Janet Approved Flashcards
Simple Hyperopic Astigmatism
After minus or plus transposition: Plano +
Parallel rays of light
come to two line foci,
one falling on the retina
and the other falling
behind the retina
Simple Myopic Astigmatism
After minus or plus transposition: Plano -
Parallel rays of light
come to two line foci,
one falling on the
retina and the other
falling in front of the
retina
Compound Hyperopic Astigmatism
After minus or plus transposition: + +
Both parallel light rays fall
behind the retina
* Both major meridian powers
indicate hyperopia
Compound Myopic Astigmatism
After minus or plus transposition: - -
Both parallel light rays come
to two line foci in front of
retina
* Both major meridian powers
indicate the refraction is
myopic
Mixed astigmatism
After minus or plus transposition: + -
Parallel light rays come to two-line foci,
one falling in front of the retina and the
other falling behind the retina
* One major meridian indicates the
refraction is hyperopic and the other
meridian indicates the refraction is
myopic
Dk/L
refers to the amount of oxygen which pass
through a lens material of specified thickness
Myoflange design
an increase in edge thickness to aid in better centering lenses that position low on the cornea.
Extra edge thickness creates greater lid interaction.
Hyperflange design
a decrease in edge thickness is indicated in many high minus power lens designs to limit
lid interaction, allowing the lens to position more centrally
on the cornea.
Vertex Distance
the distance between the back vertex of
the correcting lens, and the front surface of the eye
Wetting angle
the spreadability of water over a lens
surface. The lower the angle, the more wettable the
surface.
Lescometer
An attachment that holds
the calibration balls for
the keratometer
Also contains a lens
holder which enables the
keratometer to be used
to measure the base
curve of a rigid contact
lens
when you can’t locate the kertometric mires
The instrument and/or patients is not aligned properly
Keratometer has transient mire clarity
ask the patient to blink and measure quickly
Transient mire focus in keratometer
ensure patient’s forehead is against the headrest
Unstable patient gaze in keratometer
close the other eye
H and v mires cannot be measured concurrently in keratometer
irregular astigmatism
Only 1 minus sign is visible in the keratometer
patient’s eyelid is drooping
Only 1 plus sign is visible in the keratometer
occluder is in the way
The modulus of a lens material is the measurement of the
material’s resistance to deformation under tension. In
practical terms, the ____ the lens material, the _____ the
lens modulus
stiffer
higher
Visibility tint
blue or light green
Spin casting
this process, the liquid polymer mix is introduced into a spinning, open top, concave mold that will determine the
front surface configuration of the lens.
The back surface of the lens is formed in air.
Lathe Cutting
- have exhibited the greatest consistency from lens to lens,
based on the ability to very closely control surface
curvatures. - In this process the polymerized plastic, in a dehydrated,
rigid state, is formed into lens blanks, mounted in a base
curve lathe, and the posterior curves
Cast Molding
- In overcoming the previous inconsistency and quality
disadvantages. The result has been the increasing
availability of improved quality products at lower costs. - Hydrogel lenses produced in a molding process may be
formed in the rigid, dehydrated state, resulting in a finished
product that will subsequently be immersed in saline and
hydrated to the specified degree
3-point touch
for soft lenses
Who much astigmatism induced by back surface toric
40%
WIth LARS each minute is….
6 degrees
With LARS 5 minutes is…
30 degrees
purposes for cleaning the lens
Clean the lens that is exposed to sebaceous secretions
* Clear the collected protein and debris
* Lower the bacterial count before the disinfection process
Protein removers
Enzymatic cleaner
pancreatin enzyme
subtilisin and subtilisin-a
Papin
Surfactant cleaners
without use of surfactant cleaner- inadequate disinfection can occur
reduces build-up
used immediately after lens removal
Solution sensitivities and incompatibilities
Sensitives normally come from preservatives: BAK, Chlorhexidine, Chlorobutanol, polyquad, dymed, PHMB, potassium sorbate
chemical disinfection
marked multi-purpose solutions and no-rub
contain cleaner, disinfectant, enzyme cleaner, and lubricant
Hydrogen peroxide
Use highly purified 3% hydrogen peroxide
perservative free
cannot be placed directly in eye
Three borate buffers in this system produce a trace
amount of hydrogen peroxide that protects the solution from pathogens while remaining
non-toxic to the patient. The buffering agents keep the pH level stable
Antimicrobial Buffer System (ABS)
It has wide antifungal and antibacterial effectiveness. a
tendency to bind corneal protein, which may produce superficial punctate keratitis in soft lens
patients.
benzalkonium chloride (bak)
chlorhexidine
this preservative has limited effectiveness against yeast and fungus
organisms, it is often mixed with other solutions for increased strength. Can cause binding of
proteins that could cause corneal sensitivity.
chlorobutanol
This preservative reacts slowly in killing bacteria and fungus. It is only used in
conjunction with other preservatives like benzalkonium chloride.
polyquad, dymed and phmb
low concentration preservatives, and are used as disinfecting
agents in multi-purpose solutions.
