Clinical: Subjective Refraction 3 Flashcards
Binocular balance purpose
To equalize the accommodative stimulus from the two eyes at distance
Binocular balance is ____ equalize acuity
Not to
Binocular balance requires that the patient has ____ VA in each eye
Similar
Binocular balance can only be performed if both eyes reach acuity….
Within 1 line of each other after monocular refraction
Binocular balance set up:
Eyes
What sin phoropter
Illumination
-Both eyes open
-Results of subjective refraction should be in phoropter
-llumination is dim by 50%
What are the three different methods for BV
Prism dissociation
Alternative occlusion
Duochrome balance
What is prism dissociation?
Uses simultaneous comparison- the patient sees two separate images at the same time to compare
Prism dissociation can only be performed if patients VA in each eye is ….
Within one line of each other
Target for prism dissociation
Single line of letters 3 lines above the best VA
Prism: fog patient by
+o.50 OU
Prism: You place Ridley prisms in front of eyes with 4___ OD and 4___ OS
BD OD
BU OS
Prism: The right eye is seeing the ___ image. Th left eye is seeing the ____ image
Top, bottom
When light enters a prisms the rays are refracted towards the ___ and the image goes towards the ___
Base, apex
Why does the patient see the top image with the right eye when the base is down?
the image goes towards the apex
Why does the patient see the bottom image when base is up over the left eye?
The apex is down and the image goes towards the apex
Prism: What do you ask the patient after you have put the prisms in front of them?
Which line of letters looks clearer to you- the top or bottom?
Prism: ADD ____ to the better seeing eye, the better seeing eye is the one the patient reports as ___.
+0.25D, as clearer
Prism: continue adding plus sphere to the better seeing eye until the patient reports ….
Equally blurred images
Prism: when the endpoint is reached, remove the prisms and perform
Binocular MPMVA
Prism: before you perform binocular MPMVA, make sure you are…..
Unfogged the patient - 0.25D
Prism: if there is immediate reversal, you should
Leave the dominant eye clearer or ask which option appears the most similar, leave the patient there
Prism: if there are multiple equal points for the patient , you should
Use the first equal points
Prism: if the initial response is “equal”, verify it by
Adding +0.25D to OD, and confirm the bottom image(OS) is clearer then remove it
Adding +0.25D to OS and confirm the top image (OD) is clearer then remove it
Leave patient at the equal points
Binocular MPMVA steps
- Remove prism
- Present VA chart with 20/15 at bottom
- Check acuity OU(should still be fogged)
- Reduce fog -0.25 D sph OU at a time, pushing patient to read lowest line
- When best acuity is reached, stop and check OD, OS, OU acuity
- Record OD/OS lens powers
What are the two monocular sphere tests?
MPMVA
Duochrome
What are the three monocular astigmatic tests?
JCC
Astigmatic dial
Stenopaic slit
What are the four binocular subjective tests?
Binocular balance
Binocular MPMVA
Polaroid vector graph
Turville infinity balance
Duochrome sphere check uses ___ aberrations to refine sphere power
Chromatic
Two other names from Duochrome sphere check
Bichrome test and Red-green test
Duochrome can be used for initial and/or final ____
MPMVA
Shorter wavelengths like green bend more, focusing _____
First
Longer wave lights liek red bend less, focusing ___
Second
Can you use Duochrome sphere check on patients that have color vision anomalies
Yes, the color refracts the are way no matter the eye
Duochrome first step
Fog liek a regular MPMVA
Target fro Duochrome
Snellen chart with R/G filter on
Duochrome: Ask the patient after…
on which side of the chart/ color do the liters appear clearer, or are they equal
Duochrome: proper fog should result in the letters on the __ side of the chart appearing clearer
Red
Duochrome: If red appears clearer -> add ____
If green looks clearer-> add____
Red-> add -0.25 sphere
Green-> add +0.25 sphere
Duochrome: way to remember what you do by what color appears clearer to the patient
RAM GAP
Red Add Minus, Green Add Plus
Duochrome: endpoint is where
Both sides appear equal, continue past the equal to confirm reversal
Duochrome; if there is not equal point then you
Use the first power at which the green side appears clearer
Duochrome: last step
Remove R/G filter and recheck VA
Duochrome: Why does red appear clearer for the patient?
Red is closer to the retina so it will appear clearer
Duochrome: Why do you add minus if the patient sees the red side as clearer?
Adding minus will cause more divergence, pushing the focus back closer to the retina
Duochrome: Where are all the color rays focused when the patient sees the green as the clearer side?
