TRIAL FRAME REFRACTION:

Transcription

1 TRIAL FRAME REFRACTION: MORE THAN JUST 1 OR 2? Sarah Wassnig, B.Optom, MPH May This presentation has been created for Orbis International trainees by New England College of Optometry Volunteer Faculty. This presentation is property of the New England College of Optometry and any attempt to reproduce material will be in violation of US copyright law.

2 LECTURE OBJECTIVES 1. To understand the steps of trial frame refraction 2. To understand use of trial frame refraction equipment 3. To have the knowledge of how to adjust your refraction technique for challenging patients and testing environments

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6 QUESTION? HOW MANY PEOPLE TRIAL FRAME REFRACT? A. Never B. I trial frame refract only low vision patients C. I sometimes trial frame refract D. I only trial frame refract

7 QUESTION? HOW MANY PEOPLE LEARNED TO DO A FULL TRIAL FRAME REFRACT IN THEIR DEGREE? A. No, I was only taught phoropter refraction B. I was only taught trial frame refraction C. I was trained equally in phoropter and trial frame refraction D. I was only trained in trial frame refraction in the context of a low vision patient

8 QUESTION? HOW MANY PEOPLE REFRACT IN ENVIRONMENTS OUTSIDE OF CLINIC? A. Never, I only refract in the clinic B. I do school and/or community screenings C. I visit remote towns and/or nursing homes to do full eye examinations

9 HOW IS TRIAL FRAME DIFFERENT TO PHOROPTER REFRACTION?

10 REFRACTION THE PHOROPTER CONTRAINDICATIONS: Young children Older adults People with disabilities Deaf or hard of hearing patients

11 REFRACTION THE TRIAL FRAME INDICATIONS AND BENEFITS 1. Children 2. Persons with disabilities 3. Persons with low vision 4. Illiterate people 5. Those speaking a different language 6. Elderly 7. High prescriptions

12 THE EQUIPMENT NEEDED FOR TRIAL FRAME REFRACTION

13 THE EQUIPMENT THE TRIAL FRAME

14 THE EQUIPMENT THE TRIAL FRAME

15 THE EQUIPMENT THE TRIAL FRAME

16 THE EQUIPMENT THE TRIAL FRAME

17 THE EQUIPMENT THE TRIAL FRAME

18 THE EQUIPMENT THE TRIAL FRAME

19 THE EQUIPMENT THE TRIAL FRAME

20 THE EQUIPMENT THE LENS SET

21 THE EQUIPMENT THE LENS SET Jackson Cross Cylinder Lenses JCC

22 THE EQUIPMENT THE LENS SET red and green lenses

23 THE EQUIPMENT THE LENS SET Occluder

24 THE EQUIPMENT THE LENS SET Stenopaeic Slit

25 THE EQUIPMENT THE LENS SET Pinhole

26 THE EQUIPMENT THE LENS SET Maddox Rod

27 THE EQUIPMENT THE LENS SET Prisms

28 THE EQUIPMENT Risley Prisms and handheld prism equipment

29 THE EQUIPMENT THE LENS SET

30 THE EQUIPMENT THE LENS SET

31 THE EQUIPMENT THE LENS SET

32 HOW DO I WORK WITH A LOOSE LENS SET?

33 WORKING WITH A LENS SET KEEP IT TIDY! KEEP YOUR FINGER PRINTS OFF THE LENSES

34 WORKING WITH A LENS SET But what if I want to reserve a lens? Put the lens back but turn the hand to the inside

35 WORKING WITH A LENS SET Right hand takes from the right side, left hand takes from the left side.

36 WORKING WITH A LENS SET Use the gaps in the lens set to put the lenses away faster

37 TRIAL FRAME REFRACTION WHAT ARE THE STEPS?

38 REFRACTION PROCEDURE 1. Test the patient s vision with current glasses or no glasses if they do not have a pair. Test both eyes individually and binocularly. Show the full chart Always push the patient to the best acuity Great! Can you read any of letters on the next line below? Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