This preservative was first used as a replacement for thimerosal It also
has a tendency to bind to organic deposits on the lens surface and can cause discoloration of
certain contact lens materials.
Potassium Sorbate
Used primarily as a substitute for thimerosal in soft lens solutions, this
preservative has limited antimicrobial effect on the yeast and fungus groups.
sorbic acid
thimerosal
Many patients have shown adverse sensitivity to solutions containing thimerosal.
Thimerosal and another mercurial, phenylmercuric nitrate, are not as effective against gram
negative organisms as some other preservatives. Thimerosal is rarely used in care systems in
the United States.
… Instructions must be provided on insertion, removal,
re-centering, solutions, storage, wearing time signs and symptoms of
possible complications as well as wearing schedules.
written
Rigid lenses that are not worn for long periods of time should be
stored …
dry
rigid lens wear: sharp pain upon instertion or suddenly
foreign body, damaged lens
Soft lens wear: pain after several hours of wear
poor fit
rigid lens wear: pain after several hours of wear
lens rubs the cornea, either centrally due to flat lens/ cornea relationship, or peripherally due to poor edge.
corneal tomography
produces high-resolution imaging of the cornea,iris, and anterior chamber (eye ultrasound)
burning upon insertion
reaction to solution
Soft lens wear: burning after several hours of wear
Tight lens, improper blinking
Rigid lens wear: burning after several hours of wear
improper blinking, tight fit, poor lens movement
Soft lens wear: excessive blinking
Lens awareness, lens damage
Rigid lens wear: excessive blinking
lens awareness
Rigid lens wear: excessive tearing
damaged or dirty lens
Soft lens wear: excessive tearing
lens damage
Soft lens wear: itching
allergic reaction to solutions, lens deposits, or material
Rigid lens wear: itching
allergic reaction to solutions, environment, or material
Rigid lens wear: scratchy feeling
foreign body,lens damage, improper edge design
Soft lens wear: scratchy feeling
foreign body,lens damage, lens deposits, edge standoff
Rigid lens wear: photophobia
edema, dirty lens, corneal abrasion
Soft lens wear: photophobia
edema, dirty lens
poor visual acuity
dirty lens, switched lenses, corneal changes
Rigid lens wear: foggy or smokey vision
edema, dirty lens
Soft lens wear: foggy or smokey vision
edema
Rigid lens wear only: flare
too small optical zone, decentration, large pupil
Rigid lens wear: ghost images
residual astigmatism, warped lens
Soft lens wear: ghost images
residual astigmatism, oily film on lens
headaches
wrong power, edema
problems reading
wrong power, onset of presbyopia
Every ____mm of radius equals approximately ____diopters.
0.05
0.25
Slit lamp filter that enhances the view of fluorescein dye in the eye’s tear film. Typically used for fluorescein staining and Goldmann tonometry
Cobalt blue
Symbol: Blue filled Circle
Slit lamp filter used to enhance the view of blood vessels and hemorrhages
Red free
Symbol: green filled circle
Slit lamp filter that decreases maximum brightness for photosensitive patients
neutral density
Symbol: Circle with hashed lines
Slit lamp filter that decreases patient discomfort
Head absorbing
Built in to slit lamp
Slit lamp filter that decreases maximum brightness for photosensitive patients
Grey
Symbol: Circle with thick line
Slit lamp filter good for contrast enhancement when using fluorescein and cobalt blue filter.
Yellow filter
Symbol: Yellow filled circle located in the observation system
Slit lamp filter used for general overall observations of the eye and adnexa
Diffuser
Symbol: May be a flip-up filter placed on the illumination source
A … in the optic zone flattens the fit by enlarging the peripheral curve.
decrease
A decrease in sagittal vaulting creates a … lens to cornea relationship.
flatter
Decreasing the overall lens diameter also … the sagittal depth.
decreases
When classic keratometry is performed by having the patient sight on the mirrored image of their eye, alignment of what is accomplished
The optical axis with the visual axis
Inadequate limbal coverage change diameter
Mess with diameter
Sam and fap is swapped when
Effective power is used
Fam and sap
