cornea Flashcards
define and RFsbacterial keratitis
Bacterial infection of the cornea is common and sight-threatening.
epithelial defect -> entrance into stoma -> inflammation
It is more common in contact lens wearers (soft lenses > rigid lenses), especially with overnight wear and poor lens hygiene.
common organisms of bacterial keratitis
RFs for bacterial kertatitis
● Pseudomonas aeruginosa (most common cause of keratitis in contact lens wearers). - GRAM -VE BACILLI
● Staphylococcus aureus and Streptococci infections.
GRAM POSITIVE COCCI
grown on blood agar
RFs
- contact lens wearer
- trauma
- contaminated eye drops
- immunosuppresion
clinical features of bacterial keratitis
presentation
● Unilateral sudden-onset pain, redness, blurred vision and photophobia with associated discharge and dVA.
● Purulent or mucopurulent discharge.
SIGNS
stromal oedema
● Circumcorneal injection.
● White infiltrates epithelial and stromal involvement.
● Anterior chamber cells and
rapid progression of infiltration hypopyon in severe keratitis.
- epithelial defect w infiltration
complications of bacterial keratitis
organisms doesn’t cause epithelial defect
Corneal perforation; this is more likely with the following organisms additionally they do not need epithelial defect
● Neisseria gonorrhoeae
● Corynebacterium diphtheriae
● Haemophilus influenzae
Ix for bacterial keratitis
corneal scrapping (blood/chocolate agar)
- staph aureus grown on blood agar forming golden colonies with a shiny surface
- neiserriea gonorrhoea grown on chocolate agar
gram/giesma stain
Most bacteria Fungi Mycobacterium Acanthamoeba
INVESTIGATIONS
Blood/chocolate agar and gram/Giemsa stain Sabouraud agar and gram/Giemsa stain Ziehl-Neelsen stain and Lowenstein Jensen medium Non-nutrient agar with Escherichia coli
Mx of bacterial keratities
• Usually 7 day topical antibiotic course, initially hourly day and night for 2 days then taper.
1st line:
• Topical fluorquinolones (levofloxacin and moxifloxacin)
Symptomatic control:
• Topical cycloplegic (cyclopentolate, atropine) for comfort + to prevent posterior synechiae if marked inflammation.
fluoroquinolones - ciprofloxacin
discontinuation of contact lens
mydriatics - prevent formation of posterior synaechiae and to reduce pain
causes and RFs of fungal keratitis
yeasts - Candida
RFs who are immunocompromised (AIDS diabetics immunosuppressant such as steroids). contact lens
Filamentous fungi such as Aspergillus or Fusarium - ocular trauma, classically from contaminated plant matter or a tree branch.
features of fungal keratitis
specifically for
candida
filamentous
unilateral redness
tearing
blurred vision
mild pain
photophobia.
● Candida: Small ulcer with an expanding infiltrate in a ‘collar stud’ formation.
● Filamentous: Feathery branching-like infiltrate pattern.
ix for fungal keratitis
scrapings for microscopy
corneal biopsy if Sx does not improve after 3-4 days
confocal microscopy
Mx of fungal keratitis
● Natamycin drops for proven filamentous.
● Voriconazole or amphotericin B drops for proven Candida.
acanthamoeba keratitis
acanthamoeba
RFs - improper lens hygiene (showering/swimming in contact lenses).
features of acanthamoeba keratitis
● with pain that is out of proportion to clinical signs, - photophobia
- blurred vision.
● In early disease - not specific to Acanthamoeba. mistaken for HSV due to dendrites
Late disease, perineural infiltrates and ring-shaped stromal infiltrates can be seen.
Ix for acanthameoba keratitis
corneal scrapping - periodic aid-schoff or caloflour white
confocal miscroscopy - identify amoebic cysts
grown on non-nutrient agar seeded with ecoli
Mx for acanthamoeba keratitis
debridement
topical polyhexamethylene biguanide or chlorhexidine.
what is HSV keratitis
DSDNA
HSV 1 - anything above the waist
HSV 2 - anything sexual
Primary infection results in blepharoconjunctivitis.
Latent in the trigeminal ganglion.
Reactivation usually results in recurrent keratitis.
Keratitis may affect the epithelial, stromal or endothelial layers of the cornea.
features of epithelial keratitis
Reactivation of the HSV presents
- pain
- dVA
- lacrimation
- foreign body sensation.
- blurred vision
signs of epithelial keratitis
histology
● Superficial punctate keratitis which
1) causes a stellate (star-shaped) erosion
2) classic dendritic ulcer which can be clearly seen with fluorescein. (Note: Epithelial cells at the dendrite margin stain well with rose Bengal.)
