and be normal) 5. check with both eyes! -rare exceptions: deep ulcers

Question 32

describe fluorescein stain

Answer 32

1. water soluble dye impregnated in a paper strip 2. multiple uses: -detect defects of ocular surface (epithelial defects) -assess tear film/health deficiencies -assess patency of nacolacrimal tear drainage (jones test): hold nose down and examine for dye passage within nostrils or mouth within 5 minutes -detect leakage via ocular defect including surgical wounds (seidel test) 3. intact corneal/conjunctival epithelium is hydrophobic and does not retain dye -if epi is missing, hydrophilic stroma retains dye = erosion or ulcer -descemet's membrane does not take up dye 4. moisten strip with saline and apply to ocular surface, then rinse and assess for retention with cobalt blue illumination

Question 33

describe tonometry

Answer 33

1. measurement of intraocular pressure (IOP) 2. normal values 15-25mmHg 3. elevated IOP is a sign of glaucoma 4. low IOP may be a sign of uveitis (IO inflammation) 5. check both eyes (rare exceptions) for individual variation frame of reference -differences greater than 5-10mmHg between eyes suggests an issue even if both values WNL 6. methods/equipment: -applanation: tono-pen, pneumatonometer -induction-impact/rebound: TonoVet

Question 34

describe tono-pen technique

Answer 34

1. topical anesthesia 2. easy to get false elevated readings! be careful with the pressure YOU apply; try to put on orbit and not globe

Question 35

describe TonoVet

Answer 35

1. no topical anesthesia 2. probe must be parallel to the ground 3. rebound tonometer: assess characteristics of probe bouncing off cornea to determine pressure 4. unknown accuracy with corneal disease 5. use appropriate species setting

Question 36

what 3 factors affect IOP?

Answer 36

1. pathology: -uveitis decreases -glaucoma increases 2. patient related factors: -age (IOP increase with age) -stress/excitement (increase) -breed: brachycephalics often measure a bit higher; tougher to get accurate IOP 3. tonometry technique: can falsely elevate -heavy hand -restraint -eyelid manipulation

Question 36

describe corneal or conjunctival culture and sensitivity

Answer 36

1. if infection suspected due to corneal infiltrate and/or mucopurulent discharge 2. perform early in exam; prior to topical anesthesia or soon after 1 drop 3. using mini-tip swabs, culture affected area, avoiding contamination of the eyelids 4. be careful of deep ulcers and plate quickly bc small sample 5. goof for aerobic bacteria +/- fungal

Question 37

describe corneal or conjunctival cytology

Answer 37

1. if infection suspected due to corneal infiltrate and/or mucopurulent discharge 2. after application of topical anesthesic 3. use the back of a blade or brush and take from the affected area over the infiltrate, scraping in one direction 4. be careful with deep ulcers! 5. use dif quick or WG stain