Orthokeratology

Specialty Contact lens

1. ORTHOKERATOLOGY RICHA GUPTA M.OPTOM 2 nd year BVDU(MC) SCHOOL OF OPTOMETRY

2. PRESENTATION LAYOUT Introduction History Old and new method of Ortho - k Lens Design How its works -Effect on Myopia, Hyperopia And Astigmatism Fitting – Pre and Post fitting Types of Ortho k Insertion and removal Indication and Contraindication Advantages and disadvantages Adverse effects Trouble shoot Ortho k availability

3. INTRODUCTION According to Ziff(1968) “the systemic and purposeful designing of contact lenses to change corneal curvature, which result in emmetropia of the eye, as applied to patients with myopia, hyperopia and astigmatism”. Reference – IACLE MODULE -8

4. Alternative Terminology

5. HISTORY In 1965 Ziff reported the first study of Orthokeratology. Dr George N. Jessen introduced “Orthofocus” Conventional Geometry lenses in 1960. Fontana was the first to use a Reverse geometry lenses in 1972. Reference – IACLE MODULE -8

6. Spectacle Vs OK lens in myopic eyes Diagram illustrating the concepts of (A) peripheral hyperopic defocus, which may occur in myopic eyes wearing conventional spectacle or contact lens correction, and (B) peripheral myopic defocus, which may be induced in myopic eyes after corneal reshaping with overnight OK. Diagram courtesy of Dr. Edward Lum. OK, orthokeratology.

7. Orthokeratology Methods Conventional Geometry First to attempt to change refracted error Technique used Plano PMMA lenses Flat central fitting(flattest k fitting) This method is failed due to disadvantage of PMMA Lens ,decentration of lens inducing astigmatism, Took long time to achieve a small amount of reduction ,Lens fit was unstable ,costly Reference – IACLE MODULE -8

8. Early Reverse Geometry Design

9. Reverse Geometry Ortho k used the temporary correction of low to moderate myopia It uses 4 to 5 curves reverse geometry lenses in high Dk material in an overnight lens wearing modality Reference – IACLE MODULE -8

10. Reverse Geometry Principle The fundamental reverse geometry lens design incorporates three distinct zones. The central zone or base curve of the lens is fitted flatter than the central corneal curvature and may comprise a spherical or aspheric curve or curves. The central zone serves to flatten the central cornea, reducing its power to correct myopia. Surrounding the central zone, a reverse curve zone comprising one or more curves steeper than the base curve gives this particular lens design its name. Spherical, aspheric or sigmoid curves have been used in this reverse curve zone, which acts to maintain lens centration and may also supplement the forces flattening the central cornea through negative pressure in the post-lens tear film. Finally, peripheral to the reverse curve zone is a zone of alignment to the underlying midperipheral cornea. The alignment curve zone bears the weight of the lens and aids in lens centration. Tangent or aspheric peripheral curves are often used for the alignment zone, which is surrounded by an edge lift to facilitate tear circulation.

11. Modern RG Lens Design BASE CURVE : flatter than the flattest central apical radius REVERSE CURVE: Steeper secondary curve form a tear reservoir for excess tear ALIGNMENT CURVE: Allow the shaping lens to centre and position properly on the eye PERIPHERAL CURVE : Allow for tear circulation under the sharper and easy removal of debris trapped

12. Base curve – 0.30 to 1.40mm flatter than the flattest corneal curvature Optical zone – 6.0mm to 8.0mm Reverse curve – 0.6 to 1.0mm(steeper than the base curve radius) Reservoir zone – 3.00 to 5.00D (steeper than the base curve radius) Peripheral curve radius having a edge lift -0.06 to 0.07 mm IDEAL PARAMETERS

13. Eccentricity and R efracted error The research of Mountford has shown that for each change of 0.21 in e – value, 1.00D reduction in Myopia is Possible. ∆e = 0.21∆Rx More e value – more amount of refractive change More eccentricity – more sagittal depth

14. How its works

15. MYOPIA

16. HYPEROPIA

17. Patient selection High motivation Previous contact lens wear Level of patient desire Pupil diameter(measure under a range of illumination) Progressive myopes Refracted error falls within FDA approval(lower refracted error can be easily corrected) Free of spectacles Laser surgery patients who decide not to have surgery

18. Fitting Pre fitting Lens selection Evaluation Further Evaluation Retainer lens

19. Different Ways of Fitting Reverse Geometry Lenses Three ways to fit reverse geometry lenses: Empirical Trial lens Topography based Fitting method

20. Pre-fitting Uncorrected visual acuity HVID Pupil size Keratometry Corneal Topography requirement Eccentricity measurement Maps interpretation Apical ROC values Sagittal and tangential maps Differential Maps Subjective refraction Slit lamp Examination Anterior segment Examination Ocular Surface Health Tear evaluation with fluorescein

21. Lens Diameter Ortho k lens diameter are usually larger than conventional GP designs and typically between 10-11 mm to optimize the size of the treatment zone which should at least 5 mm to cover the pupil under most light condition.

