Copyright 2016, Phernell Walker, BSB, ABOM

Transcription

1 Trouble hooting the Difficult Prescription Trouble hooting the Difficult Prescription Phernell Walker, II, BB, ABOM National peaker Brief Biography: Phernell Walker, II, BB, NCLC, ABOM Master in Ophthalmic Optics Bachelor of cience in Business Associate of cience in Opticianry ABO Certified NCLE Certified Author of text-book, Pure Optics Beverly Meyers Achievement Award in Optics Reference: Pure Optics by Phernell Walker, II, BB, ABOM Goal of olving Problems What is the Gifted Mind Reader? Protocol for olving Problems Isolating Rx Problems Discuss pecific Case tudies Heart of America Contact Lens 2016

2 Goal of olving Problems Patient satisfaction Negative comments travel quickly and far Limit re-do s Limit chair-time for refraction problems Can I have a Hug? I pulled them out of the case and they broke by them self. Copyright 2016 Pure Optics, Phernell Walker, II, ABOM More Kool Aid Please Using the HPP for Problems termine the History of Present Problem (HPP): Chief Complaint Onset Location everity Duration Modifying Factors

3 The Gifted Mind Reader Make Time chedule glasses check as a regular appointment Be positive, concerned, apologetic it down, listen Have patient bring their old glasses You may have to refract, do lensometry 10 Base Line Information Confirm Rx with lensometer Mark optical centers with lensometer Measure base curves with lens clock Measure patient s PD Measure VA at distance and near 11 Common Errors Refractionist Commit Poor refraction A. Changing distance changes add power B. 50/50/15 rule C.Poor binocular balancing Poor handwriting, transcription error Diabetic with fluctuating blood sugar Contact lens wearer with corneal edema Unrealistic expectations Copyright 2016 Pure Optics, Phernell Walker, II, ABOM 12

4 When Things Go Wrong 13 Glasses not made to Rx Undetected convergence insufficiency Change in lens material Change in vertex distance Poor glasses fit Change in vision since the refraction David Letterman Has His Top Ten- Opticians do Too! 1) My eyes feel like they re pulling 2) One side of the table is higher than the other 3) I can t see with my new progressive lenses 4) I have to move my head to the right or left to read 5) I see better through my clear glasses vs. my sunglasses 6) I see better through my old glasses vs. new glasses 7) I see multiple colored lines through the left lens 8) Objects viewed are skewed through my glasses 9) I see ghost images in my progressive lenses 10) I see double with my new glasses 14 My Eyes Are Pulling My Eyes Are Pulling Discuss & olve: Verify patient s P.D. Verify spectacle P.D. Compare previous eyewear Adjust parabolic angle

5 One ide is Higher Than the Other Ask: Which side of the table appears higher? One ide Of The Table Is Higher Than The Other Horizontal objects that appear at a slant result from prism induced in the 180 th meridian. The side that appears higher is the location of the base of the prism. 18 earch for Prism Verify the patient s P.D. with the new eyewear and remake the lenses to the correct P.D. Check the previous eyewear for accidental prism Prism Occur's Prism occurs under two conditions: Accidental Prism Prescribed Prism 20

6 Accidental Prism Accidental Prism occurs when: Eyewear P.D. does not match patient's P.D. Optical Center does not match O.C. ordered Difference between the OD & O Optical center 21 Prentice Rule The amount of prism experienced by the patient can be calculated using Prentice s Rule: P = (h cm ) (D e ) P = prism h cm = distance expressed in centimeters D e = dioptric power in the specific meridian 22 Meridian of Dioptric Power Calculate the exact amount of prism in a given meridian (i.e. axis 180 and axis 090) requires us to calculate the amount of total power in a given meridian. 23 Meridian of Dioptric Power pherocylindrical lenses have only a percentage of the total dioptric power present in each meridian. Consequently, each meridian has a different focal length. Either a meridian of dioptric power (MDP) chart can be used or it can be calculated using a formula. 24

