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Duke Elder 2020 > Cornea > Flashcards

Cornea Flashcards

(93 cards)

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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
What are specific signs in filamentous keratitis?
feathery branching-like infiltrate pattern
26
what investigations can aid in fungal keratitis?
confocal microscopy
27
how is fungal keratitis managed?
natamycin drops for proven filamentous infection variconazole or amphotericin B drops for proven candida
28
What is a risk factor for acanthamoeba keratitis?
improper lens hygiene (showering / swimming in contact lenses)
29
What are the features of acanthamoeba keratitis?
pain out of proportion with clinical signs, photophobia blurred vision later disease: perineural infiltrates and ring shaped strmal infiltrates can be seen
30
what are the investigations for acanthamoeba?
corneal scraping and / or confocal microscopy to identify the presence of amoebic cysts
31
how is acanthamoeba keratitis treated?
topical polyhexamethylene biguanide or chlorhexidine
32
What additional condition does HSV corneal infection lead to?
blepharoconjunctivitis
33
where does HSV remain after infection?
in the trigeminal ganglion
34
Which layers of the cornea can keratitis affect?
epithelial, stromal or endothelial layers of the cornea
35
Describe the presentation of patients with reactivated HSV keratitis?
pain dVA lacrimation foreign body sensation
36
What are the signs of HSV keratitis?
superficial punctate keratitis which causes a stellate (star-shaped) erosion which later becomes a dendritic ulcer - seen with fluoroscein reduced corneal sensation
37
What is disciform keratitis?
this usually occurs from HSV antigen hypersensitivity, not reactivation insidious onset
38
how does disciform keratitis present?
painless dVA
39
Describe the signs of disciform keratitis
central circular stromal oedema there is usually mild anterior chamber activity keratitic precipitates WESSLEY RING: due to antigen/antibody complex
40
What are the investigations used in disciform keratitis?
clinical, aided by swabs for PCR or Giemsa staining which shows multinuclear giant cells
41
Describe the management of disciform keratitis
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
What virus causes herpes zoster ophthalmicus?
VZV
43
What is herpes zoster opthalmicus?
shingles in CNV1 dermatome
44
What are the cutaneous features of HZO?
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
What are the ophthalmic features of HZO?
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
How is HZO managed?
oral aciclovir 800mg five times a day amitryptyline for neuropathic pain
47
What is interstitial keratitis?
describes stromal inflammation +/- neovascularisation caused by the invasion of microorganism or an immune reaction to a foreign antigen
48
Describe the features of interstitial keratitis
pain dVA photophobia non-ulcerate stromal keratitis characterised by mid-stromal scarring with ghost vessels
49
Describe the syphilis aetiology of interstitial keratitis
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
describe the aetiology of lyme disease that leads to Interstitial keratitis
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
What are some viral causes of interstitial keratitis:
HSV, VZV, EBV
52
Describe cogan syndrome that leads to interstitial keratitis
autoimmune disorder interstitial keratitis with sensoriuneural hearing loss, vertigo and tinnitus complications: polyarteritis nodosa
53
What is marginal keratitis?
a type of peripheral corneal inflammation due to type III hypersensitivity reaction to staphylococcal exotoxin associated with rosacea and blepharitis
54
What are the features of marginal keratitis?
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
What is the management of marginal keratitis?
lid hygiene and mild topical steroids
56
What is peripheral ulcerative keratitis?
group of conditions that leads to peripheral corneal thinning most common systemic assoc: rheumatoid arthritis others: Wegners, polyarteritis nodosa, relapsing polychondritis
57
What are the features of peripheral ulcerative keratitis?
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
What is the management of ulcerative keratitis?
oral prednisolone +/- systemic immunosuppression, topical steroids by exacerbate thinning
59
What is ocular rosacea?