39 REFRACTION SET UP PATIENT POSITION Sitting comfortable, not forward ILLUMINATION Depends on the chart TRIAL FRAME POSITION Trial frame adjusted for vertex distance Trial frame adjusted for inter-pupillary distance Trial frame straight Trial frame adjusted behind the ears EXAMINER POSITION To the side of the patient Need to be able to manipulate lenses and, possibly, chart Don t block the patient s view

40 ADJUSTING THE TRIAL FRAME PROPERLY Make sure your temple is straight! Adjust your temple to fit snuggly behind the ear!

41 ADJUSTING THE TRIAL FRAME PROPERLY Make sure the frame is straight! Make sure the pupillary distance of the trial frame matches the pupillary distance of the patient! Make sure the nose rest is up on the nose! Make sure the patient is looking through the center of the lens!

42 REFRACTION THE STARTING POINT RETINOSCOPY Objective Difficult with smaller pupil Cycloplege??? AUTOREFRACTOR Accommodation affects the result Assumes a normal lens and corneal shape Less accurate for higher prescriptions Patient must have forehead on rest PREVIOUS GLASSES PRESCRIPTION Know what they are use to, especially astigmatism, re: likely adaptation

43 REFRACTION THE STARTING POINT YOU CAN DO RETINOSCOPY WITH LOOSE LENSES! Retinoscopy racks are a helpful tool but not necessary to do retinoscopy outside of a phoropter. Go in 1.00D steps It s faster! Count up 4 lenses from the lens you just used minimizes the number of lenses you touch Easy to keep track of Helps bracket easily to within +/-0.75D Use sphere lenses to neutralize both the sphere and the cylinder meridians Saves you fiddling with cylinder axes in dim lighting Do the math for the final cylinder once you ve separately neutralized both meridians. Stay tidy!!!

44 WHEN DO I CYCLOPLEGE? Vergence of light is altered by accommodation We want to suspend a patient s accommodation to ensure the distance refractive error is accurate BUT is cycloplegic always necessary? Don t cycloplege if: 1. the patient s age suggests the accommodation system is not at it s peak, 2. the clinical setting does not allow for checking of anterior chamber angles, and/or 3. if you plan to refract and binocular test the patient after completing retinoscopy. Cyloplegic refractions are not always well accepted by patients with active accommodation When thinking of prescribing a full cycloplegic refraction in a patient without strabismus or amblyopia, prescriptions should be trialed on the patient in a trial frame without cyclopegia before prescribing. We can minimize accommodation in other ways that are less permanent and give us a more realistic idea of how much prescription the patient will take.

45 HOW DO WE MINIMIZE ACCOMMODATION Misconception: we have the perfect refraction when we have fully relaxed accommodation. We accidently stimulate accommodation when we over minus the refraction. 1. Fogging through out this lecture I will refer to fogging the eye, this means I want to add plus over the refraction I have to blur the vision and therefore fully relax accommodation. You will hear me tell you to slowly reduce the fog until the patient can read their best visual acuity the reason we are doing this is to find the point at which the patient can see their best visual acuity with the most plus refraction. 2. Binocular Balance at the end of a refraction we binocular balance in patients who have active accommodation and who have equal vision between both eyes. 3. Duochrome throughout the refraction we can use duochrome to check the patient has not been over minused.

46 QUESTIONS BEFORE WE MOVE ON?

47 REFRACTION PROCEDURE 2. Occlude the left eye Refract the right eye first 3. Measure best visual acuity with your starting point Retinoscopy, auto-refraction or previous refraction. Show the full chart Sphere lens is in the lens well behind Cylinder lens is in the front Lens well

48 MY STARTING VISUAL ACUITY IS BAD!?!? Not everyone sees 20/20 (6/6, 1.o) and that s okay! Trust your retinoscopy if you get a few lines worse than 20/20 (6/6, 1.0) then that means you re most likely only a few steps away from the true refraction.