7 Meridian of Dioptric Power Chart The MDP chart can be used to determine the total dioptric power of a lens in a specific 5 degree meridian. tep 1: termine the difference from the prescriptions axis and a given meridian. tep 2: Locate the difference on the MDP chart and multiply the prescriptions cylinder power by the percentage tep 3: Algebraically add the amount in tep 2 to the prescriptions sphere power. 25 Meridian of Dioptric Power Chart grees from Axis Percent of CYL. 0 0% 5 1% 10 3% 15 7% 20 12% 25 18% 30 25% 35 33% 40 41% 45 50% 50 59% 55 67% 60 75% 65 82% 70 88% 75 93% 80 97% 85 99% % 26 Example I: termine the dioptric power in the 180th meridian using the following: Rx: X 090 tep 1: tep 2: tep 3: Compute difference in axis = 090 Multiply cylinder power by ratio from MDP chart x 100% = D Add result to sphere power = D 27 Power hift Formula The dioptric power in a specific meridian can also be calculated without the MDP chart with the following formula: D e = + [C (sine a)2] D e = = C = (sine a)2 = dioptric power in the specific meridian sphere power cylinder power the sine of the angle between the axis and a given meridian 28

8 Prentice s Rule: Example #1 The patient s PD is 66mm, but for some unfortunate reason the lab cut the lenses 60mm apart using the following prescription: OD: X 090 O: X Let's Do the Two tep tep 1: Find Power at x180 tep 2: Multiply by Amount off (per lens) Calculate Prism Power P = (hcm) (D e ) P =? (hcm) = (6mm) = (.6cm) D e = OD: 180 O: 180 OD: P = (.3cm)(+2.00) =.60 O: P = (.3cm)(+2.00) =.60 P(OD) + P(O) = Total P = 1.20 D 31 I Can't Read With My New Progressives

9 I Can't Read With My New Progressives Discuss & olve: First verify the O.C. placement (mark lenses, etc.) Most common reasons: O.C. too low (measured or edged). Incorrect vertex distance Incorrect type of progressive used. Incorrect add power (typically not enough plus). 33 I Have To Move My Head To The Right Or Left To Read (Progressive Lenses) Ask: Have you worn progressive lenses before? I Have To Move My Head To The Right Or Left To Read (Progressive Lenses) Discuss & olve: Verify lenses were edged to correct monocular P.D. Check for convergence problems - shade the lenses near point circle, check visual axis while reading. Are you seeing through, or to the left or right of the shaded circle? 35 I Have To Move My Head To The Right Or Left To Read (Progressive Lenses) Verify your findings with a pupilometer set on 40cm. Adjust or remake lenses based on the findings from both the pupillometer and the subjective findings. 36

10 I ee Better with My Clear Glasses Vs. My unglasses A common problem that arises when a patient receives two pair of glasses Prescription unwear & Eyewear. Ask: Do you also have decreased acuity in dim light or at night with your clear lenses? 37 I ee Better Through My Clear Glasses Vs. My unglasses Discuss : The iris acts as a lens stop, which eliminates spherical aberration of light entering the eye As the pupil dilates to receive additional light (e.g., with dark sun wear), spherical aberration increases, resulting in decreased visual acuity 38 pherical Aberration pherical aberration occurs when broad peripheral light rays focus at a different point than paraxial rays. ince pupils are only 3 to 5mm in diameter, the effect of spherical aberration is limited. 39 Copyright 2006, Pure Optics, Phernell Walker, II, ABOM

11 I ee Better Through My Clear Glasses Vs. My unglasses olve: Try lightening the tint ½ to 1 shade Change the tint color to an amber or brown. 41 I ee Better with My Old Glasses 42 I ee Better Through My Old Glasses Vs. New Glasses Don't ay What You're Thinking: If you see so well with your old glasses, why did you come to see me for a new exam? 43 Confusion ay What?????? 44

