Course #

902Introduction to Refractive Data Collection

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Introduction to Refractive Data Collection

Ryan Gustus, OD 3/5/15

Biography

• Indiana University 2011 graduate • Residency in Ocular Disease – Fort Wayne VA

Hospital • 7th SECO, 5th Presenting • Wife & 3 daughters

Biography

• 2.5 Doctors • 11 Staff

Objectives

• learn basic parts and mechanics of the phoropter • learn the principles of refraction • learn the basic techniques of refraction and how

to perform a complete refraction • learn how to determine a plausible endpoint to

the refraction • learn common pitfalls to refraction • discuss examples where a refraction by para-

optometric can benefit the practice

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Introduction

• Refraction is a measurement – Data point

• Prescribing is a science/art – Optics – Accommodation – Visual Pathway – Ocular Motor System – Retina/Ocular Health

Introduction

• Refraction – The Patient’s Perspective – “Most important part” • Depending on mode of practice • Doctor: only one of the many things we address

– “what if I give a wrong answer?” • Can be a nerve-wracking experience • Doctor: most of process is directed, it’s hard to give us a

wrong answer, or if you do we know it

Probably A True Statement…

• If you were to choose 20 Optometrists in a room and have them perform a refraction, you would see 20 different ways to perform a refraction.

Source for Refraction Protocol

Clinical Procedures for Ocular Examination, 3rd edition

Authors • Nancy B. Carlson, OD

Professor of Optometry New England College of Optometry Boston MA

• Dan Kurtz, OD, PhD Professor of Optometry The New England College of Optometry Boston, MA 02115

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BRIEF REVIEW OF REFRACTIVE CONCEPTS

Prescription Review Sphere Cylinder Axis

Refractive Error

-3.25 -0.75 x180 Sphere Cylinder Axis

Myopia (with astigmatism) -3.25 -0.75 x180 Hyperopia (with astigmatism) +3.25 -0.75 x180

Refractive Error

http://en.wikipedia.org/wiki/Myopia#mediaviewer/File:Myopia.gif

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Accommodation

20 ft. = Optical ∞ ≥

Accommodation Example

40cm or 16 inches

Accommodation Magnitude

40cm or 16 inches

Accommodation Age Ranges

Most will achieve absolute presbyopia by this age

Note: the values decrease with age

Accommodation Key

• Short of Absolute Presbyopia (add +2.25 or +2.50) need to control, otherwise no concern

• Plus power relieves accommodation

• “over-minused Rx” means patient is overly accommodating through Rx

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REFRACTION SETUP

Clean Phoropter • Begin by disinfecting areas that contact the patient Face Plates & Vertex/forehead plate

Set Pupillary Distance • Set patient’s PD

– If not known prior; estimate and then adjust after

Set Entering Refractive Data

• Set phoropter prescription based on – Autophoropter values – Previous refraction – Current glasses reading

• Assumption: Patient’s begin with reasonable refractive data and have mild to moderate changes in Rx

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Set Entering Refractive Data

• Sphere Wheel

• Cylinder Power Knob

• Cylinder Axis Knob

Set Entering Refractive Data

• Cylinder Power Knob

• Cylinder Axis Knob

Position Phoropter • Carefully pull phoropter over and then down parallel

to face plane

Position Phoropter • Lock in position • Level phoropter to be “on bubble”

2

3

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Position Phoropter • Set vertex distance

13mm < PD < 17mm

Lock Phoropter • Do not

forget to lock arm too

ROUTINE DISTANCE SUBJECTIVE REFRACTION

Distance Subjective Refraction

� Patient handling and instructions are very important to: � Control refraction � Control patient anxiety � Obtain correct answers

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Distance Subjective Refraction

Outline: 3 parts

• Maximum Plus to Maximum Visual Acuity “MPMVA” – First sphere check “Step down”

• The Jackson Cross Cylinder procedure “JCC” – Astigmatism check

• Second“MPMVA” – Second sphere check “Step down”

Set Chart and Eye • Project Full Chart = 20/20 bottom line, 20/50 top line

• Begin with OD (occlude OS)

Initial MPMVA

• This step is to help control accommodation – Prevents “too much minus”

• If patient can see 20/40 or better, 1. Fog patient by adding + until can only read top line (blur out 20/40) Pt Instruction: “Tell me when you can just barely read only the top line”

Initial MPMVA

• Egger’s Rule +0.25 DS = 1 line of loss -1.00 Diopter Cyl = 1 line of loss

+1.25 +1.00 +0.75 +0.50 +0.25

For 20/20, expect +1.25 or +1.00 to get 20/50

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Initial MPMVA

• Begin reducing + (adding -) until the line of no improvement

• Patient must achieve ½ line of VA per click, when the patient does not improve = Stop

• Should follow Egger’s Rule (+0.25 = 1 line)

Initial MPMVA

• Pt Instruction: “Please read the lowest line possible after each lens change that I make”

• Example Patient: 18 year old male

OD Beginning Rx in phoropter: -3.00 -0.75 x 180 OD Beginning VA in phoropter: 20/30

Initial MPMVA

• Picture of phoropter wheel turned

+0.25 +0.50 “Stop, I can just barely read the top”

“Tell me when you can just barely read only the top line”

