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

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Ophthalmology PPT 27 Diseases Of The Cornea 1 Lecture Notes


DISEASES OF THE CORNEA

Department of Ophthalmology


DIMENSIONS

n Ant surface

n Posterior surface

elliptical

circular

11.5mm



11-12 mm

10- 11 mm

11.5mm

? Shape - Prolate



n Thickness centre 0.5-0.6 (thinner)

periphery 0.7-1.0mm

n Radius of ant.surface 7.8mm
curvature post surface 6.5mm (steeper)

n Refractive index 1.376

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

refractive power of the eye


LAYERS OF CORNEA

n Epithelial Layer ? Regenerates

n Bowman's Layer- Resistant to trauma and

infection

n Stroma ? Collagen bundles with keratocytes

n Descemets layer- very tough

n Endothelium ? hexagonal cells ?

3000cells/mm2
Limbus

n 1-1.5 mm

n anatomy

n Cells at limbus are unique ? Limbal stem

cells

n Responsible for growth and regeneration of

epithelial cells

NERVE SUPPLY OF CORNEA

Cornea has body's highest no. of nerve endings

5th cranial nerve (Trigeminal)

Ophthalmic division

Nasociliary branch

Long ciliary nerves

Annular plexus around limbus

Subepithelialplexus Intraepithelial plexus


NUTRITION METABOLISM

n Perilimbal capillaries

n Epithelium &

endothelium

metabolically very

n Aqueous humour

active

(glucose diffussion)

n Both aerobic &

n Atmospheric oxygen

anaerobic metabolism

(tear film)

CORNEAL TRANSPARENCY

n Avascularity

n Uniform refractive Index of the cornea

n Arrangement of corneal lamellae

n State of relative dehydration(78%)


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

n Transmission of light/Refractive medium

n Structural integrity of globe/Protects the eye

PATHOLOGICAL CHANGES IN

THE CORNEA

n Keratitis Superficial

Deep Stromal

Endothelial
n Corneal abrasion/erosion

n Corneal ulcer

n Corneal opacity Nebular, Macular, Leucomatous

n Corneal oedema

n Vascularisation
KERATITIS

MORPHOLOGICAL CLASSIFICATION

ULCERATIVE



NON

ULCERATIVE

Superficial

Diffuse sup. Keratitis

n Suppurative/non

suppurative

SPK

Deep

Non suppurating

Interstitial/disciform

n Superficial/deep/

Suppurating

perforated

Central/posterior corneal

abscess

KERATITIS

ETIOLOGICAL CLASSIFICATION

?

Infective

? Asso. with systemic

collagen vascular ds

?

Allergic





? Traumatic

?

Trophic

? Idiopathic

?

Asso. with skin &

mucous memb. ds

Moorens ulcer








INFECTIVE KERATITIS

PATHOGENESIS



Epithelial damage Infection



Corneal abrasion Exogenous

Epith. Drying Spread from ocular

tissue

Epith. Necrosis

Epith. desquamation Endogenous

PREDISPOSING FACTORS

n Ocular

- Trauma
- Contact lens
- lids and adenexal infections

- Topical medications

n Ocular surface diseases

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

ectropion
- Epi. Defect ? Entropion , Trichiasis
PREDISPOSING FACTORS

n Systemic

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

n Occupational

- Farmers
- Animal handlers
- Gardeners

HISTORY

n Pain

n Redness

n Photophobia

n Discharge

n Lacrimation

n Decrease visual aquity
EXAMINATION

n Eyelids

n Lacrimal Sac

n Conjuntiva

n Corneal ulcer

- size
- shape
- location
- margins
- infiltration
- corneal sensation

EXAMINATION

n Anterior chamber

n Iris

n Pupil and Lens

n Scleral involvment

n Posterior segment/ USG
Bacterial corneal ulcers

n Agents :
Staphlococcus aureus/ albus

Streptococcus

Pseudomonas
Pneumococcus
N. gonorrhoeae
C. diphtheriae
E. coli

PATHOLOGY OF CORNEAL

ULCER

nStage of ulceration- desquamation of the epithelium

and tissue necrosis resulting in saucer shaped ulceration

nProgressive infiltration- progression of ulceration

with leucocytes infiltration and purulent suppuration

nRegression ? characterized by relatively smooth and

transparent ulcer area

nCicatrization ? Scar formation


BACTERIAL CORNEAL ULCER

SYMPTOMS

SIGNS

Pain/ FB sensation

Lid oedema

Redness

Blepharospasm

Watering

Conj.chemosis

Photophobia

Infiltration

Blurred vision

Corneal oedema
Hypopyon +/ -
n Symptoms are acute

n Severe clinical signs

n Rapid progression

n Wet looking ulcer area

n Purulent discharge

TREATMENT

OF BACTERIAL KERATITIS



UNCOMPLICATED ULCER

? Identify & treat the cause
Corneal scraping
staining/culture
Antibiotics
? Rest to eye Cycloplegics

? Antiglaucoma medications

? Systemic antibiotics
PERFORATED ULCER

Small < 3mm
? IOP lowering drugs

? Pressure bandage

? Bandage contact lens

? Tissue adhesives

? Conj. flap
Large >3mm
? Therapeutic PK

Fungal keratitis

n Incidence is low

n Most common organism is Aspergillus

n Infections are more common when there is

high humidity
Classification

n Filamentous
1. Septate
- Nonpigmented ? Fusarium
Aspergillus
Penicillium
- Pigmented - Curvularia
Alternaria
2. Nonseptate
Rhizopus

n Yeast
Candida

FUNGAL (MYCOTIC)

CORNEAL ULCERS

? Etiology Trauma with organic matter

Injury with animal tail

Systemic/ local immune suppresion

? Causative agent Aspergillus , Fusarium

Candida , Cryptococcus

Curvularia, Alternaria

? Indolent course

? Symptom ? foreign body sensation , photophobia , blurred

vision and discharge




SIGNS MORE THAN

SYMPTOMS

SIGNS
Soft creamy raised exudates

Fungal

ulcer

Dry looking
Feathery margins
Satellite lesions
Immune ring of Wesseley
Hypopyon +/-
Endothelial plaque
Posterior abscess





DIAGNOSIS TREATMENT

n History Organic

?

Topical antifungals

matter

Natamycin 5%

Itraconazole 1%

n Typical clinical picture

Fluconazole 0.2%

Amphotericin B 0.1-

n Corneal scrapings

0.2%

KOH wet mount

?

Systemic antifungals

Gram, Giemsa staining

?

Cycloplegics

Calcoflour white

?

Anti inflammatory drugs

Culture on SDA

?

Therapeutic PK in

unresponsive cases


COURSE OF CORNEAL ULCER

Healing Deep penetration Sloughing

Descemetocele Pseudocornea

Perforation Ant. Staphyloma


Adherent leucoma
COMPLICATIONS

n Toxic iridocyclitis

n Secondary glaucoma

n Descemetocele

n Perforation

Iris prolapse

Ant. Capsular cataract

Corneal fistula

Spontaneous expulsion of lens & vitreous

Intraocular haemorrhage Expulsive hmg.

Purulent uveitis Endophthalmitis/

Panophthalmitis

?

Corneal scarring/ opacification

This post was last modified on 07 April 2022