Cornea

Question 1

Topographical classification of corneal inflammation

Answer 1

Ulcerative keratitis
Depending on
Location(central / peripheral)
Purulence( purulent / non)
Association of hypopyon
Depth of ulcer
Superficial
Deep
With impending perforation
Perforated
Slough formation(sloughing / non)
Non - ulcerative keratitis
Superficial (diffuse / punctate)
Deep
Non-supurative
Suppurative

Question 2

Types of non-ulcerative, deep, non- suppurative keratitis

Answer 2

Iterstitial
Disciform
Keratitis
Sclerosing

Question 3

Types of Non- ulcerative, deep, suppurative keratitis

Answer 3

Central corneal abscess
Posterior corneal abscess

Question 4

Etiological classification of keratitis

Answer 4

Infectious
Non- infectious

Question 5

Types of infectious keratitis

Answer 5

Bacterial
Viral
Fungal
Chlamydial
Protozoal
Spirochaetal

Question 6

Types of Non-infectious keratitis

Answer 6

Allergic (immune mediated)
Trophic
Associated to skin+mucous membrane
Associated to systemic collagen vascular disorders
Traumatic
Idiopathic

Question 7

Types of allergic keratitis

Answer 7

Phlyctenular
Vernal
Atopic

Question 8

Types of trophic keratitis

Answer 8

Exposure keratitis
Neurotrophic keratopathy
Keratomalacia
Atheromatous ulcer

Question 9

Idiopathic keratitis

Answer 9

Mooren’s corneal ulcer
Superior limbic keratoconjunctivitis

Superficial punctate keratitis of Thygeson

Question 10

5 layers of cornea

Answer 10

Epithelium
Bowman’s membrane
Substantia propria ( corneal stroma)
Pre- Decemet’s membrane ( Dua’s layer)
Decement’s membrane
Endothelium

Question 11

Epithelium of cornea

Answer 11

Stratified squamous non-keratinized epithelial.
Continuous with bulbar conjunctiva
5-6 layers
Deepest / basal layer (columnar cells)
2-3 layers (wing / umbrella cells)
Superficial layer (flat cells)
Tight junction prevent tear fluid in stroma.
Ant. Cell wall contain glycocalyx (helps in absorption of mucus layer of tear film) (convert hydrophobic corneal surface into hydrophilic)
Limbal epithelium (limbal stem cells) (amplify, proliferate and differentiate into corneal epithelium)

Question 12

Bowman’s membrane

Answer 12

Acellular mass of condensed collagen fibrils.
Not true elastic membrane
Unable to regenerate
Heals by scarring

Question 13

Substantia propria / stroma of cornea

Answer 13

Collagen fibrils
Lamellae arranged in many layers
Continuous with scleral lamellae
Alternating layers at right angles
Cells (keratocytes, macrophages, histiocytes, leucocytes)

Question 14

Pre - Descemet’s membrane of cornea

Answer 14

Acellular
Very strong
Imprevious to air

Question 15

Descemet’s membrane / post. Elastic lamina)

Answer 15

Resistant (chemicals, trauma, pathological processes)
Descematocele maintain integrity of eyeball.
Collagen
Glycoproteins
Remains in tension state
Curls inwards when torn
As Schwalbe’s line (ring) at trabecular meshwork.

Question 16

Endothelium of cornea

Answer 16

Single layer (flat polygonal epithelial cells)
Corneal decompensation (when >75% cells are lost)
Contains active pump mechanism (keeps cornea dehydrated)

Question 17

Nerve supply of cornea

Answer 17

Long ciliary nerves (br. Of nasociliary)
5th cranial nerve
Nerve loses myelin sheath and form 3 plexuses (stromal, subepithelial, intraepithelial)

Question 18

Factors contributing in corneal transparency

Answer 18

Anatomical
Physiological

Question 19

Anatomical factors in corneal transparency

Answer 19

Epithelium + tear film (homogeneity of refractive index)
Peculiar arrangements of lamella
Peculiar regular refractive index
Avascularity of cornea

Question 20

Physiological factors of corneal transparency (dehydration)

Answer 20

Barrier function ( limiting layers)
Endothelial pumps (most important)
Evaporation
Normal IOP
Swelling pressure (SP)(counters inhibition effect on IOP)
Corneal crystallins (water soluble proteins of keratocytes)

Question 21

Metabolism of cornea

Answer 21

Epithelium
Endothelium

Solutes (glucose)(simple diffusion / active transport)(anaerobic glycolysis)
Oxygen (directly from air via tear film)

Lactica cid accumulate (anaerobic glycolysis)
Corneal hypoxia in contact lens over wear.

Question 22

Anomalies of cornea

Answer 22

Megalocornea ( >13mm horizontal diameter)
Microcornea (< 10mm horizontal diameter)
Cornea plana ( bilateral cornea flat)(marked astigmatic refractive error)

Question 23

Anomalies of Corneal Transparency

Answer 23

Ant. Embryotoxon(broad limbus)
Post. Embryotoxon (thick+displaced Schwalbe’s line)
Congenital corneal opacity
Sclerocornea (cloudy cornea)
Dermoids at limbus

Question 24

Etiology of Bacterial keratitis

Answer 24

Breach in corneal epithelium
Eroded cornea
Trauma (Accidents, assualt, injury, surgery)
Abrasion (Foreign body, contacts)
Epithelial drying (xerosis, exposure)
Epithelial necrosis (keratomalacia)
Epithelial desquamation (oedema)
Trophic changes ( neuroparalytic keratitis)

