Refractometry: Retinoscopy and Refinement 5% Flashcards
Devices that are integrated into each other to automatically input data and to work together to determine the patients refractive error.
Automated Refractors
Automated Refraction systems may include:
phoropters, lensmeters, autorefractors, keratometers and may be integrated with the electronic records.
Group of ophthalmic devices used to determine refractive error.
Automated refraction system
Used as a starting point for subjective testing
Auto refractor
What are some advantages of automated Refraction systems?
Lens manual labor
More automation of repetitive tasks in the refraction
ability to present former and new values quickly for validation
Reduced risk of human error due to direct transmission of results EMR
Improved office efficiency
The amount of light that one candle generates from 1 foot away from a surface.
One foot candle of light(1 lumen)
The intensity of light which on candle casts on a surface from a distance of one foot
One foot candle of light
The amount of light cast is inversely related to the distance the candle is from the ______
surface
The further away you move the light from what you want to illuminate the _____bright the light seems
less
If you measure he amount of light intensity right at the light it is ______ but when you measure at the object you have illuminated it is ___light the further away you are from that object
just as bright
less
The light that is measure on an object is inversely proportional to the ______the object is from the light source.
distance
The closer you are to the light bulb the ____ the bulb is.
brighter
You can’t change the amount of light coming from a bulb so in order to make more light on an object you have to move it ____ or ____
closer or add more light
Law that describes the relationship between the 2 angles and the index of refraction of the medium through which the light passes
Snell’s Law
A measurement of the angle between the incident ray and the normal line
angle of incidence
A measurement of the angle between the refracted ray and the normal line.
angle of refraction
When light passes from air into water it is bent towards the normal line,__________
angle of incidence.
Physics principle that describes optics and the relationship between the angle of incidence and the angles of refraction when referring to light that passes through a boundary between 2 different media, such as water, glass or air. In optics it is used to compute the angles of incidence or angles of refraction and find the refractive index of the given material.
Snell’s law
In a glass of water with a straw….
the theoretical line that is placed perpendicular to the interface between the 2 substances air and water. This line is used to measure angles from.
Normal line
With a glass of water with a straw:
The straw as it enters the water is he
incidence ray
With glass of water with straw….
The part of the straw that is in the water is our….
Refracted Ray
With glass of water with straw.:
When light passes air into water the ray of light is refracted or bent. The refracted ray is bent/refracted toward the _______. Our _________ is a measure of angle between the incident ray and the normal line. Our ________ is a measurement of the refracted ray and the normal line. When light passes from air into water it is bent towards the normal line.
normal line
angle of incidence
angle of refraction
A measure between the angle of the incident ray and the normal line is _____
the angle of incidence
A measurement of the refracted ray and the normal line is_____
angle of refraction
angle of incidence is always______ than your angle of refraction
larger
Prism fragments the light into
the different colors of the spectrum
If you look closely in the refracted ray you will see….
the colors of the rainbow in order by wavelength.
What color has the longest wavelength
Red
What color has the shortest wavelength
violet
What is the Mnemonic for colors and wavelengths
ROYGBIV
start with the longest and end with the shortest
What is the definition of 1D
that lens which brings light to a focal point at a distance of 1M
The higher power the lens the _____it’s focal length
shorter
The lower the power of the lens the ____it’s focal length
longer
4D lens has a ____focal length and a .25D lens has a ______focal length
short
long
What is the formula to figure out focal length
D=1/F
Note : 100cm=1M
Eyes that form a focal point behind the macula
Hyperopia (eye is short)
Convex lens pull focal length in ____
closer to the macula
converge
Eye that form a focal point in front of the macula
myopic
Concave lens pulls focal point _______ so that it falls on the macula
further back into the eye
diverge
Rebounding of light is called…
reflection
When light is reflected off of a plane mirror
The light is reflected at the same angle you direct it at
angle of incidence = angle of reflection
holding light at 45 degree reflects light at 45 degrees
A flat mirror
plane mirror
angle of incidence =
angle of reflection
Projectors are put into position so that the light is _______
reflected off the mirror and into the pts eye.
