Gp lens_


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Gp lens_

  2. 2. THE DEMISE OF RGPs???? <ul><li>In the 1990s, Nathan Efron forecast the demise of RGP lenses by the year 2,000 </li></ul><ul><li>Then 2001, 2002, 2003, 2004 etc, and, at the latest count, 2010 </li></ul><ul><li>Horror of horrors, could he actually be correct?! </li></ul>
  3. 3. PHILIP MORGAN - WORLD SURVEY Of PRESCRIBING HABITS <ul><li>The number of RGPs prescribed in the USA is 7%, 8% in the UK and 5% in Hong Kong. </li></ul><ul><li>In Australia, the figure is also 5% with 27% of these being prescribed for Ortho-k and around three quarters of the rest being for refits or where RGPs are essential e.g. keratoconus, post-grafts, trauma, etc </li></ul>
  4. 4. <ul><li>So have we effectively already stopped prescribing RGPs? Again, has Nathan’s prediction already come true? </li></ul><ul><li>Yet in New Zealand the prescribing rate of RGPs is 23% and in Holland is 39% </li></ul><ul><li>So what is it that they know that we don’t? </li></ul><ul><li>Are we right - or are they??? </li></ul>
  5. 5. WHAT I WANT TO COVER <ul><li>To remind ourselves why we should be prescribing RGPs - and not lose the art! </li></ul><ul><li>Understand why the current situation has arisen </li></ul><ul><li>Finally give you twenty-one ways in which to improve your RGP practice! </li></ul>
  6. 6. THE REASONS FOR PRESCRIBING RGPs <ul><li>Refitting of existing RGP wearers </li></ul><ul><li>Some conditions can ONLY be fitted with RGPs e.g. karatoconics, post-grafts, corneal trauma, etc. </li></ul><ul><li>RGP lenses may be easier to handle e.g. narrow VIPs, enophthalmics, babies, etc. </li></ul><ul><li>Easier to maintain and last longer than many soft lenses. </li></ul>
  7. 7. THE REASONS FOR PRESCRIBING RGPs <ul><li>Some patients will get better acuity with RGPs e.g. irregular astigmats, uncorrected small cyls in soft lens wearers, etc. </li></ul><ul><ul><li>But is this no longer applicable since aspheric SCLs are now available???? </li></ul></ul><ul><li>Nathan Efron - “Modern approaches using aspheric optical designs result in vision with soft lenses that is just as sharp as that which can be achieved with soft lenses” </li></ul><ul><ul><li>Is this true? </li></ul></ul>
  8. 8. RGPs and V.A. <ul><li>The results of one 2008 study stated: </li></ul><ul><li>“… the fitting of aspheric design soft contact lenses does NOT result in superior visual acuity, aberration control or subjective appreciation compared with equivalent spherical soft lenses” and – </li></ul><ul><li>“… .all indicate that the aspheric abberation-controlled design actually reduces vision” </li></ul><ul><li>And who said this???? </li></ul>
  9. 9. <ul><li>The man himself! </li></ul>
  10. 10. RGPs and VA <ul><li>In conclusion on VA and the aspheric lens debate, Trusit Dave stated in the BCLA journal, 2008: </li></ul><ul><li>“ If the patient has a high refractive error, spherical aberration will play an important role in visual blur. However, in higher prescriptions also be aware that other factors such as lens movement and rotation will also play a significant role in vision quality. Currently, lenses that are designed to correct spherical aberration have not been shown to be more effective than conventional spherical lenses ” </li></ul><ul><li>By implication, RGP’s will provide better visual quality than most soft lenses </li></ul>
  11. 11. VA and RGPs <ul><li>Refractive Surgeon, Dr B Allan, writing in the UK journal ‘Optometry Today’ (2008) stated: </li></ul><ul><li>“ The best qualitative approximation of what patients can expect from their vision post-LASIK is what they can see in soft contact lenses. Most post-LASIK patients do not have zero refractive error and it is important to emphasise that some sharpness may be lost. This is particularly important for RGP wearers ” </li></ul>
  12. 12. REASONS FOR PRESCRIBING RGPs <ul><li>RGP lenses perform better physiologically because there is: </li></ul><ul><ul><li>Less corneal coverage </li></ul></ul><ul><ul><li>Better retro-lens tear flow </li></ul></ul><ul><ul><li>Often greater oxygen permeability </li></ul></ul><ul><li>Often better and sometimes the only alternative in cases such as GPC, recurrent SEALs, marginal dry eye, etc. </li></ul>
