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Duke Elder 2020 > Cornea > Flashcards

Cornea Flashcards

1
Q

How is the cornea different to the sclera?

A

transparent

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2
Q

Describe the refraction power of the cornea?

A

HIGHEST REFRACTION POWER IN THE EYE: 40D

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3
Q

What is the average diameter of the cornea in the adult and newborn?

A

10-13MM IN ADULTS AND 9.5-10.5MM IN NEWBORNS

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4
Q

What is the thickness of the cornea?

A

535um

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5
Q

Where does the cornea receive its nutrients from?

A

anteriorly - tear film

posteriorly - aqueous humour

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6
Q

Describe the sensory supply of the cornea?

A

CNV1 via long ciliary nerve

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7
Q

What are the layers of the cornea?

A 
Epithelial layer
Bowman layer
Stromal layer
Descemet membrane 
Endothelium
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8
Q

Describe the epithelial layer of the cornea

A

STRATIFIED NONKERATINIZED SQUAMOUS EPITHELIUM

high regenerative potential to injury due to the presence of limbal epithelial stem cells

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9
Q

Where are palisades of Vogt more prominent?

A

superior and inferior limbus

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10
Q

Describe the bowman layer

A

Avascular layer (no regeneration potential) that contains collagen fibres and terminates at the limbus

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11
Q

Describe the stromal layer

A

thickest corneal layer

continuous with the sclera at the limbus

mainly made up of keratocytes and regularly orientated collagen fibrils (type 1 collagen)

it can undergo scarring

no regenerative potential

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12
Q

Describe the descent membrane

A

An elastic layer containing type IV collage fibres

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13
Q

Describe the endothelium

A

Function by pumping excess fluid from the stroma to keep the cornea dehydrated to maintain its transparency

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14
Q

Describe bacterial keratitis

A

common and sight threatening

more common in contact len wearers (soft > rigid), especially in overnight wear / poor hygiene

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15
Q

What are the common organisms in bacterial keratitis?

A

P aerguinoa (most common cause in contact lens wearers)

S aureus and strep

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16
Q

Describe the features of bacterial keratitis

A

unilatera sudden-onset pain, redness and photophobia with associated discharge and dVA

purulent / mucopurulent discharge

circumcorneal injection

white infiltrates, epithelial and stromal involvement

anterior chamber cells and hypopyon in severe keratits

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17
Q

What are some complications of bacterial keratitis?

A

Corneal perforation, esp if:

N gonorrhoea
Corynebacterium diptheriae
H influenzae

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18
Q

How are fungi stained?

A

sabouraud agar and gram/giemsa stain

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19
Q

How are acanthamoeba stained?

A

non-nutrient agar with e coli

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20
Q

How is bacterial keratitis investigated?

A

corneal scrapings for microbio

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21
Q

how is bacterial keratitis managed?

A

topical broad spec ABx BEFORE lab results return

usually fluoroquinolones (ofloxacin) are typically used

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22
Q

Which patients is fungal keratitis common in?

A

AIDS
diabetics
immunocompromised

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23
Q

what fungus is more common in those with ocular trauma, esp with plant / tree branch?

A

filamentous

aspergillum and fusarium

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24
Q

What are specific signs in candidda infections?

A

small ulcer with an expanding infiltrate in a collar stud formation

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25
Q

What are specific signs in filamentous keratitis?

A

feathery branching-like infiltrate pattern

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26
Q

what investigations can aid in fungal keratitis?

A

confocal microscopy

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27
Q

how is fungal keratitis managed?

A

natamycin drops for proven filamentous infection

variconazole or amphotericin B drops for proven candida

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28
Q

What is a risk factor for acanthamoeba keratitis?

A

improper lens hygiene (showering / swimming in contact lenses)

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29
Q

What are the features of acanthamoeba keratitis?

A

pain out of proportion with clinical signs,
photophobia
blurred vision

later disease: perineural infiltrates and ring shaped strmal infiltrates can be seen

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30
Q

what are the investigations for acanthamoeba?

A

corneal scraping and / or confocal microscopy to identify the presence of amoebic cysts

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31
Q

how is acanthamoeba keratitis treated?

A

topical polyhexamethylene biguanide or

chlorhexidine

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32
Q

What additional condition does HSV corneal infection lead to?

A

blepharoconjunctivitis

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33
Q

where does HSV remain after infection?

A

in the trigeminal ganglion

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34
Q

Which layers of the cornea can keratitis affect?

A

epithelial, stromal or endothelial layers of the cornea

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35
Q

Describe the presentation of patients with reactivated HSV keratitis?

