Cornea REVISION NOTES

Cornea
• transparent ,
• avascular structure,
• forming 1/6th of the outer fibrous coat of eyeball
TONY SCARIA 2010 KMC

• Refractive power is – 43-44 D
• Refractive index – 1.369
• Thickness - Central →550 μm

Microcornea Normal megalocornea
<10mm Anterior Posterior >13mm
Elliptical Circular • Of adult size at birth
• >13 mm @ 2 years of birth
 Marfan syndrome
 Ehlers danlos syndrome
 Apert down syndrome

Cornea
• Most of refraction occurs in anterior surface

Histology of cornea
• 1. Epithelium
• 2. Bowman’s membrane
• 3. Substantia propria or stroma
• 4. Descemet’s membrane
• 5. Endothelium

Anterior epithelium Stratified squamous epithelium
Bowmans membrane • Condensed superficial part of stroma
• Once destroyed it doesnot regenerate
Substantia propria • Collagen fibrils in matrix of proteoglycans
• Thickest layer
Descmets membrane a thin acellular layer that serves as the modified
basement membrane of the corneal endothelium
• Toughest layer
Endothelium • Regeneration occur rapidly after injury
• Contain active pump mechanism in maintaining
transparency of cornea
• Cell density of endothelium  3000 cells/mm2
• Most metabolically active layer

Schwalbes line  termination of descmets
membrane

Metabolism in cornea
• Major pathway of metabolism anaerobic glycolysis
• Metabolically active layers
• Anterior epithelium
• Endothelium  most active

Corneal transparency
Anatomical factors
• Homogenity of refractive index through out
epithelium
• Presence of unmyelinated N fibres
• Peculiar uniform regular arrangement of stromal
lamellae in a regular lattice
• Relative dehydration of cornea, which itself is
maintained by
• a. Anatomic integrity of the endothelium &
epithelium
• b. Endothelial pump removes fluid from the
stroma most important mechanism
 Na+-K+ ATPase pump
• c. Evaporation of water from the tear increases
osmolarity of tear, which draws water from cornea
• d. Normal intra-ocular pressure ( if too high,relative
hydration occurs)TONY SCARIA 2010 KMC

Prominent or enlarged corneal nerves
Systemic diseases Local ocular diosrder
• NF1
• MEN IIb
• Refsum ds
• keratoconus,
• keratitis (most characteristically seen
in acanthamoebic keratitis),
• Fuchs endothelial dystrophy,
• trauma
• congenital glaucoma

Corneal investigations

Pachymeter Measures corneal thickness
Specular microscopy Photographs corneal endothelium and delineates
various cellular characteristics, like size, shape, density
and distribution
Keratometry Measures corneal curvature
Scrapings and Stain • Flourescein stains corneal defects, ulcers
• Rose bengal stains mucus and dead & damaged
cells
Corneal biopsy
Cochet bonnet anesthesiometer Qualitative assessment of corneal sensation

Pachymeter

SPECULAR MICROSCOPY  TO VISUALISE
CORNEAL ENDOTHELIUM

Keratometry  corneal curvature

Fluoroscein stain for corneal ulcer
Rose Bengal stain for corneal
keratinisation dessication

Confocal microscope to study all layers of
cornea

TEAR FILM

• Secreted by • Function • Deficiency
• MUCUS LAYER • Innermost &
thinnest
• Conjunctival
goblet cells
• Crypts of henle
(corneal &
conjunctival
epithelial glands)
• Glands of Manz
• Converts
hydrophobic
corneal surface
into hydrophilic
one
• Hypovitaminosis
(xeropthalmia)
• AQUEOUS LAYER • Thickest part • Main& accessory
lacrimal glands
• Keratoconjunctivi
tis sicca
• LIPID LAYER • Outermost • Meibomian
glands
• Glands of zeis
• Moll glands
• Prevents
evaporation of
aqueous layer
• Extremely rare