  13. 13. RGPs & ADVERSE REACTIONS <ul><li>Annual incidence of microbial keratitis in different lens types </li></ul>
  14. 14. RGPs & ADVERSE REACTIONS <ul><li>Insight, September, 2008: </li></ul><ul><li>“ Online/mail order purchase of contact lenses carries five times the risk (of microbial keratitis): 2 Studies” </li></ul><ul><li>Nathan Efron - textbook: “The incidence of virtually all forms of adverse physiological events is lower in RGP lenses versus soft lenses”. </li></ul>
  15. 15. THE REASONS FOR PRESCRIBING RGPs <ul><li>RGP wearers appreciate the skill involved and become loyal, happy patients </li></ul><ul><li>Alan Saks writing in Insight, September, 2008 wrote: </li></ul><ul><li>“ Most days I see at least one long-term RGP wearer with at least thirty to forty years of very successful hard/RGP wear. They are generally some of the most trouble-free, loyal and happy patients one can ever hope to see. They make going to work a pleasure” </li></ul>
  16. 16. THE REASONS FOR PRESCRIBING RGPs <ul><li>RGP wearers rarely, if ever, reorder through the internet </li></ul><ul><li>RGP bifocal and multifocal lenses generally give better results in terms of clarity. </li></ul>
  17. 17. REASONS FOR PRESCRIBING RGPs <ul><li>RGPs can be repolished or modified in power within small limits </li></ul><ul><li>A good knowldge of RGPs is essential if you contemplate doing ortho-k work </li></ul><ul><ul><li>As ancillary to this, if ortho-k is shown to slow down or stop the progression of myopia it will hugely take off. </li></ul></ul><ul><ul><li>Holden - approximately 30% of the world’s population are myopic (1.92 billion) </li></ul></ul>
  18. 18. REASONS FOR PRESCRIBING RGPs <ul><li>RGPs are less affected by dryness and blinking: </li></ul><ul><ul><li>Edwards (2008)”The current investigation showed that the tear film evaporation with soft contact lenses in situ is significantly higher than that from the bare optical surface” </li></ul></ul><ul><ul><li>Tomlinson (1994) “The reduction in visual performance induced by the blink during soft toric lens wear appears to last longer than that produced in RGP lens wear” </li></ul></ul>
  19. 19. SO WHY HAS THE PROBLEM ARISEN? <ul><li>Inadequate University teaching </li></ul><ul><li>Difficulty in Universities getting appropriate patients </li></ul><ul><li>Laboratories like volume and the simpler lens type the better </li></ul><ul><li>Optometrists’ fear of charging reasonable fees for their time </li></ul><ul><li>The longer adaptation period for RGPs </li></ul>
  20. 20. SO WHY HAS THE PROBLEM ARISEN? <ul><li>Patient pressure </li></ul><ul><li>Perceived as quicker and easier for practitioners and, particularly,: </li></ul><ul><li>if their own RGP knowledge is rather mediocre and/or they don’t have appropriate fitting sets and equipment. </li></ul>
  21. 21. FEES <ul><li>In Jim Kokkinakis’s excellent article in Mivision (March, 2009) he pointed out that the sales economy is hour glass shaped: </li></ul><ul><li>The top 60% of the market seek quality over cost </li></ul><ul><li>The lower 37% are cost driven and </li></ul><ul><li>3% are internet purchasers </li></ul><ul><li>Very few are in the middle! </li></ul>
  22. 22. FEES <ul><li>The bottom part of the hour glass is divided between the large corporations since all they can advertise is how cheap they are. The quality of </li></ul><ul><li>the eye examination is </li></ul><ul><li>not vital to most patients. </li></ul><ul><li>Volume is paramount </li></ul><ul><li>The larger, top end of </li></ul><ul><li>the hour glass expect a </li></ul><ul><li>high standard of care </li></ul><ul><li>and represent a golden </li></ul><ul><li>opportunity for specialist, </li></ul><ul><li>professional image </li></ul><ul><li>practice including RGP fitting. </li></ul>
  23. 23. SO WHAT CAN BE DONE TO IMPROVE THINGS? <ul><li>More help/enthusiasm from the Universities with undergrad and post-grad courses. More RGP clinical work </li></ul><ul><li>More help from the CCLSA e.g. travelling post-grad courses on RGPs </li></ul><ul><li>Development of better wetting materials etc. by labs </li></ul><ul><li>Awareness by practitioners that it is their own interest to learn more on the subject e.g. CCLSA Fellowship, and to acquire the necessary equipment and fitting sets </li></ul>