All rays are focusing behind the retina
Duochrome: Why do you add plus when the patient reports that the green side is clearer?
Adding plus will cause more convergence, pushing the focus up closer to the retina
Duochrome: when the patient reports ‘equal’ what do the rays look like on the retina?
Yellow light on the retina
Red and green straddle the yellow light that dominates daytime vision by about 0.25D
Three limitations of Duochrome:
- Some patients may always choose one side regardless of lens power in place (children)
2.one filter may be appear darker/brighter than the other(projector charts particularly) - Cataracts (yellowing can cause a red bias)
Stenopaic slit allows you to locate the two ____ meridians of the eye by …
Principal, rotating the slit
Stenopaic slit is useful for patients with ___ ____, _______, or other significant optical anomalies
Low vision, keratoconus,
Stenopaic slit : first step
Fog patient and remove all cyl power
Stenopaic slit: instructions for patient
Look at the distance acuity chart and tell you when it appears the cleats while you rotate the slit
Stenopaic slit: the clearest orientation =
Minus cyl axis
Stenopaic slit: once it is clear for the patient, leave the slit at the minus cyl axis and perform ____. This determines the _________ power of the Rx
MPMVA, spherical
Stenopaic slit: Rotate the slit 90 degrees away and repeat MPMVA. The difference between this total power and the sphere power is the ___ ____ ____
Net cyl power
Binocular balance- alternate occlusion:
Alertanting comparsion
Performed if BVA of each eye is within 1 line of the other
No prism
Binocular balance- alternative occlusion procedure
- Fog
- Occluded eye while asking patient which appears clearer
- Alternate occluding each eye while asking patient which appears clearer
- Add +0.25D sphere to the clearer eye
- Equality endpoint
- Perform binocular MPMVA to finish
Alternate occlusion limitations:
-Simultaneous comparison may be easier for the patient to discern
-The targets may move during occlusion with a high heterophoria
Binocular balance- Duochrome:
-Simultaneous comparison
- does not require the same acuity in each eye***
Binocular balance- Duochrome procedure
- Fog the patient
- Introduce vertical prism as in prism dissociation method
- Target R/G filter - line of letters 3 lines above worse- seeing eye or verhoeff rings
Binocular vs biocular
Binocular- both eyes are open with fusion- sees one image
Biocular- both eyes are open without fusion - sees two images
Polaroid vectograph uses polarized lenses to show separate targets ________ to each eye
Simultaneously
Polaroid vectograph is monocular refraction under _____ viewing conditions
Binocular
theory behind Polaroid vectograph
Binocularity during refraction offers better control of accommodation
Binocular balance is technically a ___ test
Biocular test
turville infinity balance uses ______ occultation under binocular conditions to refine refraction
Partial
During Turville infinity balance the ___ on the phoropter divides the acuity chart in half
Septum
Turville infinity balance does monocular refraction under ____ conditions
Binocular
Delayed subjective refraction attempts to ….
Maximally relax patient’s accommodation to allow acceptance of more plus power without cycloplegia
Delayed subjective refraction is useful for
Latent hyperopia
Accommodative spasm
Delayed subjective refraction is performed after
A routine subjective refraction attempts
Delayed subjective refraction procedure:
- Perform the negative relative accommodation test (NRA)
-determines the maximum amount of plus power the patient can accept at near - Leave the plus power in the phoropter while directing the patient to view a distance target (should be blurry)
- Perform binocular MPMVA until letters are clear
- performed slowly - Record
Cycloplegic refraction:
-useful in pediatric exams
- paralyze the ciliary body
-performed refraction with accommodation
Knowing ocular dominance is useful for:
-binocular balance endpoint
-contact lenses
-cataract and refractive surgery
-sports vision
Ocular dominance in office tests
Sighting test
Sensory test
Sighting test target
Isolated letter 2-3 liens larger than BCVA
Ocular dominance sensory test
-Direct patient’s attention to acuity chart with both eyes open
-using a 1.50 D loose lens, alternating it
-ask patient to compare blue and tell you where the blue is most noticeable
- the most blue = the dominant eye
Is sensory test or sighting test more reliable
Studies show they are fairly comparable
** DO NOT tell patient the purpose of either test
Uses for trial frames
-demonstrate glasses prescription to patient
-perform a refraction(low vision)
-perform additional testing through the trail frame
-BV and accommodative tests
Ocular dominance sighting test:
-put letter in middle of triangle with hands
-occlude an wye and if they can no longer see the target, the occulted eyes is their dominant eye
