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contact lenses fitting for KCN

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contact lenses fitting for KCN

  1. 1. Contact lens fitting and keratoconus Sedaghat M.R M.D MASHAD EYE RESEARCH CENTER Khatam-al-Anbia Hospital
  2. 2. Natural Course <ul><li>KCN typically progresses for 3 to 8 years </li></ul><ul><li>Difficult to predict rapidity or severity of progression </li></ul><ul><li>Difficult to predict termination of progression </li></ul><ul><li>The end point of the progression may be: </li></ul><ul><ul><ul><li>Slight corneal irregularity </li></ul></ul></ul><ul><ul><ul><li>Moderate corneal distortion </li></ul></ul></ul><ul><ul><ul><li>Severe corneal distortion and apical scarring </li></ul></ul></ul><ul><li>Careful monitoring is important </li></ul>
  3. 3. Diagnosis <ul><li>Earliy diagnosis is important </li></ul><ul><ul><ul><li>Early appropriate management </li></ul></ul></ul><ul><ul><ul><li>Early adequate education </li></ul></ul></ul><ul><li>Earlier diagnosis depends on: </li></ul><ul><ul><ul><li>Awareness of clinical symptoms </li></ul></ul></ul><ul><ul><ul><li>Awareness of clinical signs </li></ul></ul></ul>
  4. 4. Symptoms <ul><li>Guiding symmptoms include: </li></ul><ul><ul><ul><li>Monocular diplopia or polyopia </li></ul></ul></ul><ul><ul><ul><li>Photophobia </li></ul></ul></ul><ul><ul><ul><li>Halos around lights </li></ul></ul></ul><ul><ul><ul><li>Ghost images </li></ul></ul></ul><ul><ul><ul><li>Distortion of letters </li></ul></ul></ul><ul><ul><ul><li>Asthenopic complaints </li></ul></ul></ul><ul><ul><ul><li>Gradual decrease in visual acuity </li></ul></ul></ul><ul><ul><ul><li>Having multiple unsatisfactory spectacles </li></ul></ul></ul>
  5. 5. Signs <ul><li>Variable auto refractometer results </li></ul><ul><li>Unsatisfactory BCVA </li></ul><ul><li>Irregular retinoscopy reflexes </li></ul><ul><li>Irregular keratometry mires </li></ul><ul><li>Check for SLE clinical signs </li></ul><ul><li>Check for localized corneal steepening in topography </li></ul>
  6. 6. PATIENT CONSULTATION <ul><li>Inform the patients about the diagnosis ( or possible diagnosis ) as soon as possible </li></ul><ul><li>Describe the progressive nature of KCN </li></ul><ul><li>Describe the algorithm of therapy including corneal transplantation </li></ul><ul><li>Mention about the inevitable possible changes in the patient’s quality of life </li></ul>
  7. 7. Optical Therapy <ul><li>Needs both art and science </li></ul><ul><li>M anagement must always be tailored : </li></ul><ul><ul><ul><li>V isual needs </li></ul></ul></ul><ul><ul><ul><li>Comfort </li></ul></ul></ul><ul><ul><ul><li>T olerance </li></ul></ul></ul><ul><li>Good physician- patient communication is necessary to determine the best next step in managing a particular case of KCN: </li></ul><ul><ul><ul><li>A nisometropia due to asymmetric involvement </li></ul></ul></ul>
  8. 8. Optical Therapy <ul><li>Most KCN patients start with wear ing spectacles </li></ul><ul><li>Spectacles have their best application early in the disease because: </li></ul><ul><ul><ul><li>Co rneal irregularity g radual ly increases </li></ul></ul></ul><ul><ul><ul><li>Spectacles do not optimally cover the irregular cornea </li></ul></ul></ul><ul><ul><ul><li>The RE can change quite rapidly </li></ul></ul></ul><ul><ul><ul><li>A nisometropia due to asymmetric involvement </li></ul></ul></ul>
  9. 9. SPECTACLE MANAGEMENT <ul><li>The management of keratoconus usually begins with spectacle correction </li></ul><ul><li>Ther e are two methods of refraction: </li></ul><ul><ul><li>Objective : </li></ul></ul><ul><ul><ul><li>Your r easurement , irrespective of the patient's responses </li></ul></ul></ul><ul><ul><li>Subjective : </li></ul></ul><ul><ul><ul><li>Measurement is mainly depende nt o n the patient’s responses to your questions </li></ul></ul></ul>
  10. 10. Optical Therapy <ul><li>Once glasses fail to provide adequate visual function, contact lens fitting is required </li></ul>
  11. 11. Contact Lens Management <ul><li>Contact lens wear : </li></ul><ul><li>I mproves VA by creating a regular anterior refractive surface </li></ul><ul><li>D o es not prevent progression of KCN </li></ul><ul><li>M ay occasionally induce or hasten progression of KCN </li></ul>
  12. 12. Contact Lens Management <ul><li>CL therapy should never be withheld for fear of causing progressive KCN </li></ul><ul><li>Many KCN patients are successfully fitted or refitted if: </li></ul><ul><ul><ul><li>Reasonable patient motivation </li></ul></ul></ul><ul><ul><ul><li>Physician and patient patience </li></ul></ul></ul><ul><ul><ul><li>Fitting expertise </li></ul></ul></ul><ul><ul><ul><li>Access to all available contact lens modalities </li></ul></ul></ul>
