Disease of the cornea

Question 1

What Is cornea

Answer 1

The front transparent part of the globe that covers and protects the interna structures of the eye .

Question 2

Horizontal and vertical length of cornea?
It’s coverage of the front globe

Answer 2

Vertical: 11mm
Horizontal: 12mm
Covers 1/6 of the front globe

Question 3

It’s function?

Answer 3

It functions like a window that controls and focuses the entry of light into the eye.

Question 4

How much does it contribute to the eye’s total focusing power?

Answer 4

65-75 %

Question 5

It’s blood vessel and innervation?

Answer 5

It has no blood supply but highly innervated hence very sensitive

Question 6

Where does it get it’s nutrition from?

Answer 6

tears and the aqueous humor (a watery fluid) in the anterior chamber provide the cornea with nutrients

Question 7

Layers of cornea

Answer 7

1. The epithelium
2. Bowman’s layer
3. The stroma,
4. Descemet’s membrane
5. The endothelium

Question 8

Disease if the cornea

Answer 8

1. Bacterial keratitis
2. Herpes simplex eye d.
3. Herpes zoster ophthalmic
4. Fungal keratitis

Question 9

1. Keratitis

Answer 9

Inflammation of the cornea

Question 10

Infectionous causes of keratitis

Answer 10

. Bacteria
. Virus
. Fungus
. Acanthamoeba

Question 11

Bacterial keratitis onset?

Answer 11

a common sight threatening condition
Onset can be Rapid (explosive) or rarely Slow

Question 12

Risk factors of bacterial keratitis

Answer 12

.Break in the barrier function
.Contact lens wear

.Trauma

.Contaminated ocular drugs

.Impaired defense mechanism

Question 13

Which bacterias exceptionally penetrate an intact corneal epithelium?

Answer 13

. Nisseria gonorrhea
. Corynebacterium diphtheria
. Haemophilus aegyptius
. Listeria monocytogenes

Question 14

What is the etiology for b.keratitis?

Answer 14

. S.aureus/ S.epidermidis/St.pneumonia

. Moraxella/Serratia/ P.aeruginosa
.
Mycobacteria/Anaerobes

Question 15

Clinical presentation?

Answer 15

.Pain
.Redness
.Photophobia
.Reduced vision
.purulent eye discharge
.Corneal ulcer which has sharp demarcation with underling suppuration
.In Sever cases with pus in the anterior chamber(Hypopyon)

Question 16

Diagnosis

Answer 16

.Clinical
.Identifying the causative agent by gram stain and culture

Question 17

Treatment

Answer 17

.First with broad spectrum antibiotics for both gram positives and gram negatives
.Once the organism is identified with culture patient can be treated with monotherapy
.Route of administration : Topical/Sub conjunctival/Systemic

Question 18

Drugs of choice

Answer 18

For gram positives:
• Vancomycin
•Bacitracin
•Cefuroxime

For gram negatives:
•
Tobramycin
•Gentamicin
•Amikacin

For monotherapy:

     •Ciprofloxacin
     •Levafloxacin
     •Ofloxacin     Corticosteroids:
     •Should be started once the organism is identified or once the patient has shown response to antibiotic therapy!

Question 19

Surgery

Answer 19

●Penetrating keratoplasty(PK)

A full-thickness transplant procedure, in which a full-thickness resection of the patient’s cornea is followed by placement of a full-thickness donor corneal graft.
- Indication: Progressive disease despite antibiotic therapy
: Decematocele or Corneal perforation

Question 20

2. Herpes simplex eye diseaseOccurance?

Answer 20

•Herpes simplex virus infection is ubiquitous in human.
•Almost 100% of those older than 60 years of age harbor HSV in their trigeminal ganglion.
•60% of corneal ulcer in developing countries
•HSV Causes recurrent infection

Question 21

Types of HSV?

