unit 2 cont.. (quiz 3) Flashcards
what is lens surface crazing
-surface cracks in the GP
-appear as multple cracks or a mesh-like lattice
symptoms of lens surface crazing
poor or fluctuating vision
causes of lens surface crazing
-matierial related problems
–weakness in the structure of the lens material or surface stress induced lens manufacture
-patient use of alcohol based cleaners
treatment for lens surface crazing
-it is not possible to remove the surface cracks
-GP lenses must be replaced
dimple veiling
-trapped air bubbles underneath the GP lens -> causes pits to form in the cornea
-Not true staining
-DO NOT move with the tear film when blinking
-appear as bright green dots
-once CL is moved it goes away
symptoms of dimple veiling
sometimes reduced vision
-reduces the corneas optics
causes of dimple veiling
steep fitting GP CL
treatment for dimple veiling
flatten the lens
-flatten the BC or decrease diameter
why does wettability matter?
- a non-wet surface allows lens depostis to attach to the lens easily
-A non-wet surface decreases a pxs VA
-a non-wet surface increases friction with the inner eyelid which can cause discomfort
how does poor surface wettability appear?
-appears as “beads” of liquid on the lens surface
-can also have a filmy or deposit like apperance
Causes of poor wettability
-matieral or manufacturing problem of the GP
-Lenses may have a waxy residue from the production proccess
-px related issues..
-improper cleaning
-dry eye disease
-use of lanolin-containing soap/lotion
treatment options for poor wettability for CL issues
-pre soak the lens overnight prior to dispense
-use a solvent followed by reconditioning with wetting solution
-plasma treatment to remove waxy residue
-refit to a diff lens matieral
treatment causes for poor wettability in respect to px cause
-make sure the px learns proper technique for care including rubbing lenses and using the solution properly
-avoid lanolin creams and soap prior to handling lens
-treat dry eye desease
5 layers of cornea
-epithelium
-bowmans layer
-stroma
-descemets membrane
-endothelium
how corneal infection develops
- corneal epithelium is damaged
- microbes invade cornea
- immune response activated
- cornea becomes inflamed
- microbes penetrate deeper and cause scaring
The avascular cornea
-the cornea is avascular (without blood vessels)
-when a px wears CLs, oxygen flow to the cornea is reduced
-can lead to cornea hypoxia (lack of oxygen to cornea)
corneal hypoxia
-primarily caused by CL wear
-causes a series of events to occur which impacts corneal health
how to reduce risk of corneal hypoxia
-using contact lens materials with high oxygen transmisibility (DK/t)
-avoid over wear of extended wear of CLs
corneal neovasularization
-happens when the cornea continues to receive limited oxygen, this can cause new blood vessels to grow from the conjunctiva into the cornea
symptoms of corneal neovascularization
-sometimes no symptoms (if mild)
-cloudy/hazy vision (if severe)
-from damage to the clear corneal tissue (loss of transparency)
-from blood veseels blocking or bending light entering the eyes
treatment options for neovascularization
-refit to a more breathable lens
-discontinue CL wear until resolved
-px education
Limbal vessel encroachment
-Precursor or ‘warning sign’ of future neovascularization
-increase in limbal vasculature and extension into the hazy zone of the limbus
what is corneal infiltrates
-inflammatory cells in the corneal tissue
-grey or white in apperance
-Indicates that white blood cells have migrated to the stroma
symptoms of corneal infiltrates
-sometimes asymptomatic
-irritated, watery eyes
types of corneal infiltrates
- Infectious -> Bacteria, viruses
- Sterile-> means NOT infectious
-CL wear is the most common cause of sterile infiltrates
what is a corneal ulcer
-an open sore in the outer layer of the cornea
-most commonly caused by an infection
-other causes .. severe dry eyes, abrasions or burns
-ulcer is best visualized with fluorescein (appear green)
apperance of a corneal ulcer
white spot or mark on the cornea that stains with fluroscien
Main risk factor of corneal ulcer
CL wear is the #1 risk factor
-in contact lens wearers, ulcers can cause permanent vision loss
-treat quickly to avoid corneal staining
-URGENT REFERRAL
difference between infiltrate and ulcer
-Infiltrate= white blood cells in corneal stroma, hazy/white with no fluroscein stain
-ulcer= loss of stromal tissue, causing a divot, can also be hazy but ALWAYS stains with fluroscein
can infiltrates sometimes later turn into an ulcer?
yes, but not always
do infiltrates and ulcers represent a sign of another disease?
