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👁🤓Ophthalmology 101 > Disease of the cornea > Flashcards

Disease of the cornea Flashcards

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1
Q

What Is cornea

A

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

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2
Q

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

A

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

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3
Q

It’s function?

A

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

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4
Q

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

A

65-75 %

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5
Q

It’s blood vessel and innervation?

A

It has no blood supply but highly innervated hence very sensitive

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6
Q

Where does it get it’s nutrition from?

A

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

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7
Q

Layers of cornea

A
  1. The epithelium
  2. Bowman’s layer
  3. The stroma,
  4. Descemet’s membrane
  5. The endothelium
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8
Q

Disease if the cornea

A
  1. Bacterial keratitis
  2. Herpes simplex eye d.
  3. Herpes zoster ophthalmic
  4. Fungal keratitis
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9
Q
  1. Keratitis
A

Inflammation of the cornea

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10
Q

Infectionous causes of keratitis

A

. Bacteria
. Virus
. Fungus
. Acanthamoeba

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11
Q

Bacterial keratitis onset?

A

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

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12
Q

Risk factors of bacterial keratitis

A

.Break in the barrier function
.Contact lens wear

.Trauma

.Contaminated ocular drugs

.Impaired defense mechanism

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13
Q

Which bacterias exceptionally penetrate an intact corneal epithelium?

A

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

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14
Q

What is the etiology for b.keratitis?

A

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

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

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15
Q

Clinical presentation?

A

.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)

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16
Q

Diagnosis

A

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

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17
Q

Treatment

A

.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

18
Q

Drugs of choice

A

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!
19
Q

Surgery

A

●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

20
Q
  1. Herpes simplex eye diseaseOccurance?
A

•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

21
Q

Types of HSV?

A

HSV1- Orofacial & ocular infection HSV2 – Genital infection

22
Q

Route of transmission

A

direct contact with infected lesion or secretion

23
Q

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

A

• 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)

24
Q

Recurrent ocular infection
. Mechanism
. Risk fa’

A

• 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.

25
Q

Clinical manifestation

A

.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

26
Q

Diagnosis

A

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

27
Q

Treatment

A

●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
28
Q

Complications

A

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

29
Q

Herpes zoster ophthalmicus
AKA
Shingels/ zoster

A

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

30
Q

It’s mechanism

A

occurs from reactivation of VZV infection

31
Q

Epidemiology

A

self limited in children but sever in elderly or immunocompromized

32
Q

CLINICAL PRESENTATION

A

.Blepharo conjunctivitis
.Epithelial keratities
.Stromal keratities

33
Q

Diagnosis

A

Clinical

34
Q

Treatment

A

●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)

35
Q

Treatment of post herpetic neuralgia

A

Amitriptyline ( 25mg po/day )

36
Q

Fungal keratitis

A

•Less commen
•More difficult to diagnose and treat

37
Q

Risk factors

A

Trauma with plant or vegetable material
Contact lens wear

Prolonged topical corticosteroid use
Corneal surgery

Chronic keratities( E.g HSK, HZVK)

38
Q

Clinical presentation

A

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

39
Q

Etiology

A

.Candidia
.Aspergillus
.Fusarium

40
Q

Diagnosis

A

.Clinical
.Laboratory(KOH)

41
Q

Treatment

A

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

👁🤓Ophthalmology 101 (3 decks)

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