  13. 13. Contact Lens Management <ul><li>In 1888, a French ophthalmologist, Eugene Kalt, tried to correct keratoconus by compressing the steep conical apex of a keratoconic cornea by a glass shell </li></ul><ul><li>This was the first known application of a contact lens for the correction of keratoconus </li></ul>
  14. 14. Contact Lens Management <ul><li>Contact lenses give sharper vision than spectacles e ven in m ildest cases of KCN </li></ul><ul><li>A s KCN progresses spectacle best corrected acuity becomes unsatisfactory </li></ul><ul><li>Contact lens fitting in a keratoconic cornea is much more difficult </li></ul><ul><ul><li>Because of the irregular anterior surface of the keratoconic cornea </li></ul></ul><ul><li>Acceptable fitting results require a high level of patience </li></ul><ul><ul><li>Explaining this to the patient at the initial fit is helpful in establishing an effective, long lasting relationship between the patient and the physician </li></ul></ul>
  15. 15. Contact Lens Management <ul><li>The CL management of keratoconus is most often in the form of rigid gas-permeable (RGP) CL s </li></ul><ul><li>RGPs improve VA by neutrali zing much of the distortion/optical aberrations of the anterior corneal surface </li></ul><ul><li>There are reports suggesting that rigid CL s may cause keratoconus due to mechanical pressure and hypoxia , but </li></ul><ul><ul><ul><li>I t is difficult to establish a cause-and-effect relationship </li></ul></ul></ul><ul><ul><ul><li>The patients may have been corrected with contact lenses before being diagnos ed as KCN </li></ul></ul></ul>
  16. 16. Contact Lens Management <ul><li>Keratoconic patients who are no satisfied with CLs may need PK: </li></ul><ul><ul><ul><li>S tudies have shown that more than 70% of keratokonic patients referred for PK can avoid surgery and re main satisfied by refitting CLs </li></ul></ul></ul><ul><li>Multiple fitting algorithms are available to assist in fitting the keratoconic cornea </li></ul><ul><ul><li>T he process is as much an art as a science </li></ul></ul><ul><ul><li>These lenses may be fit ted </li></ul></ul><ul><ul><ul><ul><li>S teep or flat </li></ul></ul></ul></ul><ul><ul><ul><ul><li>L arge or small </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Spheric or Aspheric </li></ul></ul></ul></ul>
  17. 17. Contact Lens Management <ul><li>Three objectives are required for successful CL fitting in KCN : </li></ul><ul><ul><ul><li>Minimal physical trauma to the cornea </li></ul></ul></ul><ul><ul><ul><li>Stable visual acuity during the entire wearing schedule </li></ul></ul></ul><ul><ul><ul><li>All day wearing comfort </li></ul></ul></ul><ul><li>It may be impossible to meet all of these objectives for every patient, but do your best to achieve the best possible outcomes </li></ul>
  18. 18. Contact Lens Management <ul><li>Three rigid lens-to-cornea fitting relationships are proposed in KCN: </li></ul><ul><ul><ul><li>Apical bearing (Reshape or splint method) </li></ul></ul></ul><ul><ul><ul><li>Apical clearance </li></ul></ul></ul><ul><ul><ul><li>Three-point touch </li></ul></ul></ul>
  19. 19. Contact Lens Management Apical Bearing <ul><li>A large diameter lens with flat base curve radius ( BCR ) is fitted </li></ul><ul><li>The fluorescein pattern shows excessive central bearing accompanied by mid peripheral and peripheral pooling </li></ul>
  20. 20. Contact Lens Management Apical Bearing <ul><li>Fitters believe that: </li></ul><ul><ul><li>it slows down or halts progression of KCN </li></ul></ul><ul><ul><li>they are treating KCN, not just correcting the induced RE </li></ul></ul><ul><li>Excessive pressure on the thin fragile apex causes distortion, scarring, and swirl staining </li></ul><ul><li>This method is rarely used today </li></ul>
  21. 21. Contact Lens Management Apical Bearing- Flat fitting <ul><li>The flat fitting method places almost the entire weight of the lens on the cone </li></ul><ul><li>The lens tends to be held in position by the top lid </li></ul><ul><li>Good visual acuity is obtained as a result of apical touch </li></ul><ul><li>Wide edge stand-off cannot usually be eliminated </li></ul>
  22. 22. Contact Lens Management Apical Bearing- Flat fitting <ul><li>Alignment can be obtained in early keratoconus; however, flat fitting lenses can lead to progression/ acceleration of apical changes and corneal abrasions </li></ul><ul><li>This type of fitting philosophy is useful where the apex of the cone is displaced </li></ul>
  23. 23. Contact Lens Management Apical Bearing- Flat fitting
  24. 24. Contact Lens Management Apical Clearance <ul><li>A small, steep lens is fitted </li></ul><ul><li>The lens leans on the slope of the cone, and vaults over the thinned apex </li></ul><ul><li>There is no mechanical rubbing on the thinned corneal apex </li></ul>