Corneal ulcer

Bacterial Keratitis
Corneal ulcer after epithelial injury Capable of penetrating intact epithelium
• Staphyloccus
• Pseudomonas
• Pneumococcus
• Moraxella
• Neisseria gonorrhoea
• Corynebacterium diphtheria
• Haemophilus aegypticus
• Listeria species

commonest organism Staphylococcus
Commonest in India Streptococcus pneumoniae
Commonest organism in contact lens wearers Pseudomonas

Symptom
• Photophobia earliest symptom
• Pain
• lacrimation
• Foreign body sensation
• Blurred vision

Signs
• Blepharospasm
• Ciliary congestion
• corneal ulcer with or without stromal suppuration
• Corneal rings
• In gram negative infection due to infiltrates in stroma in response to
endotoxins
• Hypopyon – May or may not be present (in pneumococcal keratitis
called “ Ulcus serpens”)

Hypopyon
Bacterial Fungal
Mobile Immoblile
Sterile (formed d/t bacterial toxins ) Contain fungus

• Hypopyon corneal ulcer with rapid progression & perforation 
pseudomonas

Complication of bacterial corneal ulcer
• Anterior staphyloma or ectatic cicatrix
• keratocele or descemetocele
• Perforation
• Long standing ulceration→corneal thinning →corneal perforation
→iris may adhere to it ( leucoma adherens) →Pseudo cornea
formation.

Descmetocele
Some ulcers, especially those due to pneumococci
and septic organisms, extend rapidly in depth so that the
whole thickness of the cornea, except Descemet's membrane
and a few corneal lamellae, may be destroyed.
Descemet's membrane, like other elastic membranes,
offers great resistance to inflammatory processes. It is,
however, unable to support the intraocular pressure by
itself and, therefore, herniates through the ulcer as a
transparent membrane called a keratocele or descemetocele

Mycotic corneal ulcer

Fungal Keratitis – (Kerato mycosis)
• Fungal infection –
• Generally associated with trauma to eye with vegetable matter
• Most common fungi in India – Aspergillus fumigatus

CF
• Mild watering, photophobia, redness, pain, mild discharge
• Fungal ulcer- dry like parchment paper
• Greyish white colour
• Wessely ring -around central lesion
• Satellite lesions in periphery
• Associated hypopyon is dirty yellow, infected and fixed

Greyish white dry looking ulcer
Non sterile hypopyon
Feathery finger like extension

Satellite lesion in mycotic ulcer

Wessley ring

wessely immune ring

Diagnosis
•Aspergillaus fumigatus
•Fusarium
Filamentous
hyphae
•Candida
Non
filamentous
hyphae

• Culture
• Sabouraud’s glucose agar
• Czapek- dox medium
• liquid brain- heart infusion broth

Treatment:
• Antifungal therapy – commonly used drugs are
• Topical – Natamycin , fluconazole (0.2%)
• Oral – Fluconazole, Itraconazole in immunocompromised patients, diabetics,
stromal lesions endothelial plaques etc.
• Adjunctive / concurrent therapy
• cycloplegic (1 % atropine )

Herpes simplex corneal ulcer

Primary herpes Recurrent ocular herpes
u/l blepharoconjunctivitis
which characterised by
which is characterised by
vesicles on skin lids
,follicular conjunctivitis
,preauricular
lymphadenopathy &
punctate jeratitis
After primary infection
recurrent ds may involve
any or all of the layers of
cornea
Rx

Primary herpes
• u/l blepharoconjunctivitis
• Vesicles on skin
• Follicular conjunctivitis
• Preaurciular lymphadenopathy
• Punctate keratitis

Punctate epithelial erosions (multiple
superficial erosions)
are the most common manifestation
of viral infections

Recurrent herpes
Epithelial keratitis Stromal keratitis Metaherpetic keratitis
• Corneal vesicles coalesce to
form dendritic or geographic
ulcer
• Dendritic ulcer
• Geographic ulcer
•
• Disciform
keratitis
• Diffuse
stromal
necrotic
keratitis
• Epithelial sterile trophic
ulceration
• Not an active ds but it’s a
mechanical healing problem @
site of previous herpetic ulcer• Damage to
endothelial
cells d/t
hypersensiti
vity reaction
to HSV
antigen