• Rose Bengal stains heaped-up epithelium/ Fluorescein stains ulcer
● Reduced corneal sensation.
- topical steroid may worsen it and cause geographic ulcer which is bigger
- elevated IOP may occur
histology
intranuclear inclusions bodies
what is disciform keratitis (endothelial)
hypersensitivity reaction to viral antigen, rather than reactivation
presentation of disciform keratitis
insidious onset of painless dVA.
ass w haloes around lights
signs of disciform keratitis
● Central circular stromal oedema
● There is usually mild anterior chamber activity
● Keratitic precipitates
● Wessely ring: Antigen/antibody complex
Ix of disciform keratitis
aided by corneal swabs for PCR or Giemsa staining which shows multinuclear giant cells.
Mx of epithelial keratitis
Topical acyclovir.
Avoid steroids: May lead to geographic ulcer and corneal perforation.
Mx of disciform keratitis
- Oral acyclovir 400 mg five times a day and low dose steroids
- Avoid topical steroids until epithelium is intact. Use the lowest effective dose of dexamethasone or prednisolone if indicated.
herpes zoster opthalmicus infection caused by
varicella zoster virus (VZV). Primary infection usually leads to chickenpox.
reactivation leads to shingles (herpes zoster) of the affected dermatome. Thus, HZO refers to shingles affecting the dermatome supplied by CNV1
cutaneous features of herpez zoster opthalmicus
- malaise, fever, headache
● Rash (vesicles or papules).
● Painful neuralgia.
● Hutchinson sign: Involvement of the tip of the nose. Indicates a higher
likelihood for ocular disease due to the involvement of the nasociliary nerve.
opthalmic features of HZO and what differentiates HZO from HSV
● Epithelial keratitis: Pseudo-dendrites are the differentiating feature from HSV keratitis. - grey, not ulcerated - less branching - lacking in terminal bulbs. - These stain poorly with fluorescein. ● Conjunctivitis. ● Elevated IOP. ● Stromal and disciform keratitis are less common.
chronically - neutrotriphic keratitis
Mx of HZO
● Oral acyclovir 800 mg five times a day.
● Amitriptyline for neuropathic pain.
what is interstitial keratitis
stromal inflammation WITHOUT PRIMARY INVOLVEMENT OF EPITHELIUM OR ENDOTHELIUM ± neovascularization
pathophysiology of interstitial keratitis
invasion of microorganism or an immune reaction to a foreign antigen.
features of interstitial keratitis
● Pain, dVA and photophobia.
● Non-ulcerated stromal keratitis characterized by feathery mid-stromal
scarring with ghost vessels.
aetiology of interstitial keratitis
syphillis
lyme disease
viral - HSV and VZV, EBV
cogan syndrome
syphillis features of interstitial kertatitis
TREPONEMA PALLIDUM
Congenital disease usually causes bilateral corneal involvement, while acquired disease is usually unilateral.
acutely - anterior uveitis and blurring of vision
Hutchinson triad of congenital syphilis (late feature): Interstitial keratitis, notched teeth and sensorineural deafness.
SIGNS
- obscuration of perfused vessles - ‘salmon-patch’ appearance
- corneal clouding
- vessles become non perfused - GHOST VESSELS
- healed - stromal scarring
Treatment: IM benzylpenicillin and topical steroids.
lyme disease features for interstitial keratitis
Caused by the spirochete bacteria Borrelia, which is transmitted to humans via a tick bite.
Causes erythema migrans (bull’s-eye skin rash), arthralgia, facial palsy, loss of temporal eyebrows and interstitial keratitis.
cogan syndrome features of interstitial keratitis
complications
mx
Autoimmune disorder.
- intraocular inflammation
- vestibuloauditory dysfunction
Interstitial keratitis with sensorineural hearing loss, vertigo and tinnitus.
- redness, pain, photophobia and blurred vision
Complications: Polyarteritis nodosa.
Mx - topical steroids
what is marginal keratitis
A type of peripheral corneal inflammation due to a type III hypersensitivity reaction to staphylococcal exotoxin, mainly Staphylococcus aureus.
marginal keratitis is ass wi what
rosacea and blepharitis
Features of marginal keratitis
signs
● Epiphora, redness and photophobia.
SIGNS
● Chronic blepharitis.
● Subepithelial infiltrates separated from the limbus by a clear zone.
● Typically occurs in regions where the eyelid contacts the cornea.
Mx of marginal keratitis
lid hygiene and weak topical steroids
what is peripheral ulcerative keratitis
group of conditions that leads to peripheral corneal thinning.
most common system ass w peripheral ulcerative keratitis
rheumatoid arthritis.
