Final Flashcards
Top 3 considerations with SCL
wet ability, mechanical, o2 perm
Polymer in CL
Bind H20 or oxygen permeability.
How to make CL
Hema background, polymerize, add water.
Ways to make SCL
Lathe cutting, spin casting, cast molding.
SCL Advantages
comfort, large size, easy to fit, decreased flare/glare, decreased spectacle blur, eye color change.
SCL Disadvantages
cost, doesn’t mask astigmatism, VA, Optics, more risks, hard to verify, increased risk, life expectancy.
When to prescribe SCL
spherical, low astigmatism, sports, part time, good tear film, previous GP failure, extreme refractive errors, anisometropia.
CI with SCL
compromised eye: surgery, oc dz, systemic dz, poor hygiene, atopic disease, vascularization. High astigmatism or irregular.
Extended wear
6 days
DW
Only during the day
FW
Flexible wear. Sometimes DW and sometimes EW
Low CL H20
20-40
Medium CL H20
41-60
High CL H20
Greater than 60
How is water content determined
by weight
High water content dehydrates ______
More quickly.
Low water content
Has more structural integrity. Stiffer.
High water content lens ____ quicker and _____ sooner
dehydrates; equilibrates.
Hydrophilic monomers
HEMA, GMA, VA, MA
Non-ionic hydrophilic
HEMA, GMA, VA. Interaction without a formal charge
Ionic hydrophilic
MA. Needs a formal charge.
Hydrophobic monomers
Mechanical strength. Silicone.
Cross Linking agents
mechanical strength and thermal stability.
Silicone Hydrogel
Good oxygen permeability, also referred to as SCL, similar diameters.
DK for overnight wear
Needs to be 125 to sonly 4% occurs. 4% is swelling that occurs in closed eye.
What are the only lenses that meet the ability for NW
Silicone hydrogel
How to optimize oxygen transmission
Silicone, H20, decreased thickness.
DK vs H20
Increasing DK results in decreased H20. DK does not like water.
Biofinity
An outlier. Somehow has high water and high DK.
Silicone hydrogel
High DK and low H20
Conventional hydrogel
Low DK and high H20
Limbal hypermia and lenses
Less hyperemia with silicone hydrogel.
SCL Optics
Tear lens does not go under the tear. Don’t need to take it into account. Refractive index changes with hydration and temperature.
Aspheric CL
Controls spherical aberrations. Get power at center but may change as leaves center. Doesn’t compensate though. All peripheral rays center in the same place.
Spherical CL
Power is constant. Central and peripheral rays are not focused at a single point.
FDA Ionic division
Ionic if >0.2% ionic material
FDA water content division
Low >50. High
FDA Group 1
Low water and non-ionic
FDA Group 2
High water content and non ionic
FDA group 3
Low water content ionic
FDA group 4
High water content and ionic.
Time for a group 5
Silicone hydrogels are unique and some think they should have their own group
Unique silicone hydrogel
Low protein deposits, high lipid deposits, surface wet ability varies, unique solution interactions.
Silicone hydrogel protein deposits
Low. Less uptake than hydrogel. Concentration near the surface. More denatured. Presents as GPC.
Silicone hydrogel lipid deposits
more attraction. Sometimes require surfactants.
Modulus
High=stiffer and longer wear time. Pro: easier handling and removal. Con: comfort and moves on eye
Modulus of silicone hydrogels
LOW
Who determines replacement schedule?
ODs
Does replacement schedule =wear time
NO
Disposable
Remove and discard. Right after taken from eye throw away.
Quarterly replacement
Speciality CL
Typical SCL parameter
13.8-14 mm. 38-60%. .06-.2 mm. Sphere +6-12. Cylinder: 0 to -2.25
SCL fitting
Measure patients HVID and pick one 2 mm larger. Obtain central Ks. Select a BC. Evaluate
Time for equilibrations
5-10 minutes
Ideal SCL fit
1 mm from limbus, .25-.5mm with blink, .5-1.25mm with blink on up gaze.