Why do we use mirrors to check visual acuity?
so we don’t have to have the 20 foot room
The angle that the projector is from the mirror must….
be the exact same angle at which the pt is from the mirror in order for the pt to view the eye chart.
______mirrors reflect light convergently
concave
Mirrors that magnify images(like the round mirror in department store)
concave
____mirror reflect light divergently
Convex
Mirrors that minimize images (like the side view mirror on car)
Convex
Name the parts of the phoropter.
Occluder, sphere power display, sphere power dial, cylinder power knob, axis dial, VD knob, jackson cross cylinder, cylinder power display, level, PD knob
What should you do first before starting the refraction and retinoscopy?
Level the phoropter
Why must we level the phoropter prior to refracting the pt?
to make sure we are accurately representing the pts astig axis. If we don’t the axis is inaccurate
When refracting start with….
The AR, Retinoscopy, or WRx
What are the steps to take before refracting?
- Start with AR, Retinoscopy, or WRx
- Position the phoropter in front of the pt
- level the phoropter
- Occlude the left eye so the pt is looking with the right eye only
- Open the eye chart to one line larger than the line they read with their glasses
- Tell pt Look at a letter you can see easily
- Encourage pt blinking
Steps of refracting:
- Sphere(0.50 increments) offer more plus first
- Determine axis then cyl with Jackson Cross Cylinder (JCC) (use Dots, Landolt’s Broken ring chart, or one line larger than BCVA on Snellen)
- Balance Sphere & Cyl (for each 0.50 change in cyl power, you must adjust the sph power by 0.25 in the opposite direction)
4.Refine Sphere (0.25 increments) offer more plus first.
The smallest cross-section of the blur circle between two focal lines formed by an astigmatic lens. (the macula will ideally be in between the 2 focal planes)
Circle of least confusion
An eye that has_____forms two focal plans, not 2 focal points ( 2 lines of light rather than to points of light.
astigmatism
The 2 focal planes in an astigmatic eye are typically separated by __degrees and one or both of the planes are not on the macula
90
What is the goal when refracting an astigmatic eye
to get the 2 focal planes as close to each other as possible and as close to the macula as possible. Ideally the macula will be right in between the 2 focal planes
Theoretical point in the eye formed by a spherocylinder lens that represents the area of the least amount of blur
circle of least confusion
Why do we have to balance our sphere and cylinder
without adjusting them you make the focal planes further apart instead of closer together, inducing blur
What is the purpose of the +1.00 Blur test?
To avoid over minus-ing patient
How do you perform +1.00 blur test?
1.After monocular refraction is complete
2. ck monocular va
3. Add +1.00 sph (tell pt it will be blurry)
4. Check VA (should be approx 2 lines worse if not, add + sph until it is)
5. Reduce + sph in 0.25D increments
6. ck VA after each click (do not ask “better one or two”)
7. Stop removing +sph as soon as BVA attained
When is over minusing an issue?
When pt is young or latent hyperope
(usually done if supsected latent hyperope or under age 45)
What is the purpose of binocular balancing?
to equalize the accommodation efforts of the 2 eyes.
You can only perform binocular balancing when pt has….
approximately equal visual acuity in each eye
A slight imbalance in favor of dominant eye is ..
ok
Be careful ______to reverse the natural dominance of the 2 eyes.
never
All methods of binocular balancing are only for refining_____
sphere
Explain how to perform Binocular Balancing with low plus blur.
-Remove occluder so pt is binocular
-ck binocular VA
-Tell pt you’re going to make things look blurry
-Add+1.00D sph over refraction(RF) in both eyes (this fogs and relaxes their accommodation)
-Measure VA again (should be 2 lines worse. If not, add more plus until it is)
-Reduce plus power in 0.25 increments until BVA obtained(do not ask better one or two)
Binocular balancing with the DuoChrome exploits the fact that
Light of a longer wavelength is refracted more than light of a shorter wavelength. (red being the longest and green has a much shorter wavelength)
Red and green filter test for binocular balancing
DuoChrome
Explain how to perform binocular balancing with DuoChrome.