22. Select Initial lens Design radius 0.3 to 0.5mm flatter than flat k Use topical Anesthetic (not mandatory. basically for avoiding excessive tearing) Lens insertion(prepare patient, need viscous wetting solution to fill in reverse curve area without bubbles) Apply fluorescein and then slit lamp examination Assessment of fluorescein pattern – Central bearing , tear reservoir, edge width, Edge clearance, Assess quality of lens centration PROCEDURE

23. Ideal Fluorescein Pattern Wide central touch (3mm in diameter) Central bearing 3.0 to 4.5mm Wide , deep tear reservoir around central bearing zone Good lateral centration(pupil coverage) Minimal movement with blink Achieve tear exchange(no or small bubble in tear reservoir) Peripheral Edge width – 0.2 to 0.4mm

24. Ideal End Point Uncorrected visual acuity 6/6or better Sight hyperopia of 0.50D Bull eye pattern in topography Minimal regression over 10-12 hrs. after lens removal RETAINER LENSES Once the stage has reached where further changes is either impossible or not required , the treatment phase of OK program is complete and the retainer lens is commenced Convenient way to use retainer lens is overnight schedule

25. Wearing schedule Instructed to place lens in eye 15-20min before going to sleep and remove half an hour after getting up. Schedule of overnight wear Day 1 – not to exceed 6 hrs. Day 2 – 6 hrs. Day 3 - 8 hrs. Day 4 – overnight wear with follow up visit within 24 hrs.

26. Follow up 1 Day -To assess centration of treatment and corneal staining due to adhesion 1-2weeks –To assess treatment efficacy , Can make changes if treatment is not acceptable 1-3 months – To assess long term efficacy and safety vision throughout the day, consistency from day to day Corneal /conjunctival problems Every 6 months thereafter – Watch for effects of deposits build up, lens damage , lens parameter changes

27. Follow up procedure Unaided visual acuity Subjective refraction (avoid Auto-refraction) Corneal topography Slit lamp examination with or without fluorescein Lens quality Axial length measurement (for myopia control)

28. Corneal Topography A typical corneal topography difference map following overnight wear of a reverse geometry OK lens for myopia correction. Note the central zone of corneal flattening or reduced corneal power, surrounded by an annulus of relative corneal steepening. OK, orthokeratology. Bull Eye Pattern

29. Fluorescein Pattern The characteristic fluorescein pattern observed with a reverse geometry OK lens on the eye. The lens has been designed for myopia correction. The fluorescein pattern reveals central corneal bearing (although the lens does not physically touch the underlying epithelium), an annulus of midperipheral clearance under the reverse curve zone, and an peripheral zone of alignment surrounded by a small edge lift. OK, orthokeratology

30. Types of Ortho K design Toric Ortho k lens Bifocal Ortho K Multifocal Ortho k

31. Bifocal Ortho k Orthokeratology gives a lot of freedom to our patients and increases quality of life . Presbyopia should no longer considered as impossible for Orthokeratology. The 2009 presented Bifocal Design works very well and patients love to be relieved from their visual aids. Especially patients with dry eye problems during multifocal contact lens wear could have a huge improvement visually and for comfort as well.

32. Bifocal Orthokeratology Design (Falco Switzerland)

33. Insertion and removal video

34. Reference – IACLE MODULE - 8

35. Reference – IACLE MODULE -8

36. Adverse Reaction Anterior eye infection Microbial keratitis Overnight lens adherence Corneal iron lines/rings- apparent within 2 weeks and its reversible Increase irregular astigmatism Increase spherical aberration Decreased contrast sensitivity Coma aberration if lens is decentered

37. Three important findings Firstly, of the 129 cases of MK in OK in this analysis, over 75% of the cases had occurred in East Asian countries, predominantly in China (38%) and Taiwan (28%). This pointed to a distinctly regional problem, indicating that measures to reduce risk needed to be targeted to these countries. The second major finding of the analysis was that of the 126 patients affected, most were children (8–15 years; 56%) or young adults (16–25 years; 39%). Clearly, the emotions stirred by this epidemic were exacerbated by the very young ages of affected patients, but also suggested that OK was being used predominantly in this age group for myopia control rather than simple refractive correction. It also raised concerns that children may be more susceptible than adults to infections during contact lens wear. Although 17% of cases were culture-negative or did not report on causative organisms, the most common organism implicated in these infections was Pseudomonas aeruginosa (38%). But an unexpected finding was that Acanthamoeba infection had occurred in 33% of cases. This is a very high proportion given that in other forms of contact lens wear Acanthamoeba is a rare infection. This discovery led the authors to conclude that exposure of OK lenses to contaminated or tap water during care and wear may be an important modifiable risk factor in these infections. This has resulted in a strong recommendation that tap water must be strictly avoided in the care and storage of OK lenses, and indeed in all forms of contact lens wear.