  25. 25. Contact Lens Management Apical Clearance <ul><li>Fitters who follow this philosophy believe that apical contact by a lens will increase the likelihood for corneal compromise and scarring </li></ul><ul><li>If apical clearance lens fitting is utilized, the fluorescein pattern should be monitored to ensure that peripheral seal - off and adherence of lens to cornea do not occur </li></ul>
  26. 26. Contact Lens Management Apical Clearance
  27. 27. Contact Lens Management Apical Clearance <ul><li>In this type of fitting technique, the lens vaults the cone and clears the central cornea, resting on the paracentral cornea </li></ul><ul><li>This type of lens was suggested as it was argued that apical clearance would minimise trauma to the central cornea </li></ul><ul><li>These lenses tend to be small in diameter and have small optic zones; the small BOZD can result in glare problems </li></ul>
  28. 28. Contact Lens Management Apical Clearance <ul><li>The potential advantages of reducing central corneal scarring are outweighed by the disadvantages of: </li></ul><ul><ul><li>poor tear film </li></ul></ul><ul><ul><li>corneal oedema </li></ul></ul><ul><ul><li>poor visual acuity as a result of bubbles becoming trapped under the lens </li></ul></ul>
  29. 29. Contact Lens Management Apical Clearance vs Apical Bearing <ul><li>In a study 30 keratoconic eyes were fitted with an apical clearance lens design: </li></ul><ul><ul><ul><li>The average wearing time increased from a baseline of 10.5 h daily to 13.7 h daily at 12 months </li></ul></ul></ul><ul><ul><ul><li>There was no decrement in visual acuity in comparison with the baseline values </li></ul></ul></ul><ul><ul><ul><li>In only one eye of the 22 completing the study scarring developed </li></ul></ul></ul>
  30. 30. Contact Lens Management Apical Clearance vs Apical Bearing <ul><li>In a study seven keratoconus patients without corneal scarring were fitted randomly such that one eye had the apical clearance design and the other eye had the apical bearing design </li></ul><ul><li>At the end of 1 year: </li></ul><ul><ul><ul><li>4/7 eyes with apical bearing had scarring </li></ul></ul></ul><ul><ul><ul><li>N one of the eyes with the apical clearance had scarring </li></ul></ul></ul>
  31. 31. Contact Lens Management Three - point Touch
  32. 32. Contact Lens Management Three - point Touch
  33. 33. Contact Lens Management Three - point Touch <ul><li>A relatively flat fitting meth od in which the CL leans on a relatively large area </li></ul><ul><li>The re is a mild (feather) touch over the cone apex accompanied by, at least , two other areas of touch at the corneal mid periphery </li></ul><ul><li>Four zones are created: </li></ul><ul><ul><ul><li>Slight apical touch </li></ul></ul></ul><ul><ul><ul><li>Paracentral clearance </li></ul></ul></ul><ul><ul><ul><li>Mid-peripheral bearing </li></ul></ul></ul><ul><ul><ul><li>Peripheral clearance </li></ul></ul></ul>
  34. 34. Contact Lens Management Three - point Touch-steep fitting
  35. 35. Contact Lens Management <ul><li>The proven role for lenses in the keratoconic eye is to improve visual function </li></ul><ul><li>Fitters should choose the approach they are most comfortable with </li></ul><ul><li>The relatively flat-fitting RGP with light apical touch (three point touch technique) remains the mainstay of contact lens treatment for keratoconus </li></ul>
  36. 36. Contact Lens Management <ul><li>Contact lens fitting in keratoconus i s described separately for : </li></ul><ul><ul><ul><li>E arly keratoconus </li></ul></ul></ul><ul><ul><ul><li>A dvanced keratoconus </li></ul></ul></ul>
  37. 37. Keratoconus Topographic Characteristics <ul><li>E arly keratoconus is characteri zed by initial steepening mid-peripherally below the corneal midline , while the superior cornea remains relatively normal </li></ul><ul><li>As the condition progresses, individual corneas show different topographical shapes : </li></ul><ul><ul><ul><li>Nipple </li></ul></ul></ul><ul><ul><ul><li>Oval </li></ul></ul></ul><ul><ul><ul><li>Globus </li></ul></ul></ul>
  38. 38. Early & Advanced keratoconus
  39. 39. Early Keratoconus <ul><li>There are two f i tting methods for early keratoconus: </li></ul><ul><ul><ul><li>Superior a lignment f itting t echnique </li></ul></ul></ul><ul><ul><ul><li>The i ntra- p alpebral t hree p oint t ouch f itting t echnique </li></ul></ul></ul>
  40. 40. Early Keratoconus Superior Alignment Fitting Technique <ul><li>The goal is to provide a superior alignment fitting relationship across the more normal portion of the keratoconic cornea </li></ul><ul><li>Use aspherical lens designs with: </li></ul><ul><ul><ul><li>OAD of 9.5 mm </li></ul></ul></ul><ul><ul><ul><li>OZD of 8.3 mm </li></ul></ul></ul>
  41. 41. Early Keratoconus Superior Alignment Fitting Technique