Push up test
Push up and then see force required and how long to decenter.
Normal BC Radius
The normal BC will fit many different corneas.
Flat CL
May be uncomfortable due to excessive movement. May have fluting.
Which lens move the most
very flexible lenses as they confirm to the eye.
How to fix a CL that is too flat
Steepen the base curve or increase the overall lens diameter.
Steeping the BC ____ the fit
tightens.
Steep Soft lens fit.
Will not move with blink, may be initially comfortable but become tired later. Difficult to dislodge.
How to fix a steep CL
Decrease lens diameter, decrease BC.
Labeled vs. actually BC
Different brands will label different. A 8.4 BC is flatter than an 8.7 cooper vision.
Lid with SCL
can decenter lens. Often overlooked
Tear exchange with RGP
20% per blink
Tear exchange with SCL
1% per blink
Importance of tear exchange
oxygen, nutrients, debris, eliminate waste
IF patient tearing with lens suspect
FB beneath lens, lens inside out, solution sensitivity, Lens damage.
Thin lens and water evaporation
A thin lens will take water from TF.
Corneal radius and sagital height
greater radius=deeper.
Corneal diameter and sagital height
Greater diameter=greater sagittal height.
A steep cornea often goes with what?
A small cornea
Effective K
Used to assist in the selection of BC radius. Incorporated central corneal radius and corneal diameter.
How to calculate effective K
For every .2 mm mean K smaller than 11.8 mm subtract 1 D. For every .2 mm mean K greater than 11.8 add 1 D.
Selecting a SCL
Find Mean K. Calculate Effective K. Take diameter of eye. Add from the BC chart.
When was the first hydrogel lens approved?
1971
Next way to disinfect lenses?
Use heat disinfectant but since with non sterile saline. Also tired salt tablets and distilled water.
When was the first chemical disinfectant for SCL invented
1977.
Solution sensitivity
Thimerosal and/or chlorhexidine
Heat disinfectants
Very effective. However can denature tear secretion on the lens and affect the lens. Could do a 90s microwave.
Modern SCL
Affective against many organisms. Compatible with ocular tissue, lens polymers. Continue to work under many condition. Less than 1 hour for disinfection. Easy to use and cheap.
MPS
Cleans, rinses, disinfects.
Modes of Cl disinfection
- Rub, rinse, soak 2. Rinse soak 3. immersion only
Recalled lens care products
Gave fungal keratitis and acanthamoeba.
What makes up the TF
mucous, aqueous, inorganic, organics, proteins, lipid lay.
What is SCL drops out due to
51% discomfort (41% dryness) 13% vision problems (reading 6%, General vision 7%)
Silicone Hydrogel and TF
High oxygen transmission, dehydrate slower then HEMA, SH have less protein and more lipid. May have reduced wet ability due to silicone.
POLYQUAD/ALDOX
Less corneal staining
Best cleaning for silicone hydrogel
Hydrogen peroxide
Disinfection times with hydrogen peroxide
Platinum disc (longer) vs. catalase.
Clear Care cleaning
3% peroxide for 10 minutes. Platinum disc neutralization replace the disc every 90 cycles or 3 months. Cleaning from short 5 s rinse.
what cleaning regime had the greatest dryness.
Clear care.
When are blink rates decreased
When doing cognitive tasks.
What cleaning system had a higher blink rate
clear care. The more frequent blink rate=dryness.
Oxysept peroxide system
3% peroxide for 20 min catalase enzyme neutralization in 2 hours. For all Heme and SH lenses. no preservative. Use a catalase tablet.
Saffron one step
FDA approved. Only one step.
Purilens System
UV Generating lamp, subsonic agent, preservative free saline. Use 265 nm.
Private label SCL care products
Older generation FDA approved MPS lens care products.
Enzymatic cleaners
Use to get rid of protein. ultrazyme with H202 and enzyme with h202.
Rinsing salines
Rinses and hydrates. Does NOT disinfect.
Antimicrobial lens case
Forms an electrochemical coil or battery formed with saline. Release antimicrobial silver ions.
how often to replace lens case
Every 3 months.
