Orthokeratology, also known as corneal reshaping therapy, uses specially designed contact lenses to temporarily reshape the cornea and reduce or eliminate refractive errors. It allows patients to have clear unaided vision for most of the day by modifying the corneal curvature through overnight lens wear. Studies have shown orthokeratology can slow the progression of myopia in children by an average of 50%. A trial fitting is performed to assess the fluorescein pattern and ensure proper centration, bearing, and tear reservoir before beginning overnight wear to achieve the desired refractive change. Orthokeratology provides an alternative to glasses or surgery and is reversible.

1. PRESENTED BY – ASHITH
TRIPATHI

2. Orthokeratology
A purposeful attempt to modify the corneal curvature to
result in a reduction or elimination of a refractive anomaly
by a programmed application of contact lens.
Alternative Terminology –
Corneal Reshaping Therapy (CRT)
Reversible Corneal Therapy

3. The main purpose of Orthokeratology is
to be free of both contact lenses and
spectacles for all waking hours.
Ideal for sportsmen and women,
swimmers or those who work in dusty or
dirty environments.
School age children benefit greatly:- No
more lost contact lenses or broken frames.
Surgery is not always in your comfort
zone.

4. Can Ortho-K Slow Myopia ?
In late 2004 a study published
in an international journal
found that Orthokeratology
can slow myopia progression
by an average of 50%

5. For most people it is possible to go
straight to night therapy. This gives a
fast and easy way of arriving at myopia
correction.
Lenses are inserted before going to
sleep and removed in the morning.

6. As the therapy progress and the
cornea is moulded, the lenses
give good unaided vision for
longer periods of time.
Gradually the lens wearing time
may be decreased to a level,
which gives the desired
reduction in myopia.

7. Corneal Topographer
• axial, tangential, and refractive maps
Precision fitting
• extensive knowledge of RGP lens fitting
Large set of special OK trial lenses

8.  Rx – 0.50 to -4.00 D Sph
- higher Rx.s are possible but outcome is less predictable
 1.50 D Cyl. of cornea astigmatism
- consider lenticular astigmatism when predicting vision
- purely lenticular cyl. is problematic
 Central Kflat readings ≥ 42.00D
 Corneas that flatten in the periphery
- non – spherical, esp. prolate elliptical corneas

9. Trial Fitting Routine
Select initial lens’ radius/design
◦ 0.3 to 0.5 mm flatter than Kflat
◦ based on topography measurements
Use topical anaesthetic
◦ prevents excessive tearing
Assessment of fluorescein pattern
◦ central bearing
◦ tear reservoir (paracentral zone)
◦ edge width and edge clearance
◦ assess quality of lens centration
Overnight-wear trial

10. Overnight wear advantages
◦minimizes need for adaptation
◦reduces discomfort
◦maximizes orthokeratology effect
◦high Dk/t lenses are available
◦easier for patients
TRIAL FITTING ROUTINE

11. IDEAL FITTING PATTERN
3 - 4.5 mm of central bearing
Wide, deep tear reservoir around central bearing zone
Good lateral centration
◦ vital for wearing success
◦ pupil coverage
◦ good vision
Minimal movement with blink
◦ depends on total diameter
Active tear exchange
◦ no or small bubbles in the tear reservoir

12. IDEAL FLUORESCEIN FITTING PATTERN
(Lens) Total Diameter
Treatment Zone Diameter
HVID
Pupil ‘Reverse’ curve
Alignment curve
Edge curve
(tear reservoir)

14. Ortho – k costs less and is a
reversible procedure.
It is also more appropriate for
people whose eyes are still
changing.
Both eyes altered at the same
time
Option for children (may slow
myopia progression)

15. Everyone