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opthalmology > The cornea > Flashcards

The cornea Flashcards

1
Q

what are the layers of the cornea ?

A

the epithelium
bowman’s layer
the stroma
descement membrane
dua layer
the endothelium

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2
Q

when does bacterial keratitis usually develop ?

A

when ocular defenses have been compromised

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3
Q

what are the most common causative organisms associateed with bacterial keratitis ?

A

pseudomonas aeruginosa
staph aureus
S. pyogens

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4
Q

what are the risk factors associated with bacterial keratitis ?

A

contact lens wear
trauma including refractive surgery, agricultural injury
ocular surface disease such as herpetic eye disease, dry eyes
systemic immunosuppression and vitamin A deficiency

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5
Q

what are the symptoms associated with bacterial keratitis ?

A

pain
photophobia
blurred vision
mucopurulent discharge

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6
Q

what are the signs associated with bacterial keratitis ?

A

epithelial defects with infiltrates
stromal oedema and descement membrane folds
anterior uveitis with a hypopyon
chemosis and eyelid swelling
severe ulceration

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7
Q

what aree the investigatiions for cases of bacterial keratitis ?

A

corneal scraping
conjuctival swabs
contact lens cases
gram staining
culture and sensitivity

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8
Q

what is the treatment for bacterial conjunctivitis ?

A

refer to an opthalmologist
topical antibiotics - broad spectrum ciprofloxacin
mydriatics - to avoiid posterior synechiae

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9
Q

when should systemic antibiotics be administered in cases of bacterial conjunctivitis ?

A

in systemic involvement
severe corneal thinning and perforation
or scleral involvement

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10
Q

what type of infection does HSV1 cause vs HSV2 ?

A

HSV-1 infection above the waist
HSV-2 genital infection , or may occur to newborns through vaginal births

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11
Q

difference between primary and secondary infection in herpes ?

A

primary - never been exposed to the virus
secondary - virus is latent and resides in the neuronal ganglia now

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12
Q

what are the symptoms associated with Herpes simplex keratitis ?

A

mild to moderatee discomfort
redness
photophobia
watering
blurred vision

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13
Q

what are the signs associated with herpes simplex keratitis ?

A

reduced visual acuity
opaque epithelial cells arranged in a punctate or stellate pattern
central desquamation resulting in dendritic ulcers
reduced corneal sensation
follicular conjunctivitis

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14
Q

how can dendritic ulcers be seen ?

A

dendritic bed is stained with fluroscein
whilst the border stains well with rose bengal

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15
Q

what must be taken into consideration when using topical steroids in herpes simplex keratitis ?

A

too much steroiid use can promote progressive enlargement of the ulcer to a geographical or ameboid ulcer

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16
Q

what investigations should be done in cases of herpes simplex keratitis ?

A

usually unnecessary its more of a clinical diagnosis
PCR if needed

17
Q

what is the treatment for herpes simplex keratitis ?

A

refer to an opthalmologist
topical acyclovir
debridement may be useful for resistant cases
cycloplegia

18
Q

when should oral therapy be used for cases of herpes simplex keratitis ?

A

oral acyclovir in
immunocompromiised
children
patients with ocular surface disease

19
Q

what is meant by cycloplegia ?

A

paralysis of the ciliiary muscles to prevent posterior synechiae

20
Q

what is the most appropriate management for a case of glaucoma and herpes simplex keratitis at the same time ?

A

prostaglandin analogues should be avoided

21
Q

what is acanthomoeba often confused for ?

A

herpes simplex keratitis

22
Q

what are the symptoms of acanthamoeba ?

A

blurry vision and discomfort
washes lenses with tap water
pain is often severe and not proportionate to the clinical signs

23
Q

what are the signs associated with acanthamoeba ?

A

epithelial pseudo dendrites - resembling herpetic lesions
radial keratoneuritis
ring abscess
corneal melting

24
Q

what investigatiions are performed in cases of acanthamoeba ?

A

staining of corneal scraping with periodic acid-schiff
corneal biopsy may be needed

25
Q

what is seen on corneal biopsies in acanthamoeba ?

A

cysts in the cornea

26
Q

what is the treatment for acanthamoeba ?

A

PHMB, Chlorhexidine - both topical amoebicides
debrideement of involved epithelium
pain control with oral NSAID
therapeutic keratoplasty may be needed for resistant cases

27
Q

how does keratoconus happen ?

A

central or paracentral corneal thinning resulting in a cone shaped cornea

28
Q

at what age group is the presentation common ?

A

teens to twenties and only in one eye

29
Q

what are the systemic associations of keratoconus ?

A

Down’s
osteogenesis imperfecta
Ehlers Danlos
Marfan’s syndrome

30
Q

what are the symptoms of keratoconus ?

A

progressive myopia and astigmatism

31
Q

what is the first presentation of keratoconus ?

A

acute hydrops

32
Q

what are the signs of keratoconus ?

A

oil droplet reflex
scissoring sign on retinoscopy
Vogt striae
Munson sign

33
Q

what are the investigatiion for keratoconus ?

A

corneal topography
keratometry - steep readings

34
Q

what is the pattern of normal corneal astigmatism ?

A

bow tie shaped

35
Q

what is the treatment for keratoconus ?

A

eye rubbing should be avoided
spectacles or soft lenses in the beginning
hard lenses if late presentation
corneal cross linkage
Intracorneal ring segments
keratoplasty - penetrating or DALK

36
Q

what must be routinely checked before performing LASIK surgery ?

A

corneal thickness
so keratoconus patients are contraindicated for LASIK

37
Q

what is the age related degenration of the cornea ?

A

arcus senilis

38
Q

what are thee types of corneal opacities ?

A

nebular CO
Macula CO
Leucomatous CO

39
Q

what are the differences between the different types of corneal opacities ?

A

nebular - fog or mist details of the iris can be seen
Macular - spot or stain , half of the cornea is included
Leucomatous - white , more than half of the cornea is included

opthalmology (14 decks)

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