Other associations include polyarteritis nodosa, Wegener granulomatosis and relapsing polychondritis.
signs of peripheral ulcerative keratitis
- crescenteric ulceration and stromal infiltration at the limbus
● Episcleritis and/or scleritis may be present.
● The disease usually begins peripherally, but eventually progresses centrally and posteriorly. - End stage is a thin vascular cornea. - ‘contact lens cornea’
● Interpalpebral peripheral corneal stromal thinning with an epithelial defect.
Mx of peripheral ulceratu
Oral prednisolone ± systemic immunosuppression. Note that topical steroids may exacerbate the thinning.
features of acne rosacea
telangiectasia, papules and pustules on the face, facial flushing and rhinophyma.
ocular rosacea
ocular features of ance rosacea
● Dry eyes, redness, epiphora and photophobia
● Eyelids: Telangiectasia and posterior blepharitis
● Conjunctival hyperaemia
● Cornea
- Marginal keratitis - inferior
- Inferior corneal thinning
- Superficial erosions
- Peripheral corneal vascularization
Mx of ocular rosacea
● Lid hygiene and hot compression
● Topical lubricants
● Oral tetracycline
define filamentary keratopathy
corneal epithelium degenerates, leading strands/ filaments and mucus to adhere to the corneal surface.
RFs of filamentary keratopathy
● Dry eye syndrome
● Corneal epithelium erosions
● Laser eye surgery
● Contact lens wear
features of filamentary keratitis
● The main presenting feature is foreign body sensation.
● Redness, epiphora and blepharospasm and dry eyes.
● ‘Comma-shaped’ lesions (strands of epithelial cells) that move up and down
on blinking which
- stains well with rose bengal stains.
what is keratoconus
This is a bilateral and asymmetrical condition characterized by progressive central stromal thinning and apical protrusion of the cornea, usually presenting in early adulthood.
associations of keratoconus
● Down syndrome ● Marfan syndrome ● Ehlers-Danlos syndrome ● Leber congenital amaurosis ● Retinitis pigmentosa ● History of atopy
features of keratoconus
- unilateral impairment of vision due to progressive myopia
● Irregular astigmatism.
● Lower eyelid protrusion on downgaze (Munson sign).
SIGNS
● Vertical striations in the stroma, seen on slit lamp (Vogt striae).
● Iron deposit often within the epithelium around the base of the cone
(Fleischer ring) = best seen with cobalt blue filter
● ‘Oil drop’ reflex on ophthalmoscopy.
● ‘Scissoring’ reflex on retinoscopy.
CONES Central Scarring & Fleischer Ring Oil Drop Reflex / edema (hydrops) Nerves prominent Excessive bulging of lower lid on down gaze (Munson’s Sign) Striae (Vogt’s)
complication of keratoconus
Acute hydrops
● Tear in Descemet membrane leading to corneal oedema.
● Presentation: dVA, pain and photophobia.
Ix of 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 asymmetrical ‘bow-tie’ pattern in early disease and progresses into a steep cone that is displaced off the visual axis.
Mx of keratoconus
● Mild: Spectacle correction.
● Moderate: Rigid/hard contact lenses or corneal collagen cross-linking using
riboflavin drops and ultraviolet-A.
● Severe: Penetrating or deep anterior lamellar keratoplasty.
● LASIK is generally contraindicated.
what is microphtthalmia
A condition in which the whole eye is smaller than the average by at least two standard deviations.
what is simple microphthalmos
- Bilateral involvement; the eye is small but otherwise normal.
- Associated with angle-closure glaucoma, uveal effusion syndrome, hypermetropia, amblyopia and strabismus.
what is complex micropththalmos
- A small eye associated with other abnormalities including orbital cysts or colobomas (hole in ocular structure).
- Associated with fetal alcohol syndrome and intrauterine infections.
what is wilson disease
An AR genetic disorder causing deposition of copper in the body. The most common areas affected are the liver, brain and eyes.
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 subcapsular sunflower cataracts.
what is band keratopathy
calcium deposition in the Bowman’s layer.
aetiology of band keratopathy
● Idiopathic ● Old age ● Hypercalcemia and hyperphosphatemia (renal failure) ● Silicone oil ● Chronic anterior uveitis
features of band keratopathy
● Often asymptomatic.
● Interpalpebral peripheral zone calcification (band-like chalky plaque) with a
clear zone separating it from the limbus.
Mx of band keratopathy
● Treat underlying cause.
