Clinical: Subjective Refraction 3 Flashcards by Bella Forster

Binocular balance purpose

To equalize the accommodative stimulus from the two eyes at distance

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Binocular balance is ____ equalize acuity

Not to

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Binocular balance requires that the patient has ____ VA in each eye

Similar

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Binocular balance can only be performed if both eyes reach acuity….

Within 1 line of each other after monocular refraction

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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%

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What are the three different methods for BV

Prism dissociation
Alternative occlusion
Duochrome balance

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What is prism dissociation?

Uses simultaneous comparison- the patient sees two separate images at the same time to compare

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Prism dissociation can only be performed if patients VA in each eye is ….

Within one line of each other

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Target for prism dissociation

Single line of letters 3 lines above the best VA

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Prism: fog patient by

+o.50 OU

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Prism: You place Ridley prisms in front of eyes with 4___ OD and 4___ OS

BD OD
BU OS

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Prism: The right eye is seeing the ___ image. Th left eye is seeing the ____ image

Top, bottom

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When light enters a prisms the rays are refracted towards the ___ and the image goes towards the ___

Base, apex

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Why does the patient see the top image with the right eye when the base is down?

the image goes towards the apex

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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

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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?

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Prism: ADD ____ to the better seeing eye, the better seeing eye is the one the patient reports as ___.

+0.25D, as clearer

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Prism: continue adding plus sphere to the better seeing eye until the patient reports ….

Equally blurred images

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Prism: when the endpoint is reached, remove the prisms and perform

Binocular MPMVA

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Prism: before you perform binocular MPMVA, make sure you are…..

Unfogged the patient - 0.25D

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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

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Prism: if there are multiple equal points for the patient , you should

Use the first equal points

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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

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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

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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:

1. 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) 3. 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

1. Fog 2. Occluded eye while asking patient which appears clearer 3. Alternate occluding each eye while asking patient which appears clearer 4. Add +0.25D sphere to the clearer eye 5. Equality endpoint 6. 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

1. Fog the patient 2. Introduce vertical prism as in prism dissociation method 3. 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:

1. Perform the negative relative accommodation test (NRA) -determines the maximum amount of plus power the patient can accept at near 2. Leave the plus power in the phoropter while directing the patient to view a distance target (should be blurry) 3. Perform binocular MPMVA until letters are clear - performed slowly 4. 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