yes, they can exist as their own conditino but also represent a sign of another disease state such as
-contact lens specific conditions
-keratits
CLARE - contact lens acute red eye
-inflammation of the outer surface of the eye
-only occurs in pxs wearing CLs (most common from extended wear)
-inflammation results from lack of oxygen, contamination of the CL with bacteria or protein deposits
NOT A TRUE CORNEAL INFECTION
what do you see when someone has CLARE
-corneal infiltrates
-conjuctival redness
signs of CLARE
-360 degrees red eye, often worse near the limbus
-infiltrates, often multiple
-ususally unilateral
-NO staining w/ fluroscein
symptoms of CLARE
-Typically in extended wear CL pxs who wake up with red and painful eye (after sleeping in CL)
-watery
-irritated
treatment of CLARE
-discontinue CL wear until resolved
-Refer - might need medicated eye gtts like a steroid
-prescribe new CLs: daily, or lenses with higher Dk/t
-improve px habits
CLPU - contact lens peripheral ulcer
-inflammatory condition causing loss of epithelial and stromal tissue
-a sterial ulcer (NOT INFECTIOUS)
apperance of CLPU
-infiltrate with fluroscein stain in peripheral location
-small
-circular
-well defined
how to reduce bacterial sources to prevent reocurrence
-lid hygiene
-increase CL replacement
-chance care system/solution
what happens when you discontinue CL wear when you have CLPU
typically heals is 3-4 days
-faint scar may persist for several months
what is Keratits
-inflammation of the cornea
-may or may not be associated with an infection
-generally affects one eye
-all cases require an urgent referral to prevent permanent vision loss
2 types of keratits
-Non infectious keratits
-infectious keratits
Types of noninfectious keratits
- Toxic keratits
- Vascularized limbal keratits
-caused by an eye injury (scratch or damage to corneal surface)
types of infectious keratits
- bacterial keratits
- fungal keratitis
- acanthamoeba keratits
- viral keratitis
symptom of keratitis
- red eye
-eye pain
-blurry vision
-watery eyes
Keratitis signs
-Possible infiltrate
-possible ulcer
toxic keratitis
-direct contact of hydrogen peroxide cleaning solutions with the eye
-appear as small dot-like opacities on the cornea that stain w/ fluroscein
treatment for toxic keratitis
-irrigate eyes
-artifical tears
-no CLs until resolved
-px education
Vascularixed limbal keratitis (VLK)
-rare complication of GP lens wear
-most commonly from extended wear of GP lenses which damage the limbal stem cells
-chronic 3 and 9 staining can lead to the development of VLK
3 clinical signs associated with VLK
- severe 3 and 9 staining
- raised, inflamed, semi-opaque epithelial lesion
- localized vascularization of conrea
symptoms of VLK
-lens awareness
-localized ocular pain
-red eye w/ elevated corneal mass upon self inspection in mirror
treatment of VLK
-ATs
-evaluate lens and fit
-evaluate lens diameter
(consider smaller diameter to decrease mechanical irritation to limbus and cornea)
CL related risk factors for developing infectious keratits
-sleeping in CLs
-swimming/showering in CLs
-poor CL hygeine habits
-improper CL solution use
-not disposing of CLs as directed
How common is infectious keratitis
-approx 2-20 cases per 10,000 contact lens wearers each year
-90% of cases were in soft CL
-10% of cases were in GP
Bacterial keratitis
-most common form of keratitis (90% of cases)
-develops rapidly (2-3 days)
-In CL wearers, bacterial keratitis is most commonly caused by a bacterial called pseudomonas aeruginosa
-round/oval white lesions
what do pseudomonas do
easily attach to the surface of CLs and survive in ocular enviroments
signs and symptoms of bacterial keratitis
-eye pain
-blurry vision
-red eye
-mucopurulent discharge
-eyelid swelling
-hazy cornea (infiltrate)
-hypopyon
-anteriror chamber reaction
treatment of bacterial keratitis
-emergency referral
-antibiotic eye drops (depending on severity. may use gtts as frequently as every 30mins)
-possibly oral antibiotics
-no CL wear until resolved
-can use eye gtts to control pain (cycloplegic)
viral keratitis
-history of cold sores
-dendritic ulcer (branching epithelial defect)
fungal keratitis
-trauma, vegetative/outdoor
-infiltrate with feathery edges
-grey-white lesion
protozoal keratitis AKA acanthamoeba
-contact lenses (poor hygeine)
-ring shaped infiltrate
how thick is the cornea?
540um
corneal anatomy
-no blood vessels to supply nutrients or protect against infection
-Nutrients via diffusion
~tear film/air
~aqueous humor
~closed eyelids
-robust limbal blood supply
-transparent
~nonvascular
~dehydrated