How much do CL wearers make up of a practice
49%
Cl drop out and growth
New=29%. Drop out=16%
Meibomian Gland Dysfunction
Obstruction causes keratinization of office, increased meibum viscosity, long term atrophy. Gland structures change with age.
Meiobomian gland dysfunction and CL
High MG atrophy in CL wearers. Correlates with duration of lens wear. Upper lid affected more. No difference with lens material.
MG Early stage
No symptoms
MG moderate stage
minimal to moderate discomfort, vascularization of lid margin, plugging, meibum is thicker
MG severe
Ocular discomfort, irregular and vascularized lid margin, meibum in thick.
Tx for MG
warm compress, hygiene, AT/ointment qPM, Omega3, fish oil, flax seed oil, doxycycline, azithrocycline, lipiflow. (more studies to prove Cl causes)
Lid wiper epitheliopathy
Proposes that inadequate lubrication creates friction and inflammation of the upper lid. Upper and lower. Stain with NaFL and Rose Bengal. Occurs 5-6 hours after Cl wear.
conditions associated with lid wiper epitheliopathy
Associated with dry eye disease. Exposure keratopathy, decreased mucin production, incomplete blinking, dry eye.
Tx for lid wiper epitheliopathy
AT
Dry eye disease stats and types
40% Of US has dry eye. Can be evaporative (lipid) or aqueous (aqueous)
CL and TF
CL splits the CL into two different section. Pre lens and pre cornea. Pre lens TF evaporates quicker.
Dry eye disease TX
CL change, Warm compress, punctual plugs, AT, steroids, cyclosporine, Doxycycline, Omega 3 fish oil.
Mucin balls
Small particles of lipid, protein, and mucin. Tear film collapses and lid interacts with epithelium and rolls these. Will be indention in cornea following lens removal. Cause no discomfort, VA decrease, or health concerns.
CL and mucin balls
70% have mucin balls with silicone hydrogels. Not related to age, gender, run. Higher with steep cornea, EW, and no use of rewetting drops.
Limbal epithelial hypertrophy
No symptoms. Seen in some long term wear HEMA wearers. Possible precursor to corneal neovascularization.
How to view gimbal epithelial hypertrophy
NaFL (Cannot be viewed with white light only)
TX for LEH
It will resolve after stop wearing CL for 3-5 days. Decrease wear time. Suspect a steep fitting lens.
CL papillary conjunctivitis Signs and symptoms
See blepharitis and papillae. Same as GPC. Mucus discharge in the nasal cornea of eye when wakening, itching with lens removal, decrease wear time.
Stage 1 CLPC
Preclinical. Tarsal conj. is normally with only a slight velvet appearance. Some mucus discharge in the AM and itching upon lens removal
Stage 2 CLPC
Early clinical. Increase in size and elevation of papillae. Mild itching while wearing lens. Increased lens awareness and decrease WT.
Stage 3 CLPC
Moderate. Increase in papillae. Increased itching and discharge. Great decrease in wear time.
Stage 4 CLPC
Papillae often 1 mm or larger. Severely coated lenses and decentered. Severe itching. Almost total lens intolerance.
What causes GPC
Antigen on CL so body starts immune response. Can get from prosthetic eye as well.
CLPC Tx
Rule out mechanical GPC. Manage Cl deposits. Change to preservative free. AT. Mast cell stabilizer, topical steroids, consider GPs. Surface coat SiHy with plasma coating to make more hydrophilic.
Surfactants
Improve cleaning
Preservatives
increase disinfection efficacy
Viscosity
Buffer the ocular tissue from preservative disinfectants.
Hydra-PEG
Allows more water to bind CL. Some CL already have this.
what causes Contact lens acute red eye
Appears as a response to endotoxins from gram neg bacteria on cl.
CLARE signs/symptoms
Modesto to severe bulbar hyperemia that is circumferential or sectoral. Peripheral to mid peripheral diffuse or focal infiltrations. None to mild VA reduction. Uncommon to be bilateral, A/C run, epithelial involvement.