  25. 25. 1. Improve your knowledge! <ul><li>How many of you have read a recent text-book or current paper(s) on RGP fitting? </li></ul><ul><li>There are several good text-books on the market (well, at least one!) </li></ul>
  26. 27. 2. Understand how to write a prescription properly! <ul><li>Please supply: </li></ul><ul><li>R. C3/7.80:8.30/8.50:8.80/9.90:9.80 -6.50D </li></ul><ul><li>Green XO ct 0.15 FOZD 7.40 </li></ul><ul><li>et 0.16 – 018 </li></ul><ul><li>VWB Engrave ‘R’ and ‘XO’ </li></ul>
  27. 28. 3. Understand how to manipulate the ‘numbers’ to achieve what you want <ul><li>With very little practice you can understand how to change the curves and diameters to achieve what you want. </li></ul><ul><li>Those attending the workshop will be experts by the time they leave! </li></ul>
  28. 29. 4. Reject the obvious potential failures in the first place! <ul><li>High cyls but spherical corneas </li></ul><ul><li>Those with corneal cyls but little or no refractive cyl </li></ul><ul><li>Those who work in very dusty atmospheres </li></ul><ul><li>Those who spend a great deal of their time doing contact sports </li></ul><ul><li>Those who want intermittent wear only </li></ul>
  29. 30. 5. Use the Correct Terminology <ul><li>The correct or incorrect use of wording can have a major effect on the patient’s perception. </li></ul><ul><li>Andrew Hogan in Optometry Pharma, 2008: </li></ul><ul><li>“… practitioners who see patients with central serous chorioretinopathy should consider recommending that they cease taking sildenafil (Viagra) which will, of course, be a hard decision” </li></ul>
  30. 31. Use the Correct Terminology <ul><li>Imagine if you said to a patient: </li></ul><ul><li>“ Your first choice is a soft lens. Compared to the alternative, these are: </li></ul><ul><ul><li>Rather slippery, somewhat slimy </li></ul></ul><ul><ul><li>Will give you a slightly poorer standard of vision </li></ul></ul><ul><ul><li>Will be more expensive to wear </li></ul></ul><ul><ul><li>Will significantly increase your chance of a serious infection </li></ul></ul><ul><ul><li>Are more difficult to handle than the alternatives </li></ul></ul><ul><ul><li>Will tend to dry out more easily,” etc </li></ul></ul><ul><ul><li>How many would go for them?!!! </li></ul></ul>
  31. 32. Use the Correct Terminology <ul><li>Avoid the word ‘Hard’ </li></ul><ul><li>Even avoid the use of the word ‘Rigid’ </li></ul><ul><li>Just talk about ‘Gas Permeable’ or ‘GP’ lenses </li></ul><ul><li>If necessary, just say that GP lenses are like soft lenses but just a more rigid material and with specific advantages </li></ul>
  32. 33. 6. If in doubt? <ul><li>Start with an RGP lens first. It’s much harder going from a soft to an RGP than vice versa! </li></ul><ul><li>Also, most RGP wearers, if they are going to fail will usually fail in the first month whereas SCL wearers may take many months to show up as failures (e.g. from mediocre VA, marginal dry eye, unstable toric, etc) </li></ul><ul><li>Better to start with an RGP and fail quickly than have problems cropping up along the way over the next two years with soft lenses before they give up </li></ul>
  33. 34. 7. Use an anaesthetic at the fitting appointment <ul><li>The urban myth is that this gives a false impression and can lead to corneal damage </li></ul><ul><li>Purslow et al, BCLA Jnl 2008 concluded that ; </li></ul><ul><li>“ The use of Proxymetacaine prior to lens fitting had no significant effect on redness or corneal staining compared to a placebo drop and subjects prefer its use for the procedure” </li></ul>
  34. 35. Use an anaesthetic at the fitting appointment <ul><li>Ed Bennett and Cristina Schnider, CL Spectrum 1993: </li></ul><ul><li>“ A study performed at the Pacific University College of Optometry showed that… no significant physiological problems resulted from the use of one drop of Proparacaine prior to lens application at the fitting visit. In addition, subjects who received the anaesthetic seemed to adapt more rapidly to their lenses and to display a more positive outlook throughout the first month of lens wear .” </li></ul>