Corneal vesicles
Dendritic ulcer Geographical ulcer

Dendritic ulcer
• Typical lesion of herpes keratitis
• a/w marked diminution of vision

Geographical ulcer / amoeboid ulcer

Damage to endothelial cells d/t
hypersensitivity reaction to HSV antigen

Diffuse stromal necrotic keratitis
Caused by an active disease & tissue
destruction

Primary ocular herpes Recurrent ocular herpes
Epithelial keratitis Stromal keratitis Metaherpetic keratitis
• Topical antiviral to limit
fungal involvement of
cornea
• Cycloplegics
Topical antivirals
(acyclovir /idoxuridine)
Topical steroids are C/I
Topical steroids + topical
antiviral
Neither topical antivirals
nor steroids are useful

Herpes zoster opthalmicus

Herpes zoster opthalmicus
• Involvement of ophthalmic division of trigeminal nerve
• Frontal branch is more commonly involved than lacrimal & nasocilairy
branches
• In patients with depressed CMI
• Cancer / leukemia /AIDS/immunosuppressed organ transplant patient

• Cutaneous lesion along course of nerve
• Ocular lesions
• Conjunctivitis
• Zoster keratitis
• Episcleritis
• Secondary glaucoma
• Associated neurological conditions
• Motor CN palsies  3 4 6 & 7 CN

Corneal lesion 
zoster keratitis
Uveal tract retina sclera
Conjunctivitis  Mc
ocular lesion
• a/c follicular
conjunctivitis
• Punctate keratitis
• Microdendritic
corneal
ulcer(pseudoden
dritic keratitis)
• Nummular
anterior stromal
keratitis
• Disciform
keratitis
• Endothelitis
• Iridocyclitis
• Choroiditis
• Acute retinal
necrosis
• Neuroretinitis
• Sclerokeratitis

Pseudodendrites in HZO
No knobs at the ends

• In c/c HZO
• Neurotrophic keratitis develops decreased corneal sensation

Hutchison sign
• Involvement of tip of nose signifies
increased risk of ocular involvement
• Tip of nose is supplied by external
nasal branch a terminal branch of
nasociliary N

• Corneal lesions:
• 1. Punctate epithelial keratitis – may be associated with filamentary keratitis
• 2. Micro dendritic ulcers ( Pseudo dendrites)  (No Knobs at end)
• 3. Nummular keratitis – Involves superficial stroma
• Complications-
• Cranial nerve palsies
• Optic neuritis
• Post-herpetic neuralgia

Nummular keratitis  superficial keratitis

Rx of HZO
• Oral acyclovir 400mg five times a day for 2 weeks

Acanthamoeba keratitis

Acanthameba keratitis
• Contact lens wearers who use tap water to store lenses are at
increased risk of acanthamoeba keratitis

• Initial epithelial lesion
• typical reticular pttern of
involvement d/t radial
perineuritis
• Pseudodendrites +
• Advanced cases (stromal lesion)
• Central or paracentral ring
lesion

Initial lesions  epidermal lesion Advanced cases  stromal involvement

Pseudodendrites in acanthamoeba keratitis

• Clinical Features
• Blurred vision and pain which is characteristically severe and
disproportionate to the extent of ocular involvement
• Multifocal patchy anterior stromal infiltrates stromal ring abscess
• Pseudo dendrites
• Stromal thinning and descemetocele
• Radial Keratonuritis (Pain out of propotion to ulcer)

• Calcofluor white : cysts stain bright green
• KOH mount
• Lactophenol blue
• Culture Medium : E.COLI ENRICHED NON NUTRIENT AGAR

• Treatment:
• Combination of dipropamidine and polyhexamethylene biguanide
drops (PHMB)
• Other drugs –
• 1. Propamidine isethionate
• 2. Neomycin

