Download CORNEA

CORNEA
ANATOMY
&
PHYSIOLOGY
Three Coats of Eye Ball
1.OUTER COAT
2.MIDDLE COAT
3.INNER COAT
Outer Coat
Tough Fibrous Coat
Post 5/6th of Globe
White & Opaque
Sclera
Radius---12mm
Outer Coat
Tough Fibrous Coat
Ant 1/6th of Globe
Transparent
Cornea
Radius---8mm
Corneoscleral Limbus
Junction of Cornea and Sclera
Contains
1.Trabecular Meshwork
2.Canal of Schlemn
Size of Cornea
Verticle-------10.6 mm
Horizontal---11.7 mm
Thickness
Central portion----0.52 mm
Peripheral portion----1 mm
Structure
Three Layers
1. Epithelium & its Basement
2. Stroma & its ant condensation
( Bowman Zone)
3.Endothelium & its Basement
(Descemet Membrane)
Layers of Cornea
Structure
From Anterior to Posterior
1.
2.
3.
4.
5.
Epithelium
Bowman Zone
Stroma
Descemet Membrane
Endothelium
Epithelium
• 50-60 µm thick
• Covers the stroma anteriorly
• Continuous with epithelium of
conjunctiva
• Life of epithelial cells is 7 days
• Prevent aqueous solutions to
penetrate
Epithelium
• Surface cell layer
• Wing cell layer
• Basal cell layer
• Basement membrane
Stroma
90% of the corneal thickness
• Bowman Zone
• Lamellar Stroma
Once deformed its typical
structure is not restored
Inner Lining
• Descemet membrane
(Regenerates)
• Endothelium
Single layer of cells
Cells are tightly bound together
Responsible for dehydration
Never regenerates
Blood supply
• Central cornea is avascular
• Corneoscleral limbus is
generously supplied by anterior
conjuntival branches of the
anterior ciliary arteries
• Aqueous humor and tear film
provides nutrients
Nerve Supply
• Branches of the ophthalmic division
of trigeminal nerve and are solely
sensory
• Most are concentrated in the
anterior stroma beneath the
Bowman zone and send branches
forward into epithelium
• Descemet membrane and
endothelium are not innervated
Cornea
• The microvilli of the anterior
surface of the squamous cell
layer are wet by the mucin of
tear film
• These cells are joined by tight
junctions that exclude water
soluble substances
Transparency
• Tight junctions of the epithelial
cells
• Endothelial pump mechanism
• Absence of blood vessels
• Absence of pigments
• Scarcity of cell nuclei in stroma
• Regular structure of stroma
Signs of Corneal Disease
Superficial
1.Punctate epithelial erosions
Tiny ,slightly depressed, epithelial
defects which stain with flourescein
but not with rose Bengal
PEE are non specific and may
develop in a wide variety of
keratopathies
Signs of Corneal Disease
Superficial
2.Punctate epithelial keratitis
It is the hallmark of viral
infections.
• Swollen epithelial cells
• Visible unstained
• Stains with rose bengal
Signs of Corneal Disease
Superficial
3.Epithelial Oedema
Sign of
• Endothelial decompensation
• Severe acute elevation of IOP
Signs of Corneal Disease
Superficial
4.Filaments
Small coma shaped mucus
strands lined with epithelium.
One end attached with epithelium
Signs of Corneal Disease
Superficial
5.Pannus
Inflammatory or degenerative
ingrowth of fibro vascular tissue
from limbus
Signs of Corneal Disease
Stromal Lesions
1.Infiltrates
Focal areas of active stromal
inflammation
2. Oedema
Increased corneal thickness
Decreased transparency
3. Vascularization
Signs of Corneal Disease
Lesions of Descemet Membrane
1.
Breaks
Corneal enlargement
Keratoconus
Birth trauma
2. Folds (Striate Keratopathy)
Surgical trauma
Ocular hypotony
Stromal oedema
PRINCIPLES OF
MANAGEMENT OF
CORNEAL DISEASE
•
•
•
Control of infection
Control of inflammation
Promotion of re-epithelialization
– lubrication
– lid closure
– bandage soft contact lens
• Prevention of perforation
– tissue adhesive glue
– conjunctival flap
– systemic immunosuppressive agents
• Corneal grafting
MICROBIAL KERATITIS
( Bacterial)
• Ocular surface disease: Trauma,
post-herpetic corneal disease,
bullous keratopathy, corneal
exposure, dry eye and
diminished corneal sensation.
• Contact lens wear
MICROBIAL KERATITIS
( Bacterial)
Pathogens which can produce
corneal infection in intact
epithelium.
• 1.Neisseria gonorrhoeae
• 2.Corynebacterium diphtheriae
• 3.Listeria
• 4.Haemophilus
Staph. aureus and strep.
pneumoniae
• Oval, yellow-white, densely
opaque stromal suppuration
surrounded by relatively clear
cornea
Psuedomonas
• Thick mucopurulent exudate,
diffuse liquefactive necrosis
and semi-opaque ground glass
appearance of adjacent stroma
Enterobacteriaceae
• Shallow ulceration, grey-white
pleomorphic suppuration and
diffuse stromal opalescence.