49 REFRACTION PROCEDURE 4. Refine the sphere Take a +0.25D lens and a -0.25D lens in one hand Show the patient the two lens options asking which makes their lowest visual acuity clearer. Add the lens that makes it clearer careful not to over minus here, they need to READ more letter if they want more minus! Keep repeating until the patient reports same or cannot read more with the preferred lens. Show the full chart Direct the patient's attention to the line of their best acuity.

50 REFRACTION PROCEDURE 4. Refine the sphere Take a +0.25D lens and a -0.25D lens in one hand Show the patient the two lens options asking which makes their lowest visual acuity clearer. Add the lens that makes it clearer careful not to over minus here, they need to READ more letter if they want more minus! Keep repeating until the patient reports same or cannot read more with the preferred lens. Show the full chart Direct the patient's attention to the line of their best acuity.

51 REFRACTION PROCEDURE 5. Duochrome Clearer in the red, add minus (-0.25D) the myopia is under-corrected or the hyperopia is over-corrected. Clearer in the green, add plus (+0.25D) the hyperopia is undercorrected or the myopia is overcorrected. Stop when equal or 1 step on green for accommodating patients This test does not always work if the patient continues to say red then, they most likely have a red preference so go back to your original prescription and skip this test. Cannot be preformed on patients with vision worse than 20/30 (6/9, 0.63) Equal Red Green

52 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART? YOU HAVE THESE LENSES!

53 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART?

54 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART? Clearer in the red Add +0.25D Sphere

55 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART?

56 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART? Clearer in the green How do I now! choose which lens!?!?! Leave the patient 1 step in the green.

57 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART?

58 WANT TO DO DUOCHROME BUT HAVE NO COMPUTERIZED CHART? Same = leave the power

59 QUESTIONS BEFORE WE MOVE ON?

60 REFRACTION PROCEDURE 6. Astigmatism/cylinder: Isolate the line 1 step larger than current VA Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

61 AXIS REFINEMENT REFRACTION PROCEDURE Align the HANDLE of the Jackson Cross Cylinder (JCC) with the lens axis (so the dots are straddling the axis) If the tentative or starting astigmatism is more -0.50DC = refine your axis first as being off axis will alter your power.

62 -1.25 AXIS CHECK Flip the JCC one side being lens or option 1 and the other side being lens or option 2 Advise the patient that neither lens will be completely clear, but ask which option is best.

63 REFRACTION PROCEDURE If the two lenses are equal, move straight on to power determination. If not, rotate the cylinder LENS axis toward the minus axis (red dot) of the JCC. Repeat this question If the response is in the opposite direction move the axis back by half the amount changed the first time. If the response was in same direction as last, make another change of axis towards the red, until the response is in the opposite direction. Continue with this bracketing until the patient notices no difference between the two lens positions. Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

64 POWER REFINEMENT REFRACTION PROCEDURE Align the POWER dots of the Jackson Cross Cylinder (JCC) with the lens axis. If tentative or starting astigmatism is -0.50DC or -0.25DC it is best to refine power first it may not even be a real astigmatism!

65 POWER CHECK Advise the patient that neither of the lens will be completely clear, but ask which option is best Flip the JCC lens to give the two power options

66 REFRACTION PROCEDURE If the two lenses are equal, you are finished! If the patient prefers the red (minus) axis dots, add -0.25DC. If the patient prefers the white (plus) axis dots, remove -0.25DC. Repeat until both views are clearer If you change cylinder power by more than -0.75DC, check axis again. MAINTAIN SPHERICAL EQUIVALENT For every -0.50DC you increase add +0.25D Sphere For every -0.50DC you decrease remove +0.25D Sphere Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

67 NO INITIAL ASTIGMATISM?? REFRACTION PROCEDURE Align the JCC so the axes are at 135/45, flip lens and take note of which axis is red preferred Align the JCC so the axes are at 180/90, flip lens and take note of which axis is red preferred Add 0.50 DC between the two preferred red axes Add +0.25DS for spherical equivalent Refine the power and then the axis If prefers white, there is no cylinder in the prescription. Remember to remove the +0.25D from the sphere to maintain spherical equivalent.