CLARE Tx
D/C cl wear, lubricants and cycloplege. Steroids with severe symptoms or infiltration. Recurrence possible.
Superior Limbus keratoconjuctivitis
Strong association with lens care products that have thimerosal preservative (not used today).
SLK signs/symptoms
Increased lens awareness, burning, itching, light sensitivity, vision loss (when there is extensive pants), injection in superior bulbar conj, infiltrates, panes, cornea and conj staining, haze (v shapes towards pupil), sub-epithelial opacities, superior gimbal edema, hypertrophy, staining, and injection. Pseudo-Dendrites.
If you see a contact lens red eye and it is symmetrical is is CLARE or SLK?
SLK! Bilateral with symmetry but variable onset.
TX for SLK
discontinue SCL. Stop thimerosal exposure. New Cl (GP has no additional benefits). Scraping affected epithelium.
Prognosis for SLK
3 weeks-9 months. Papillary changes take longer.
Theodores SLK
SLK without CL wear. Over 40, F, linked to thyroid disease.
Superior Epithelial Arcuate Lesion Symptoms
Pt. relatively asymptomatic with maybe a slight FB sensation. usually found during routine Cl exam.
SEAL Signs/Symptoms
Linear breaks seen in the superior cornea of SCL wearers. In most cases eroded down to BM. Usually unilateral. Lesion .5 mm wide and 2-5 mm in length. Little or no injection of the superior bulbar conj.
What causes SEAL
Stiff, thick lens and high levels of dehydration
SEAL treatment
D/CL Cl wear. Lubricants. Topical AB? long term change base curve. Change OAD. Change material.
Inferior arcuate corneal staining
Coarse punctate epithelial disruption in the inferior cornea. Seen in patient with clean, well fitted wet lenses in DW or EW. May occur during lens removal. Does not depend on water content, lens thickness.
Solution comfort
In longer term more comfort with hydrogen peroxide
Dryness of MPS vs. hydrogen peroxide
Less dryness with hydrogen peroxide
Fusarium infection
From Renu brand.
Complete moisture plus infection
Acanthomoeba. infections.
Rub vs. no rub
Rub is much better on cleaning lens.
Opta-Free perservative
Aldox/polyquad
Preservative associated transient hyperfluorescence
Staining is though to be binding of the Nail to preservatives on eat epithelium. Preservatives have different peaks of incidence of binding. Polyquad/aldox-30 minutes. PhMB-2 hours
PATH Presentation
Noted after lens application. Diffuse corneal staining. Epithelium unaffected. Generally bilateral. Asymptomatic. Non-pathological. Resolution in 6-8 hours post lens removal.
Micro cysts
Vision is asymptomatic but comfort is symptomatic. As you decrease wear time and DK you get more cysts.
Micro cysts description
Small translucent or grey irregular shaped or ovoid inter epithelial cysts. Form near the BM and move toward anterior surface. Do not stain until they break through the surface. Reversed illumination tells you it is a micro cyst. Response to high levels of hypoxia.
Micro cyst time course
Onset is slow usually after 2 months of lens wear. Number increase and decreases in cycles. Takes 3 months to clear.
Micro cyst tx
decrease wear time. Change to higher Dk/T
What things can be seen with reversed illumination
micro cyst and mucin balls. Micro cysts don’t stain with NaFL though. Mucin much bigger too. Mucin superior too.
Limbal hyperemia
Increased in blood flow at the gimbal arcades resulting in dilation and distention of gimbal blood vessels. Can have dilation of blood vessels and some lipid leakage.
Hypoxia theory for corneal vascularization
Tissue hypoxia resulting in an increased production of lactic acid which may result in venous draining. Chronic edema results in stroll softening or loss of physical barrier to vessel penetration. Hypoxia alone cannot do this
Vasostimulation theory for corneal vascularization
Contact lens induced epithelial trauma results in a release of enzymes. Inflammatory cells migrate to this sit and release vasostimulating agents
What is minimum DK for patient sleeping in lenses
125.