Neuroparalytic
• d/t sensory impairement of Vth CN(trigeminal Nerve)

Interstitial keratitis
• inflammation affecting chiefly the stroma of the cornea
Cogans syndrome Interstitial keratitis and deafness

• Non suppurative inflammation
• Cellular infiltration of stroma

Causes of interstitial keratitis
Viral Bacterial Others
• HSV
• HZV
• EBV
• Mumps
• Measles
• TB
• Syphilis
• LGV
• Leprosy
• Sarcoidosis

Stages of interstitial keratitis
Initial progressive Florid stage Stage of regression
• KP
• Pain / lacrimation
/blepharospasm / circumcorneal
congestion
• Diffuse corneal haziness
ground glass appearance
• Deep vascularisation of cornea
reddish pink salmon patch
appearance
Resolution leaves behind some
opacities & ghost vessels

Ghost vessels in resolution of interstitial
keratitis

Mooren's Ulcer
• peripheral ulcerative
keratitis caused by ischemic
necrosis due to vasculitis of
limbal vessels (caused by
the enzymes-collagenase
and proteoglycans
produced from adjacent
conjunctiva)

Mooren’s ulcer
• Chronic serpiginous ulcer or
• rodent ulcer
• degenerative disease and occurs in old people,
• starting at the corneal margin and spreading over whole of the cornea.
• accompanied by persistent and severe neuralgic pain and lacrimation.
• The ulcer undermines the epithelium and superficial lamellae at the
advancing border and forms a whitish overhanging edge which is
characteristic.
• Rarely this ulcer perforates. It is diagnosis of exclusion

Rx of moorens ulcer
• Excision of a 4-7 mm strip of adjacent conjunctiva may prove
successful by eliminating conjunctival source of collagenase,
proteoglycanase and other inflammatory mediators.
• Topical antibiotics and steroids are usually ineffective.
• If perforation occurs, ulcer debridement, cyanoacrylate adhesive and
soft contact lenses may be tried.
• Lamellar keratoplasty with intravenous methotrexate therapy may
halt the process.

Corneal dystrophy

Corneal dystrophy
Anterior corneal dystrophy Stromal dystrophy Posterior dystrophy
Epithelial dystrophy Bowmans membrane
dystrophy
• Epithelial basement
membrane dystrophy
 MC
• Meesman dystrophy
• Reis –buckler
dystrophy
• Thiel behnke
dystrophy
• Lattice dystrophy 
MC
• Granular dystrophy
• Macular dystrophy
• shnyder crystalline
dystrophy
• Fuchs’ endothelial-MC
(seen in elderly pts)
• Posterior
polymorphous
• Congenital hereditary
endothelial dystrophy
• Rx  phototerapeutic keratectomy • Rx keratoplasty • Rx  keratoplaty

Stromal dystrophy
Macular AR MPS Alcian Blue stain
Granular AD Hyaline Massons trichrome stain
Lattice AD Amyloid deposit Congo red stain
Avellino Hyaline + amyloid Massons trichrome +
congo red
Shnyder crystalline
dystrophy
Cholestrol deposition Oil red O

Fuchs endothelial dystrophy
• Posterior corneal dystrophy
• in elderly people
Stage of cornea
guttate
Edematous stage or
stage of endothelial
decompensation
Stage of bullous
keratopathy
Stage of scarring
• Guttata in central
part of cornea
beaten metal
appearance
• Thickening of
descmets
membrane
• Early stromal
edema &
epithelial
dystrophy
Formation of bullae
following long
standing edema
Opaque &
vascularised cornea
• Rx  5%
hypertonic saline
Bandage soft contact
lens
Penetrating
keratoplastyTONY SCARIA 2010 KMC

Keratoconus

Keratoconus
• more common in females
• inherited as autosomal recessive trait.
• The cornea is thin near the center and progressively bulges forward.
• Although the cornea is at first transparent the vision is impaired due to
protrusion and alteration in curvature. Patients become myopic with
irregular astigmatism
• The condition is almost invariably bilateral.
• 6. Descemet's membrane may rupture.

