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Ophthalmology > Cornea > Flashcards

Cornea Flashcards

1
Q

Topographical classification of corneal inflammation

A

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

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2
Q

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

A

Iterstitial
Disciform
Keratitis
Sclerosing

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3
Q

Types of Non- ulcerative, deep, suppurative keratitis

A

Central corneal abscess
Posterior corneal abscess

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4
Q

Etiological classification of keratitis

A

Infectious
Non- infectious

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5
Q

Types of infectious keratitis

A

Bacterial
Viral
Fungal
Chlamydial
Protozoal
Spirochaetal

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6
Q

Types of Non-infectious keratitis

A

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

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7
Q

Types of allergic keratitis

A

Phlyctenular
Vernal
Atopic

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8
Q

Types of trophic keratitis

A

Exposure keratitis
Neurotrophic keratopathy
Keratomalacia
Atheromatous ulcer

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9
Q

Idiopathic keratitis

A

Mooren’s corneal ulcer
Superior limbic keratoconjunctivitis

Superficial punctate keratitis of Thygeson

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10
Q

5 layers of cornea

A

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

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11
Q

Epithelium of cornea

A

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)

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12
Q

Bowman’s membrane

A

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

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13
Q

Substantia propria / stroma of cornea

A

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

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14
Q

Pre - Descemet’s membrane of cornea

A

Acellular
Very strong
Imprevious to air

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15
Q

Descemet’s membrane / post. Elastic lamina)

A

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.

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16
Q

Endothelium of cornea

A

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

17
Q

Nerve supply of cornea

A

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

18
Q

Factors contributing in corneal transparency

A

Anatomical
Physiological

19
Q

Anatomical factors in corneal transparency

A

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

20
Q

Physiological factors of corneal transparency (dehydration)

A

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)

21
Q

Metabolism of cornea

A

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.

22
Q

Anomalies of cornea

A

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

23
Q

Anomalies of Corneal Transparency

A

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

24
Q

Etiology of Bacterial keratitis

A

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

25
Pathogens invade INTACT corneal epithelium
N.gonorhhea + meningitidis C. Diphtheria Haemophilus aegyptius Listeria species
26
Causatives of bacterial keratitis
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
27
Pathogenic stages of corneal ulcer (localised)
Stage of progressive infiltration Stage of active ulceration Stage of regression Stage of cicatrization Ulcer may be loaclised + heal / penetrate deep (corneal perforation)
28
Stage of progressive infiltration
Breached epithelium Bac. adhesion Toxins to receptors + glycocalyx coat Infiltration of polymorphonuclear / lymphocytes Necrosis of tissue
29
Stage of active ulceration
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)
30
Stage of regression
Natural host defence mechanism Line of demarcation (leucocytes) Initial enlargement of ulcer (digestion of necrotic debris) Superficial vascularization Epithelium over edges
31
Stage of Cicatrization
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)
32
Pathology of perforated ulcer
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
33
Clinical features of corneal ulcer
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)
34
Characteristic feature by bacteria in ulcer
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)
35
Complications of corneal ulcer
Toxic iridocyclitis Secondary glaucoma Descemetocele Perforation Iris prolapse Subluxation of lens Ant. Capsular cataract Corneal fistula Purulent uvietis / Endophthalmitis IO haemorrhage Corneal scarring
36
Clinical evaluation of corneal ulcer
History Physical examination Ocular examination Diffuse light exam Regurgitation test , Syringing Biomicroscopic exam
37
Lab investigations of corneal ulcer
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
38
Hypopyon corneal ulcer
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)

Ophthalmology (16 decks)

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