The cornea Flashcards
what are the layers of the cornea ?
the epithelium
bowman’s layer
the stroma
descement membrane
dua layer
the endothelium
when does bacterial keratitis usually develop ?
when ocular defenses have been compromised
what are the most common causative organisms associateed with bacterial keratitis ?
pseudomonas aeruginosa
staph aureus
S. pyogens
what are the risk factors associated with bacterial keratitis ?
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
what are the symptoms associated with bacterial keratitis ?
pain
photophobia
blurred vision
mucopurulent discharge
what are the signs associated with bacterial keratitis ?
epithelial defects with infiltrates
stromal oedema and descement membrane folds
anterior uveitis with a hypopyon
chemosis and eyelid swelling
severe ulceration
what aree the investigatiions for cases of bacterial keratitis ?
corneal scraping
conjuctival swabs
contact lens cases
gram staining
culture and sensitivity
what is the treatment for bacterial conjunctivitis ?
refer to an opthalmologist
topical antibiotics - broad spectrum ciprofloxacin
mydriatics - to avoiid posterior synechiae
when should systemic antibiotics be administered in cases of bacterial conjunctivitis ?
in systemic involvement
severe corneal thinning and perforation
or scleral involvement
what type of infection does HSV1 cause vs HSV2 ?
HSV-1 infection above the waist
HSV-2 genital infection , or may occur to newborns through vaginal births
difference between primary and secondary infection in herpes ?
primary - never been exposed to the virus
secondary - virus is latent and resides in the neuronal ganglia now
what are the symptoms associated with Herpes simplex keratitis ?
mild to moderatee discomfort
redness
photophobia
watering
blurred vision
what are the signs associated with herpes simplex keratitis ?
reduced visual acuity
opaque epithelial cells arranged in a punctate or stellate pattern
central desquamation resulting in dendritic ulcers
reduced corneal sensation
follicular conjunctivitis
how can dendritic ulcers be seen ?
dendritic bed is stained with fluroscein
whilst the border stains well with rose bengal
what must be taken into consideration when using topical steroids in herpes simplex keratitis ?
too much steroiid use can promote progressive enlargement of the ulcer to a geographical or ameboid ulcer
what investigations should be done in cases of herpes simplex keratitis ?
usually unnecessary its more of a clinical diagnosis
PCR if needed
what is the treatment for herpes simplex keratitis ?
refer to an opthalmologist
topical acyclovir
debridement may be useful for resistant cases
cycloplegia
when should oral therapy be used for cases of herpes simplex keratitis ?
oral acyclovir in
immunocompromiised
children
patients with ocular surface disease
what is meant by cycloplegia ?
paralysis of the ciliiary muscles to prevent posterior synechiae
what is the most appropriate management for a case of glaucoma and herpes simplex keratitis at the same time ?
prostaglandin analogues should be avoided
what is acanthomoeba often confused for ?
herpes simplex keratitis
what are the symptoms of acanthamoeba ?
blurry vision and discomfort
washes lenses with tap water
pain is often severe and not proportionate to the clinical signs
what are the signs associated with acanthamoeba ?
epithelial pseudo dendrites - resembling herpetic lesions
radial keratoneuritis
ring abscess
corneal melting
what investigatiions are performed in cases of acanthamoeba ?
staining of corneal scraping with periodic acid-schiff
corneal biopsy may be needed
what is seen on corneal biopsies in acanthamoeba ?
cysts in the cornea
what is the treatment for acanthamoeba ?
PHMB, Chlorhexidine - both topical amoebicides
debrideement of involved epithelium
pain control with oral NSAID
therapeutic keratoplasty may be needed for resistant cases
how does keratoconus happen ?
central or paracentral corneal thinning resulting in a cone shaped cornea
at what age group is the presentation common ?
teens to twenties and only in one eye
what are the systemic associations of keratoconus ?
Down’s
osteogenesis imperfecta
Ehlers Danlos
Marfan’s syndrome
what are the symptoms of keratoconus ?
progressive myopia and astigmatism
what is the first presentation of keratoconus ?
acute hydrops
what are the signs of keratoconus ?
oil droplet reflex
scissoring sign on retinoscopy
Vogt striae
Munson sign
what are the investigatiion for keratoconus ?
corneal topography
keratometry - steep readings
what is the pattern of normal corneal astigmatism ?
bow tie shaped
what is the treatment for keratoconus ?
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
what must be routinely checked before performing LASIK surgery ?
corneal thickness
so keratoconus patients are contraindicated for LASIK
what is the age related degenration of the cornea ?
arcus senilis
what are thee types of corneal opacities ?
nebular CO
Macula CO
Leucomatous CO
what are the differences between the different types of corneal opacities ?
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