68 option 2! option 3!

69 If there is any astigmatism the axis must be between 135 degrees and 180 degrees! -0.50

70 QUESTIONS BEFORE WE MOVE ON?

71 REFRACTION PROCEDURE 7. Refine best sphere Fog the vision Add +0.75DS to bring 2-4 lines worse than current VA). ** warn the patient it will be blurry ** Show the full chart Direct the patient's attention to the line of best acuity as their vision clears up. Slowly reduce the plus by 0.25D steps, each time checking visual acuity. Stop when VA does not improve NO MORE THAN -0.25DS OVER

72 REFRACTION - PROCEDURE Occlude the right eye and move onto the left eye REPEAT THE PROCESS!

73 REFRACTION - PROCEDURE 8. Binocular Balance - Humphriss INDICATIONS: patients who are old enough to participate, equal visual acuity, patients with peripheral. CONTRAINDICATIONS: strabismus, unstable or decompensating heterophoria Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

74 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss Add D to the eye that is not being tested (left). Check visual acuity is decreased to 6/12. If the visual acuity has not been reduced in the left eye, add plus +0.25D until 6/12. Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

75 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss Compare to -0.25, ask the patient which lens is clearer If one lens is clearer adjust the sphere in that direction. Repeat the comparison until equal Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

76 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss Compare to -0.25, ask the patient which lens is clearer If one lens is clearer adjust the sphere in that direction. Repeat the comparison until equal Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

77 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss *** Only minor adjustments are made this way. If more than 0.50D change, check the fog on the eye not being tested *** Fog this eye and unfog other eye Repeat for the left eye Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

78 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss Compare to -0.25, ask the patient which lens is clearer If one lens is clearer adjust the sphere in that direction. Repeat the comparison until equal, remove the right fogging lens. Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

79 REFRACTION - PROCEDURE 8. Binocular Balance Humphriss Compare to -0.25, ask the patient which lens is clearer If one lens is clearer adjust the sphere in that direction. Repeat the comparison until equal, remove the right fogging lens. Hrynchak, P. (2013). Clinical Optometric Procedures. Brien Holden Institute Academy

80 QUESTIONS BEFORE WE MOVE ON?

81 CLINICAL PEARLS FOR REFRACTING WITH A TRIAL FRAME

82 ADDITIONAL BINOCULAR BALANCE METHOD - SUCCESSIVE ALTERNATE OCCLUSION Successive alternate occlusion Only works with equal best corrected VA Add sphere power OU Target: isolate the line 20/50 (6/15, 0.4) or 20/60 (6/18, 0.32) Directions: Can you see the line with your right eye? And now your left eye? I m going to cover one eye at a time. Both views will be blurry, but I want you to tell me which view is clearer or if they look the same.

83 ADDITIONAL BINOCULAR BALANCE METHOD - SUCCESSIVE ALTERNATE OCCLUSION Add +1.00D Sphere over each eye Direct the patient s gaze to the 20/40 (6/12, 0.5) line, but show the whole chart.

84 ADDITIONAL BINOCULAR BALANCE METHOD - SUCCESSIVE ALTERNATE OCCLUSION Continue to switch between the two eyes to give the patient a chance to compare views. Open the VA chart to show multiple lines. Reduce the plus power binocularly, checking the VA after each step.

85 ADDITIONAL BINOCULAR BALANCE METHOD - SUCCESSIVE ALTERNATE OCCLUSION Continue to switch between the two eyes to give the patient a chance to compare views. Open the VA chart to show multiple lines. Reduce the plus power binocularly, checking the VA after each step.

