Cornea And Layers

Question 1

What’s the nerve supply of cornea

Answer 1

TON

Trigeminal’s - opthalmic branch’s— nasociliary branch

Question 2

Corneal anaesthesia causes ( corneal reflex absent)

Answer 2

HDL ACTS
Herpes
Diabetes
Leprosy
Acoustic neuroma
Contact lense
Topical timolol
Surgical trauma

Question 3

Layers of eye

Answer 3

Outer- cornea, sclera, limbus
Middle(aka uvea)-iris,ciliary body, choroid
Inner- retina

Question 4

Corneal reflex pathway

Answer 4

Afferent—sensory NV 5
Efferent— motor 7th NV to orbicularis oculi

Orbicularis oculi is the muscle of eyelids

*Bell’s palsy-orbicularis oculi palsy- inability to blink —lagopthalmus

Question 5

Layers of cornea

Answer 5

6 layers
Epithelium
Bowmans 
Stroma
Duas
Descemets
Endothelium

Question 6

Corneal transparency is maintained B y

Answer 6

Tear film
Avascularity
Collagen fibres in stroma have uniform diameter
Corneal dehydration maintained by endothelium
Normal intraocular pressure
Crystallins in corneal stroma reduce teh backscatter of light

Question 7

Microcornea is a

Answer 7

Autosomal dominant ul/bl condition
Horizontal corneal diameter is <10mm or lessover 2 years of age

Saved ques 1 module

Question 8

Organisms capable of penetrating intact cornea ( penetrates cornea without presence of ulceration)

Answer 8

~~~
Cornybacterium dipthriae
Nessaria meningitidis
Gonorrhoea
H.influenzae
H.aegypticus
Shigella
Listeria
Shigella

CHaNNeLS

Question 9

Corneal investigations

Answer 9

Keratometry- measure corneal curvature, diagnose astigmatism, contact lens curvature fitting, diagnose keratoconus

Pachymetry
Measure corneal thickness(0.54mm)
In case of LASIK
IOP Measurement

Topography
Corneal surface

Question 10

Bacterial keratitis causes

Answer 10

Staph aureus (mcc)

Staph aureus mcc

Pneumococcus in india mcc (ulcer serpens)

Psudomonas in contact lens wearers ( pseudomonas can cause corneal perforation in just 48 hrs)

Atypical mycobacterium mcc in prior LASIK surgery

Nocardia cause wreth shaped ulcers
Or pin head ulcers

Mc fungi aspergillus

Question 11

Treatment of corneal ulcer

Answer 11

Fortified antibiotics

1. Fortified cefazolin and fortified tobramycin (5%)
2. Atropine eyedrops
3. steroids are c/i as they promote epithelial thinning
4. In case of impending perforation use doxycyclin

In fungal corneal ulcer hypopion is immobile and asterile
satellite lesion( more signs than symptoms)
Antifungals
Natamycin 5% eyedrops( natamycin is the DOC for filamentous fungi)
Amphotericin B

Acanthamoeba keratitis ( contact lens + contaminated water—- more symptoms than signs)
Doc PHMB ( polyhexamethyl biguanide)
Propamidine
Chlorhexidine

Viral keratitis — hsv( dendritic ulcer on fluorescent staining)
3% acyclovir eye ointment

Question 12

Characteristics of fungal corneal ulcer

Answer 12

Caused by trauma with vegetative or organic matter
Signs are more pronounced than symptoms
Corneal ulcer appears dry
Feathery finger like extension present
Sterile, immune ring ( yellow line of demarcation) may be present( presence of immune ring is type 3 hypersensitivity reaction)
Small satellite lesions maybe present around ulcer
A big nonsterile hypopion
Perforation in mycotic ulcer is rare but can occour
Mcc is aspergillus
Pigmented ulcer maybe caused by some species of fungi

Question 13

Ocular lesions in heroes

Answer 13

Primary herpes- fine and coarse epithelial punctate keratitis
Dendritic ulcer

Recurrent herpes - punctate epithelial keratitis, dendritic ulcer, geographical ulcer, disciform keratitis, diffuse stromal necrotic keratitis

Question 14

Hutchinsons rule

Answer 14

Related to herpes zoster opthalmicus. It states that if the tip of nose is involved there will be significant risk of ocular involvement. This is due to involvement of nasociliary nerve

Question 15

Microcornea
Megalocornea

Answer 15

Horiz dia <10 mm or <9mm in newborn
Horiz dia >12 mm or >13 mm in >2 yr old