  42. 42. Early Keratoconus Superior Alignment Fitting Technique <ul><li>In superior alignment fitting technique: </li></ul><ul><ul><li>C entral keratometry (“K”) readings are of little valu e </li></ul></ul><ul><ul><li>T he more normal nasal , temporal , and superior mid-peripheral cornea is the most important fitting consideration </li></ul></ul>
  43. 43. Early Keratoconus Superior Alignment Fitting Technique <ul><li>Topography of a patient with early keratoconus </li></ul><ul><li>Inferior steepening and superior flattening </li></ul><ul><li>Central K readings : </li></ul><ul><li>46.25 / 49.75 D </li></ul><ul><li>Inferiorly, the cornea steepens to 51.25 D and superiorly it flattens, to 42.00 D </li></ul>
  44. 44. Early Keratoconus Superior Alignment Fitting Technique <ul><li>If a standard spherical contact lens is fitted on flat K (46.25 D) or steeper than flat K : </li></ul><ul><ul><li>There is discrepancy between the lens and the more normal superior cornea </li></ul></ul><ul><ul><li>T he lens will not show acceptable centration </li></ul></ul>
  45. 45. Early Keratoconus Superior Alignment Fitting Technique <ul><li>If a standard spherical contact lens is fitted on flat K (46.25 D) or steeper than flat K : </li></ul><ul><ul><li>There is discrepancy between the lens and the more normal superior cornea </li></ul></ul><ul><ul><li>T he lens will not show acceptable centration </li></ul></ul>
  46. 46. Early Keratoconus Superior Alignment Fitting Technique <ul><li>Choose a diagnostic lens with BCR equal to the radius of curvature 4.0 mm to the temporal side of the cornea </li></ul><ul><li>Place t his lens on the cornea and evaluate th e fluorescein pattern </li></ul><ul><li>S uperior alignment fitting technique is possible only in the early stages of keratoconus because: </li></ul><ul><ul><ul><li>In advanced central ectasia , It causes greater apical bearing </li></ul></ul></ul>
  47. 47. Early Keratoconus Superior Alignment Fitting Technique <ul><li>The ideal fitting should have the following characteristics : </li></ul><ul><ul><li>The BCR should be flat enough to provide lens alignment across the flatter superior cornea </li></ul></ul><ul><ul><li>T he BCR should be steep enough to provide slight touch mid peripherally at 3 and 9 o’clock </li></ul></ul><ul><ul><li>The re might be slight bearing at the apex of the cornea </li></ul></ul><ul><ul><li>The re might be slight edge lift across the inferior steeper portion of the cornea </li></ul></ul>
  48. 48. Early Keratoconus Three Point Touch Fitting Technique <ul><li>The ideal fitting characteristics : </li></ul><ul><ul><li>The BCR should be steep enough to provide three touch point: </li></ul></ul><ul><ul><ul><li>A slight central apical touch </li></ul></ul></ul><ul><ul><ul><li>Two slight touch es mid-peripherally at 3 and 9 o’clock </li></ul></ul></ul><ul><ul><li>Th is lens will most likely position centrally or slight low on the cornea </li></ul></ul>
  49. 49. Early Keratoconus Three Point Touch Fitting Technique <ul><li>Select a spherical lens design with: </li></ul><ul><ul><ul><li>OAD of 8.0 to 8.5 mm </li></ul></ul></ul><ul><ul><ul><li>OZD of 6.4 to 6.9 mm </li></ul></ul></ul><ul><ul><ul><li>BCR equal to the flat K </li></ul></ul></ul><ul><li>Place this lens on the cornea and evaluate the fluorescein pattern </li></ul>
  50. 50. Early Keratoconus Three Point Touch Fitting Technique <ul><li>Four zones are created: </li></ul><ul><ul><li>Slight apical touch </li></ul></ul><ul><ul><li>Paracentral clearance </li></ul></ul><ul><ul><li>Mid-peripheral bearing </li></ul></ul><ul><ul><li>Peripheral clearance </li></ul></ul>
  51. 51. Early Keratoconus Three Point Touch Fitting Technique <ul><li>Three-point-touch actually refers to the area of apical central contact and two other areas of bearing or contact at the mid-periphery in the horizontal direction </li></ul><ul><li>This type of fitting philosophy works very well for small central cones </li></ul>
  52. 52. Early Keratoconus RGP Fitting Approach <ul><li>Perform and evaluate the topography </li></ul><ul><li>Identify the steepest (red) and the flattest ( blue ) areas of the cornea, quantitatively: </li></ul><ul><ul><ul><li>Location </li></ul></ul></ul><ul><ul><ul><li>Size </li></ul></ul></ul><ul><ul><ul><li>Shape </li></ul></ul></ul><ul><li>Identify the dioptric curvature of the corneal apex </li></ul><ul><li>Select a diagnostic lens with a BCR equal to the dioptric curvature of the corneal apex </li></ul><ul><li>Place this lens on the eye and evaluate the fluorescein pattern </li></ul>
