Orthokeratology uses reverse geometry contact lenses to temporarily reshape the cornea overnight and correct refractive errors. It was first reported in 1965 and uses modern reverse geometry lenses made of high Dk materials. Orthokeratology works by inducing peripheral myopic defocus to flatten the central cornea. It is generally used for low to moderate myopia but can also be used for astigmatism and presbyopia. Fitting involves evaluating corneal topography and achieving a fluorescein pattern with central touch and a tear reservoir before overnight wear begins. Orthokeratology has advantages of reversibility and potential to slow myopia progression but requires continued lens wear to maintain effects.

1. ORTHOKERATOLOGY
RICHA GUPTA
M.OPTOM 2nd 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
Ortho-
k
Corneal
refractive
therapy
Accelerative
Orthokeratology
Controlled
Kerato
Reformation
Corneal molding
system
Overnight
Orthokeratology
CL Corneal
shaping
Compression
Ortho k
Corneal
reshaping
Treatment
Vision shaping
treatment

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

15. • 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

16. Eccentricity and Refracted 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

17. How its works

19. MYOPIA

20. HYPEROPIA

21. 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

22. Fitting
• Pre fitting
• Lens selection
• Evaluation
• Further Evaluation
• Retainer lens

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

24. 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

25. 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.

26. • 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

27. 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

28. 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

29. 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.

30. 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

31. 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)

32. 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

33. 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

34. Types of Ortho K design
• Toric Ortho k lens
• Bifocal Ortho K
• Multifocal Ortho k

35. 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.

36. Bifocal Orthokeratology Design (Falco Switzerland)

38. Insertion and removal
• video

40. CONTRAINDICATION
• Previous failure with RGP lens wear
• Disease of cornea , conjunctiva or adnexa
• A C inflammation
• Dry eye
• Keratoconus
• Older patients
• Unrealistic Patient Expectation
• Low sphere power with high cylinder
Reference – IACLE MODULE -8

41. Advantages
• Reversible
• Both eyes altered at the same time
• No disruption to vision during treatment
• Less(or no) pain compare with PRK
• Therapy can be halted if untoward effects are experienced
• Option for children(slow myopia progression)
• Not age dependent
Disadvantages
• Not a permanent solution
• Patient may become a Regular RGP lens wearer i.e. use OK lens conventionally
• Amount of refracted error correctable by OK is limited
• Potential for non- compliance
• Retainer lens needed
• Several visit required
Reference – IACLE MODULE -8

42. 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

46. 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.

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

54. 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.

55. Current availability of Ortho k

56. 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/-

58. • 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

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

60. ORDER DREAM LENS

62. Johnson & Johnson

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

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

65. 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

66. 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

67. 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

68. 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

69. 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

70. Conclusion
• Overnight 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

71. References

72. • 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

73. THANK YOU
THANK YOU