Final Exam Revision Flashcards
What 4 things can we do to improve a loose fitting lens?
- Select a larger total diameter.
- Select a steeper radius.
- Use a more rigid or lower water content material.
- Use a different lens thickness.
What 4 things can we do to improve a tight fitting lens?
- Select a flatter radius.
- Select a smaller total diameter.
- Use a less rigid or higher water content material.
- Use a different lens thickness.
Where does the lipid layer of the tears (outermost layer) get produced from?
Meibomian glands
What is the primary function of the lipid layer of tears?
to prevent evaporatioon
Where does the aqueous layer of the tears (middle layer) get produced from?
lacrimal glands
What is the primary function of the aqueous layer of tears?
provide nutrients to eye
Where does the mucin layer of the tears (innermost layer) get produced from?
goblet cells in the conjucntiva
What is the primary function of the mucin layer of tears?
to adhere the tear to the eyes
The K readings have 2 or more difference between them. What kind of lens should we consider/do?
RGP
How is wettability best described?
Ability of a drop of liquid to SPREAD over a surface
A keratometer is primarily used to measure……..
the central corneal curvature
For observing aqueous flare, which illumination should be used?
conical beam
What is the purpose of diffuse illumination?
for a general look at the ocular tissues and lids under low magnification
Identify the three types of direct focal illuminations
Conical Beam
Parrellapiped
Optic section
Which illumination method is best for examining Descmet’s membrane deposits and corneal blood vessels?
Specular reflection
Which 3 illuminations are set ‘out of click’?
Sclerotic scatter
Indirect Retro Illumination
Indirect Proximal Illumination
Sterile water can be used to rinse both soft and gas permeable lenses. T/F
FALSE
What are 4 uses for saline solution?
Heat disinfection
rinsing lenses prior to insertion
ocular irrigation
wetting fluorescein strips
Soft lens in situ refers to a lens that………
is on the cornea
Tear break up time is assessed using………
fluorescein
When removing an RGP lens, the patient should be asked to look…………
Up
Contact lenses benefit pxs with refractive anisometropia. T/F
TRUE
If a px requires correction for near vision only this is a contrindication for cl use. T/F
TRUE
A visual contraindication for cls is……..(prism related)
prism required horizontally or more than 3 prism vertically
Name on situation where cls should not be dispensed to a non-compliant px?
poor general hygiene
What is a disadvantage of silicone hydrogel lenses?
more liable to lipid deposits
Given a rx of OD:-2.75 and OS: -3.00 with horizontal and vertical keratometers both at 180/090, what is the first option for cls?
soft spherical lens OU
Given a rx of OD:-2.75/-1.75 x 180 and OS: -3.00/-1.75 x 180 with horizontal and vertical keratometers both at 180/090, what is the first option for cls?
soft toric lens OU
One disadvantage of RGP lenses is:
1-not being able to correct corneal astigmatism
2-difficult to maintain
3-not able to modify
4-3 and 9 o’clock staining
2-difficult to maintain
When observing a client’s blinking during a cls exam, what is important?
completeness of blink
Which symptoms indicate marginal dry eye? 10 (name a couple)
burning
itching
foreign body sensation
sore
tiredness
grittiness
dryness
photophobia
irritation
lid heaviness
For marginally dry eyes, the best type of lens to use is……..
a lower water content
Reduced height of tear prism indicates a reduced tear volume. T/F
TRUE
Advantages of low water content lenses include: 3
-better reproducibility
-less dehydration on the eye
-great tensile strength
Advantages of high water content lenses include: 3
-Better comfort because of material softness
-can be made thinner
-longer life span
One of the main reasons for the clinical success or failure of a particular lens is:
lens dehydration
Desides DK value, which factors affect comfort, vision, and lifespan? 6
-fitting method
-lens design
-mechanical stability
-manufacturing technique
-optical quality
-surface wetting qualities
Which type of lens is used as a therapeutic lens?
bandage lens
Silicone hydorgel lenses have a high DK value. T/F
TRUE
Why is peripheral clearance important in an RGP lens design?
1- allows the lens to be designed as a spherical, aspheric or a combination of both
2-allows the transition between the central portion and the periphery to be sharp
3- Allows for adequate tear exchange
4-stabilizes lens so it does not fall out
3- Allows for adequate tear exchange
A gas permeable lens that fits too flat will result in………. 2 (relation to movement)
less attraction and stability
The most commonly accepted method of rigid lens fitting is……………
alignment method (central, not steep, not flat)
Base curve selection of the trial lens in rigid lens fitting is based on………….
K readings
The colbalt blue filter in a slit lamp exam is used to:
enhance contrast when looking at fluorescein
A hydrophilic lens material is……..
water loving
Which manufacturing method involves using a liquid monomer?
spin-casting
How can a small chip on the edge of the lens also be described as?
small piece of lens material missing from lens edge
A condition caused by insufficient oxygen to the cornea is?
Corneal Edema
What is the back surface radius of a cls also known as?
back optic zone radius
Reflex tears on the lens surface may ………
1-pose a problem when trying to insert the lens
2-improve the lens fit
3-not affect the lens at all
4-always mean the lens is defective
1- pose a problem when trying to insert the lens
What are 3 ways we can evaluate the fit of a cls?
the lens centration
the lens movement
the lens rotation
Cls can be used to correct astigmatism. T/F
TRUE
A lens that shows too much movement is likely to be………….
a flat/loose fitting lens
A good movement range for a soft cls during a blink is…………
0.5mm
Excessive movement of a cls can lead to discomfort. T/F
TRUE
A lens that is inverted (inside out) when placed on the eye will cause discomfort. T/F
TRUE
A cls that rides too low on the eye is considered……..
a flat lens
The mnemonic ‘LEFT ADD RIGHT SUBTRACT’ is used for:
compensating for lens rotation
When a contact lens rotates to the left, you should…………
add the rotation to the cylinder axis
If the lens has poort wettability what might be seen in the keratometer?
distorted mires
Which type of astigmatism is more difficult to fit due to sideways decentration?
ATR
When the lens on the eye changes in Base Curve, what is this called?
Flexure
When a rigid lens is hydrated does it become flatter or steeper?
Flatter
Name 3 advantages of rigid lenses.
-increased corneal O2
-reduced risk of microbial keratitis and allergy
-superior vision for px with corneal astig
What is the main method of cls manufacture?
cast molding
What does hydrophobic mean?
Water hating
What allows for adequate tear exchange in an RGP? 2
Peripheral clearance
Fenestration
What is the best illumination to use if you suspect the patient may have protein in their aqueous?
conical beam
What solution is toxic to the eye prior to neutralization?
Hydrogen Peroxide
Name 5 types of therapeutic lenses.
Bandage
Myopia control
OrthoK
Scleral
Drug Delivery
What type of dry eye staining is usually related to RGP wear?
3 and 9 o’clock
What does SEAL stand for?
Superior epithelial arcuate lesion