A

pain
dVA
lacrimation
foreign body sensation

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36
Q

What are the signs of HSV keratitis?

A

superficial punctate keratitis which causes a stellate (star-shaped) erosion which later becomes a dendritic ulcer - seen with fluoroscein

reduced corneal sensation

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37
Q

What is disciform keratitis?

A

this usually occurs from HSV antigen hypersensitivity, not reactivation

insidious onset

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38
Q

how does disciform keratitis present?

A

painless dVA

39
Q

Describe the signs of disciform keratitis

A

central circular stromal oedema
there is usually mild anterior chamber activity
keratitic precipitates

WESSLEY RING: due to antigen/antibody complex

40
Q

What are the investigations used in disciform keratitis?

A

clinical, aided by swabs for PCR or Giemsa staining which shows multinuclear giant cells

41
Q

Describe the management of disciform keratitis

A

Epithelial: topical aciclovir, avoid steroids: may lead to geographic ulcer and corneal perforation

Disciform:
oral aciclovir 400g five times a day
avoid topical steroids until epithelium is intact

42
Q

What virus causes herpes zoster ophthalmicus?

A

VZV

43
Q

What is herpes zoster opthalmicus?

A

shingles in CNV1 dermatome

44
Q

What are the cutaneous features of HZO?

A

rash (vesicles / papules)
painful neuralgia
HUTCHINSON SIGN: involvement of tip of nose, indicates a higher likelihood for ocular disease due to the involvement of nasociliary nerve

45
Q

What are the ophthalmic features of HZO?

A

epithelial keratitis: pseudo-dendrites are the differentiating features from HSV keratitis, grey, less branching and poor staining with fluoroscein

conjunctivitis

elevated IOP

stromal and disciform keratitis are less common

46
Q

How is HZO managed?

A

oral aciclovir 800mg five times a day

amitryptyline for neuropathic pain

47
Q

What is interstitial keratitis?

A

describes stromal inflammation +/- neovascularisation

caused by the invasion of microorganism or an immune reaction to a foreign antigen

48
Q

Describe the features of interstitial keratitis

A

pain
dVA
photophobia

non-ulcerate stromal keratitis characterised by mid-stromal scarring with ghost vessels

49
Q

Describe the syphilis aetiology of interstitial keratitis

A

congenital disease usually causes bilateral corneal involvement, while acquired disease is usually unilateral

Hutchinson triad of congenital syphilis (late feature): interstitial keratitis, notched teeth and sensorineural deafness

treatment: IM benzylpenicillin and topical steroids

50
Q

describe the aetiology of lyme disease that leads to Interstitial keratitis

A

caused by spirochete bacterial borrelia, which is transmitted to humans via tick bite

causes erythema migrans (BULL’S EYE SKIN RASH), arthralgia, facial palsy, loss of temporal eyebrows and interstitial keratitis

51
Q

What are some viral causes of interstitial keratitis:

A

HSV, VZV, EBV

52
Q

Describe cogan syndrome that leads to interstitial keratitis

A

autoimmune disorder
interstitial keratitis with sensoriuneural hearing loss, vertigo and tinnitus

complications: polyarteritis nodosa

53
Q

What is marginal keratitis?

A

a type of peripheral corneal inflammation due to type III hypersensitivity reaction to staphylococcal exotoxin

associated with rosacea and blepharitis

54
Q

What are the features of marginal keratitis?

A

epiphora, redness and photophobia

chronic blepharitis

subepithelial infiltrates separated from the limbus by a clear zone

typically occurs in regions where the eyelid contact the cornea

55
Q

What is the management of marginal keratitis?

A

lid hygiene and mild topical steroids

56
Q

What is peripheral ulcerative keratitis?

A

group of conditions that leads to peripheral corneal thinning

most common systemic assoc: rheumatoid arthritis

others: Wegners, polyarteritis nodosa, relapsing polychondritis

57
Q

What are the features of peripheral ulcerative keratitis?

A

begins peripherally eventually progresses centrally and posteriorly, end stage thin vascular cornea

interpalpebral peripheral corneal stromal thinning with an epithelial defect

episcleritis and / or scleritis may be present

58
Q

What is the management of ulcerative keratitis?

A

oral prednisolone +/- systemic immunosuppression, topical steroids by exacerbate thinning

59
Q

What is ocular rosacea?

A

acne rosacea leads to facial changes and ocular disease

causes telangiectasia, papules and pustules on the face, facial flushing and rhinophyma

60
Q

What are the ocular features of ocular rosacea?

A

dry eyes, redness, epiphora and photophobia

eyelids: telangiectasia and posterior blepharitis

conjunctival hyperaemia

61
Q

What are the corneal features of ocular rosacea?

