TORIC AND MULTIFOCAL GP AND SCL PRESCRIBING Edward S. Bennett OD, MSEd, FAAO

Transcription

1 TORIC AND MULTIFOCAL GP AND SCL PRESCRIBING Edward S. Bennett OD, MSEd, FAAO l Dr. Bennett is a consultant to the Contact Lens Manufacturers Association SOFT TORICS: Good Candidates l Astigmatic and do not desire GPs l Poor vision with spherical soft lenses l Athletes and any astigmatic patient who desires occasional wear l Refractive astigmatism 0.75D FITTING PEARLS l Wait 5 10 minutes before assessing l Is lens stable on eye? l Evaluate fit first; if variable or excessive rotation it is preferable to then refit l Rotation is judged from fitter s perspective l Use LARS and add to refractive axis From Bennett ES, Henry VA: Clinical Manual of Contact Lenses (4 th edition) Methods of Rotation Evaluation l Conventional: n Trial Frame n SWAG 7 l Today! FITTING PEARLS (cont.) l Know available lens parameters l When in doubt, under-prescribe on cylinder l Vertexing very important with 4D in either or both meridians l Example: x 180 = x 180; x 180 = x 180 1

2 x 180 = x Cross Cylinder Calculators l AOA E-Z Fit l Eyedock.com l Therightcontact.com l Most contact lens companies So What Lens Do I Select? l Replacement Schedule (1 month, 2 weeks, 1 day) l Daily for dry eyes, occasional wear l Daily wear versus extended wear GPS AND HIGH ASTIGMATISM With > 2.00D corneal cylinder the following problems can occur with a spherical GP: Flexure Decentration Corneal Warpage Corneal Desiccation Lens Awareness BACK SURFACE VS. BITORIC l Both indicated with 2.50D corneal cyl l Back surface toric only lenses have a toric back surface (identical in curvature to a bitoric) as verified with a radiuscope l Back surface torics induce a residual cylinder equal to about one-half of the back surface cylinder of the lens due to differences in refractive indices between lens and tear film BACK TORIC l Determination of Base Curve Radii: l (Mandell-Moore) l Corneal Cyl Flat Meridian Steep Meridian D On K 0.50D Flat D 0.25D Flat 0.50D Flat D 0.25D Flat 0.75D Flat D 0.25D Flat 0.75D Flat 2

3 D 0.25D Flat 0.75D Flat D 0.25D Flat 0.75D Flat 5.0D 0.25D Flat 0.75D Flat BACK SURFACE TORIC: INDUCED CYLINDER l Exp: x 180; 41/45: Toric BCR: 40.75/44.25; desired powers: +1.25/-2.25 l BST induces cylinder equal to 40 50% of back surface cylinder l If there is 3.5D of back surface cylinder induced is to -1.75D x 180; this will be present via over-refraction l On lensometer there will 3/2 x back surface cylinder or 5.25D; if most plus meridian is unchanged, power in other meridian = -4D BITORICS l When you correct for induced cylinder (ie, in previous example, add x 180) on front surface, you have a bitoric design l Provides good centration; should fit like a spherical lens on low astigmatic cornea l Provides good vision l Results in good corneal integrity l When induced cylinder (only) is corrected, this results in a spherical power effect Why Bitorics in 2014 (Bennett/Parker Jan 2014, CL Spectrum) l Back torics induce cylinder (to reduce cyl you have to reduce back surface toricity; therefore, fit may be compromised) l The high quality lathes in common use today can manufacture a bitoric lens as easily as a back toric l In fact today laboratories charge close to the same for both designs l Bitorics = Good Vision! Empirical Fitting of High Astigmatism with GP Vs. Soft Toric Lenses (Michaud et al, July 2009 Optometry) 3

4 l 20 subjects: > 1.75D corneal cyl; avg. refractive cyl = -3.62D l Baseline: 10 = soft torics, 2 GP back torics, 7 previous CL failures l In 2 groups: wore each modality for one month l Results: 14/19 preferred vision of GP lenses; 11/19 preferred to remain in GP lenses FITTING l Empirical l Diagnostic EMPIRICAL METHODS l Mandell-Moore Guide Calculator l GPLI Toric and Spherical Calculator l Newman Guide DIAGNOSTIC FITTING l Polycon SPE is an excellent diagnostic set; as it is no longer available if desired you can obtain a similar set from a CLMA member laboratory) l Three different sets: 2D, 3D & 4D back surface cylinder l Recommend 3D set: (40.50/43.50 to 45/48D in 0.50D steps; powers = Pl/-3.00D) BASE CURVE RADII DETERMINATION l Base curve radii are not typically equal to the K values: n For example: if K s are 44.00/47.50; Select BCR = 43.50/46.50 This allows for a slight amount of toricity which assists in tear pumping and centration SPE DIAGNOSTIC FITTING l Select diagnostic lens 0.12 to 0.50D FTK l Perform spherical over-refraction l Add OR to powers in the flat and steep meridians of diagnostic lens 4