“Go ahead and read that top line for me” “V T K P A”

Phoropter: -2.50 -0.75 x 180

Initial MPMVA

• Picture of phoropter wheel turned

-0.25 “TYKOB” -0.50 “TYKOB” -0.75 “TYKOB” -1.00 “TYKOB”

• Image of chart

“Please read the lowest line possible after each lens change that I make”

The patient read 20/25 twice

STOP Phoropter: -3.50 -0.75 x 180

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JACKSON CROSS CYLINDER “JCC”

Astigmatic Testing

• Jackson Cross Cylinder

• The JCC is a set of cross cylinders, one plus cylinder one minus cylinder, set at 90°

• Determines the astigmatism axis

• Refines the astigmatism power

Astigmatic Testing

• The JCC is a set of cross cylinders, one plus cylinder one minus cylinder, set at 90°

-0.25 between the axes

+0.12

-0.12

Jackson Cross Cylinder (JCC)

• The JCC is mounted so that it can be “flipped” by a small flip knob

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Jackson Cross Cylinder (JCC)

• The JCC has two “click positions” • “axis check position”

• “power check position”

AXIS DETERMINATION

Axis Determination • How the JCC works for axis determination

– The JCC is placed straddling the cylinder axis in the cylinder bank

– The “red dots” are followed, as they increase the cylinder power in the direction of the axis

– If the patient reports “no difference” then the patient’s axis and the cylinder bank axis match

Axis Determination • Project Chart: isolate one line above best VA – Example: patient 20/25 VA = isolate 20/30 line

• Move the JCC auxiliary arm over

• Set the JCC to “Axis Check”

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Axis Determination

• Patient Instruction: “I am going to show you two views. I want you to tell me which is sharper and easier to read, or if they are about the same.”

• “This is #1” (wait 1 sec) *Flip the JCC lens* �needs to be quick! • “This is #2.”

Axis Determination

• Follow the Red Dot – Move the axis 15° in the preferred red dot

direction – Continue to move 15° in that direction until the

patient reverses – Re track in 5° steps until Patient Reverses Again “Same”

• Goal is “Same” = STOP

Axis Example

• Example Patient: 18 year old male

OD Current Rx in phoropter: -3.50 -0.75 x 180 OD Current VA in phoropter: 20/25

“#1”

“#2”

“I like #1”

15° x 15

Axis Example “#3”

“#4”

“I like #4”

°5 x 10

“#5”

“#6”

“same”

stay x 10

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Axis Determination

• Question: – What if they reverse again while doing 5°? • Move back in 2° increments

– What if the patient cannot decide!? • You must stop the madness… • Set the axis closer to the patient’s habitual Rx

– What if patient moves you back and forth between two 5°? • Set the axis midway

Axis Determination

• Question: – How many flips is too many? • Try to keep it to 5 cycles or less (1&2, etc) • Don’t count above 10

– When in doubt… • Consult the doctor

POWER DETERMINATION

Power Determination • When the axis has been finalized the JCC is then

rotated 45° to the next “click” position lining up the “P” on the JCC with the cylinder bank’s axis

•

•

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Power Determination

• Flipping the JCC changes the cylinder power

– Red Dot increases the power by -0.25 decreases the power by +0.25

• Special Consideration: – For every 0.50 you change the cylinder power, you

must adjust the sphere power by 0.25 in the opposite direction

Power Determination

• Instruct the patient “I am going to show you two views. I want you to tell me which is sharper and easier to read, or if they are about the same.”

Power Determination

• Start with the with the axis and

*Flip to Red • “This is #1” (wait 1 sec)

* �needs to be quick! • “This is #2.”

Power Determination

• Red = increase the cylinder by -0.25

= decrease the cylinder by +0.25

• Continue to flip until patient calls “same” then

STOP

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Power Determination • Questions: – What if patient reverses? • Choose power closer to the habitual Rx

– Don’t forget to change the sphere power 0.25 per each 0.50 cylinder power change, in the opposite direction

Power Example

• Example Patient: 18 year old male

OD Current Rx in phoropter: -3.50 -0.75 x 010 OD Current VA in phoropter: 20/25

“#1”

“#2”

“I like #1”

-3.50 -1.00 x 010 -0.25

Power Example

“#5”

“#6”

“same”

“#3”

“#4”

“I like #3”

-3.25 -1.25 x 010 -0.50 +0.25

-3.25 -1.25 x 010

VA OD: 20/20

Second MPMVA

Pt Instruction: “Tell me when you can just barely read only the top line”

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Second MPMVA

1. Fog patient by adding + until can only read top line (blur out 20/40) Pt Instruction: “Tell me when you can just barely read only the top line”

Second MPMVA

• Begin reducing + (adding -) until the line of no improvement

• Patient must achieve ½ line of VA per click, when the patient does not improve = Stop

• Should follow Egger’s Rule (+0.25 = 1 line)

Integrating Para-Refraction

• Increases Dr. efficiency

• Contact lens over-refraction

• Medical vs refractive visits

http://www.optometrial.com/phoropter_simulator

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Thank You!

Ryan Gustus, OD ryan.gustus@gmail.com

Eyecare Associates of Bluffton 980 North Main St

Bluffton, IN 46714

(260) 824-2020

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