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