5 diagnostic lens CYLINDER POWER EFFECT If the patient has residual astigmatism resulting in blurred vision with spherical OR, a cylinder power effect bitoric is recommended This lens must remain stable on the eye as any rotation could blur vision CYLINDER POWER EFFECT POWER DETERMINATION (Silbert): If axes are at or near the principal corneal meridians, add the appropriate power in the refraction to the air power of the corresponding meridian in the diagnostic lens, then order. OTHER CONSIDERATIONS: TORIC PERIPHERAL CURVES add 1mm to BCR for secondary curve radii add 2mm to SCR for peripheral curve radii 25 Presbyopic Market l 74 million Baby Boomers born between l In 2010, about 1/3 of US population was between years of age. l In 2000 US census there were 100 million US citizens over the age of 45, in 2010-over 120 million l In the next decade, 28% of all contact lens wearers will be >50 y.o. l 90% of all CL wearers between have worn CL s majority of their life 26 Are consumers aware of multifocal CLs? 20/20 (August 15, 2007) Contact Lens Council survey concluded: 40% of presbyopic population unaware of multifocal availability 5

6 40% of presbyopic population unaware of multifocal availability If made aware, 75% of CL wearers and 60% of spectacle wearers were interested in trying them 27 Prescribing Trends l 63% of presbyopic CL wearers are not wearing presbyopic corrections 29% MF/BF 8% monovision l Good thing we ve got the CLMA and GPLI! l Turn that trend around! n Morgan P.B., Efron N., Woods C.A. The International Contact Lens Prescribing Survey Consortium. An international survey of contact lens prescribing for presbyopia. Clin Exp Optom. 2011;94: PATIENT SELECTION AND COMMUNICATION Patient Selection l Positive Outlook for MF s in general Patients that currently wear GP lenses without significant dryness or other comfort issues New CL wearers that are motivated to remain free from glasses Patients that are willing to accept some vision compromise at some distances in order to gain freedom from spectacles for most daily activities - 80 / 20 rule - 20 / Happy PATIENT SELECTION l Positive Outlook for GP Multifocal Contact Lenses Those that habitually wear GP corneal lenses - Central to mild lid-attached fit 6

7 - Central to mild lid-attached fit Centration of optics is important! A high fitting lens may be difficult to recenter l Highly motivated new lens wearers with complex Rx s If you educate and they elect to proceed, they can be happy wearers Patient Communication l Address visual needs prior to selecting lens design Which visual demand motivated your patient to seek MFCLs? Computer, cell phone, watch, deskwork, etc Often times, just achieving that need creates a happy experience! l Setting expectations I want you to be able to do most things, most of the time. Remember the 80-20! Patient Communication l Setting expectations: Use words like: balancing the vision demand in the contact lenses, functional vision, freedom from glasses Avoid using: less than perfect, less crisp, glasses will always be better Patient Communication l Encourage adaptation Reassure, remind them changes can be made minutes in office 1-2 weeks after dispense Vision may improve with time Remind them the fitting process is a marathon, not a sprint and can often take 6-8 weeks with a lens exchange or two. 34 Multifocal Fitting Measurements l Manifest refraction and add l Topography or K s 7

8 l Topography or K s l Pupil size Measure at room lighting and low-medium light to get an idea how much change may happen l Tear film Imperfections cause blur, fluctuating vision, glare and haloes Don t assume it s the contact lens Multifocal Fitting Measurements l Lower eyelid positioning l Eye lid tonicity l Dominancy I like to test more than once - Spotting scope with hands - Fogging method - Winking GP LENS OPTIONS Lens Selection Understanding Lens Designs l Aspheric (GP, hybrid and soft) Gradual change in the curvature of the lens surface to create a change in power toward the lens periphery Can be center distance or center near l Annular / Concentric (Mostly GP) Defined area in the center of the lens with a single power surrounded by one or more rings of alternating powers 38 Lens Selection 8

9 More GP lens designs l Translating / Alternating l Combination l Great optics, maybe the best! l Often require lid interaction, more awareness l Rule of 3 s Aspheric Multifocals l Very popular design Comfortable easy transition from SV GPs because it feels the same! (good lens to start with!) l Fits aligned to slightly steep Lens has minimal movement with blink ( 1mm), which makes it great for active patients and easier to adapt to Advances in technology have improved the near vision for our patients Combination back and front surface asphericity to increase add powers Aspheric Multifocals l Best candidates: Low-Mod adds, but higher adds are available Active patients Patient is willing to be 20/Happy Avg-Small Pupils - Small pupil? Just increase the add! - Big pupil? Patient may struggle with vision quality 41 More on Aspherics l Evaluating the lens fitting High eccentricity lenses will have an area of NaFl pooling in the center - Rare today with improved technology: Back surface fit 1D STK; Front surface aspherics On K - We have the ability to use low eccentricity (0-2D steeper than K), then add more add power to front surface of lens if 9