Endotoxins may induce ringshaped corneal infilterates
MANAGEMENT
• History
• Clinical examination (including
staining and sensitivity)
• Hospitalization
• Corneal scrapping
• Treatment
Treatment
• Topical antibiotics – combination
therapy with fortified amino
glycoside and fortified cephalosporin
or monotherapy with
fluoroquinolone. Initial instillation at
hourly intervals.
• Subconjunctival injections
• Systemic ciprofloxacin 750mg BD
• Cycloplegics
• Steroid therapy (controversial)
• Corneal biopsy or excisional
keratoplasty
Poor response to
treatment
• Wrong diagnosis
• Wrong treatment
• Drug toxicity
FUNGAL KERATITIS
• Filamentous fungal keratitis
–Aspergillus
- Fusarium
History of vegetable
matter injury
• Greyish-white ulcer with
indistinct margins
• Surrounded by feathery
infilterates
• Ring infilterate
• Endothelial plaque
• Hypopyon
Candida keratitis
• Usually develops in pre-existing
corneal disease or
immunocompromised patient
• Yellow-white ulcer
• Dense suppuration
D/D of fungal keratitis
• Suppurative bacterial keratitis
• Herpetic stromal necrotic
keratitis
MANAGEMENT
• Culture
• Biopsy
• Antifungal therapy – Initially broadspectrum econazole 1% topically –
Then depending upon sensitivity
natamycin or imidazole for 6 weeks
• Systemic ketoconazole
• Therapeutic penetrating
keratoplasty
ACANTHAMOEBA
KERATITIS
• Protozoan
–active (trophozoite)
–dormant (cystic)
• Common in swimmers and CL
wearers
CLINICAL FEATURES
• Blurred vision and disproportionate
pain
• Patchy anterior stromal infilterates
• Perineural infilterates (radial
keratoneuritis)
• Infilterates coalesce –ring abcess,
ulceration and hypopyon
• White satellite lesions
MANAGEMENT
• Corneal scrappings stained with
calcoflour white
• Corneal biopsy
• Treatment with chlorhexidine,
polyhexamethylenebiguanide drops,
dipropamidine and propamidine.
• Therapeutic penetrating
keratoplasty
HERPES SIMPLEX
KERATITIS
Primary ocular herpes:
- Blepharoconjunctivitis
- Keatitis (punctate epithelial)
DENDRITIC ULCER
• Opaque cells arranged in a course
punctate or stellate pattern
• Central desquamation leads to a
linear branching ulcer.
–Fluorescein stain
– Rose Bengal stain
–Diminished corneal sensitivity
• Anterior stromal infilterates
• Geographical or amoeboid ulcer
Differential diagnosis
• Herpes zoster keratitis
• Healing corneal abrasion
• Pseudodendrites due to soft
contact lens
• Acanthamoeba keratitis
• Drug toxicity
TREATMENT
• Antiviral therapy
– Acycloguanosine 3% ointment
– Trifluorothymidine 1% drops
– Adenine arabinoside 3% ointment,
0.1% drops
– Idoxuridine
• Debridement (with sterile cottontipped bud 2mm beyond the edge of
ulcer)
OTHER ENTITIES
• Stromal necrotic keratitis
• Disciform keratitis
PHLYCTENULOSIS
• Predominantly affects children
• Etiology
– Tuberculosis
– Delayed hypersensitivity
reaction to staphylococcal or
other bacterial antigen
PRESENTATION
• Photophobia, lacrimation and
blepharospasm.
SIGNS
• Conjunctival: Pinkish-white
nodule surrounded by
hyperaemia
• Corneal: May resolve
spontaneously or extend
radially to the cornea. May
cause severe ulceration or
perforation.
TREATMENT
• Short course of topical steroids
• Topical antibiotics
KERATOCONUS
• Onset at puberty
• Central or paracentral stromal
thinning
• Apical protrusion
• Irregular astigmatism
• Autosomal dominant
transmission with incomplete
penetrance proposed
CLASSIFICATION
• By keratometry:
- Mild (< 48 D),
- moderate (48-54 D)
- severe (> 54 D)
• By morphology:
- Nipple cones
– Oval cones
– Globus cones
Early signs
• Ophthalmoscopy: Oil droplet reflex
• Retinoscopy: Irregular scissor reflex
• Keratometry: Irregular astigmatism
(principal meridians no longer 90
degree apart and mires cannot be
superimposed)
• Placido disc: Irregular reflected ring
• Slit-lamp: Very fine deep stromal
striae (Vogt lines).
LATE SIGNS
• Decreased
visual acuity
• Munson sign
• Fleischer ring
• Corneal scarring
• Acute hydrops
Keratoglobus
MANAGEMENT
• Spectacle correction
• Contact lenses
• Penetrating keratoplasty