Diseases of the cornea

Zoltan Z. Nagy

Department of Ophthalmology, Mária u.

Budapest

The human cornea

Transparent, contains no blood vessel

Special spherical shape

Represents the largest refractive power within the

eye (cc. +43,0 D)

Only 0,5 mm thick in the center

Elastic, during trauma non-linear behaviour

I. Morphology of the cornea (macroscopic and

microscopic)

II. Developmental anatomy of the cornea, developmental

anomalies

III. Methods of corneal examination

IV. Diseases of the cornea

– Inflammation, degenerations, dystrophies, tumors, trauma

V. Keratoplasty (corneal transplantation)

VI. Refractive surgery of the cornea

I. Morphology of the cornea

Macroscopic

Microscopic

Macroscopic anatomy

– Special attachment to the sclera

– Corneal radius: 7,8 mm

– Horizontal diameter: 11,7 mm

– Vertical diameter: 10,6 mm

– Thickness at the center: 530 µm, in limbus 700 to 1000 µm

– Adult size achieved in the age of 2 years

Microscopic anatomy

– Epithelium

– Lamina limitans anterior (Bowman layer)

– Substantia propria (stroma)

– Lamina limitans posterior (Descemet layer)

– Endothelium

II. Developmental anatomy of the

cornea

Epithelium: ectodermal, others layers:

mesodermal.

Following lens vesiculum, superficial ectoderma

differentiates to corneal epithelium.

Mesenchyma cells appear between the lens and

epithelium, producing collagen fibers.

Endothelium originates from the distal part of the

mesenchyma.

Developmenal anomalies

Microcornea

Megalocornea

Embryotoxon posterius

Cornea plana

Leucoma corneae congenitalis

III. Examination of the cornea

Slit lamp

Topography

Pachymetry (optical and ultrasonic)

Ultrasound biomicroscopy (UBM)

Specular microscopy

Measurement of corneal sensitivity

IV. Diseases of the cornea

1. Inflammation

2. Degenerations and dystrophies

3. Proliferative diseases and tumors

4. Corneal scars

5. Trauma

IV. 1. Corneal inflammations

(Keratitis)

A.) Bacterial (pus)

B.) Viral

C.) Fungal

D.) Trophic

E.) Immuno-specific

F.) Unknown origin

G.) Other

General symptoms of keratitis:

– Pain, photophobia, epiphora (tear)

– Epithelial opacities, infiltrates in stroma and between

the endothel cells

– Corneal neovascularisation.

IV. 1. A.) Bacterial keratitis

Keratitis punctata superficialis

Ulcus corneae

– Staphylococcus epidermidis

Ulcus serpens corneae cum hypopyo

– Diplococcus pneumoniae, Moraxella lacunata

Abscessus annularis

– Pseudomonas pyocyanea, Acanthamoeba

IV. 1. B.) Viral keratitis

Pathogens:

– Herpes simplex virus (HSV)

– Varicella zoster virus

– Adenoviruses

– Cytomegalia (rare)

HSV keratitis

Three main forms:

Superficial form

– Keratitis dendritica, stellata, punctata

Stromal form (deep inflammation)

– Keratitis interstitialis

Endothelial form

– Keratitis disciformis, endotheliitis

Keratitis dendritica

– Pain, foreign body sensation, tearing

– Usually affects one eye, conjunctivitis is also present

– Objective symptoms: dendrit-like infiltrations in the

epithelium, epithelial defects, staining with fluorescein

Keratitis herpetica interstitialis

– Visual deterioration depending the localization of the

infiltrates.

– Objective symptoms: irregular stromal infiltrates with

whitish-greyish colour. No epithelial defect.

Keratitis disciformis

– Subjective symptoms: visual deterioration.

– Objective symptoms: disciform stromal infiltrates,

where stromal edema is present. On the posterior

surface of the infiltrate there are Descemet folds (loss

of endothel cells). Precipitates on the posterior surface

of the cornea.

Keratitis metaherpetica

– Due to basal membrane damage, epithelial adhesion decreases.

– Edema in the epithelium, bullae may appear under the epithelium.

– If there is an epithelial defect, the process may be ulcerative.

– It is difficult to differentiate from real recurrance.

Therapy

– Acyclovir (Zovirax, Virolex)

– Trifluorthymidin (Triherpin)

– Iod-dezoxy-uridin (IDU)

– Local corticosteroids

Herpes zoster ophthalmicus

– Varicella zoster, characteristic changes in skin

– Always one-sided (n. trigeminus)

– Slit lamp finding is similar to HSV keratitis

– Other: trabeculitis (sec. gl.), optic nerve inflammation,

paralysis of the ocular muscles

Keratoconjunctivitis epidemica

– Type 8 and 19 of Adenovirus (incubation time: 8

days)

– Foreign body sensation, photophobia

– First one-sided, serous discharge with

pseudomembrane formation. Edema and red colour of

the caruncule and semilunar plica

– Keratitis punctata spf, subepithelial whitish-greyish

infiltrates (maybe permanent).

IV. 1. C.) Fungal keratitis

Possible pathogens: Candida albicans, Apergillus

fumigatus, Actinomyces

Features: dense whitish-greyish infiltrate in

stroma, base is dry, satellit infiltrates, corneal

ulcer, hypopyon

Therapy: Nystatin, Natamycin, Amphotericin-B

IV. 1. D.) Trophic dystrophies

Keratitis e lagophthalmo

Keratitis neuroparalytica

Corneal damage due to local anaesthetic therapy

IV. 1. E.) Immunospecific, or

endogenous keratitis

Atopic keratitis

Keratoconjunctivitis phlyctenulosa, ekzematosa

Keratitis interstitialis (parenchymatosa)

Keratitis rosacea

Atopic keratitis

– Usually together with allergic reaction of the

conjunctiva, symptoms similar to superficial keratitis.