What must you do with neovascularization
Document it. Location, depth, degree of penetration, severity
Corneal vascularization tx
Discontinue lens wear, treat underlying pathology, minimize physiological insult.
Other signs of hypoxia
Vertical striae, folds in descents.
Epithelial vacuoles
10% nonsense wearer. Unknown etiology. Spherical fluid or gas filled vacuoles in the periphery. Generally asymptomatic and good prognosis as big turn over
Epithelial bullae
Low prevalence in CL wearers. Indicates chronic epithelial edema. When it breaks through the surface the patient comes in with pain.
Keratitis
Involves multiple layer of the cornea
What is an infiltrate
A focus accumulation of cells or tissue in the anterior storm. PMN leukocytes. Can be sterile or infectious
When will you see infiltrate with CL
with almost any chronic irritation to the cornea
Infiltrative Keratitis signs/ symptoms
Inflammatory reaction of cornea. Mild to moderate irritation. Redness. Occasional discharge. Can be bilateral. Va may or may not be infected. No A/C or lid edema.
Infiltrative keratitis causes
FB entrapment, mechanical trauma, bacterial toxins, MPS reaction.
Risk forzctors for infiltrative ceratisis
CL wear
Infiltrative keratitis Tx
D/C Cl wear temporarily. Steroids if moderate symptoms or VA decrease. Ocular lubricants. Rarely scars. Recurrence possible.
Contant lens peripheral ulcer signs/symptoms
Peripheral location, Modert to severe discomfort, FB sensation, slight irritation, slight redness, tearing, infiltrate, no lid edema, unilateral, no a/c reaction.
CLPU cause
inflammatory reaction to G+ exotoxins. Toxins release by S. Aureus on lens surface.
Tx for CLPU
Anti-infective agent, cycloplegia, steroids after re-eptithelium, monitor
Prognosis with CLPU
will always have bull’s eye scaring
What is Microbial keratisis
Focal defect or excavation of the sub-epethial surface. Produced by sloughing of necrotic inflammatory tissue. Not the same as a corneal ulcer.
What causes microbial keratitis
Bacteria, protozoan, fungal, viral. Must have an acute inflammatory infiltrate of the epithelium and stroma in the presence of infectious microorganism.
Symptoms with microbial keratisi
can be severe to mild. May have pain, photophobia, tearing, blepharospasm, red eye, floaters, AM lid crusting, purulent discharge.
Signs with microbial keratitis
Central or paracentral. Large, irregular focal. Satellite lesions. Anterior stromal to full thickness. Corneal edema. Full thickness epithelial loss. Anterior chamber reaction. Lid edema. Severe bulbar and gimbal redness. Unilateral. Hypopyon.
MK and CL
More likely to get more severe if you sleep in them
CL with least chance of MK
GP
Peak in age of infiltration in cl
15-25 years
Contact lens risk survery
15-25 year olds more likely to nap in lens, sleep in lenses, expose to water.
Greatest risk for CL
Napping and showering in cl
Water exposure with CL
Some rinse CL in water. M>F. We fear acanthamoaeba.
Bacterial keratitis caues
Pseudomonas. Intact epithelium (corynebacterium diphtheria, listeria, haemophilus)
Protozoa keratitis
Appear dendritic or patchy stromal infiltrate. Symptoms dispropriate to signs. Risk factors with CL wear.
Fungal Keratisis
Large white infiltrate with fluffy or branching margins. Significant edema. High risk of loss of BCVA. NO STEROIDS!
Viral keratitis
Simplex: Terminal end bulbs. Zoster: no terminal end bulbs on psudodendrites.
Principals risk factor for MK
Overnight wear.
Endothelial Bedewing
Endothelial deposits of unknown etiology in patient who are CL intolerant. Fine white precipitates or pigment dusting of cells. Idiopathic. 20% occur in noncl wearers
Endothelial blebs
Black, no reflecting ares. Occurs in 100% CL wearers. Rapid onset of 10 minutes after application and resolution 2 minutes post removal. Adaption of the endothelium.