Put the green and red filter over the snellen eye chart
(Test each eye seperately)
Fog the eye with +0.75sph
Gradually remove in 0.25 increments until backgrounds are equally clear
As you remove the 0.25 increments ask which letters are the clearest and sharpest (letters in green or red back ground)
If they say letters on red background are clearer you add more minus
If they say letters on green background are clearer you add more plus
Mnemonic=RAM GAP (Red add minus, Green add plus)
In DuoChrome test, if the letters on the green side are the sharpest you add more____
plus
In DuoChrome test, if letter in Red are the clearest add_____
minus
In Duochrome test test each eye _____
seperately
What is the approximate ADD power at age 40-45
+1.00
What is the approx ADD power for age 45-50
+1.50
What is the approx ADD power for ages 50-55
+1.75
What is the approx ADD power for age 55-60
+2.00
What is the approx ADD power for ages 60-65
+2.50
What is the approx ADD power for ages 65+
+3.00
List the age ranges and corresponding ADD power.
Age 40-45 +1.00
Age 45-50 +1.50
Age 50-55 +1.75
Age 55-60 +2.00
Age 60-65 +2.50
Age 65+ +3.00
Accommodative amplitude _______as we age.
decreases
Computer ADDS are typically _____ the power of the reading ADD
1/2
(ex: if they normally require 2.50D to read at their preferred distance, their computer ADD would be approx +1.25)
Most peoples computer monitors are ____
25-30” away
Refract for computer the same way you do for reading, but___________
at the further distance
Most peoples axis are ______to one another in the 2 eyes.
mirror image
Most axis are oriented near or around ___or ____
180 ore 90
Younger people tend to be at around axis ____and older people tend to be around_____in plus cyl.
90
180
The higher the ADD power the ______the pt will have to hold the reading card.
closer
If pt is tall with long arms, he will generally need _____ADD power than someone who is small with shorter arms.
less
Is the astigmatic clock subjective or objective
subjective
A subjective test used to determine approx axis of pt astig
Astigmatic clock
How do you perform Astigmatic Clock.
Blur pt to about 20/50
Ask pt which lines are darkest and most distinct
Take the lower number of the line they choose and multiply by 30
This will give you the approx axis of astig
When performing astigmatic clock you multiply the ____number by___
lower
30
A way to estimate a pt refractive error with objective measurements
Retinoscopy
Is Retinoscopy subjective or object
objective
Retinoscopy doesn’t require any _______response on the pts part
subjective
The retinoscope has and _____system, which shines ____lights into the pts eye, which is then _______as a reflex in the pt pupil.
Illuminating
Diverging
Reflected back
What is the working distance in Retinoscopy?
67cm or 26” (+1.50 lens)-average arms
50cm (+2.00 lens)-shorter arms
It is the distance between the pts eye and the retinoscope
Why is it important to know the working distance in retinoscopy?
Because you must account for it and subtract the +1.50D from the Refraction (or +2.00 for shorter arms)
A wet streak uses ____, a dry streak does not
Cycloplegia
In Retinoscopy have the pt focus on _____
Have pt focus on 20’ non accommodative target(Typically the big E)
In Retinoscopy you must ____the fellow eye
fog
In retinoscopy what are some causes of irregular reflexes?
KCN
Warped K from ill fit CL
Subluxated lens
K Scar
Lens opacities
Dirty soft CL
Post op Ks
Why should you streak in plus when performing retinoscopy?
Because it’s easier to recognize with motion
When performing retinoscopy we are comparing the _____________
Size, shape and movement of the retinoscope’s light with the reflected light from the patient’s pupil
What is the light that comes from the retinoscope called?
the intercept
The retinoscope has a ____system and a _____system
viewing
illuminating
The illuminating system shines _____rays of light into the pt eye
diverging
All retinoscopes have 2 basic setting, a ______mirror setting and a ____mirror setting.
Plane
Concave
For retinoscopy we use the ___mirror setting in order to have parallel light rays entering the eye
plane
What are the 2 basic types of Retinoscopes?