38. Troubleshooting Smiley face Smile face with a fake central island Central Island Frowny Face Lateral Decentration

39. Lens care Use multipurpose solution or hydrogen peroxide based solution approved for RGP lens Like Boston simplex, clear care, Conta care etc. Menicon progent to remove protein deposits every 3 months. Yearly replacement of lenses Do not use saline or tap water, No saliva.

40. Current availability of Ortho k

41. PARAGON On the basis of Jessen factor OD (K) – 42.00D, Power - -2.00D First to subtract the power from the Keratometry value it become 40.00D and then subtract Jessen factor -0.50 It become 30.5D Cost is 21000/-

42. BOZR = Flattest k – (target reduction +0.75) Range - 0.50D to 3.00D(Mountford et al,2004) BC/BOZR is made flatter than flat k by the target prescription and an additional amount called Jessen factor JESSEN FACTOR

43. It is suggested by Mountford The amount of tissue displaced in Orthokeratology S = (treatment zone diameter) 2 * Desired dioptric change/3) MUNNERLYN FORMULA

44. ORDER DREAM LENS

45. Johnson & Johnson

46. GOV(Global OK Vision) ON Flat k Cost – 23000/-

47. NAME: Dinesh Parmar MR NO. DEL-G-19-07-49** AGE: 27/M PROFESSION: Student Date: 20/7/2019 DEMOGRAPHIC DATA

48. Pt. came for CL opinion Pt. was using glass since 5 years There was no history of past illness or systemic disease Nutritional status seemed to be normal MEDICAL HISTORY

49. Unaided visual acuity was recorded OD 6/9 improving to 6/5 with pinhole OS 6/18 improving to 6/5 with pinhole Dry Retinoscopy was done OD -0.50 DS OS -1.00 DS Subjective acceptance was taken OD -0.50 DS 6/5 OS -1.00 DS 6/5 OU DUOCHROME BALANCED NEAR VISION N6 VISION AND REFRACTION

50. RIGHT EYE LEFT EYE LIDS FLAT FLAT CONJUNCTIVA QUIET QUIET CORNEA CLEAR CLEAR AC DEEP/QUIET DEEP/QUIET PUPIL R/C/R R/C/R LENS CLEAR CLEAR STERILE AT @ 2:34 pm 14 mm of hg 15 mm of hg SLIT LAMP EXAMINATION

51. OD trial done with 7.76/-1.50/10.6 OS trial done with 7.80/-1.50/10.6 OU binocular vision was recorded as 6/6 after 2 hour Advice: repeat trial in next visit BASE CURVE OD 7.76 mm OS 7.80mm LENS POWER OU -1.50 D LENS DIA OU 10.6 mm Trial fitting

52. Trial was done with OD 7.76/-1.50/10.6 OS 7.80/-1.50/10.6 After 2 hours of fitting… Monocular vision (OU) was recorded as 6/6 binocular vision was recorded as 6/5 Lens was order on same parameters FOLLOW UP

53. C onclusion O vernight OK provides a temporary correction for low to moderate myopic refractive error through corneal reshaping. The safety of this modality compares favorably with other conventional modalities of contact lens wear, as long as the lenses are fitted appropriately by suitably educated practitioners, and that patients are compliant with safe lens wear and care practices. Overnight OK is also effective in slowing eye growth in young progressive myopes, with an average myopia control efficacy of approximately 45% over 2 years. A major challenge for this modality is to determine ways in which treatment efficacy can be optimized for individual children, and to investigate the role of combination and sequential therapies in the management of myopic progression in children. Source: Google image

54. R eferences

55.   Orthokeratology Principles and practice by John Mountford, David Ruston Trusit Dave Orthokeratology practice in children in a university clinic in Hong Kong  – Clinical and Experimental Optometry. March 2008 . http ://theeyestore.co.uk/orthokeratology-corneal-refractive-therapy   " Orthokeratology | Ortho-K lenses | Myopic degeneration prevention" . 2018-07-04. Orthokeratology contact lenses cause permanent vision loss in children  – American Academy of Ophthalmology media release, 1 March 2004] Research in Orthokeratology  – University of New South Wales (Sydney, Australia). Orthokeratology: part I historical perspective.  Journal of the American Optometric Association ARTICLES

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