  53. 53. Early Keratoconus RGP Fitting Approach <ul><li>An ideal fitting should have the following characteristics: </li></ul><ul><ul><li>S light clearance across the corneal apex with no fixed, mid-peripheral bubbles </li></ul></ul><ul><ul><li>T ouch in mid-peripheral cornea at 3 and 9 o’clock </li></ul></ul><ul><ul><li>M inimal impingement across the flatter superior cornea </li></ul></ul><ul><ul><li>S light lower edge lift is common: </li></ul></ul><ul><ul><ul><li>I ntermittent bubbles inferiorly </li></ul></ul></ul><ul><ul><li>Any attempt to decrease the inferior edge lift by : </li></ul></ul><ul><ul><ul><li>S teepening the base or peripheral lens design </li></ul></ul></ul><ul><ul><ul><li>M ay result in a tight lens fit superior ly </li></ul></ul></ul>
  54. 54. Early Keratoconus RGP Fitting Approach
  55. 55. Early Keratoconus RGP Fitting Approach <ul><li>Having achieved the desired fit : </li></ul><ul><li>Perform over-refraction to determine the final CL power </li></ul><ul><li>O rder t he lens in a moderate to high Dk RGP material </li></ul><ul><li>T he diagnostic lens design should match the final lens </li></ul><ul><li>M anufactur ers follows slightly different aspheric lens design s </li></ul>
  56. 56. Best – fit contact lens / KCN
  57. 57. Best – fit apical clearance and good fluorescein circulation
  58. 58. Excessive vaulting with trapped bubble
  59. 59. Inadequate vaulting with apical touch
  60. 60. TIPS FOR PARAMETERS SELECTION IN KCN THREE POINT TOUCH NORMAL LENS DESIGN ROCK & EXCSSIVE EDGE LIFT
  61. 61. Advanced Keratoconus Topographic Characteristics <ul><li>E arly keratoconus is characteri zed by initial steepening mid-peripherally below the corneal midline , while the superior cornea remains relatively normal </li></ul><ul><li>As the condition progresses, individual corneas show different topographical shapes , e.g. </li></ul><ul><ul><ul><li>Nipple </li></ul></ul></ul><ul><ul><ul><li>Oval </li></ul></ul></ul><ul><ul><ul><li>Globus </li></ul></ul></ul>
  62. 62. Advanced Keratoconus Topographic Characteristics, Nipple Cone <ul><li>The nipple form of keratoconus characteristically consists of a small, near central ectasia, less than 5.0 mm in cord diameter </li></ul>
  63. 63. Advanced Keratoconus Topographic Characteristics, Oval Cone <ul><li>The most common type </li></ul><ul><li>A pex is displaced below midline: </li></ul><ul><ul><li>I nferior mid-peripheral steepening </li></ul></ul><ul><ul><li>N ormal or flat 180 degrees away </li></ul></ul>
  64. 64. Advanced Keratoconus Topographic Characteristics, Globus Cone <ul><li>T he largest (often nearly 75% of corneal surface ) </li></ul><ul><li>N early all keratoscopy rings are located within the ectatic area </li></ul><ul><li>Almost n o island of normal cornea above or below the midline </li></ul>
  65. 65. Advanced Keratoconus Fitting Process <ul><li>Due to the varying peripheral corneal topographies </li></ul><ul><ul><li>No single lens design or fitting philosophy will universally result in an optimal fit </li></ul></ul><ul><li>Different fitting approaches must be employed </li></ul><ul><ul><li>Based on the central and mid - peripheral corneal topography </li></ul></ul><ul><li>Fitting approachs for advanced keratoconus based on the nipple, oval, and globus photokeratoscopy </li></ul>
  66. 66. Advanced Keratoconus Fitting Process, Nipple Cone <ul><li>The lens should have multiple spherical peripheral blending curves that gradually fatten the lens periphery </li></ul><ul><ul><li>The resulting lens design is a non-definable aspheric surface </li></ul></ul><ul><li>The aspheric lens fitting technique is identical to that described for the fitting of early keratoconus , but: </li></ul><ul><ul><li>I t is often necessary to increase the amount of posterior lens asphericity , due to : </li></ul></ul><ul><ul><ul><li>R apid topographical flattening from center to periphery </li></ul></ul></ul>
  67. 67. Advanced Keratoconus Fitting Process, Nipple Cone
  68. 68. Advanced Keratoconus Fitting Process, Nipple Cone, Fitting Set
  69. 69. Advanced Keratoconus Fitting Process, Oval Cone <ul><li>The oval cone consists of an inferior steepening with varying degrees of normal superior cornea l topograph y </li></ul><ul><li>C areful attention to the status of the superior and horizontal corneal topography is important </li></ul><ul><li>I f the superior and horizontal topography are relatively normal : </li></ul><ul><ul><li>C onsider superior alignment fitting technique similar to that described for early keratoconus </li></ul></ul><ul><ul><li>S uperior alignment fit is sufficient ly supported by the normal cornea at 9, 12, and 3 o'clock </li></ul></ul>
  70. 70. Advanced Keratoconus Fitting Process, Oval Cone
  71. 71. Advanced Keratoconus Fitting Process, Oval Cone, Fitting Set
  72. 72. Advanced Keratoconus Fitting Process, Globus Cone <ul><li>The globus cone consists of ectasia involving cornea , almost total ly </li></ul><ul><li>T he only normal portion of the cornea may be the superior limbal area </li></ul><ul><li>Because of the large size CL fitting for globus cones requires large lenses with: </li></ul><ul><ul><ul><li>Large OAD of 9.1 mm </li></ul></ul></ul><ul><ul><ul><li>OZD of 6.5 mm </li></ul></ul></ul>
