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Cognition & Senses - wk 3 > the ocular surface > Flashcards

the ocular surface Flashcards

1
Q

what makes up the ocular surface

A
  • conjunctiva
  • corna
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2
Q

conjunctiva

A
  • most exposed of all the mucous membranes
  • relatively transparent
  • blood vessels, globlet cells, lymphoid tissue, collagen and elastin
  • variable amount of melanosis normal in dog
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3
Q

conjunctiva innervation

A

ciliary nerves

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4
Q

what does the conjunctiva line

A

eyelids, third eyelid, and reflects onto the globe

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5
Q

different parts/areas of conjunctiva

A
  • palpebral conjunctiva
  • nicitating membrane
  • bulbar conjunctiva
  • conjunctival fornix
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6
Q

layers of conjunctiva from superficial to deep

A
  • bulbar conjunctiva
  • episclera (loose fibrous elastic tissue)
  • tenon’s capsule (thin fascial sheath)
  • sclera
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7
Q

function of conjunctiva

A

increases mobility of eyelids and globe

  • freely moveable except at limbus
  • redundancy at fornix

barrier against microorganisms and prevent desiccation of cornea

  • muscin produced by globlet cells
  • traps debris
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8
Q

what is the cornea

A
  • transparent front of outer fibrous tunic
  • avascular - pre-corneal tear films
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9
Q

what is the limbus

A
  • cornea meets the sclera
  • transition zone between cornea and conjunctival epithelium
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10
Q

cornea innervation

A

ciliary nerves

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11
Q

histology

A

epithelium

  • firmly adhered to underlying stroma
  • 6-15 layers

stroma

  • regularly arranged collagen
  • avascular

single endothelial cell layer

  • descemet’s membrane
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12
Q

transparency

cornea

A
  • essential for vision
  • results from (avascular, regularly arranged collagen, relatively dehydrated - endothelial Na, K-ATPase pump, epithelial barrier)
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13
Q

function of cornea

A

refraction of light

  • smooth outer surface
  • continuously replaces epithelium
  • pre-corneal tear film

main barrier to penetration by micro-organisms

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14
Q

slit lamp biomicroscope

A

use to look at changes in corneal transperancy and integrity

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15
Q

SD-OCT (spectral domain optical coherence tomography)

A
  • accurate evaluation of each component of cornea
  • real-time evaluation with absence of corneal contact
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16
Q

conjunctival disease

A
  • very common
  • conjunctival vessels sensitive to irritation, easily congested
  • conjunctivitis (most common)
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17
Q

corneal disease

A
  • trauma - corneal ulcer
  • tear film abnormalities - dry eye (KCS)
  • corneal edema
  • keratitis
  • results in loss of transperancy, integrity, distrubed vision
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18
Q

loss of transparency

A
  • corneal pathology results in loss of transparency
  • disturbed vision
19
Q

conjunctiva and cornea diagnostic tests

A
  • schirmer tear test
  • fluorescein dye
  • rose bengal stain
  • cytology, culture
  • biopsy
  • PCR
  • corneal sensitivity and thickness
20
Q

fluoresceine dye

A
  • corneal integrity
  • dye is hydrophilic (readily binds to exposed stroma, repelled by epithelium)
  • corneal ulcer stains green
21
Q

rose bengal stain

A
  • devitalized epithelial cells (stain pink)
  • FHV-1 dendritic ulcers
22
Q

cytology

A
  • frequently useful

normal

  • sheets of epithelial cells
  • large, round homogenous nuclei
  • abundant cytoplasm

abnormal

  • examine for cellular alterations, bacterial and inclusion bodies
23
Q

0.5% proparacaine

A
  • local anesthetic (dogs - 15-25 min, cats - 5 min)
  • refrigerate
  • epithelial toxic
24
Q

culture

A
  • bacteria cultured from conjunctival sac normal animals
  • reserve for persistent, recurrent or non-responsive conjunctivitis
25
Q

corneal sensitivity

A
  • evaluates ophthalmic branch of CNV
  • esthesiometer (semi-quantified device, sensitivity in different areas)
26
Q

corneal thickness

A
  • pachymetry
  • simple, quick way to measure corneal thickness
27
Q

pre-corneal tear film (PCTF)

A
  • nourish, lubricate, cleanse ocular surface
  • optical activity
  • antibacterial
  • alterations in tears dynamics (compromise function, inflammation, metaplasia, necrosis of ocular surface cells)
28
Q

PCTF secretion

A
  • tri-laminar fluid comprises (lipid, aqueous, mucin)
  • complex interactions between layers
  • transparent, tri-laminar tear film
29
Q

function of aqueous layer

A

serves metabolic needs of avascular cornea (lubricates and cleanses

30
Q

what is the aqueous layer produced by

A
  • orbital lacrimal gland (majority)
  • gland or third eyelid/accessory
31
Q

aqueous layer innervation

A

by both sympathetic and parasympathetic

32
Q

lipid layer

A
  • meibomian glands (cholesterol waxy lipids
  • retards evaporation
  • contributes to tear film stability
33
Q

mucin layer

A
  • conjunctival globlet cells (mucin, conjunctival fornix)
  • promotes smooth ocular surface
  • traps bacteria, foreign material
  • contributes to tear film stability
34
Q

tear drainage

A
  • lacimal puncta (tear ducts)
  • slit-like openings at mucocutaneous junction upper and lower lids
  • only inferior punctum rabbits
  • enter puncrta by combination of gravity, capillary pull, and pump mechanism
35
Q

nasolacrimal duct system

A
  • tears flow through canalicular system, which coverges at lacrimal sac (lacrimal bone)
  • continues as nasolacromal duct to nasal opening (puncta)
  • nasal puncta (located in nasal vestibule at margin or alar fold)
36
Q

PCTF disorders

A
  • desiccation, inflammation of conjunctiva and cornea
  • KCS (aqueous deficiency, dry-eye is most common ocular disease in dogs)
  • melbomianitis/bleparitis (loss of tear film stability)
37
Q

tear drainage abnormalities

A
  • tear overflow (epiphoria)
  • obstruction of nasolacrimal duct system (foreign body)
38
Q

PCTF diagnostic tests

A
  • schirmer tear test
  • tear film breakup time
39
Q

schirmer tear test

A
  • measures volume of aqueous tears
  • dog 15-20 mm/min
  • values vary with age, breed
  • cat - often lower than expected
  • compare both eyes
  • diagnostic test of choice for KCS
40
Q

tear film break up (TBUT)

A
  • lipid and mucin abnormalities - tear film stability
  • time taken for first “dry spot” to appear on cornea after complete blink
  • cats - 12-21 sec, dog - 20sec
41
Q

abnormalities of drainage

A
  • nasolacrimal patency (jones test, nasolacrimal duct flush)
  • dacryocystohinography
42
Q

jones test

A
  • apply fluorescein and wait 4-10 min for it to appear in nares
  • positive test = nasolacrimal duct system patent
  • negative test = suspicious for obstruction
43
Q

flush nasolacrimal duct

A
  • syringe attached to lacrimal cannula or blunted needle
  • cannulate superior punctum
  • negative test confirms obstruction

Cognition & Senses - wk 3 (13 decks)

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