Copeland or Nikon and all others
For Copeland and Nikon retinoscopes the sleeve is _____ for the plane mirror affect. For all other types of retinoscopes the sleeve is ____for the plane mirror affect.
up
down
The primary disadvantage of the Copeland or Nikon retinoscope design is that it is _______, all other scopes use a hallogen light source that makes visualization of the retinoscopic reflex much easier, particularly when doing through _____pupils and _____
non hallogen light source
small
media opacities
When performing Retinoscopy on the left eye you hold the scope in you ____and turn the dials on phoropter with the ____hand
left
right
When performing retinoscopy on the right eye you hold the scope in your_____hand and move the dials on phoropter with _____
right
left
When performing retinoscopy should both eyes be open or should one eye be closed?
both open
What is the first things that should be done before performing Retinoscopy?
Level phoropter
What are the basic steps in performing Retinoscopy?
- Level phoropter
- Fog fellow eye with +1.50
- Add minus until both meridians are with motion
- While sweeping in both meridians, gradually add plus until one meridian is neutral (this is the sphere meridian)
- Move to opposite meridian. If it is at neurality, the refraction is spherical. If it’s not at neutrality gradually add plus cyl until this meridian is neutral. (This is your cylinder meridian and your approx axis)
What power should you fog the fellow eye with when performing retinscopy?
+1.50
Retinoscopy;
Add minus until both meridians are _______
with motion
Retinoscopy:
While sweeping in both meridians, gradually add plus until_____
one meridian is neutral
Retinoscopy:
The first meridian to become neutral is_____
The Sphere
Retinoscopy:
The second meridian to become neutral in the opposite meridian of the first is ______
The cyl and approx axis
How do you confirm neutrality with retinoscopy?
move in slightly closer than your working distance and streak both meridians and you should see with motion, move back slightly and you should see against motion
Retinoscopy:
Refine axis using visual clues such as ____ and ____ phenomena and ____techniques.
Break
Skew
Straddling
Retinoscopy:
___________means that the reflected light through the pupil is moving in the same direction as your intercept.
With Movement
Retinoscopy:
When you see with motion the focal point is _____
behind you
Retinoscopy:
When you see with movement you add…
plus
Retinoscopy:
Against movement means that the reflex through the pupil is …..
moving in the opposite direction of your intercetp
Retinoscopy:
When you see against movement the focal point is ….
in front of you
Retinoscopy:
When you see against movement you need to add….
minus
Retinoscopy:
When you approach neutrality the light becomes much___
brighter and moves much faster as refractive error becomes less
Retinoscopy:
Small refractive errors will have a ______reflex and larger ones will have a _____reflex
bright faster
dull slow
Retinoscopy:
When the reflex fills the entire pupil the refracted error has been eliminated and your are at the focal point this is ________
neutralization
Retinoscopy:
Myope-against movement, add____
Hyperope-with movment, add___
minus
plus
Just before reaching neutrality in retinoscopy you’ll see the_____
zone of doubt
Retinoscopy:
The point at which you don’t definitely have with motion but you may not be sure you’re at neutrality.
Zone of Doubt
Retinoscopy:
When you are at Zone of Doubt what should you do?
Move in slightly streak both meridians(should see with motion)
Move back slightly streak both meridains (should see against motion)
If you do you’re at neutrality at working distance
Retinoscopy;
Explain the “Skew” phenomena?
As you sweep watch the relationship between the direction of the movement between the intercept and the reflex. If the intercept is ‘off axis’ the intercept will appear to move in a ‘skewed’ direction compared to the reflex in the pupil
Retinoscopy:
Explain Axis “Break” Phenomena.
Do not ‘sweep’…‘spiral’ by rotating your intercept
Notice that the intercept and reflex are not aligned
Reflex is less enhanced when break phenomena is present (reflex is clearer when you’re on axis)
If present, this tells you if you’re off axis
What is the straddling technique used for?
To confirm your axis
Explain Axis Straddling in retinoscopy
At the end of the retinoscopy, lean slightly toward the pt. The intercept is positioned and compared at 45 degrees on each side of the axis
If your retinoscopy is correct, the width of the reflex 45 degree on each side of the axis will be the same. If not, turn toward the brighter/narrower band until straddle reflexes are equal in width
If you see dual reflex in axis straddling you are ____away from the actual axis.
further
The bright, narrow band seen inf axis straddling is known as the ___
guide
The guide(narrow light) in axis straddling is _____to the actual axis.
closer
In Axis Straddling if both lights are equal width this means….
you are at the correct axis