86 ADDITIONAL BINOCULAR BALANCE METHOD - SUCCESSIVE ALTERNATE OCCLUSION Continue to switch between the two eyes to give the patient a chance to compare views. If the patient says Right add +0.25D sphere to the left eye If the patient says Left add +0.25D sphere to the right eye If the patient keeps switching between right and left, leave the dominant eye slightly clearer. If the patient says the same leave. Open the VA chart to show multiple lines. Reduce the plus power binocularly, checking the VA after each step.

87 CHECKING FOR EYE DOMINANCE Which eye does the body visually prefer and use to line up with objects in visual space? E E E Both eyes open Close right eye = no change Close left eye = image no longer lined up Which is the dominant eye? LEFT EYE! The image didn t move when the left eye was open because binocularly it was responsible for lining up with the visual target E

88 STEADY YOUR JJC LENS Use your other hand to steady the JCC lens! It s essential that you remain on axis!

89 WHAT IF I CANNOT ISOLATE A LINE OR AN O FOR JACKSON CROSS CYLINDER? Point to a D Ask the patient which lens looks more like the letter D and which lens makes the letter look more like a letter O? The round dots are a great target for Jackson Cross Cylinder! Ask the patient which side of the lens make the dots rounder and darker?

90 WHAT IF MY PATIENT ALWAYS THINKS 2 IS ALWAYS THE ANSWER? I am going to show you two lenses and each time I want you to tell me which lens makes the line of letters look clearer Lens 1 or 2? These are the first pair Which is clearer, lens 1 or 2? Great. Now between lens 3 or 4? Now 5 or 6? Again, 1 or 2?

91 I HAVE THIS CHART BUT NO JCC LENS FAN AND BLOCK! After getting the best vision SPHERE 1. Ask the patient which lines on the fan are the clearest and darkest 2. Move the arrow so it is 90 degrees to where the patient reports clearest (the two limbs of the arrow will be equally clear). 3. Add positive sphere equal to half of the estimated astigmatism. 4. Ask the patient to look at the blocks and ask which block is clearest add negative cylinder lenses -0.25DC at a time with the axis aligned with the clearer block lines. 5. Continue until both blocks are equally clear. 6. Refine spherical lens power by decreasing the power by 0.25DS at a time

92 I HAVE THIS CHART BUT NO JCC LENS FAN AND BLOCK! 1. Ask the patient which lines on the fan are the clearest and darkest 1. Move the arrow so it is 90 degrees to where the patient reports clearest (the two limbs of the arrow will be equally clear).

93 I HAVE THIS CHART BUT NO JCC LENS 3. Add positive sphere equal to half of the estimated astigmatism. What if I don t know the estimated astigmatism? 20/20 (6/6, 1.0) 0.00 to 0.75DC 20/32 (6/9.5, 0.63) 1.00DC to 1.25DC 20/40 (6/12, 0.5) 1.50DC to 1.75DC 20/63 (6/18, 0.32) 2.00DC to 2.25DC 20/80 (6/24, 0.25) 2.50DC to 3.00DC 20/100 (6/30, 0.20) 3.25DC to 4.00DC

94 I HAVE THIS CHART BUT NO JCC LENS FAN AND BLOCK! 4. Ask the patient to look at the blocks and ask which block is clearest add negative cylinder lenses -0.25DC at a time with the axis aligned with the clearer block lines. 5. Continue until both blocks are equally clear.

95 I HAVE THIS CHART BUT NO JCC LENS CLOCK CHART! Add a +1.00DS lens in front of best vision sphere. Ask the patient which clock position has the darkest, sharpest lines? Multiply the smaller o clock position by 30 E.g.: 30x2 = 60degrees Place a -0.25DC lens at that axis Ask again which line is darkest/sharpest? Continue adding -0.25DC until all lines are the same. KEEP ADJUSTING SPHERICAL EQUIVALENT!

