Orthokeratology by Optom Ankit Varshney

Optom. Ankit S. Varshney
B.Optom, M.Optom, Ph.D. in Optometry (pursuing) Fellow of IACLE (Aus.), Fellow of ASCO(Mum.)
Prof. at (Shree Bharatimaiya College of Optometry & Physiotherapy, Surat)
Life Member of Indian Optometric Association (IOA)
Associate Member of Association of Schools and Colleges of Optometry(ASCO)
Member of Optometry Council of India(OCI)
Educator Member of International Association of Contact lense Educators (Australia)(IACLE)
Mail id: ankitsvarshney@yahoo.com
Whatsapp no. +918155955820

 I have no affiliation, nor do I received financial
compensation from any of the companies or
brands used in this presentation.
14 July 2020 Optom.AnkitVarshney 2

 SPECTACLES
 CONTACT LENSES
 LASIK/ZYOTIX
 PRK
 SMILE
 ICL

Purpose
Cosmetic
Spherical
Toric
Presbyopic
Optical
Keratoconus
Bandage Lens
Drug Delivery
Myopia
Control
Therapeutic
Enhances
Performance
Color Filters

Greek derivation
 Aim is to ‘reshape’ the cornea
 Non-surgical, topographical
approach to effecting a correction
 Sometimes abbreviated to OK
ORTHO KERAT OLOGY
straight cornea knowledge

 Kerns (1976): ‘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 lenses’

 In some ways it is similar to the use of dental
braces by an orthodontist to straighten
crooked teeth.
 The main difference is that if a tooth position
is corrected for some months it will usually
stay in the new position.

 Ortho-K
 OK
 Overnight Corneal Reshaping
(OCR)
 Corneal Reshaping Therapy™
(CRT™)
 Vision Shaping Treatment™
(VST™)
 Corneal Refractive Therapy™
• Gentle Vision Shaping
System™
• Overnight Orthokeratology
(OOK)

 An effective & relatively safe way of ↓ or eliminating
manifest refractive error
 Mainly for myopia
 Hyperopia not yet treated routinely
 Not permanent
 Subject to significant variability
‒ within an individual
‒ between individuals

 School age children benefit greatly:-No more
lost contact lenses or broken frames.

 Contact lens wearers that have developed dry eyes,
discomfort or sensitivity to their lenses.
 Surgery is not in your comfort zone.

 The main purpose : 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 like:-
Firemen, Farmers, Builders
To have a lens free day.!!!

 In late 2004 a study published in an international
journal found that Orthokeratology can slow
myopia progression by an average of 50%

 Reversible
 Both eyes ‘altered’ at the same time
 No disruption to vision during treatment
 Less (or no) pain compared with Refractive Sx.
 Therapy can be halted if unfortunate effects are
experienced
 Option for children
 may slow myopia progression
ADVANTAGES OF OK

 Not a ‘permanent’ solution
 Patient may become a regular RGP
lens wearer, i.e. uses OK lens conventionally
 Amount of refractive error correctable by OK
is limited
 Potential for non-compliance
DISADVANTAGES OF OK

1508 Leonardo da Vinci illustrates the concept of contact lenses
1823 British astronomer Sir John Herschel conceptualizes practical lens design
1887 First contact lens manufactured from glass, and fitted to cover the entire eye
1939 Contact lenses first made from plastic
1948 Plastic contact lenses designed to cover only the eye's cornea
1971 Introduction of soft contact lenses
1978 Introduction of GP contact lenses
1981 FDA approval of new soft contact lenses for extended (overnight) wear
1986 Overnight wear of GP contact lenses becomes available
1987 Introduction of disposable soft contact lenses
1987 GP contacts available in next-generation fluorosilicone acrylate materials
1996 Introduction of one-day disposable soft lenses
2002 Silicone-hydrogel contact lenses first marketed
2002 Overnight orthokeratology approved by FDA
2010 Custom-manufactured silicone-hydrogel lenses become available

 Ancient Chinese thought to sleep with (small sand
bags) on the eyes to correct vision.
 Jessen Method introduced in 1962 outlined
the fundamental theory.
after Coon, 1982