A

marginal keratitis
inferior corneal thinning
superficial erosions
peripheral corneal vascularisation

62
Q

What is the management of ocualr rosacea?

A

lid hygiene
topical lubricants
oral tetracyclic

63
Q

What is filamentary keratitis?

A

a condition where corneal epithelium degenerates, leading strands / filaments and mucus to adhere to the corneal surface

64
Q

What are the risk factors for filamentary keratitis?

A

dry eye syndrome
corneal epithelium erosions
laser eye surgery
contact lens wear

65
Q

What are the features of filamentary keratitis?

A

sensation of foreign body

redness, epiphora and blepharospasm

dry eyes

‘COMMA SHAPED LESION’, MOVE UP AND DOWN ON BLINKING AND STAIN WITH ROSE BENGAL

66
Q

What is keratoconus?

A

bilateral and asymmetrical condition characterised by progressive central stromal thinning and apical protrusion of the cornea, usually presenting in early adulthood

67
Q

What are the features of filamentary keratitis?

A

irregular astigmatism
lower eyelid protrusion on downgaze (munson sign)
vertical striations in the stroma, seen on slit lamp (vogt striae)

iron deposit often within the epithelium around the base of the cone (felischer ring)

‘oil drop’ reflex on ophthalmoscopy
‘scissoring’ reflex on retinoscopy

68
Q

What is a complication of keratoconus?

A

acute hydrops

  • tear in descemet membrane leading to corneal oedema
  • presentation: dVA pain and photophobia
69
Q

What investigations are used in keratoconus?

A

KERATOMETRY: GRADING OF KERATOCONUS INTO MILD, MODERATE AND SEVERE: <48D = MILD AND >54D = SEVERE

VIDEO KERATOGRAPHY (CORNEAL TOPOGRAPHY): ESSENTIAL TO PICK UP EARLY KERATOCONUS

  • VERY USEFUL FOR MONITORING AND HAS REPLACED KERATOMETRY
  • IT SHOWS AN ASYMMETERICAL BOW-TIE PATTERN IN EARLY DISEASE AND PROGRESSES INTO A STEEP CONE THAT IS DISPLACED OF THE VISUAL AXIS
70
Q

How is keratoconus managed?

A

MILD: SPECTACLE CORRECTION

MODERATE: RIGID / HARD CONTACT LENSES OR CORNEAL COLLAGEN CROSS-LINKING USING RIBOFLAVIN DROPS AND ULTRAVIOLENT-A

SEVERE: PENETRATING OR DEEP ANTERIOR LAMELLAR KERATOPLASTY

LASIK IS GENERALLY CONTRAINDICATED

71
Q

What is microophthalmia?

A

CONDITION IN WHICH THE WHOLE EYE IS SMALLER THAT THE AVERAGE BY AT LEAST TWO STANDARD DEVIATIONS

72
Q

What is simple microphthalmos?

A

BILATERAL INVOLVEMENT; THE EYE IS SMALL BUT NORMAL

ASSOCIATED WITH ANGLE CLOSURE GLAUCOMA, UVEAL EFFUSION SYNDROME, HYPERMETROPIA, AMBYLOPIA AND STRABISMUS

73
Q

What is complex micropthalmos?

A

A SMALL EYE ASSOCIATED WITH OTHER ABNORMALITIES INCLUDING ORBITAL CYSTS OR COLOBOMAS (HOLE IN THE OCULAR STRUCTURE)

ASSOCIATED WITH FETAL ALCOHOL SYNDROME AND INTRAUTERINE INFECTIONS

74
Q

What is wilson disease?

A

AN AUTO RECESSIVE GENETIC DISORDER CAUSING DEPOSITION OF COPPER IN THE BODY

THE MOST COMMON AREAS AFFECTED ARE LIVER, BRAIN AND EYES

75
Q

Describe the features of wilson disease?

A

HEPATIC CIRRHOSIS LEADING TO PORTAL HYPERTENSION, ASCITES, VARICES AND HEPATIC ENCEPHALOPATHY

MOVEMENT DISORDERS AND ATAXIA

KAYSER-FLEISCHER RING: COPPER DEPOSITION IN DESCEMET’S MEMBRANE

ANTERIOR SUBSCAPULAR SUNFLOWER CATARACTS

76
Q

What is band keratopathy?

A

it’s a sign due to calcium deposition in the Bowman’s layer

77
Q

Describe the aetiology of band keratopathy

A

IDIOPATHIC

OLD AGE

HYPERCALCAEMIA AND HYPERPHOSPHATAEMIA

SILICONE OIL

CHRONIC AVTERIOR UVEITIS

78
Q

What are the features of band keratopathy?