  35. 36. 8. Generally, go larger in Total Diameter <ul><li>Initial comfort is often better with a larger TD lens </li></ul>
  36. 37. Choice of diameter <ul><li>Lindsay and Bruce recommend choosing the TD according to the lid position </li></ul><ul><li>As most eyelids cover the upper part of the cornea and are level or slightly below the lower limbus, most corneas allow a larger TD to be selected. </li></ul>
  37. 38. Choice of Total Diameter <ul><li>As stated before: </li></ul><ul><li>Go for the largest TD possible </li></ul><ul><li>Aim for lid attachment if possible </li></ul><ul><li>Consider the effect of the eyelids </li></ul>
  38. 39. 9. Fitting Sets <ul><li>From the foregoing it will be essential to have: </li></ul><ul><li>at least three TD sets e.g. 9.50, 10.00 and 10.50mm diameters </li></ul><ul><li>Toric sets e.g. 0.4 mm toricity </li></ul><ul><li>With time, sets of different BVPs and e values </li></ul><ul><li>And, most importantly: </li></ul><ul><li>Know ALL the lens parameters and check them for accuracy </li></ul>
  39. 40. 10. Ensure the lens edge shape is optimal <ul><li>The ideal edge should be rounded with a tapered front surface (Donna La Hood, 1988). </li></ul><ul><li>A rounded front surface is more important than a rounded back surface or square edge </li></ul>
  40. 41. Ensure the lens edge shape is optimal <ul><li>A very simple quick way to check an edge is with a piece of plasticene pressed into a cube and your slit-lamp on the highest magnification. </li></ul>
  41. 42. Ensure the lens edge shape is optimal
  42. 43. 11. Specify and check the centre and edge thicknesses <ul><li>Look up ct in tables and check! </li></ul>
  43. 44. 12. Don’t err on the tight side <ul><li>Go for alignment or slightly steep (but not a ‘tight’ edge!) </li></ul>
  44. 45. Don’t err on the tight side <ul><li>Remember, a steep lens is not necessarily a tight lens! </li></ul>
  45. 46. 13. Get the correct Axial Edge Clearance <ul><li>Garry Andrasko in C L Spectrum (1989): </li></ul><ul><li>Tricurves with narrow peripheral curves are more comfortable than bicurves or tricurves with wide peripheral curves </li></ul><ul><li>Lenses with high axial edge lift (> 0.15mm) are less comfortable than lenses with a low edge lift (0.08mm) </li></ul><ul><li>Blended lenses are more comfortable than non-blended lenses </li></ul>
  46. 47. 14. Lenticulate <ul><li>As a general rule, lenticulate all lenses over + and – 5.00D </li></ul><ul><li>A lens of TD 9.80mm and BVP +7.00D would be 0.41mm in ct if non-lenticulated but 0.26mm ct if ordered with an FOZD of 7.00, i.e. 60% thinner. </li></ul><ul><li>This is significantly more comfortable and provides significantly better oxygen transmission </li></ul>
  47. 48. 15. Mimic any former lens design <ul><li>It is often tempting to go to a ‘modern’ fitting or your favourite design when refitting an existing RGP or PMMA wearer. </li></ul><ul><li>By all means try to head in that direction but generally speaking try to mimic what they already have. </li></ul><ul><li>Bear in mind the effect of improved oxygen transmission on corneal shape however! </li></ul>
  48. 49. 16. Don’t get them back for the first after-care too quick! <ul><li>Warn patients that there IS an adaptive period </li></ul><ul><li>Warn them that this can be very variable between individuals </li></ul><ul><li>That initial adaptation will take two or three weeks and sometimes a little longer to completely forget that they’re in their eyes </li></ul><ul><li>Whilst telling them to report any obvious symptoms, don’t get them back for after-care in under two weeks. All they’ll do is whinge! </li></ul>
  49. 50. 17. Stress hygiene and cleaning <ul><li>Good hygeine is, of course, essential with any form of contact lens. </li></ul><ul><li>The pitfalls of soft lens wear (dryness, GPC, etc.) can be avoided by good cleaning and, particularly, the use of Progent, say monthly </li></ul>
  50. 51. 18. Consider surface treated lenses <ul><li>The use of surface treated materials is equivocal but may help in certain cases. </li></ul><ul><li>Remember that they cannot be repolished or changed in power in most cases. </li></ul>