  73. 73. Advanced Keratoconus Fitting Process, Globus Cone
  74. 74. Advanced Keratoconus Fitting Process, Globus Cone, Fitting Set
  75. 75. Keratoconus Fitting Process, Over Refraction <ul><li>Over-refraction is an integral part of diagnostic fitting </li></ul><ul><li>M oderate to high amounts of residual astigmatism is not uncommon for keratoconus patients wearing RGPs: </li></ul><ul><ul><li>Correcti o n with glasses often improves visual acuity three to four lines </li></ul></ul><ul><ul><li>Front surface toric RGP s may also be fitted in this situation </li></ul></ul>
  76. 76. Keratoconus Fitting Process, Lens Dispensing <ul><li>All keratoconus contact lenses should be ordered in a moderate to high Dk RGP material to avoid : </li></ul><ul><ul><li>E pithelial hypoxia </li></ul></ul><ul><ul><li>C orneal erosion </li></ul></ul><ul><li>Before dispensing the lens c arefully evaluate : </li></ul><ul><ul><li>B ase curve, optical zone, diameter, edge, etc </li></ul></ul><ul><ul><li>Every aspect of the lens design plays an integral role in the overall success of the fitting </li></ul></ul>
  77. 77. Semi-Scleral GP Lenses <ul><li>Semi-scleral lenses are large diameter (13.5 to 16.0 mm) </li></ul><ul><li>These lenses often have a large limbal fenestration to reduce lens adhesion and facilitate lens removal </li></ul><ul><li>Sometimes traditional R GP lens designs may not provide the desired centration, optics , or comfort </li></ul><ul><li>Semi-scleral lenses have proven to be extremely beneficial for H ighly irregular and/or asymmetric keratoconic corneas </li></ul>
  78. 78. Semi-Scleral GP Lenses Fitting Process <ul><li>The u se of a diagnostic set is mandatory </li></ul><ul><li>S elect a diagnostic lens with a BCR equal to the steepest K reading </li></ul><ul><li>The ideal fitting relationship is one in which : </li></ul><ul><ul><li>T he re is apical clearance across the central cornea </li></ul></ul><ul><ul><li>The re is a 1.0 mm band of pooling adjacent to the limbus , in the area of the scleral curve </li></ul></ul>
  79. 79. Semi-Scleral GP Lenses Fitting Process
  80. 80. Soft lenses <ul><li>These (hydrogels, silicone hydrogels) have a limited role in correcting corneal irregularity: </li></ul><ul><ul><li>tend to drape over the surface of the cornea </li></ul></ul><ul><ul><li>result in poor visual acuity </li></ul></ul><ul><li>Soft lenses designed specifically for keratoconus have a useful role: </li></ul><ul><ul><li>In early keratoconus </li></ul></ul><ul><ul><li>where a patient may be intolerant of RGP </li></ul></ul>
  81. 81. Soft lenses <ul><li>Soft lenses tend to be more comfortable compared with RGPs: </li></ul><ul><ul><li>Kerasoft Lenses (Ultravision) (58% water content terpolymer), in four series, A,B,C and D </li></ul></ul><ul><ul><li>Acuity K Mark I and II (Acuity Contact Lenses) </li></ul></ul>
  82. 82. Advantages of soft contact lens <ul><li>They afford higher levels of comfort and longer wearing times, especially in: </li></ul><ul><ul><li>patients intolerant of RGP corneal lenses </li></ul></ul><ul><ul><li>in monocular keratoconus </li></ul></ul><ul><li>They are useful : </li></ul><ul><ul><li>where the cone apex may be displaced, especially if it is very low </li></ul></ul><ul><ul><li>for certain groups of patients, for example airline pilots </li></ul></ul><ul><li>They are relatively simple to fit </li></ul>
  83. 83. Disadvantages of soft contact lens <ul><li>Visual acuity may be variable in cases of very high minus lenses </li></ul><ul><li>Low-powered diagnostic lenses may not provide an accurate guide to the fit of the final lens, which may be extremely high powered </li></ul>
  84. 84. Disadvantages of soft contact lens <ul><li>There may be reduced oxygen transmissibility and the risk of neovascularisation if the lenses are overworn </li></ul><ul><li>If the condition has progressed, it may be difficult to change to RGP’s at a later stage </li></ul>
  85. 85. Keratoconus Soft CL <ul><li>Although in theory, it seems that keratoconic corneas would benefit from soft toric lenses, but this is often not the case because: </li></ul><ul><ul><li>In the toric lenses, the toric curvatures and corresponding power corrections are 90 degrees apart (orthogonal) </li></ul></ul><ul><ul><li>The keratoconus corneas typically have a high level of irregular, non orthogonal astigmatism </li></ul></ul><ul><li>Only if the cone apex is well centered and if the keratoconus is not advanced, the fitting of a bitoric is possible and has been found to be successful </li></ul>