A

OFTEN ASYMPTOMATIC

INTERPLPEBRAL PERIPHERAL ZONE CALCIFICATION (BAND-LIKE CHALKY PLAQUE) WITH A CLEAR ZONE SEPARATING IT FROM THE LIMBUS

79
Q

How is band keratopathy managed?

A

TREAT UNDERLYIN CAUSE

CHELATION WITH EDTA

80
Q

What are corneal dystrophies?

A

a group of progressive hereditary disorders that cause corneal opacification and can lead to visual impairment

can be classified as anterior (predominantly affecting the epithelium), stromal or endothelial

81
Q

What is cogan dystrophy (map-dot-fingerprint dystrophy)?

A

MOST COMMON EPITHELIAL DYSTROPHY

SPORADIC OR AD INHERITENCE

82
Q

What are the features of cogan dystrophy?

A

ONSET IS IN SECOND DECADE WITH BILATERAL RECURRENT CORNEAL EROSIONS (RECURRENT PAIN, PHOTOPHOBIA AND EPIPHORA)

SIGNS ARE BEST SSEN ON RETROILLUMINATION SLIT LAMP

  • MAP: SUBEPITHELIAL GEOGRAPHIC OPACITIES
  • DOT: INTRAEPITHELIAL MICROCYSTS
  • FINGERPRINT: SUBEPITHELIAL RIDGES
83
Q

What is Reis-buckler dystrophy?

A

An AD condition that occurs as a result of the replacement of Bowman’s layer with connective tissue

84
Q

What are the features of reis-buckler dystrophy?

A

PRESENTS WITH RECURRENT CORNEAL EROSIONS IN CHILDHOOD

BECOME LESS PAINFUL WITH AGE DUE TO DECREASED CORNEAL SENSATION

EXAMINATION MAY REVEAL SUBEPITHELIAL CLOUDY OPACITIES CENTRALLY

85
Q

What are the three types of stromal dystrophies?

A

LATTICE DYSTROPHY

GRANULAR DYSTROPHY

MACULAR DYSTROPHY

86
Q

What are the features of macular stromal dystrophy?

A

BILATERAL VISUAL LOSS IN FIRST DECADE

GREY, POORLY DEMARCATED OPACITIES IN THE STROMA

87
Q

Describe macular dystrophy

A

MARILYN MONROE ALWAYS:

  • MUCOPOLYSACCHARIDE ACCUMULATION IN STROMA
  • MACULAR DYSTROPHY
  • ALCIAN BLUE USED TO STAIN MUCOPOLYSACCHARIDES
88
Q

Describe granular dystrophy

A

Gets Her Men:

GRANULAR DYSTROPHY

HYALINE DEPOSITS IN THE STROMA

MASSON TRICHOME IS USED TO STAIN HYALINE

89
Q

Describe the features of granular dystrophy

A

DVA AND RECURRENT CORNEAL EROSIONS

BREADCRUMB-LIKE OPACITIES IN AN OTHERWISE HEALTHY STROMA

90
Q

Describe lattice dystrophy

A

LA COUNTY

  • LATTICE DYSTROPHY
  • AMYLIOD DEPOSITS IN THE STROMA
  • CONGO RED IS USED TO STAIN AMYLOID (GREEN BIREFRINGENCE IN POLZARIXED LIGHT)
91
Q

Describe the features of lattice dystrophy

A

DVA AND RECURRENT CORNEAL EROSIONS

REDUCED CORNEAL SENSATION

EXAMINATION SHOWS ANTERIOR GLOSSY STROMAL DOTS, AFFECTING THE CENTRE, FORM TOUGH TO FORM FINE FILAMENTOUS LINES

92
Q

Describe fuchs endothelial dystrophies

A

MOST COMMON CORNEAL DYSTROPHY

INHERITENCE IS SPORADIC OR AD

MORE COMMON IN ELDERLY FEMALES

DUE TO FAILURE OF SODIUM / POTASSIUM PUMP LEADING TO ACCUMULATION OF FLUID IN THE CORNEA WHICH LEADS TO ENDOTHELIAL CELLS LOSS

93
Q

What are the features of fuchs’ corneal dystrophy?

A

BLURRY VISION WORSE IN MORNING

SPECULAR MICROSCOPY MAY SHOW CORNEAL GUTTATA (‘BEATEN METAL’ APPEARANCE) AND LOW ENDOTHELIAL CELL COUNTS

PACHYMETRY MAY SHOW INCREASED CENTRAL CORNEAL THICKNESS

Duke Elder 2020 (9 decks)

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