Cornea

Question 1

Cornea refraction power and thickness

Answer 1

40D (highest in eye)
535-545 um CCT

Question 2

Cornea nutrient supply

Answer 2

aqueous humour posteriorly
tear film anteriorly

Question 3

Cornea nerve supply

Answer 3

long ciliary nerve CNV1

Question 4

Layers of cornea

Answer 4

1. Epithelial layer (limbal epithelial stem cells) - REGENERATES
2. Bowman’s layer
3. Stromal layer - colloagen 1, continuous with sclera
4. Descemet layer - collagen 4
5. Endothelium

Question 5

Bacterial keratitis

Answer 5

Organisms: pseudomonas, staph, and strep
Features: unilateral red eye, pain, ↓ VA, mucupurulent discharge, hypopyon, white infiltrates
Mx - scrapings to lab, topical abx fluoroquinolones

complications - perforation in :
Neisseria gonorrhoea
haemophilus influenzae
Corynebacterium diphtheriae

Question 6

Fungal keratitis causes

Answer 6

immunocompromised: candida
Hx of ocular trauma: filamentous fungi e.g. aspergilus or Fusarium

Question 7

Candida keratitis sign

Answer 7

small plaque ulcer with expanding infiltrate ‘collar stud’

Question 8

Filamentous keratitis sign

Answer 8

Feathery branching like infiltrate

Question 9

Mx of fungal keratitis

Answer 9

Candida keratitis - Voriconazole or amphotericin B drops
Filamentous keratitis - Natamycin drops

Question 10

Acanthamoeba keratitis

Answer 10

out of proportion pain
Acanthamoeba protozoa
Main risk factor: swimming and contact lens
Sign - Neural ring corneal infiltrates
Mx: polyhexamethyl biguanide (PHMB) or chlorhexidine

Question 11

HSV keratitis (epithelial)

Answer 11

red eye, foreign body sensation, pain, epiphora
Early - stellate (star shaped) corneal ulcer
Late - Dendritic ulcer under fluorescein dye

mx - topical acyclovir. AVOID STEROIDS

Question 12

HSV endothelial keratitis

Answer 12

Hypersensitivity to HSV antigen

Painless ↓ VA
Central circular stromal oedema
Wessely ring sign (deposition of immune complexes)

Mx - oral acyclovir

Question 13

Herpes zoster ophthalmicus

Answer 13

Hutchinson sign (nasociliary nerve involvement)
pseudodendrites - grey and not ulcerated
conjunctivitis and raised IOP

mx - oral acyclovir

Question 14

Marcus Gunn pupil

Answer 14

RAPD

Question 15

Interstitial keratitis

Answer 15

inflammation of corneal stroma without epithelial or endothelial involvement

Causes:
1. Syphilis
2. Cogan syndrome (AI, tinnitus and vertigo, sensorineural hearing loss)
3. Lyme disease (Borrelia, tick bites, erythema migrans)

Question 16

Hutchinson triad (syphilis)

Answer 16

Nothed teath
Interstitial keratitis
sensorineural deafness

Question 17

Marginal keratitis

Answer 17

Type III hypersensitivity reaction to staph exotoxin
associated with rosacea and blepharitis
typically where cornea touches the eye lid

Question 18

Peripheral ulcerative keratitis (PUK)

Answer 18

Peripheral corneal inflammation and thinning
Spread posteriorly and centrally
Causes: Infection or AI (Rheumatoid arthritis, polyarteritis nodosa, relapsing polychondritis)

Mx - oral steroids ± DMARD (not topical!)

Question 19

Ocular rosacea

Answer 19

• posterior blepharitis
• eyelid telangiectasia
• peripheral corneal vascularisation

mx: lubricants, hot compress, oral tetracycline

Question 20

Filamentary keratitis

Answer 20

Corneal epithelium degeneration > mucus and strands adhering

RF: dry eyes, LASIK, contact lens

Fx: red eye, pain, epiphora, foreign body sensation

**Rose bengal staining - comma shaped lesions move with bilinking

Question 21

Keratoconus associations

Answer 21

Bilateral irregular thinning of corneal stroma and corneal coning

Association with:
- Marfan syndrome
- Down syndrome
- Ehlers Dansol syndrome
- Leber congenital amaurosis
- Retinitis pigmentosa

Question 22

Keratoconus features

Answer 22

irregular astigmatism
Munson sign (lower eyelid v on downward gaze)
Vogt striae (vertical striae in corneal stroma)
Oil drop reflex
Scissor reflex

Question 23

Keratoconus Ix

Answer 23

Steep keratometry
Corneal topography e.g pentacam

Question 24

Keratoconus complications

Answer 24

Tear in Descement membrane - corneal oedema
Acute hydrops

Question 25

Keratoconus mx

Answer 25

Mild : spectacle correction with cylindrical lenses
Moderate : rigid contact lens or corneal collagen crosslinking with Riboflavin and UVA
Severe : keratoplasty

**LASIK is contraindicated

Question 26

Kayser Fleischer ring

Answer 26

Ring copper deposition in Descemet membrane in Wilson disease

Question 27

Wilson disease

Answer 27

AR deficiency in ceruplasmin - copper deposition
Hepatic fx
Kayser Flescher ring

Mx - chelation via Penicillamine

Question 28

Band keratopathy

Answer 28

Calcium deposition in Bowman’s layer
Mx chelation with EDTA

Question 29

Fabry disease

Answer 29

X linked recessive
lysosomal storage dx
Vortex keratopathy and posterior cataracts

Question 30

Corneal dystrophies

Answer 30

1. Epithelial
2. Anterior
3. Stromal
4. Endothelial

Question 31

Epithelial corneal dystrophies

Answer 31

1. Cogan dystrophy (map-dot-fingerprint dystrophy)
2. Meesman corneal dystrophy

Question 32

Anterior corneal dystrophy

Answer 32

Reis Buckler dystrophy (replacement of bowman’s layer with connective tissue)

Question 33

Stromal corneal dystrophy

Answer 33

‘Maryline Monroe Always Gets Her Men in L. A. County’

‘Marylin Monroe Always’ : Macular dystrophy - Mucopolysaccharide - Alcian blue (staining)

‘Gets Her Men’ : Granular dystrophy - Hyaline materials - Masson trichrome (staining)

‘L. A. County’ : Lattice dystrophy - Amyloid - Congo red (staining)

Question 34

Endothelial corneal dystrophy
(Fuch’s endothelial dystrophy)

Answer 34

Failure of Na/K pump - fluid accummulation and corneal oedema leading to endothelial cell loss

Fx: elderly woman with blurry vision worse in the morning
specular microscopy > corneal guttate (beaten metal appearance)
increaed central corneal thickness