Download MBBS Ophthalmology PPT 27 Diseases Of The Cornea 1 Lecture Notes

DISEASES OF THE CORNEA

Department of Ophthalmology

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DIMENSIONS

n Ant surface

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n Posterior surface

elliptical

circular

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11.5mm

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11-12 mm

10- 11 mm

11.5mm

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? Shape - Prolate

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n Thickness centre 0.5-0.6 (thinner)

periphery 0.7-1.0mm

n Radius of ant.surface 7.8mm

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curvature post surface 6.5mm (steeper)

n Refractive index 1.376

n Refractive power - 40-44D (70% Of total

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refractive power of the eye


LAYERS OF CORNEA

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n Epithelial Layer ? Regenerates

n Bowman's Layer- Resistant to trauma and

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infection

n Stroma ? Collagen bundles with keratocytes

n Descemets layer- very tough

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n Endothelium ? hexagonal cells ?

3000cells/mm2
Limbus

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n 1-1.5 mm

n anatomy

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n Cells at limbus are unique ? Limbal stem

cells

n Responsible for growth and regeneration of

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epithelial cells

NERVE SUPPLY OF CORNEA

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Cornea has body's highest no. of nerve endings

5th cranial nerve (Trigeminal)

Ophthalmic division

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Nasociliary branch

Long ciliary nerves

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Annular plexus around limbus

Subepithelialplexus Intraepithelial plexus

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NUTRITION METABOLISM

n Perilimbal capillaries

n Epithelium &

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endothelium

metabolically very

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n Aqueous humour

active

(glucose diffussion)

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n Both aerobic &

n Atmospheric oxygen

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anaerobic metabolism

(tear film)

CORNEAL TRANSPARENCY

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n Avascularity

n Uniform refractive Index of the cornea

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n Arrangement of corneal lamellae

n State of relative dehydration(78%)

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Barrier effect Endothelial Osmotic
of epithelium pump gradient
& endothelium
FUNCTIONS OF CORNEA

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n Transmission of light/Refractive medium

n Structural integrity of globe/Protects the eye

PATHOLOGICAL CHANGES IN

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THE CORNEA

n Keratitis Superficial

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Deep Stromal

Endothelial
n Corneal abrasion/erosion

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n Corneal ulcer

n Corneal opacity Nebular, Macular, Leucomatous

n Corneal oedema

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n Vascularisation
KERATITIS

MORPHOLOGICAL CLASSIFICATION

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ULCERATIVE

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NON

ULCERATIVE

Superficial

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Diffuse sup. Keratitis

n Suppurative/non

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suppurative

SPK

Deep

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Non suppurating

Interstitial/disciform

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n Superficial/deep/

Suppurating

perforated

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Central/posterior corneal

abscess

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KERATITIS

ETIOLOGICAL CLASSIFICATION

?

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Infective

? Asso. with systemic

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collagen vascular ds

?

Allergic

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? Traumatic

?

Trophic

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? Idiopathic

?

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Asso. with skin &

mucous memb. ds

Moorens ulcer

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INFECTIVE KERATITIS

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PATHOGENESIS



Epithelial damage Infection

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Corneal abrasion Exogenous

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Epith. Drying Spread from ocular

tissue

Epith. Necrosis

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Epith. desquamation Endogenous

PREDISPOSING FACTORS

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n Ocular

- Trauma
- Contact lens
- lids and adenexal infections

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- Topical medications

n Ocular surface diseases

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- Dry eyes ? Sjogrens syndrome,SJ synd. , Vit A def
- Prolonged Corneal Exposure - Proptosis, Lagophthalmos ,

ectropion
- Epi. Defect ? Entropion , Trichiasis

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PREDISPOSING FACTORS

n Systemic

- Diabetes mellitus

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- Sj?gren's syndrome
- Steven johnsons syndrome
- Connective tissue disorders
- AIDS
- Measles malnutrition