96 CAN I USE THIS TO FIND ASTIGMATISM? Thorington Method and the Stenopaeic Slit Not as accurate as other methods discussed. No choosing between 1 or 2 Low visual acuity because of high astigmatism. Retinoscopy reflex is difficult to see. After best spherical visual acuity is achieved, add +0.50DS. Put stenopaeic slit into the trial frame and the patient is instructed to rotate slit, whilst looking at the full chart, until best visual acuity is achieved. The slit is now aligned with the minus cylinder axis. Refract the two principle meridians separately with the stenopaeic slit in place.

97 I AM WORRIED ABOUT VERTEX DISTANCE! If you have a sphere high prescription then you are correct to be worried about vertex distance. Place the sphere lens in the back lens well of the trial frame. There is a ruler to the side for you to measure the vertex distance of the trial frame on the patient. Back lens well

98 REFRACTION OVER CURRENT GLASSES

99 Just Noticeable Difference! LOW VISION PATIENTS Hand held Jackson Cross Cylinder (JCC) lenses come in different steps! Usually we would use +/0.25 OR +/-0.50 BUT we can also buy +/ AND +/ This allows us to have bigger differences between lenses when acuity is more impaired 20/100 = JND of 1.00 or +/ /200 = JND of 2.00 or +/- 1.00

100 CHART CONDITIONS Mark where your chart distance is on the floor. Have a clean chart with white background and distinct black letters for good contrast Place the chart at eye level Test in good lighting with minimal shadows around the chart In a screening situation where you have estimated the distance of the chart, the patient may not be reading the 20/20 (6/6, 1.0) line because the chart is incorrectly positioned that s okay. You can refract to the best visual acuity as long as you don t shift the chart during refraction.

101 NEEDING TO ADJUST YOUR CHART TO FIT INTO YOUR TESTING ENVIRONMENT? LogMAR charts have uniform size progression! Can be used easily at different test distances At half the distance, expect 3 lines better At twice the distance, expect 3 lines worse Letters Tumbling E LEA symbols Landolt C

102 WHAT IF I AM NOT SURE IF THE PATIENT WILL BE COMFORTABLE WITH THIS CHANGE IN REFRACTION? Large changes in cylinder axis/power or sphere power can make the patient uncomfortable. Always get the patient to walk around and see how they feel with the trial frame on with the prescription. Alter the prescription so the patient feels more comfortable.

103 FINDING A NEAR PRESCRIPTION FOR PRESBYOPES Ask the patient to hold the chart at their reading distance We all read at different distances What prescription would you expect at each age if distance vision is corrected? Add +0.25D sphere over both eyes if you Age 45 = +0.75D add want to bring the working distance closer Age 50 = +1.00D add Age 55 = +1.50D add Age 60 = +2.00D add Age 65 = +2.50D add Add -0.25D sphere over both eyes if you want to bring the working distance away

104 IT IS AWKWARD ADDING +0.25D/-0.25D LENSES OVER BOTH EYES TO ASSESS READING! Yes it is! I LOVE my +/-0.25D flippers! I ask the patient to look at their reading target at a distance comfortable for them and the I place the +0.25D lenses over saying does this improve your vision?. If no, I revmove the flipper, flip it and place the -0.25D lenses over both eyes asking again does this improve your vision?

105 CONFIRMING REFRACTION IN KIDS WITH BLUR FUNCTION 1. Add over ret finding, binocularly. Warn child of blur and you will slowly make it clearer. 2. Ask the best line they can see and each time they start making errors reduce plus by 0.25D. 3. Keep going until they plateau or get to 6/6. *** Do this monocularly if there is a large difference between visual acuity ***

106 LECTURE OBJECTIVES 1. To understand the steps of trial frame refraction 2. To understand use of trial frame refraction equipment 3. To have the knowledge of how to adjust your refraction technique for challenging patients and testing environments

107 THANK YOU QUESTIONS?