10 - We have the ability to use low eccentricity (0-2D steeper than K), then add more add power to front surface of lens if needed Low eccentricity lenses has a smaller area of pooling in lens center (if any) 42 More on Aspherics l Evaluating the lens fitting Lens should move upward slightly in downgaze - This interaction with the lower lid is termed translation l Loose lens over-refractions can save time and be more accurate Control of pupil size More natural viewing environment Allows for any object to be the acuity test 43 More on Aspherics l Tips and Strategies for patients wearing aspheric or concentric designs ( GPs ) Be sure to communicate pupil size to the laboratory - Smaller pupils need higher adds faster - Near zones can be made larger or smaller as needed 1. Location Can t change anything reliably without centration 2. Location 5 Hit that optical sweet spot! 3. Location Change BC or diameter for a lens that is decentering 44 More on Aspherics l Tips and Strategies for patients wearing aspheric or concentric designs ( GPs ) Check lens centration prior to over-refraction 10

11 Check lens centration prior to over-refraction Ask more questions about vision quality: Is it blurry around the entire letter? Or just one side? Teach the patient how to use the lenses, just as you would a PAL. Discuss vision fluctuations and how things may change with adaptation Don t just add plus if they can t see at near! Do not confuse clarity with contrast on OR 45 ASPHERIC TROUBLESHOOTING l Inferior Decentration/Excessive Movement: Steeper Base Curve l Insufficient Add Power: n Select Higher Add Lens Design n Use Modified Bifocal 46 Concentric Design Tips l Similar to aspherics, you can improve lens centration with increased diameter and steeper base curves l You can improve acuity at distance by increasing the center zone (if center distance) or decreasing the near zone (if center near) 47 Translating Lenses l Great candidates Patients with large pupils Visually demanding patients - Engineers, architects, nurses l Poor candidates Patients with loose lower lids Patients with low positioned lower eyelids - Translating lenses rely on a reliable lower lid! 11

12 - Translating lenses rely on a reliable lower lid! Translating Lenses: For the highest visual demand Translating GP lenses l Ideal fitting qualities of a translating GP MF lens Rests on lower lid in primary gaze, segment line below the pupil Adequate translation in down gaze Limited movements on blink (less than 1 mm) Translating Lenses l Tips and Strategies for patients wearing GP translating / segmented designs n 5 things to evaluate 3 Centration 3 Rotation 3 Base Curve 3 Translation 3 Segment Height Translating Lenses l Tips for Evaluating Translating GPs Centration - Increase diameter for lateral decentration - Steepen base curve or add prism for superior decentration Rotation - Some nasal rotation is acceptable - Increase prism/flatter base curve radius Translating Lenses l Tips for Evaluating Translating GPs Base Curve - Usually near alignment fit Translation - Grab upper lid and have patient look down lens should cross upper limbus, pupil below segment line 12

13 - Grab upper lid and have patient look down lens should cross upper limbus, pupil below segment line - Increase prism or flatten edge if lacking Segment height - Can be raised or lowered - Ideal placement is design specific usually below or near inferior edge of pupil in primary gaze 53 Troubleshooting Translating Lenses Poor near vision Still a good fit? - Yes? l Check near power, with both plus and minus lenses Remember, translating lenses are closer to SRx power 54 1 l Check for consistent and adequate translation Add prism, flatter BCR/PCR if inconsistent translation Is the pupil going below the segment marker on downgaze? If not, raise segment. Multifocal Soft Lenses: Pro s and Con s l Pros n Easier adaptation n Disposal schedule n Able to provide lenses from trial sets for immediate satisfaction 55 2 l Cons n Simultaneous vision is only design option n Limited parameter changes available Patient Selection l Who are our best patient to wear these lenses? n Early Presbyopes n Moderate Presbyopes n Advanced Presbyopes 13

14 l Do we have a choice? n Presbyopic population is getting larger. and they wear contact lenses!!! 56 Patient Selection l Positive Outlook n Patients that currently wear soft lenses without significant dryness or other comfort issues n New CL wearers that are motivated to remain free from glasses n Patients that are willing to accept some vision compromise at some distances in order to gain freedom from spectacles for most daily activities 57 Patient Selection l Positive Outlook n Low Hyperopes n Already somewhat blurry at distance and worse at near n Really appreciate near VA and distance remain similar n Most Myopes n Moderate myopes may be tough to please (take specs off to read) n Low and Higher myopes typically use correction at both distances and would appreciate spectacle freedom n Little to no astigmatism in refraction 58 Patient Communication l Talking to the patient What a concept! n Address visual needs prior to selecting lens design l Which visual demand motivated your patient to seek MFCLs? 14