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n Occupational

- Farmers
- Animal handlers

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- Gardeners

HISTORY

n Pain

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n Redness

n Photophobia

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n Discharge

n Lacrimation

n Decrease visual aquity

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EXAMINATION

n Eyelids

n Lacrimal Sac

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n Conjuntiva

n Corneal ulcer

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- size
- shape
- location
- margins
- infiltration

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- corneal sensation

EXAMINATION

n Anterior chamber

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n Iris

n Pupil and Lens

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n Scleral involvment

n Posterior segment/ USG
Bacterial corneal ulcers

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n Agents :
Staphlococcus aureus/ albus

Streptococcus

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Pseudomonas
Pneumococcus
N. gonorrhoeae
C. diphtheriae
E. coli

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PATHOLOGY OF CORNEAL

ULCER

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nStage of ulceration- desquamation of the epithelium

and tissue necrosis resulting in saucer shaped ulceration

nProgressive infiltration- progression of ulceration

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with leucocytes infiltration and purulent suppuration

nRegression ? characterized by relatively smooth and

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transparent ulcer area

nCicatrization ? Scar formation

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BACTERIAL CORNEAL ULCER

SYMPTOMS

SIGNS

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Pain/ FB sensation

Lid oedema

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Redness

Blepharospasm

Watering

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Conj.chemosis

Photophobia

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Infiltration

Blurred vision

Corneal oedema

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Hypopyon +/ -
n Symptoms are acute

n Severe clinical signs

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n Rapid progression

n Wet looking ulcer area

n Purulent discharge

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TREATMENT

OF BACTERIAL KERATITIS

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UNCOMPLICATED ULCER

? Identify & treat the cause

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Corneal scraping
staining/culture
Antibiotics
? Rest to eye Cycloplegics

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? Antiglaucoma medications

? Systemic antibiotics
PERFORATED ULCER

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Small < 3mm
? IOP lowering drugs

? Pressure bandage

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? Bandage contact lens

? Tissue adhesives

? Conj. flap

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Large >3mm
? Therapeutic PK

Fungal keratitis

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n Incidence is low

n Most common organism is Aspergillus

n Infections are more common when there is

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high humidity
Classification

n Filamentous

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1. Septate
- Nonpigmented ? Fusarium
Aspergillus
Penicillium
- Pigmented - Curvularia

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Alternaria
2. Nonseptate
Rhizopus

n Yeast

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Candida

FUNGAL (MYCOTIC)

CORNEAL ULCERS

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? Etiology Trauma with organic matter

Injury with animal tail

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Systemic/ local immune suppresion

? Causative agent Aspergillus , Fusarium

Candida , Cryptococcus

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Curvularia, Alternaria

? Indolent course

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? Symptom ? foreign body sensation , photophobia , blurred

vision and discharge

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SIGNS MORE THAN

SYMPTOMS

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SIGNS
Soft creamy raised exudates

Fungal

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ulcer

Dry looking
Feathery margins

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Satellite lesions
Immune ring of Wesseley
Hypopyon +/-
Endothelial plaque
Posterior abscess

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DIAGNOSIS TREATMENT

n History Organic

?

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Topical antifungals

matter

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Natamycin 5%

Itraconazole 1%

n Typical clinical picture

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Fluconazole 0.2%

Amphotericin B 0.1-

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n Corneal scrapings

0.2%

KOH wet mount

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?

Systemic antifungals

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Gram, Giemsa staining

?

Cycloplegics

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Calcoflour white

?

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Anti inflammatory drugs

Culture on SDA

?

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Therapeutic PK in

unresponsive cases

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COURSE OF CORNEAL ULCER

Healing Deep penetration Sloughing

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Descemetocele Pseudocornea

Perforation Ant. Staphyloma

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Adherent leucoma
COMPLICATIONS

n Toxic iridocyclitis

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n Secondary glaucoma

n Descemetocele

n Perforation

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Iris prolapse

Ant. Capsular cataract

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Corneal fistula

Spontaneous expulsion of lens & vitreous

Intraocular haemorrhage Expulsive hmg.

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Purulent uveitis Endophthalmitis/

Panophthalmitis

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?

Corneal scarring/ opacification