  51. 52. 19. Do over K’s where necessary to check for lens flexure <ul><li>This can affect VA’s and may indicate the need for a toric design, especially in against-the-rule corneas </li></ul><ul><li>In with-the-rule corneas go slightly flatter if the lens flexes </li></ul><ul><li>In both cases the lens ct may need to be increased slightly </li></ul>
  52. 53. 20. Fees! <ul><li>Charge an appropriate fee for all your time, skill, equipment, ancillary staff. You’re worth it! </li></ul><ul><li>And remember, soft lenses wearers are for now, RGP wearers are for ever! </li></ul>
  53. 54. 20. Fees <ul><li>Remember that poor fitting fees is one of the main reasons for the low recommendation of contact lenses in this country </li></ul><ul><li>You need to cover the fitting session, the instruction session and at least three after-cares i.e. around $3 - 400 </li></ul>
  54. 55. 21. Don’t pre-judge! <ul><li>Keith Edwards (BCLA Jnl. 2002) tested a new B & L RGP design on 51 subjects: </li></ul><ul><li>96% wore the lenses successfully </li></ul><ul><li>Two drop-outs were former soft lens wearers </li></ul><ul><li>Two dropped out for visual problems (lenticular astigmatism - but the research protocol did not prevent their exclusion) </li></ul>
  55. 56. 21. Don’t pre-judge! <ul><li>Johnson and Schnider (1991) Int. C L Clin. carried out a cross-over study where one group of new patients were fitted with RGP lenses and the other half with soft lenses. At the end of six weeks they were swapped over. </li></ul><ul><li>In a forced choice, 60% preferred the soft lenses and 40% the RGPs. However, 35% also wore the RGPs quite successfully in terms of vision and comfort and could have worn either. In other words, 75% of the group could have successfully worn the RGP lenses and 40% actually preferred them </li></ul>
  56. 57. 21. Don’t pre-judge! <ul><li>They further noted: </li></ul><ul><li>That all subjects preferred the RGPs for VA </li></ul><ul><li>That all subjects preferred the RGPs for handling and cleaning simplicity </li></ul><ul><li>That the preference figure for RGPs of 40% would undoubtedly have risen if the trial had extended beyond six weeks </li></ul>
  57. 58. IN SUMMARY <ul><li>Improve your knowledge </li></ul><ul><li>Understand how to write prescriptions properly - and do it! </li></ul><ul><li>Understand how to manipulate the numbers </li></ul><ul><li>Reject the obvious in the first place </li></ul><ul><li>Use the correct terminology with the patient </li></ul><ul><li>If in doubt, start with an RGP </li></ul><ul><li>Use an anaesthetic at the fitting appointment </li></ul><ul><li>Use a largish TD where possible </li></ul><ul><li>Make sure you have adequate and known fitting sets </li></ul><ul><li>Ensure the edge shape is optimal </li></ul>
  58. 59. IN SUMMARY <ul><li>Specify and check the ct and et </li></ul><ul><li>Don’t err on the tight side </li></ul><ul><li>Ensure the correct aec </li></ul><ul><li>Lenticulate where appropriate </li></ul><ul><li>Mimic any former lens design </li></ul><ul><li>Don’t get them back too quick </li></ul><ul><li>Stress hygiene and cleaning </li></ul><ul><li>Consider surface treated materials </li></ul><ul><li>Do over-k’s where necessary </li></ul><ul><li>Charge appropriate fees </li></ul><ul><li>Don’t pre-judge </li></ul>
  59. 60. CONCLUSION <ul><li>So is it really worth going to all this trouble? </li></ul><ul><li>van der Worp (2002) stated: </li></ul><ul><li>“ Even small improvements in </li></ul><ul><li>RGP fits influenced comfort of </li></ul><ul><li>wear significantly. It should </li></ul><ul><li>be noted that this could </li></ul><ul><li>potentially lead to drop out </li></ul><ul><li>among patients with acceptable </li></ul><ul><li>but not optimal fits” </li></ul>
  60. 61. CONCLUSION <ul><li>Brad Giedo in CL Spectrum, 2008 </li></ul><ul><li>“ If you are truly an advocate of GP lenses and you believe the positive things that you tell your patients about them, then you need to be willing to present GPs as a first option. In my experience this is not how most of you practice so I challenge you to make a conscious effort to include GPs when you consider your initial lens selection. Resist the urge to simply default to soft lenses. You will find that there are many more opportunities to fit GP lenses than you thought possible and you and your patients will be better for it.” </li></ul>