● Chelation with ethylenediaminetetraacetic acid (EDTA).
what is corneal dystrophies
A group of progressive, hereditary disorders that cause corneal opacification and can lead to visual impairment. They can be classified as anterior (predominantly affecting the epithelium), stromal or endothelial.
what is cogan dystrophy
comes under
common epithelial dystrophy - sporadic or
anterior dystrophy
features of cogan dystrophy
best seen using which lamp
signs seen
Onset is normally in the second decade with bilateral recurrent corneal erosions (recurrent pain, photophobia and epiphora). Signs are best seen on retroillumination slit lamp.
● Map: Subepithelial geographic opacities
● Dot: Intraepithelial microcysts
● Fingerprint: Subepithelial ridges
what is reis buckler dystrophy
An AD condition that occurs as a result of the replacement of Bowman’s layer with connective tissue.
features of reis buckler dystrophy
examination findings
Presents with recurrent corneal erosions in childhood. These become less painful with age due to decreased corneal sensation. Examination may reveal subepithelial cloudy opacities centrally.
what is stromal dystrophies
lattice dystrophy
granular dystrophy
macular dystrophy
mnemonic ‘Marilyn Monroe Always Gets Her Men in LA County
three words for each
features of macular dystrophy
‘Marilyn Monroe Always’: Macular dystrophy
Mucopolysaccharide accumulation in the stroma
Alcian blue is used to stain the mucopolysaccharides.
● Bilateral visual loss in the first decade of life.
● Grey, poorly demarcated opacities in the stroma.
features of granular dystrophy
‘Gets Her Men’:
Granular dystrophy
Hyaline deposits in the stroma
Masson trichome is used to stain hyaline.
● dVA and recurrent corneal erosions.
● Breadcrumb-like opacities in an otherwise healthy stroma.
features of lattice dystrophy
‘LA County’: Lattice dystrophy, Amyloid deposits in the stroma, Congo red is used to stain amyloid (showing green birefringence on polarized light).
● dVA and recurrent corneal erosions.
● Reduced corneal sensation.
● Examination shows anterior glassy stromal dots, affecting the centre, form
together to form fine filamentous lines.
what is fuch’s endothelial dystrophy
common in who
cause
most common.
Inheritance is sporadic or AD.
COMMON - elderly females.
CAUSE - It is due to a failure of the Na+K+ pump leading to accumulation of fluid in the cornea which leads to endothelial cell loss.
features of fuch’s endothelial dystrophy
● Blurry vision worse in the morning.
● Specular microscopy may show corneal guttata (‘beaten metal’ appearance)
and low endothelial cell counts.
● Pachymetry may show increased central corneal thickness (CCT).
what is the cornea
transparent
avascular structure
separates the anterior chamber posteriorly and the tear film anteriorly
five layers of cornea
epithelium bownman's membrane stroma descemet membrane endothelium
where does cornea gets its nutrients
anteriorly tears
posteriorly aqueous humor
how thick is the cornea horizontal diameter vertical diameter refractive power of cornea central corneal thickness
The human cornea is 500-800um thick horizontal diameter of 11.7mm Average vertical diameter 10.6 mm refractive power of 40 - 44dioptres central corneal thickness 540-554 microns
blood supply for limbus
Supplied by internal carotid artery (anterior ciliary branch of ophthalmic artery) &
external carotid artery (facial branch)
innervation of cornea
Long ciliary nerves (V1) reach the cornea via the limbus
pathophysiology of bacterial keratitis
disruption of epithelium* à entrance into stroma -> inflammation
rare causes of bacterial keratitis
Cornyebacterium, H. influenzae, N.Gonorrhoeae, N. Meningitides, Listeria – these do not need epithelial defect
nmeonic
(CHNL – dig a channel into the cornea!)
pathophysiology of the cornea
direct viral invasion - conju or epithelial keratitis
secondary inflammation
reactivation - necrosis and inflammation in the affected sensory ganglia, neuropathic keratitis
RFs for HZO
Hutchinson sign
age - 60s and 70s
AIDS
what is mooren ulcer
progressive circumfrential peripheral, stromal ulceration with later central spread
signs and features and Mx of mooren ulcer
moderate-severe pain, photophobia and blurred vision
SIGNS
- peripheral ulceration 1/3 of superficial stroma
- circumferential, central stromal thinning
- vascularisation involving bed of ulcer up
- healing stage - thinning, vascularisation and scarring
Mx
- topical steroids and prophylatic ABx
what is exposure keratopathy
result of incomplete lid closure (lagophthalmos)
drying of cornea
signs and Mx of exposure keratopathy
punctate epithelial changes
epithelial breakdown
stromal melting -> leads to perforation
artificial tears
taping the lid closed
tarsorrhaphy