acne rosacea leads to facial changes and ocular disease causes telangiectasia, papules and pustules on the face, facial flushing and rhinophyma
60
What are the ocular features of ocular rosacea?
dry eyes, redness, epiphora and photophobia eyelids: telangiectasia and posterior blepharitis conjunctival hyperaemia
61
What are the corneal features of ocular rosacea?
marginal keratitis inferior corneal thinning superficial erosions peripheral corneal vascularisation
62
What is the management of ocualr rosacea?
lid hygiene topical lubricants oral tetracyclic
63
What is filamentary keratitis?
a condition where corneal epithelium degenerates, leading strands / filaments and mucus to adhere to the corneal surface
64
What are the risk factors for filamentary keratitis?
dry eye syndrome corneal epithelium erosions laser eye surgery contact lens wear
65
What are the features of filamentary keratitis?
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
What is keratoconus?
bilateral and asymmetrical condition characterised by progressive central stromal thinning and apical protrusion of the cornea, usually presenting in early adulthood
67
What are the features of filamentary keratitis?
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
What is a complication of keratoconus?
acute hydrops - tear in descemet membrane leading to corneal oedema - presentation: dVA pain and photophobia
69
What investigations are used in keratoconus?
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
How is keratoconus managed?
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
What is microophthalmia?
CONDITION IN WHICH THE WHOLE EYE IS SMALLER THAT THE AVERAGE BY AT LEAST TWO STANDARD DEVIATIONS
72
What is simple microphthalmos?
BILATERAL INVOLVEMENT; THE EYE IS SMALL BUT NORMAL ASSOCIATED WITH ANGLE CLOSURE GLAUCOMA, UVEAL EFFUSION SYNDROME, HYPERMETROPIA, AMBYLOPIA AND STRABISMUS
73
What is complex micropthalmos?
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
What is wilson disease?
AN AUTO RECESSIVE GENETIC DISORDER CAUSING DEPOSITION OF COPPER IN THE BODY THE MOST COMMON AREAS AFFECTED ARE LIVER, BRAIN AND EYES
75
Describe the features of wilson disease?
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
What is band keratopathy?
it's a sign due to calcium deposition in the Bowman's layer
77
Describe the aetiology of band keratopathy
IDIOPATHIC OLD AGE HYPERCALCAEMIA AND HYPERPHOSPHATAEMIA SILICONE OIL CHRONIC AVTERIOR UVEITIS
78
What are the features of band keratopathy?
OFTEN ASYMPTOMATIC INTERPLPEBRAL PERIPHERAL ZONE CALCIFICATION (BAND-LIKE CHALKY PLAQUE) WITH A CLEAR ZONE SEPARATING IT FROM THE LIMBUS
79
How is band keratopathy managed?
TREAT UNDERLYIN CAUSE CHELATION WITH EDTA
80
What are corneal dystrophies?
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
What is cogan dystrophy (map-dot-fingerprint dystrophy)?
MOST COMMON EPITHELIAL DYSTROPHY SPORADIC OR AD INHERITENCE
82
What are the features of cogan dystrophy?
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
What is Reis-buckler dystrophy?
An AD condition that occurs as a result of the replacement of Bowman's layer with connective tissue
84
What are the features of reis-buckler dystrophy?
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
What are the three types of stromal dystrophies?
LATTICE DYSTROPHY GRANULAR DYSTROPHY MACULAR DYSTROPHY
86
What are the features of macular stromal dystrophy?
BILATERAL VISUAL LOSS IN FIRST DECADE GREY, POORLY DEMARCATED OPACITIES IN THE STROMA
87
Describe macular dystrophy
MARILYN MONROE ALWAYS: - MUCOPOLYSACCHARIDE ACCUMULATION IN STROMA - MACULAR DYSTROPHY - ALCIAN BLUE USED TO STAIN MUCOPOLYSACCHARIDES
88
Describe granular dystrophy
Gets Her Men: GRANULAR DYSTROPHY HYALINE DEPOSITS IN THE STROMA MASSON TRICHOME IS USED TO STAIN HYALINE
89
Describe the features of granular dystrophy
DVA AND RECURRENT CORNEAL EROSIONS BREADCRUMB-LIKE OPACITIES IN AN OTHERWISE HEALTHY STROMA
90
Describe lattice dystrophy
LA COUNTY - LATTICE DYSTROPHY - AMYLIOD DEPOSITS IN THE STROMA - CONGO RED IS USED TO STAIN AMYLOID (GREEN BIREFRINGENCE IN POLZARIXED LIGHT)
91
Describe the features of lattice dystrophy
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
Describe fuchs endothelial dystrophies
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
What are the features of fuchs' corneal dystrophy?
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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