Diseases of the Cornea and Corneal Refractive Surgery - Anterior Segment & Ocular Disease Fall 2025

cornea

The _____ is responsible for 75% of the refractive power of the eye

avascular

The cornea is a (vascular/avascular) structure

comes from the AH and the tear film

Where do the nutrients of the cornea come from if it is an avascular structure?

highest

The cornea has the (highest/lowest) conc of nerves in the body

the first division of the trigeminal nerve

The subepithelial and deeper stromal corneal nerves are supplied by what?

11.5mm vertical and 12mm horizontal

Corneal diameter?

540 micometers

Avg corneal thickness?

-epithelium

-Bowman's

-stroma

-Descemet membrane

-Endothelium

What are the 5 layers of the cornea?

stratified squamous

The epithelium of the cornea is made up of _______ cells

nonkeratinized

The epithelium of the cornea is (keratinized/nonkeratinized)?

-basal cells

-wing cells

-squamous surface cells

-microplica and microvilli

What cells is the corneal epithelium composed of?

adhesion of the mucin layer of the tears to the cornea

What do the microvilli and microplica of the corneal epithelium assist in?

in the limbus

Where are corneal stem cells located?

yes

Will the corneal epithelium regenerate after trauma?

Bowman layer

acellular superficial layer of the stroma

collagen fibers

What is Bowman layer of the cornea composed of?

stroma

What makes up 90% of the corneal thickness?

regularly orientated layers of collagen fibrils

What is the corneal stroma composed of?

regular orientation and spacing of collagen

What allows the cornea to remain clear?

no

Will the corneal stroma regenerate following trauma?

Descemet membrane

What layer is composed of fine latticework of collagen that is distinct from the stroma?

2 bands

How many bands in Descemet membane?

One develop in utero and one that is laid throughout life and serves as a basement membrane for the endothelium

When do the 2 bands of Descemet membrane develop?

endothelium

monolayer of hexagonal cells that are responsible for deturgescence of the cornea

corneal edema and hazing

What are the consequences to corneal endothelium pathology?

punctate epithelial erosions

tiny epithelial defects

fluorescein or lissamine green/rose bengal

What will PEEs stain with?

corneal compromise

What are PEEs an early sign of?

throughout the cornea

Where are PEEs located?

VKC, SLK, floppy eyelid

Superior PEEs can be indicative of what diseases?

dry eye

Interpalpebral PEEs can be indicative of what diseases?

chronic blepharitis

Inferior PEEs can be indicative of what diseases?

viral

Diffuse PEEs can be indicative of what diseases?

contact lens related

Central PEEs can be indicative of what diseases?

punctate epithelial keratitis (PEK)

swollen epithelial cells

-granular

-opalescent swollen epithelial cells

What is the presentation of punctate epithelial keratitis (PEK)?

-Lissamine Green/Rose Bengal

-variable staining with fluorescein

What will punctate epithelial keratitis (PEK) stain with?

-viral infections

-Thygeson superficial punctate keratitis

When will punctate epithelial keratitis (PEK) be seen?

subepithelial infiltrates

non-staining inflammatory cells

below the epithelium of the cornea

Where are subepithelial infiltrates located?

limbal vasculature

Where are inflammatory cells released from?

adenoviral keratoconjunctivitis, HZO, marginal keratitis

What are subepithelial infiltrates seen with?

no -- they do not stain because they are under the epithelium. The epithelium is not intact

Will subepithelial infiltrates stain?

-infiltrates are not well defined

-corneal scars are well defined

Are epithelial infiltrates well defined? How are you able to tell them apart from corneal scarring?

filaments

mucus strands attached to the cornea

where there is an epithelium break

Where will filaments attach?

tear debris

What will surround a mucus strand?

with dry eye, SLK

When are filaments usually seen?

superficial punctate keratitis (SPK)

non-specific round corneal epithelial disruption of round morphology

corneal disease

What is superficial punctate keratitis (SPK) seen with?