Keratoconus
• Conical cornea
• Non- inflammatory, bilateral progressive ectasia with thinning of the
central cornea
• d/t defective synthesis of collagen & mucopolysaccharide
• more common in females and is inherited as autosomal recessive
trait.

Descemet's membrane may rupture
Thinning of cornea

• Cental stromal Thinning of cornea
• Descemet's membrane may rupture

Inherited as AR Non inherited
b/l u/l
Inherited as AR In vernal keratoconjunctivitis & down syndrome d/t
repeated rubbing
Conditions a/w keratoconus
• Marfans syndrome
• ehlers danlos syndrome
• Downs syndrome
• RP

CF
• Impaired vision
• Primarily from irregular astigmatism
• Myopia can also occur d/t increase in axial length
• Secondarily from corneal scarring

Myopia in keratoconus

Munson sign in keratoconus
by the acute V shaped bulge given to the lower lid when
the patient looks down (Munsen sign)

Slit lamp
examination
Keratometry Retinoscopy Distant direct
ophthalmoscopy
ultrasonic
pachymetry or the
Orbscan II
corneal topography
system
• vogt’s lines–
vertical folds or
tears in
descemets
membrane
• Opacity at apex
• Fleishers ring @
base of cone
• Irregular
astigmatism
• Scissor reflex
(yawning reflex)
• Oil droplet reflex Corneal thinness
can also be
measured

Vogts striae
• vertical folds or tears in
descemets membrane

• Fleischer’s ring
– iron line
encircling base
of cone
epithelium
A brownish deposition
of iron is formed in the
epithelium encircling
the cone and is known
as Fleischer's ring.

Oil drop sign
• With the ophthalmoscope or plane mirror
at a distance of 1 m a ring of shadow,
concentric with the margin, is seen in the
red reflex (resembling a droplet of oil),
altering its position on moving the mirror.
It is due to a zone through which a few
rays pass into the observer's eye, as the
emergent rays in the centre are
convergent while those on the periphery
are divergent

Yawning reflex or scissor reflex on retinoscopy

Rx
• Spectacles for regular & mild astigmatism
• Rigid gas permeable contact lens
• Epikeratoplasty
• in patients intolerant to lens & with out significant corneal scarring
• Keratoplasty

Band shaped keratopathy
• Band shaped Ca2+ deposition in anterior layers of cornea
• a/w
• blind shrunken eyes
• children suffering from Still disease.
• hyperparathyroidism,
• vitamin D poisoning or sarcoidosis.

Band shaped keratopathy

Rx of band shaped keratopathy
• improvement of vision may be obtained by scraping off the opacity,
which is usually calcareous and quite superficial, or dissolving it with
the sodium salt of ethylenediamine tetra-acetic acid (sodium EDTA).
• phototherapeutic keratectomy
• removed with the excimer laser

Vortex Keratopathy
• Cornea Verticillata
• Symmetrical, bilateral, grayish or
golden corneal epithelial deposits
• CF
• Fabry's disease (Glyco lipidosis)
• Chloroquine
• Amiodarone
• Tamoxifen.
• Indomethacin
• Chlorpromazine

Corneal opacities

Corneal opacities
• Nebular corneal opacity.
• It is a faint opacity which results due to scars involving up to a few superficial
lamellae of corneal stroma
• Macular opacity.
• It is a dense opacity produced by scars involving up to about half the thickness of the
stroma.
• Leucomatous corneal opacity (leucoma- simplex).
• It is a very dense,white opacity, which results due to scarring of more than half
thickness of corneal stroma
• Adherent leucoma.
• It results when healing occurs after perforation of cornea with incarceration of the
iris.