12 I ee Better Through My Old Glasses Vs. New Glasses Discuss & olve: Make sure the patient tries the glasses for at least 1 week with the glasses properly adjusted. Isolate the problem to either distance, intermediate or near vision. 45 I ee Better Through My Old Glasses Vs. New Glasses What's different? Check Power Check Vertex Base Curve Index 46 I ee Multiple Colored Lines Through The Left Lens Ask: Through what part of the lens are you seeing the lines? Are the lines a single solid color? When do you see the lines (activity)? 47 I ee Multiple Colored Lines Through The Left Lens (Assume these lenses have an antireflective treatment) If the lines are a single solid color, they do not represent chromatic aberration A clue is that the lines are occurring in one lens only. Internal linear reflections typically result from direct overhead light Check base curves on each lens 48

13 I ee Multiple Colored Lines Through The Left Lens The lens with the internal reflection was generated on a base curve that s too flat. Placing a lens on a base curve that is too flat (by 2 or more diopters) increases divergence on the front portion of the lens allowing the lens to refract overhead light through the lens, and through the eye s center of rotation causing glare. 49 I ee Multiple Colored Lines Through The Left Lens Resolve the problem by remaking the left lens with an increase in the base curve. This is typical on minus lenses with asymmetric base curves on each lens. 50 Objects Viewed Are kewed Through My Glasses Rx: OD: D O: D Pantoscopic Tilt = 15 deg n = (Cr-39) Vertex = 13mm 51 Mastering Optics with Formulae = [1 + (sin@) 2 / 2 n ] C = de (tan@) 2 Variable Key: = Effective phere Power = phere Power n = Refractive Index C = Effective Cylinder 52

14 tep I: = [1 + (sin@) 2 / 2 n ] = [1 + (sin@) 2 / 2 n = [1 + (sin15) 2 / 2 (1.498)] = [ / 2.996] = (-8.50) ( ) = (-8.50) ( ) = tep II: C = (tan@) 2 2 C = (tan15) 2 C = (tan15) 2 C = (-8.68) (tan15) 2 C = (-8.68) (tan15) 2 C = (-8.68) ( ) C = (-8.68) ( ) C = Final: Lens Tilt Resultant Rx Original Rx: OD: D O: D Resultant Rx: x I Feel Nauseous Rx: OD: x 180 O: x 180 Parabolic Angle = 20 deg n = Vertex = 13mm 56

15 tep I: Convert Rx to the 090th Meridian Rx: OD: x 180 O: x 180 Rx: OD: x 090 O: x tep I: = [1 + (sin@) 2 / 2 n ] = [1 + (sin@) 2 / 2 n = [1 + (sin20) 2 / 2 (1.70)] = [ / 2.89] = (-7.00) ( ) = (-7.00) ( ) = tep II: C = (tan@) 2 2 C = (tan20) 2 C = (tan20) 2 C = (-7.28) (tan20) 2 C = (-7.28) (tan20) 2 C = (-7.28) ( ) C = (-7.28) ( ) C = Final: Lens Tilt x 180 Resultant Rx Original Rx: OD: x 180 O: x th Meridian: OD: x 180 O: x 180 Resultant Effective Rx: Answer: x

16 Trouble hooting the Difficult Prescription I ee ad People - Ghost I Tell You! Ghost images - specular reflections of peripheral vision. Most common with lower diopter Rx s, thin lenses and progressive lenses. Ghost images occur for several reasons: Lenses are too thin (adding thickness or adjusting the amount of parabolic angle and pantoscopic/ retroscopic tilt) 61 Too Thin! Excessive prism thinning used during the generating process places the ghost image in the line of sight. (Verify the amount of prism thinning that was used. Typically.60 prism diopters per diopter of add power is used in the 90th meridian) 62 Visual vs. Optical Axis crease vertex and adjust frame tilt to move in opposite direction of the visual axis. 63 Martin's Tilt Formula Heart of America Contact Lens 2016

