module 1 corneal surface defects and dry eye syndrome Flashcards
corneal surface defect
when the corneal epithelium is interrupted
- trauma from foreign objects
- contact lens wearers: prolonged use of lenses
Full-thickness lacerations
can occur with ocular trauma and sometimes appear slimialr to epithelial defects
infectious keratitis
corneal ulcer
- epithelial defect with an infiltrate, or white area in the cornea.
corneal abrasion
partial or complete defect in the epithelial layer after some traumatic event or UV light exposure
causes:
- chemical or mechanical debridement -> trauma
- chemicals
- ultraviolet radiation
corneal erosions
Occur if an abrasion disrupts the Bowman layer, partial or complete with no assoc. to trauma
- dec. evaporations during sleep -> formation of a fluid layer above the non-healed bowman layer and below the epithelium.
- can lead to repeated sloughing of epithelium
- allows bacterial, viral, or fungal organisms to invade -> ulcer
Bowman layer
smooth, acellular layer of tissue just beneath the corneal surface
corneal abrasion or foreign body s/s
sudden onset severe eye pain
- resolves with topical anesthetic
foreign body sensation
blurred vision
redness
tearing
light sensitivity
eyelid swelling
blepharospasm
corneal abrasion or foreign body physical exam
vision may be limited if defect of foreign body falls within the visual axis
eyelids may appear swollen
conjunctiva is injected
cornea may have mild haze
foreign body may be visible
linear vertical lines seen with fluorescein dye
typically caused by subtarsal (under eyelid) foreign bodies
- eversion of upper eyelids to check
branching or dendritic pattern defect with fluorescein
herpetic cause
full-thickness laceration and fluorescein
irregular iris
shallow anterior chamber
pharmacological tx of corneal defects and foreign bodies
supportive care
- pain relief: oral analgesics
- prevent bacteria superinfection
topical antibiotic ointment
lubricating drops/ointment
Pressure patching should be avoided
Steroids contraindicated
Topical anesthetics should never be used/Rx’d for pain
corneal epithelium follow up (RSVP)
seek urgent ophthalmology eval if:
R: redness- sudden
S: sensitivity to light or Secretion
V: decreased Vision
P: Pain
Chemical injury tx
immediate irrigation
- Alkali injuries -> rapid damage: saponification of fats and denaturation of collagen -> penetration of the anterior chamber and damage to intraocular structures
- Acid: cause corneal surface proteins to coagulate and create a barrier that prevents deeper penetration
Recurrent corneal erosion syndrome
spontaneous erosion occurs at the site of a previous injury weeks to months later
dry eye syndrome
multifactorial disorder characterized by abnormalities in the tear film
-> damage to the ocular surface
dry eye patho
maintained by autonomic and reflexive functions of the peripheral and motor nervous system
3 layers:
- inner mucin layer
- intermediate aqueous layer
- outer lipid layer: meibomian gland production: limits evaporative loss of the underlying aqueous layer between blinks
2 categories of dry eye
aqueous-deficient
evaporative dry eye
aqueous deficient dry eye
typically localized to the lacrimal gland
gland insufficiency may be caused by:
- Sjogren disease
- other infiltrative diseases
- primary hyposecretion
evaporative dry eye
Causes:
- meibomian gland dysfunction: obstructed
- poor eyelid closure
- inadequate blinking
- ocular rosacea
Inflammation and dry eye
inflammatory cytokines affect tear film osmolarity
-> inc. tear film instability and evaporative loss
-> further inflammation
dry eye s/s
dryness
foreign body sensation
burning
stinging
itching
ocular fatigue
redness or light sensitivity
transient blurred vision relieved by blinking
- worse with activities requiring visual concentration
- Paradoxically: some patient have hypersecretion of tears
Medications that can lead to dry eye
anticholinergics
alpha blockers
antihypertensives: diuretics, beta blockers
oral corticosteroids
vitamins
Auto-immune disorders and dry eye
lupus
rheumatoid arthritis
-> secondary sjogren syndrome
Thyroid eye disease
Other causes for dry eye
- Cranial nerve VII palsy: eyelid malposition, poor closure
- Reactivation of vericella zoster in ophthalmic division
- dec. corneal sensitivity and lower blinking rate
dry eye physical exam
visual acuity
inspect: ocular adnexa
Cranial nerve V and VII function
Schrimer test
assess aqueous production:
ABNORMAL= aqueous deficient dry eye
- narrow piece of filter paper placed in inferior cul-de-sac
- tear production measured by how wet the paper is after 5 minutes.
– less than 5mm (w/ anesthesia) or less than 10mm (without anesthesia) is considered abnormal
Tear breakup time
fluorescein dye instilled and the tear film is visualized with blue filter
- amount of time between the last blink and the first discontinuity in the tear film is recorded
- less than 10 seconds is abnormal
ABNORMAL = evaporative dry eye
OSDI
Ocular Surface Disease Index
patient symptom questionnaire to assess dry eye severity and to monitor patient response to tx
Dry eye tx
Nonpharm:
- lifestyle or workplace modification
- avoid windy, smoky, low-humidity environments
- lid hygiene: warm compresses and gentle lid scrubs with baby shampoo
Pharmacological:
- artificial tears
- gels/ointments provide better tear retention but cause visual blurring
- Drops with vasoconstrictive agents discouraged d/t rebound vasodilation and conjunctival injection
complications from dry eye
chronic changes in corneal nerve morphology and neuro-transmission
chronic neuropathic ocular pain
conjunctival adhesions
scaring and neovascularization of the cornea
exposure to the ocular surface -> corneal thinning, ulceration, and infection
corneal ulcer
deeper, involves underlying stromal layer
hypopyon
pus in anterior chamber of eye