– Therapy: antiallergic eye drops.

Keratoconjunctivitis phlyctenulosa

– Tuberculotoxic, allergic-hyperergic reaction

– Poor hygene

– Severe photophobia, epiphora, facies scrofulosa, rhagads,

blepharospasmus (spastic entropium)

– Near to limbus: small pin-like infiltrates, sectoral conjunctivitis.

Phlyctenas may wander.

– Pannus formation (neovascularisation)

– Therapy: corticosteroids, antibiotic drpos

Keratitis interstitialis (parenchymatosa)

– Hyperergic reaction due to connatal lues

– Diffuse, deep keratitis (round or tongue like infiltretes

with intact epithelium). Later, deep neovascularisation

(red or brownish opacity). Later blood vessels closing.

– Hutchinson-trias: keratitis, barrel-shaped teethes,

perception hypacusis

Keratitis rosacea

– Rosacea-like skin changes on the face

– In the superficial layer of the cornea: whitish

infiltrates, ulceration, superficial and deep corneal

neovascularisation. Frequent recurrences.

– Therapy.: local antibiotic drops, corticosteroid drops.

IV. 1. F.) Keratitis of unknown

origin

Ulcus rodens (Mooren-ulcer)

– Progressive necrotizing keratitis, starts from limbus

and advancing toward the center.

– Blood vessels may grow in, thereafter scar formation.

– Prognosis: bad

– Therapy: difficult, limited keratotomy, keratoplastica,

immunosuppression, conjunctiva/amniotic membrane

transplantation.

IV. 1. G.) Other keratitis

Keratoconjunctivitis sicca (Sjögren sy)

– Cause: unknown

– Symptom: foreign body sensation, pain

– Schirmer-test

– Filaments on the surface of the cornea

– Therapy: arteficial tear products

IV. 2. Corneal degenerations

Arcus senilis (gerontoxon)

– Lipid deposition in stroma around the limbus

Kayser-Fleischer ring (Wilson-disease)

– Organic copper deposition in Descemet layer

Opacitas zonularis corneae (Band keratopathy)

– Calcium deposition in Bowman layer

Nodular corneal degeneration (Salzmann-degeneration)

Keratomalacia

– Vitamin-A deficiency

IV. 2. Corneal dystrophies

Features:

– Abnormal metabolism of cells and tissues

– Symptoms in early adulthood

– Bilateral and symmetric

– No corneal neovascularisation

– Affect the central 6-8 mm diameter of the cornea

IV. 2. Corneal dystrophies

Epithelium, Bowman layer

– Basal membrane dystrophy, Reis-Bückler dystrophy

Corneal stroma (dominant inheritance, except macular

dystrophy)

– Macular dystrophy (Groenouw I)

– Granular dystrophy (Groenouw II)

– Reticular dystrophy (Haab-Dimmer)

Endothelium

– Endo-epithelial dystrophy (sec. Fuchs)

IV. 2. Corneal dystrophies

Keratoconus

Keratoglobus

Keratotorus

IV. 3. Proliferative diseases of the

cornea and tumors

Dermoid (at the limbus)

Pterygium, pinguecula

Papilloma

Granuloma

Intraepithelial epithelioma (morbus Bowen)

IV. 4. Corneal scars

Nubecula

Macula

Leucoma

Leucoma corneae vascularisata

IV. 5. Trauma of the cornea

Epithelial erosion of the cornea

Recurrent erosion

Photoelectric keratitis

Chemical injuries (acid and base)

Burn

Foreign body (corpus alien. corneae)

Perforating injuries

V. Keratoplasty

(Corneal transplantation)

First lamellar keratoplasty: von Hippel, 1888

First penetrating keratoplasty (PKP): Zirm, 1906

Indication:

– Keratoconus, other corneal dystrophies, bullous

keratopathy, scars, herpetic infection, rejection

VI. Refractive surgery of the

cornea

History of the optical correction

13th century

– Glass blow masters from Murano and Pisa

– Correction of presbyopia

15th century

– First myopic correction

Later

– Newton and Descartes (basic laws of optics)

Surgical interventions

Bates (1894) USA

Lans (1898) Germany

– Treatment of astigmatism and keratoconus

Fukala-procedure

– Lens extraction (only for high myops)

Sato (1953)

Fjodorov, Yenaliev (1979)

Bores (1983) USA

– Radial keratotomy (RK)

Excimer laser

1975. Velazco

– Xenon reacts with halogen atoms

1976. Hoffmann

– ArF molecule

– Excimer = „EXCited diMER”

1983. Srinivarsan és Trokel

– Surgical use

Mechanism of action

Fotochemical

Fotodecomposition, or photoablation

– Laser energy: 6,4 eV

– carbon – hydrogen bonds: 4,3 eV

– Depth only: 1 µm !!

Clinical studies, animal experimetns

– 1983. Trokel, New York (USA)

– 1983. Marshall, London (Anglia)

First human treatments

– 1988. M. McDonald, New Orleans (USA)

– 1988. T Seiler, Berlin (Germany)

Features of ArF molecule

High energy, 193 nm of wavelength photon

radiation

Ultraviolet-C range of electromagnetic spectrum

Fotoablation effect

Nanosec treatment time („cold laser”)

1 µm-es effective depth

Corneal sculpting

Treatment modalities with the

excimer lasers

PRK (photorefractive keratectomy)

PTK (phototerapeutic keratectomy)

LASIK (Laser in situ keratomileusis)

LASEK (Laser intraepithelial keratomileusis)

Many thanks for your

attention!