Topical /systemic steroids
Diabetes mellitus
Immunosupressants
AIDS

Bacterial invasion

Question 25

Pathogens invade INTACT corneal epithelium

Answer 25

N.gonorhhea + meningitidis
C. Diphtheria
Haemophilus aegyptius
Listeria species

Question 26

Causatives of bacterial keratitis

Answer 26

Staph. aureus + epidermidis
Strep. pneumoniae
N.gonorhhea + meningitidis
C.diphtheria + xerosis
Bacillus cereus
Propionibacterium acne
Listeria
Clostridium
Pseudomonas aeruginosa
Enterobacteriacae
H. Influenzae

Via water - Ecanthamoeba

Question 27

Pathogenic stages of corneal ulcer (localised)

Answer 27

Stage of progressive infiltration
Stage of active ulceration
Stage of regression
Stage of cicatrization

Ulcer may be loaclised + heal / penetrate deep (corneal perforation)

Question 28

Stage of progressive infiltration

Answer 28

Breached epithelium
Bac. adhesion
Toxins to receptors + glycocalyx coat

Infiltration of polymorphonuclear / lymphocytes

Necrosis of tissue

Question 29

Stage of active ulceration

Answer 29

Necrosis + sloughing (epithelium, bowman’s mebrane, stroma)
Swelling (lamellae) (packed leucocytes)
Zone of infiltration
Sides + floor of ulcer (grey infiltration+ sloughing)

Hyperaemia (circumcorneal network)(accumulation of purulent exudate)

Vascular congestion (iris, ciliary body)(Formation of hypopyon)

Penetrate deep (Descemetocele formation) (corneal perforation)

Question 30

Stage of regression

Answer 30

Natural host defence mechanism
Line of demarcation (leucocytes)
Initial enlargement of ulcer (digestion of necrotic debris)
Superficial vascularization
Epithelium over edges

Question 31

Stage of Cicatrization

Answer 31

Progressive epithelization
Fibrous tissue (by corneal fibroblasts)
Stroma thickens (fill +push epithelium)
Degree of scarring
Superficial ulcer heals without opacity
Bowman membrane ulcer resultant scar (Nebula) (macula, leucoma after healing)

Question 32

Pathology of perforated ulcer

Answer 32

Reaches descemet’s membrane
Bulges out (Descemetocele)

Exertion causes perforation of ulcer (aqueous esxape)(IOP falls)(iris-lens diagram moves forward)

Healing by cicatrization proceeds rapidly.
Resultant is adherent leucoma

Question 33

Clinical features of corneal ulcer

Answer 33

Purulent corneal ulcer with hypopyon
Hypopyon corneal ulcer

Pain (foriegn body sensation)
Watering (reflex hyperlacrimation)
Photophobia (stimulate nerve endings)
Blurred vision (corneal haze)
Redness of eyes (congested circumcorneal conjunctival vessels)

Swollen lid
Blepherospasm
Conjunctiva (hyperaemia + congestion)
Corneal ulcer (grey-white circumscribed infiltrate)
Yellow-white ulcer area
Swollen margins
Floor (necrotic material)
Stromal edema
Anterior chamber
Hypopyon maybe / not present
Iris (slighly muddly colour)
Pupil (small)(toxin induced Iritis)
IOP (raised in inflammatory glaucoma)

Question 34

Characteristic feature by bacteria in ulcer

Answer 34

Oval, yellow white densely opaque(s.aureus, strep.pneumonae)

Itrregular sharp , greenish mucopurulent exudate, diffuse liquefactive necrosis, semiopaque(pseudomonas)(with hypopyon + spread rapidly + perforate)

Shallow, grey white, pleomorphic supppuration, diffuse stromal opalescence, ring shape corneal infiltrate (Enterobacteriae)

Question 35

Complications of corneal ulcer

Answer 35

Toxic iridocyclitis
Secondary glaucoma
Descemetocele
Perforation
Iris prolapse
Subluxation of lens
Ant. Capsular cataract
Corneal fistula
Purulent uvietis / Endophthalmitis
IO haemorrhage
Corneal scarring

Question 36

Clinical evaluation of corneal ulcer

Answer 36

History
Physical examination
Ocular examination
Diffuse light exam
Regurgitation test , Syringing
Biomicroscopic exam

Question 37

Lab investigations of corneal ulcer

Answer 37

Routine
Hb
TLC
DLC
ESR
Blood sugar
Complete urine
Stool examination
Microbiological investigation
Gram / Giemsa
10% KOH wet preparation
Calcofluor white stain(fungus)
Blood culture
Culture Sabouraud’s dextrose Agar

Question 38

Hypopyon corneal ulcer

Answer 38

Pnumococcus (ulcer serpens)
Staph, strep, gonococci, moraxella, pseudomonas pyocyanae.

Common in old diabetic and alcoholics

Mechanism
Iritis
Outpouring leucocytes
Cells gravitate at bottom (hypopyon)
Hypopyon sterile and absorbed
Outpouring PMNs due to toxins

Ulcer serpens
Grey white / yellow disc shaped
One edge more infiltration
Other edge simultaneous cicatrization.
Definite hypopyon (violent iridocyclitis)
Hypopyon increses to secondary glaucoma.
Ulcer spread rapidly (perforate early).

Management
0.5% timolol maleate
BID eyedrops
Oral acetazolamide
Dacryocystectomy (chronic dacryocystitis)