SPK - inflammation present, PEE - no inflammation present

What is the main difference between SPK and PEEs?

no

Will you be able to tell the difference between SPK and PEEs on slit lamp examination?

epithelial edema

swelling of the cornea

epithelial vesicles (bullous blistering)

What will epithelial edema present as?

endothelial compromise (dead cells or decreased number)

What will epithelial edema be seen with?

yes -- cornea is very innervated

Are the bullous (blisters) that are caused by epithelial edema painful?

corneal neovascularization

blood vessel growth into the cornea at the limbus

corneal irritation or hypoxia

What is corneal neovascularization a sign of?

pannus

superficial neovascularization with subepithelial degeneration

no -- it is a scar

Is pannus resolvable?

no -- takes a long time for pannus to present

Will pannus be acute onset?

deep infiltrate

inflammatory cells, cellular debris, and tissue necrosis located in the anterior stroma

white/grey

How will deep infiltrates of the corneal stroma appear?

conj hyperemia

What will also be present with deep infiltrates?

ulceration

excavation of corneal tissue with epithelial defect

deep infiltrate

Ulceration is seen with what?

melting

corneal tissue disintegration

maybe or maybe not

Will a corneal infiltrate be seen with corneal melting?

Folds of Descemet

dark, deep-appearing, criss-cross lines in the posterior stroma

cornea may appear hazy due to corneal edema

When folds of Descemet are present, will the cornea be completely clear? Why?

after cataract sx

When are folds in Descemet membrane typically seen?

yes -- they are transient and go away with time

Will Descemet folds go away over time?

Breaks in Descemet membrane

due to corneal enlargement (infantile glaucoma), birth trauma, or keratoconus

-opaque

-white/grey

What color will breaks in Descemet membrane be?

no -- these do not go away

Will breaks in Descemet membrane go away over time?

descemetrocele

protrusion of Descemet membrane into the anterior layers of the cornea

severe ulceration

What is descemetrocele seen with?

corneal dystrophy

group of slowly progressive usually bilateral corneal opacification that may cause a decrease in vision and discomfort

only one

A corneal dystrophy will typically affect _____ layer of the cornea

center, periphery

A corneal dystrophy will start in the _____ of the cornea and migrate to the _____ of the cornea

no -- this is a white eye condition

Are corneal dystrophies inflammatory?

yes, majority are autosomal dominiant

Are corneal dystrophies genetic?

younger patients

What population do corneal dystrophies occur in?

Epithelial Basement Membrane Dystrophy (Cogan or Map Dot Fingerprint)

What is the most common corneal dystrophy?

40%, 70% of the population over 50+

What proportion of the population does Epithelial Basement Membrane Dystrophy affect?

2nd decade of life

What is the onset of Epithelial Basement Membrane Dystrophy?

females

Is Epithelial Basement Membrane Dystrophy more common in males or females?

no clear pattern -- can be d/t trauma and some consider it more of a DEGENERATION

What is the inheritance pattern of Epithelial Basement Membrane Dystrophy?

synthesis of an abnormal basement membrane

What is the pathophysiology of Epithelial Basement Membrane Dystrophy?

faulty adhesions between the basement membrane and the epithelium of the cornea

What is the cause of Epithelial Basement Membrane Dystrophy?

Causes the epithelial tissue to heap up

In Epithelial Basement Membrane Dystrophy, the basement membrane extends into the epithelium and causes what?

map

The elevated tissue of Epithelial Basement Membrane Dystrophy will give the classic sign of a what?

develops dots and other cystic changes

Migrated cellular material becomes trapped and develops what in Epithelial Basement Membrane Dystrophy?

will develop into fingerprints

Adjacent rows of thickened and elevated epithelium will develop into what in Epithelial Basement Membrane Dystrophy?

-asymptomatic

-blurred vision worse in the AMs

-diplopia

-dry eye

-FB sensation

What are the symptoms of Epithelial Basement Membrane Dystrophy?

maps, dots, fingerprints

What is the presentation of Epithelial Basement Membrane Dystrophy?

large geographic lesions

What do the maps of Epithelial Basement Membrane Dystrophy appear as?

line (in isolation)

What do the fingerprints appear as in Epithelial Basement Membrane Dystrophy?

negative staining -- elevated epithelium

Lesions in Epithelial Basement Membrane Dystrophy will have (positive/negative) staining?