cornea human

CORNEACORNEA

Dr.H.Izar Aziz,SpM(K) 2

Function of the cornea :Function of the cornea :as Window of the globe & refractive

media:• clear & transparent with power +

42 D.• as microorganisms barrier

• Corneal endothelium maintains corneal clarity through:– Acting as a barrier to the aqueous humor– Providing metabolic pump

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Loss of transparency caused by :• endothelial damage• epithelial damage.

Corneal Edema

• Alteration of endothelial function corneal edema

• Acute altered barier effect of the endothelium/epithelium

• Chronic inadequate endothelial pump

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Causes of Corneal Edema

Acute• Trauma (ex: intraocular

surgery)• Inflammation • Hypoxia (ex: contact lens

wear)• Increased intraocular

pressure

Chronic• Trauma or toxins• Fuchs dystrophy• Posterior polymorphous

dystrophy• Iridocorneal endothelial

syndrome• Retained lens fragment

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KeratitisKeratitis : isinflammation of cornea ,caused bymicroorganism infectionantigen antibodies / allergic reaction.

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Epithelium covered by tear film :as a barrier microorganisms infection . (except N. Gonorrhoea)

• Descemet’s membrane as barrier for bacterial infection to COA .(but not for fungus)

• Etiology of keratitis : – Exogenous : bacteria ,fungus , virus, parasite– Endogenous : allergic reaction.

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• Bacteria :-Pure Pathogen : Streptococcus

pneumoniae, Pseudomonas aeroginosa

-Opportunistic bacteria : -Staphylococcus,Moraxella, Serratia(as flora at conjunctiva

. Alcoholic/ B6 deficiency .Topical steroid >>>

. Corneal abrasion

Pathogen bacteriaPathogen bacteria Corneal infection

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• Fungus (usually opportunistic)•Candida, Fusarium, Aspergillus

• Virus– VHS– VVZ

• Parasite : Acanthamoeba in Contact lens user

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Symptoms & Signs• Subjective (patient’s history )

– pain– glare (photophobia)– blur vision – tearing (lacrimation)

• Objective - loupe or slit lamp examination– blepharospasme– ciliary injection – tearing (lacrimation)– superficial infiltrate or corneal ulcer– hypopyon- in advanced cases.

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• Special examinations :– Flourescein test for corneal ulcer– Seidel test for perforating cornea

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Laboratory Studies Etiologic diagnosis.Scraping from:

infiltrate / edge of the ulcerfornices of conyunctiva

Slide Staining :Gram ( for bacteria)Giemsa (for fungus )

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Clinical courseSubepithelial

/epithelial keratitis

Recover without scar

Become corneal ulcer

Recover with scar

NebulaMakula

Leukoma

Perforating cornea, accompanied bulging of the cornea & iris prolaps

Recover with scar :Leukoma adherentstaphyloma cornea

Corneal blindness

Advanced inflamation

-endophtalmitis-panophtalmitis

recover Extirpation of the globe

Abulbi

Phtysis bulbi

Permanent blindness

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Clinical appearance of corneal ulcers

• Serpeginous corneal ulcer.– Etiology : Pneumococcus– acute, well circumscribed – gray ulcer, tends to spread to center of cornea– hypopyon is common (sterile)

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•Pseudomonas ulcer.• Etiology : Pseudomonas aerg. (present in Flourescein

sol.)• bluish-green exudate • very acute ,spread rapidly to all direction ,because proteolytic enzyme destroy the corneal stroma descemetocele

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• Marginal Ulcer – Etiology : Staphylococcus– affect limbal area

• Fungal ulcer– history: agriculture trauma – topical steroid usage >>>>

• gray Infiltrate• thick hypopyon & irregular surface• satellite lesions - in endothelium

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Herpes Simplex keratitis.Etiology : VHS type Icorneal sensibility <<<lesion : filament, punctate, dendritic, disciform

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• Mooren’s Ulcer– Etiology : antigen antibodies reaction– Progressive excavation of the limbus.

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TreatmenTreatmentt • atropine eye drops • Anti microorganisms depend on

laboratory finding (scraping & culture) – Antibiotic for bacteria– Anti fungus for fungal infection– Antiviral for viral infection

• Steroid for Mooren’s ulcer• eye bandage

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• Prognosis depends on :– depth & width of the ulcer

Corneal Corneal scarscar

Dr.H.Izar Aziz,SpM(K) 22

NebulaMakulaLeukomaLeukoma adherent

Central ,-->corneal

blindness-Periphery (No visual disturbance )

Dr.H.Izar Aziz,SpM(K) 23

PreventionPrevention

• Avoid corneal trauma• Avoid overuse of topical

steroid • Cure external eye infection as

soon as possible.• Avoid trigger factor for

relapsing H.simplex keratitis.

Keratoconus• A progressive thinning and bulging of the

central of paracentral cornea cone shape cornea

• 6-8% cases: positive family history• Onset: around puberty

Clinical Findings • Unilateral • High astigmatism and myopic blurred

vision• Munson sign: bulging of the lower lid in

downgaze

Treatment

• Spectacles• Rigid contact lens • Keratoplasty

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Reference Books• Vaughn D, Asbury T; General

Ophthalmology, 15th edition, Appleton & Lange

• Miller S; Parson’s Diseases of the eye, 17 th Edition, Churcill Livingstone, 1984

• Kanski JJ, Clinical Ophthalmology, 4th edition,Oxford Butter Worth Heineman Ltd, 1999