17 Trouble hooting the Difficult Prescription Heart of America Contact Lens 2016 Double Vision Ask: Are there two separate images or is there overlap? Are the images vertically double (stacked) or horizontally double (side by side)? 65 I ee Double with My Glasses Vertically double- check the M.R.P. of the eyeglasses Horizontally double- check the P.D. Anisometropic prescriptions- plot a power cross and determine magnification in each meridian to see if aniseikonic symptoms are being induced 66 Diabetes (Adult Onset) Morning Rx: OD: x 80 O: x 95 Afternoon Rx: OD: x 80 O: x 95 Magnification There are five factors that control magnification: Base Curve Lens Dioptric Power Thickness Vertex Distance ubstrate s refractive index 68

18 Magnification Ms = 1 / (1- (t) (D 1 )) / n Mp = 1 / (1 - (hm)) (Ms) (Mp) = Mt (Mt -1) 100 = % of X Ms = hape Factor Mp = Power Factor Mt = Magnification Practice Makes Perfect Example: A patient has the following prescription & fitting parameters: V Lenses 1.66 n Vertex (h) = 13mm BC: +2.00D What is the percentage of spectacle magnification? O.D D.. (thickness 5mm) O D.. (thickness 4mm) 70 tep I: Calculate hape Factor OD Lens Only: F = 1 / 1 (t /n) (D 1 ) F = 1 / 1 (.005/ 1.66) (2) F = 1 / 1 (.003) (2) F = 1 / F = 1 /.994 F = Calculate Mx Power O.D. Lens Only: PF = 1 / 1 (h) (D) PF = 1 / 1 (.013)(-8.75) PF = 1 / PF = 1 /.887 PF = 1.127

19 tep III: tep x Power OD Lens Only: M in % = [ (F) (PF) -1 ] 100 M = [ (1.006) (1.127) - 1 ] 100 M = [ ] 100 Answer: M = 13.30% (Minus Lenses equal 13.30% demagnification) 73 tep I: Calculate hape Power O.. Lens Only: F = 1 / 1 (t /n) (D 1 ) F = 1 / 1 (.004/ 1.66) (2) F = 1 / 1 (.002) (2) F = 1 / F = 1 /.996 F = tep II: Calculate Power Factor O.. Lens Only: PF = 1 / 1 (h) (D) PF = 1 / 1 (.013) (-6.00) PF = 1 / PF = 1 /.922 PF = Final tep tep III: Multiply hape & Power Factors M in % = [ (F) (PF) -1 ] 100 M = [ (1.004 ) (1.084) - 1 ] 100 M = [ ] 100 M = 8.80% (ince the lens is minus powered, the left lens has 8.80% demagnification) In our example the O.D. lens has 13.30% demagnification and the O.. lens has 8.80% in demagnification, which equals a differential of 4.50%. 76

20 Trouble hooting the Difficult Prescription Don't Be Fooled 77 Occupational Hazard A Day in the Life of an Optician 78 Where's My Glasses? Positive ID Heart of America Contact Lens 2016

21 Trouble hooting the Difficult Prescription You Did This to Me Lets Get Ready to Rumble Patients Prescription OD: x 090, 3 Prism B.O. O: Balance Lab Created Eyewear Made: OD: x 090 O: Plano The OD Lens was uper Thick! The O lens paper thin. 84 Heart of America Contact Lens 2016

22 BIG HOE vs. little shoe I feel like a circus clown with one BIG HOE and one little shoe Copyright 2016 Pure Optics, Phernell Walker, II, ABOM Circus Clown hoes o, did He Kill You? 87 Questions 88

23 Trouble hooting the Difficult Prescription Reference: Pure Optics by Phernell Walker, II, BB, ABOM Trouble hooting the Difficult Prescription Phernell Walker, II, BB, ABOM National peaker Heart of America Contact Lens 2016