Congenital opacities of cornea

Rx of corneal oapcities
Central nebular Central macular or leukomatous Opacities with blind eye
• Phototherpeutic keratectomy
• Lamellar keratoplasty
• Optical iridectomy • Cosmetic coloured contact lens
• Tattooing

Optical iridectomy in case of central macular
or nebular opacities

corneal tattooing
• India ink  mc used
• Chinese ink
• Gold or platinum chloride
• Carbon impregnation

Photophthalmia
• Keratoconjunctivitis d/t exposure to UV light
• Electric welding equipment
• UV lamp
• Sun
• Snow blindness (d/t reflected UV light from snow)
• Rx
• Cold compresses
• Pad & bandage
• Antibiotic Rx
• Reassuranc e

Corneal vascularisation
Superficial vascularisation Deep vascularisation
• Superficial corneal ulcer
• Trachoma
• Contact lens user
• Rosacea keratitis
• Phlyctenular keratoconjunctivitis
• Interstiital keratitis
• Disciform keratitis
• Deep corneal ulcer
• Chemical burns
• Corneal graft rejection

Decreased corneal sensation
Iatrogenic Congenital & acquired
• Topical drugs  cocaine proparacaine NSAID
timolol
• Sx  cataract & corneal
• Contact lens use
• Corneal dystrophies
• Infections  HSV , HZO,syphilis,leprosy
• Acoustic neuroma

Keratoplasty

Keratoplasty
• Corneal transplantation
• Patients diseased cornea is replaced by healthy clear cornea from
cadaver
• Collected from cadaver from with in 6 hrs of death

Short term preservation Intermediate preservation Long term preservation
With in 48-72 hrs (maxmm 96 hrs) With in 3- 4 days With in 1 year
Referigerated moist chamber @ 4 *
C
Modified MK medium Cryopreservation

c/I of keratoplasty
• Infections like HIV , Hep B , Hep C
• Intraocular malignancies like RB , choroidal melanoma
• rabies
• Septicemia
• Prion disease
• Death from unexplained cause

Types of keratoplasty
Full thickness / penetrating keratoplasty Partial thickness / Lamellar
keratoplasty
Endothelial keratoplasty
Entire tissue from epithelium to endothelium Transplantation of
epithelium & stroma is done
over host endothelium &
descmets membrane
• DSEK
• DMEK
Optical Tectonic Therapeutic
improve vision
→ replace
opaque
cornea with
clear donor
tissue
restore corneal
anatomy in stromal
thinning and
descmetoceles
removes infected
corneal tissue
unresponsive to
antimicrobial /
antiviral rx
Full thickness
corneal
opacity
Perforated corneal
ulcer
• Keratoconus
• Stromal dystrophy
• Corneal opacity
• Endothelial dystrophy
• Bullous keratopthay

Complications
• Graft rejection
• Graft infection
• Secondary glaucoma
• Graft failure

In for Endothelial keratoplasty
• Endothelial dystrophies
• Bullous kertopathy

Thickness of sclera
Thinnest  posterior to inertion of
rectus
Thickest at posterior pole

Scleritis

a/w systemic disorder

Anterior necrotizing scleritis without inflammation
(scleromalacia
perforans)
• elderly females with long-standing RA.
• yellowish patch of melting sclera (due to obliteration of arterial
supply)

Staphyloma

Anterior
staphyloma
Intercalary Ciliary Equatorial Posterior
Protrusion &
adhesion of iris to
ectatic cornea
Occurs at the limbus Affects ciliary zone
(upto 8mm behind
limbus)
@ equatorial region
of eye with
protrusion of
choroid
@ posterior pole 
protrusion of
choroid
Sloughing corneal
ulcer
• Injury to limbus
• Marginal corneal
ulcer
• Scleromalacia
perforans
• Complicated
cataract Sx
• Secondary angle
closure glaucoma
• Scleritis
• Developmental
glaucoma
• Trauma to ciliary
region
• Scleritis
• Degenerative
myopia
• c/c uncontrolled
glaucoma
• Degenerative
high axial
myopia

Ciliary staphyloma

Posterior staphyloma

Cornea REVISION NOTES

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