Answer 21

HSV1- Orofacial & ocular infection HSV2 – Genital infection

Question 22

Route of transmission

Answer 22

direct contact with infected lesion or secretion

Question 23

Primary lesion
.lesions
.epidemiology
.transmission
.symptom
.treatment

Answer 23

• Lid Vesicles
Follicular conjunctivitis
Epithelial keratitis.
• Usually occurs in childhood (but not before 6 months of life because of Maternal antibodies)
• droplet
direct transmission (not freq)
• mild fever
Malaise
URTI
blepharities (usu mild and self limited)
Follicular conjunctivitis (usu mild and self limited)
• topical acyclovir ointment (if necessary)

Question 24

Recurrent ocular infection
. Mechanism
. Risk fa’

Answer 24

• From reactivation of virus in latently infected sensory ganglion
•
In the past psychological stress, Systemic illness, sun light exposure are said to induce recurrence but currently are not proven to be risk factors for recurrence.
•
But patient with HIV are at increased risk of recurrence.

Question 25

Clinical manifestation

Answer 25

.redness .tearing .photophobia .decreased vision .Belepharo conjunctivitis .Epithelial keratities : Dendritic (linear branching ulcer with terminal bulb) or Geographic ( coalescence of dendritic ulcer) .Decreased corneal sensation is highly suggestive of viral keratitis especially of herpetic origin

Question 26

Diagnosis

Answer 26

.clinical .Viral Culture/Antigen &DNA Detection (rare)

Question 27

Treatment

Answer 27

●Anti viral Routes : Topical/Systemic Drugs :Acyclovir Trifloridine Vidarabine Valacyclovir Corticosteroids (are used for stromal keratities but are contraindicated in epithelial keratities with ulceration) ●Prophilactic treatment ; needed for recurrent stromal hsv keratitis Acyclovir 400mg po bid long term ●Surgical treatment Penetrating keratoplasty Indication _ visually significant corneal opacity or Corneal perforation

Question 28

Complications

Answer 28

.corneal opacity and blindness .Neurotrophic ulcer (which is a non healing ulcer) .Cataract .Super infection .Glaucoma .Iris atrophy

Question 29

Herpes zoster ophthalmicus AKA Shingels/ zoster

Answer 29

Viral disease chx'd by a painful skin rash in one or more dermatome distributions of the 5th cranial nerve shared by the eye and orbit

Question 30

It's mechanism

Answer 30

occurs from reactivation of VZV infection

Question 31

Epidemiology

Answer 31

self limited in children but sever in elderly or immunocompromized

Question 32

CLINICAL PRESENTATION

Answer 32

.Blepharo conjunctivitis .Epithelial keratities .Stromal keratities

Question 33

Diagnosis

Answer 33

Clinical

Question 34

Treatment

Answer 34

●With systemic antiviral Best if treatment is initiated with in 72 hrs of vesicular eruption : Famicyclovir :Valacyclovir :Acyclovir High dose (Acyclovir 800mg 5x per day 10-14 days)

Question 35

Treatment of post herpetic neuralgia

Answer 35

Amitriptyline ( 25mg po/day )

Question 36

Fungal keratitis

Answer 36

•Less commen •More difficult to diagnose and treat

Question 37

Risk factors

Answer 37

Trauma with plant or vegetable material Contact lens wear Prolonged topical corticosteroid use Corneal surgery Chronic keratities( E.g HSK, HZVK)

Question 38

Clinical presentation

Answer 38

F/B sesation slow onset pain visual reduction (clinical signs are more sever than symptoms) ●Few inflammatory signs On the cornea .Gray white infiltrates with irregular feathery or filamentous margin .Occasionally multifocal or satellite infiltrates

Question 39

Etiology

Answer 39

.Candidia .Aspergillus .Fusarium

Question 40

Diagnosis

Answer 40

.Clinical .Laboratory(KOH)

Question 41

Treatment

Answer 41

mainly topical : Natamycine Amphotericin B/Miconazole Adjunctive oral ketoconazole or fluconazole Surgery Penetrating keratoplasty for progressive disease despite antifungal therapy.