  86. 86. Keratoconus Soft CL <ul><li>Few new soft lens designs have made it possible to correct some complex optics created by keratoconu s </li></ul><ul><li>The most common use of soft lenses in keratoconus is the combination of these with rigid lenses: </li></ul><ul><ul><li>Piggyback designs </li></ul></ul><ul><ul><ul><li>Traditional </li></ul></ul></ul><ul><ul><ul><li>Custom </li></ul></ul></ul><ul><ul><li>Hybrid designs </li></ul></ul>
  87. 87. Keratoconus Traditional Piggyback Lenses <ul><li>These consist of a high Dk silicone hydrogel soft lens over which a high Dk RGP lens is fitted </li></ul>
  88. 88. Keratoconus Traditional Piggyback Lenses, Fitting Process <ul><li>Fit the diagnostic soft lens </li></ul><ul><li>Determine the radii of the new corneal surface </li></ul><ul><ul><ul><li>Perform keratometry or topography over the anterior surface of the soft lens </li></ul></ul></ul><ul><li>Selected a GP lens with </li></ul><ul><ul><ul><li>BCR equal to the flat K </li></ul></ul></ul><ul><ul><ul><li>OAD of 9.0 to 9.5 mm </li></ul></ul></ul><ul><li>Adjusted the base curve until an appropriate lens - to - lens fitting relationship is established </li></ul>
  89. 89. Keratoconus Traditional Piggyback Lenses, Fitting Process <ul><li>The ideal GP lens fitting should accomplish three fitting objectives: </li></ul><ul><ul><li>Apical clearance : </li></ul></ul><ul><ul><ul><li>T o prevent the lens from rocking and pivoting over the corneal apex </li></ul></ul></ul><ul><ul><li>Lens contact ( landing zone ) at 3 and 9 o’clock: </li></ul></ul><ul><ul><ul><li>T o center the lens along the horizontal meridian </li></ul></ul></ul><ul><ul><li>Unobstructed lens movement along the vertical meridian: </li></ul></ul><ul><ul><ul><li>For the lens to move with blinking </li></ul></ul></ul><ul><li>An over-refraction is performed to determine the final power of the RGP lens </li></ul>
  90. 90. Keratoconus Traditional Piggyback Lenses
  91. 91. Keratoconus Traditional Piggyback Lenses
  92. 92. Keratoconus Custom Piggyback Lenses <ul><li>These consist of a soft lens with a circular, recessed depression in its center </li></ul><ul><li>A high Dk RGP lens is fitted within the central depression of the soft lens </li></ul>
  93. 93. Keratoconus Custom Piggyback Lenses <ul><li>The system provides optimal performance by: </li></ul><ul><ul><ul><li>Good optics of a well centered RGP </li></ul></ul></ul><ul><ul><ul><li>Enhanced comfort provided by the soft lens </li></ul></ul></ul><ul><li>The soft lens is available in a wide range of parameters : </li></ul><ul><ul><li>BCR from 6.00 to 11.00 mm </li></ul></ul><ul><ul><li>OAD from 12.5 to 16.5 mm </li></ul></ul><ul><ul><li>The recessed cutout diameter of 7.5 to 11.5 mm </li></ul></ul>
  94. 94. Keratoconus Custom Piggyback Lenses, Fitting Process <ul><li>Goals are identical to that of any lens, with the primary fitting: objectives: </li></ul><ul><ul><ul><li>Adequate movement </li></ul></ul></ul><ul><ul><ul><li>Optimal centration </li></ul></ul></ul><ul><li>Select the optimal diagnostic soft lens : </li></ul><ul><ul><li>I nsert any rigid lens into the recessed cutout to mimic final lens weight and lid/lens interaction </li></ul></ul><ul><li>Remove the rigid lens and determine K readings over the central portion of the soft lens </li></ul>
  95. 95. Keratoconus Custom Piggyback Lenses, Fitting Process <ul><li>Select a diagnostic GP lens with : </li></ul><ul><ul><ul><li>BCR equal to flat K </li></ul></ul></ul><ul><ul><ul><li>OAD of 1.0 mm smaller than the cut out diameter </li></ul></ul></ul><ul><ul><ul><li>T o allow for some movement and tear exchange within the soft lens cutout boundaries </li></ul></ul></ul><ul><li>Place this RGP into the central cutout and evaluate the lens to lens relationship </li></ul><ul><li>Adjust BCR to obtain optimal fitting </li></ul><ul><li>Over refract to determine final RGP power </li></ul>
  96. 96. Keratoconus Custom Piggyback Lenses, Fitting Process
  97. 97. Keratoconus Hybrid Lenses, Saturn Lens <ul><li>Work on a hybrid combination GP and soft lens design began in 1977 </li></ul><ul><li>In 1985 the Saturn lens was introduced: </li></ul><ul><ul><ul><li>A central 6.5 mm rigid material with a Dk of 14 </li></ul></ul></ul><ul><ul><ul><li>Surrounded by a 13.5 mm diameter, 25% water content soft lens </li></ul></ul></ul>
  98. 98. Keratoconus Hybrid Lenses, Softperm Lens <ul><li>The Saturn lens was replaced by the Softperm lens in 1989 </li></ul><ul><ul><li>An 8.0 mm styrene center in a bi-curve lens design </li></ul></ul><ul><ul><li>Surrounded by a 14.3 mm diameter, 25% water content soft lens </li></ul></ul>
  99. 99. Keratoconus Hybrid Lenses, Softperm Lens <ul><li>The Softperm hybrid design had limited success due to : </li></ul><ul><ul><ul><li>Complications secondary to minimal oxygen permeability </li></ul></ul></ul><ul><ul><ul><li>Frequent loss of adhesion between the components </li></ul></ul></ul><ul><ul><ul><li>Limitations in lens design and parameter availability </li></ul></ul></ul>