15 l Which visual demand motivated your patient to seek MFCLs? n Computer, cell phone, watch, deskwork, etc n Often times, just achieving that need creates a happy experience! n Setting expectations l Words to use, words to avoid l I want you to be able to do most things, most of the time. 59 Patient Communication l Setting expectations: l Use words like: balancing the vision demand in the contact lenses, functional vision, freedom from glasses l Avoid using: less than perfect, less crisp, glasses will always be better, compromise l Encourage adaptation l Reassure, remind them changes can be made l minutes in office (vision is at worst) l 1-2 weeks after dispense 60 Lens Selection l Getting started on the right foot l Choose lower add first to maintain distance VA n I tell my patients, I am going to under-prescribe the reading power first, then we will make it stronger as needed l Patient does not panic if they can t see well at near with the first lenses l Patient lifestyle n Silicone Hydrogels vs Hydrogels n Extended Wear vs Daily Wear vs Daily Disposables (several options available today) 61 Soft Multifocal Lens Designs l Understanding Lens Designs 15

16 l Understanding Lens Designs l Aspheric n Gradual change in the curvature of the lens surface to create a change in power toward the lens periphery n Can be center distance or center near l Annular / Concentric n Defined area in the center of the lens with a single power surrounded by one or more rings of alternating powers Fitting Soft Multifocal Contact Lenses l Steps to Success n Multifocal Specific Measurements l Address most important vision need n Computer? Newspaper? Reading music? Needlepoint? l Evaluate pupil size in normal, bright and dim illumination l Determine Eye Dominancy Fitting Soft Multifocal Contact Lenses l Choosing the right lens design n Know the lens specifics: Soft Multifocal Contact Lenses l Use of fitting guides n Tried and true methods! n Best to follow the fitting guide even when the patient is not making huge gains in VA with lens changes l Strategic steps will make assessment easier at follow up l Allows patient to work through the lens powers with you n They appreciate the process and hopefully find improvement with each step n When you reach the final step the patient can then decide if the vision is acceptable Evaluation of Soft MFCLs 16

17 l Patience is key n Allow time to settle for optimum measurements l Initial measurements n Binocular Distance (look out window) and Near VA (no reading card) l Skip the phoropter n Loose lenses monocularly, push plus n Improve distance VA in dominant eye n Improve near VA in non-dominant eye Evaluation of Vision l Distance n Binocular VA, out of phoropter l Near n Binocular VA l Intermediate n You can have the patient hold the card at arms length Evaluation of Vision l Real life examples n This is how to measure multifocal lens success l Obviously you need to know the patient can drive safely n Distance VA: street signs and license plates out the window n Intermediate VA: Patient sits in the chair at the computer and looks at a news website like Yahoo! or USA Today n Near VA: Work paperwork or smart phone s l Adaptation n Now vs 2 weeks from now 68 Troubleshooting Soft Multifocal Lens Wear l Distance problems n Loose lens over-refract 17

18 n Loose lens over-refract l Be careful not to mistake contrast improvement with acuity improvement when adding minus l If acuity does not improve, consider decreasing add power in dominant eye or both l Possibly needs design switch 69 Troubleshooting Soft Multifocal Lens Wear n Should not need to change the distance power significantly to achieve good VA n SV dominant eye; MF non-dominant eye n Prescribe unequal adds with lesser add in dominant eye n Recheck eye dominancy 70 Troubleshooting Soft Multifocal Lens Wear l Near problems n You can start with lower add powers to start the fitting and work your way up to higher powers n If I can t achieve good near VA with max add powers, what next? l Consider prescribing unequal adds l Push plus at distance in non-dominant eye n If near is a very demanding part of patients day, they may accept some distance blur and prefer the higher add power in the dominant eye n Tell the patient to get arm extensions or use selfie stick for all material!!! 71 Troubleshooting Soft Multifocal Lens Wear l Intermediate Vision Problems n Low add power OU and encourage reading glasses at near n Pushing a little plus in non-dominant eye n MF in dominant eye; MF with IM power in Non-dom eye l Modified Monovision 18

19 l Modified Monovision n Great option for computer users n D & N series l SV Distance lens in dominant eye l Multifocal lens in non-dominant eye n Power of lens is selected to be patients intermediate power 72 SUMMARY l The future looks very promising for new contact lens designs for optimum correction of the astigmatic and presbyopic patients. l You can build your contact lens practice on the fitting of GP and soft toric and multifocal lenses. 19