 2002: Paragon CRT approved for O/N corneal
reshaping
 2004: Euclid Orthokeratology lens approved for
O/N corneal reshaping
 2004: B&L acquires Euclid (and its FDA approval)
 2004: JZS Orthokeratology lens licensed from
Euclid

 First attempt to change refractive error
 Technique used plano PMMA lenses
 Flat central fitting (Flattest k fitting)

 Failed due to Disadvantages of PMMA lens
 Decentration of lens inducing astigmatism
 Took long time to achieve a small amount of reduction
 Lens fit was unstable

 Ortho-K is used for the temporary correction of low to
moderate myopia.
 It uses four- or five curve reverse-geometry lenses in high Dk
materials in an overnight lens-wearing modality

 Centre well
 Lens are supported by their periphery curves.
 Having different zones
1. Base curve
2. Reverse (steeper) curve
3. Fitting (alignment) curve
4. Peripheral curve
4-Zone Design

Chosen 0.30 mm to 1.40 mm
flatter than the flattest
corneal curvature (flat “K”).
Reverse curve of the shaping
lens is chosen steeper than the
base curve radius.
Slightly flatter

BOZD
6.0 to 6.5
mm

Layer Thickness (mm)
Epithelium 60
Bowman’s layer 6
Stroma 450
Descemet’s membrane 10
Endothelium 6

 Significant change in corneal curvature
 Topographical change in corneal thickness:
1. primarily epithelial
2. central thinning
3. mid-peripheral thickening
4. possible alteration to corneal sagittal height

 When the pre-corneal tear film is distributed :
thinner in the center,
thicker in the periphery,
a pressure is created as the fluid tries to find equilibrium.
 This pressure is a positive (push force) in the center of the cornea
and a negative (pull force).
Positive Push Force
Negative
Pull Force

Ortho-k inhibit myopiaprogression byinducingperipheralretinalmyopic defocus*.
Peripheral hyperopic defocus
acceleratesaxial growth
Peripheral myopic defocus can
reduceaxial growth*
Ortho-K
Treatment zone
AreaofPeripheral Myopic Defocus

An example:
For a 1 D effect over a 6 mm zone, you will ‘lose’
(or redistribute) 12 mm of corneal tissue
S = Change in corneal sagittal height (mm)
td = Treatment zone diameter (mm)
D = Desired dioptric change (dioptres)
2
3
D
d
s t  BOZD
6.0
mm
Sag in
mm

ORTHOKERATOLOGY
-TREATMENT ZONE DIAMETER
• Controls degree of myopia reduction
• Smaller zone required for higher Rxs

Treatment Treatment Expected
depth diameter change
(Flattening / thinning) (‘Optic zone’)
20 mm 6.0 mm –1.75 D
20 mm 5.0 mm –2.50 D
20 mm 4.0 mm –3.75 D
20 mm 3.0 mm –6.75 D
2
3
D
d
s t 

Treatment Treatment Expected
depth diameter change
(Flattening/thinning) (‘Optic zone’)
5 mm 2-3 mm –1.00 D
7 mm 3-4 mm –1.00 D
9 mm 4-5 mm –1.00 D
11 mm 5-6 mm –1.00 D
13 mm 6-7 mm –1.00 D
15 mm 7-8 mm –1.00 D
2
3
D
d
s t 

 High motivation is required
 Level of patient’s desire for 6/6 (20/20)
 Previous contact lens wear
 Pupil diameter
▫ measure under a range of illuminations
▫ Too large pupils are problematic

1. No age restriction
2. Spherical refractive error: (-1.00 D to -5.00 D)
3. Cylindrical refractive error:
a. 1.50 D or less “with-the-rule” corneal
astigmatism
b. 0.75 D or less “against-the-rule”
astigmatism
4. Free of corneal dystrophies , degeneration and
contra indication to CL wear

 Previous failure(s) with RGP lens wear
 Diseases of the cornea, conjunctiva, or adnexa
 e.g. dry eye
 Anterior chamber inflammation/infection
 Systemic disease that affect the eye or can be
worsened by lens wear
 e.g. diabetes
 Keratoconus