  100. 100. Keratoconus Hybrid Lenses, SynergEyes <ul><li>In September 2001 a new high Dk hybrid lens called SynergEyes was introduced: </li></ul><ul><ul><ul><li>A n 8.2 mm high Dk rigid center </li></ul></ul></ul><ul><ul><ul><li>Paragon HDS 100, Dk 100 </li></ul></ul></ul><ul><ul><ul><li>Surrounded by a 14.5 mm, 28% water content non-ionic soft lens </li></ul></ul></ul>
  101. 101. Keratoconus Hybrid Lenses, SynergEyes <ul><li>The SynergEyes is available in two designs for keratoconus: </li></ul><ul><ul><li>SynergEyes A: </li></ul></ul><ul><ul><ul><li>the standard aspherical design </li></ul></ul></ul><ul><ul><ul><li>I deal for patients with early keratoconus </li></ul></ul></ul><ul><ul><li>SynergEyes KC : </li></ul></ul><ul><ul><ul><ul><li>S pecifically designed for advanced keratoconus </li></ul></ul></ul></ul>
  102. 102. Keratoconus Hybrid Lenses, SynergEyes, Fitting Process <ul><li>Select a diagnostic lens with a BCR equal to steep K </li></ul><ul><li>Pour high molecular weight fluorescein into the bowl of the lens and place the lens </li></ul><ul><li>Evaluate fluorescein pattern </li></ul>
  103. 103. Keratoconus Hybrid Lenses, SynergEyes, Fitting Process <ul><li>The RGP portion of the lens should exhibit: </li></ul><ul><ul><ul><li>Central apical clearance </li></ul></ul></ul><ul><ul><ul><li>Mid - peripheral lens bearing </li></ul></ul></ul><ul><li>The soft lens skirt should exhibit 0.25 mm of blink - induced movement </li></ul>
  104. 104. Keratoconus Hybrid Lenses, SynergEyes, Fitting Process
  105. 105. Keratoconus Hybrid Lenses, SynergEyes, Fitting Process
  106. 106. Contact lens fitting and keratoconus
  107. 107. Contact lens fitting and keratoconus
  108. 108. Contact lens fitting and keratoconus
  109. 109. KCN lens selection based on type of cone
  110. 110. Different types of RGP lens designs for KCN <ul><li>Early keratoconus: </li></ul><ul><ul><li>Aspherics or multicurve lenses </li></ul></ul><ul><ul><li>Kera I and II (No.7) </li></ul></ul><ul><ul><li>Acuity K </li></ul></ul><ul><ul><li>Rose K (David Thomas) </li></ul></ul><ul><li>Moderate keratoconus: </li></ul><ul><ul><li>Kera II </li></ul></ul><ul><ul><li>Quasar KNO7 </li></ul></ul><ul><ul><li>Rose K (David Thomas) </li></ul></ul><ul><ul><li>Woodward KC3 </li></ul></ul>
  111. 111. Different types of RGP lens designs for KCN <ul><li>Moderate/Advanced keratoconus: </li></ul><ul><ul><li>Kera II/III </li></ul></ul><ul><ul><li>Rose K (David Thomas) </li></ul></ul><ul><ul><li>Profile K (J Allen) </li></ul></ul><ul><li>Advanced keratoconus: </li></ul><ul><ul><li>Large diameter lenses </li></ul></ul><ul><ul><li>S-Lim (J Allen) </li></ul></ul><ul><ul><li>Dyna-intra limbal (No.7) </li></ul></ul>
  112. 112. Soper contact lens / KCN bicurve-10 lenses Apical clearace manner
  113. 113. Soper contact lens / KCN bicurve-10 lenses Apical clearace manner
  114. 114. VAULTING EFFECT (sagittal value of lens )
  115. 115. McGuire contact lens / KCN BCR -4 PCR-3 type - Apical clearace manner
  116. 116. Rose –K contact lens <ul><li>The Rose K is a unique keratoconus lens design with complex computer-generated peripheral curves based on data collected by Dr Paul Rose of Hamilton, New Zealand </li></ul>
  117. 117. Rose –K contact lens 85% first fit success complex lens geometry computer- generated peripheral curve system
  118. 118. Rose –K contact lens <ul><li>The system (26 lens set) incorporates a triple peripheral curve system - standard, flat, steep - in order to order to achieve the ideal edge lift of 0.8mm </li></ul><ul><li>The practitioner has a choice of peripheral curves </li></ul>
  119. 119. Rose –K contact lens
  120. 120. Rose –K contact lens <ul><li>The design starts with a standard 8.7mm diameter and works by decreasing the optic zone diameter as the base curve gets steeper </li></ul><ul><li>It is available in base curves of 4.75- 8.mm and diameters of 7.9-10.2mm </li></ul><ul><li>Toric curves are available on the front and back surfaces as well as in the periphery </li></ul>
  121. 121. Rose –K contact lens <ul><li>Standard lift lenses should work 70% of the time </li></ul><ul><li>Peripheral curves can be configured to a toric design </li></ul><ul><li>Rose K lenses are very widely used </li></ul>
  122. 122. Ni-Cone contact lens / KCN 3 separate BCRs -1 PCR
  123. 123. Bennett contact lens / KCN Three point touch fitting
  124. 124. Bennett contact lens / KCN Three point touch fitting
  125. 125. Contact lens / KCN problem solving
  126. 126. CLEK contact lens / KCN mild to moderate KCN -
  127. 127. KCN TRIAL LENSES

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