 Older patients (long-term CL wearers?)
 cornea less likely to respond well
 Unrealistic patient expectations
 Low sphere power with high cylinder
 Limbus to limbus astigmatism

 Very loose/flaccid lids
 Poor responder to initial lens wear trial

 Motivation
 What do they want from OrthoK
▪ No glasses or CL’s while awake
▪ Myopia control
▪ Slower eye growth with OrthoK (Walline J, et al Br J Ophthalmol
2009;93:1181-1185)
▪ CL induced dry eye relief
▪ Presbyopia
▪ Monovision
 Prior lens wear
 SCL can be fit now
 RGP fit after 3 weeks of lens removal

 Unaided visual acuity
 Right, left and both
 Accurate Refraction: sphere-cylinder
 balanced to BVA
 Reduction of 2.00 D. myopic realistic
 Approval -1.00 to -5.00, goal -2.00 to -3.00
▪ -1.50 or less WTR astigmatism
▪ -0.75 or less ATR astigmatism

 Keratometry Readings
 Make sure the refraction matches up to the corneal
measurements.
 moderate K’s: 41.00-46.00 best
▪ steeper & flatter do not respond as well
 Topography
 Type of corneal cylinder
 Screen out any potential problems.
 Big differences in cylinder.
 Oblique axis that do not match up.
 ATR cylinder may need special attention

 Accurate measurement of corneal diameter: HVID
 Normal is 10.5-12.5 mm
 Pupil size
 Dim and normal light
▪ Usually 4-9mm
▪ Best if <6 in normal light

 Slit lamp exam
 Lids & lashes
▪ No Blepharitis
▪ No GPC
▪ No Meibomian Gland blockage

 Cornea
▪ No staining
▪ No edema
 Tear film analysis
▪ Significant dryness can be a problem
 The eye should be healthy.

 Custom designed lenses or trial set
 Define the Diameter & CurveWidths
 Calculate the AlignmentCurve
 Calculate the Peripheral Curve
 Calculate the Base Curve
 Calculate the Reverse Curve

 Base curve flatter than
reverse curve
 Reverse curve
 Alignment curve is the
“fitting” curve
 Peripheral curve provides
edge lift

 Soak lenses prior to being place on the eye, Lens must be
hydrated!!!!!
 Look at eye before placing lens on
 Insert lenses
 Judge lens centration
 Evaluate Fluorescein pattern

 Lateral centration
 Flat center
 Reserve Pooling
 Mid-peripheral Alignment
3-6 mm
 Minimal inferior edge lift
 Movement to allow tear
exchange

Peripheral Curve
Alignment Curve
Fitting Curve
Base Curve

Ideal Fit Steep Fit

Ideal Fit Flat Fit

 Lenses MUST center
 Better to be slightly tight & centered than loose & decentered
 Over-refraction
 Practice Insertion & Removal
 Sleep at least 6 hours wearing the lenses
 Return next day in morning

 Have PATIENCE
 No changes until one week post.

 Day 1
 Weeks 1-3
 Every 6 -12 months
 Check all
 Replace lenses

 Keep the lenses clean.
 Reduces the risk of Central
Staining.
 Instruct the patient
carefully on lens cleaning.
 Stress the importance of
conditioning the lens surface
prior to wear.
 Use only the
recommended solutions

 “The final contact lens that allows adequate
tear exchange and stable uncorrected vision is
considered to be the retainer lens.”
 Determine that the ‘end point’ has been
reached
 Finalize the treatment lenses
 Determine the wear schedule
 Consider ordering a spare pair
 cessation of wear for whatever reason will result
in regression of gains

 Final set of lenses used to achieve
and maintain desired result
 Overnight wear capability
 fitting characteristics
 need good centration
 oxygen supply
 lens adherence a consideration
 lenses removed in the morning after
one hour open eye

 Paragon CRT, ZCRT
(ParagonVis. Sci.: paflufocon B & D, tisilfocon A )
 Bausch & LombVST
(Bausch & Lomb Inc. : oprifoconA)

 The technique involves the provision of specialist
Orthokeratology contact lenses and a number of visits to your
practitioner.
 Each practitioner sets their own fees which may vary
dependent on the Rx being treated.

Orthokeratology by Optom Ankit Varshney

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