contact lens fitting in post PK and post refractive surgery

1. Post surgical contact lens fitting
Presented by – Kajal Bhagat
BOVS 3rd YEAR NAMS, BEH
Facilitator: Mr. Pankaj Ray Adhakari
Lecturer NAMS

2. Contents:
• Introduction to refractive surgery
• Post refractive surgery contact lens fitting
• Contact Lens Fitting Following Radial Keratotomy (RK)
• Contact Lens Fitting Following laser refractive surgery
• Introduction to PK(Penetrating Keratoplasty)
• Contact Lens Fitting Following PK

3. Refractive surgery:
Definition: Refractive surgery is a surgical procedure performed to correct the
refractive error (including presbyopia) of the eye and decrease or eliminate
dependency on glasses or contact lens.
Aims:
• unaided visual performance.
• reliance on spectacles/contact lens.
• sporting activities
• good cosmetic appearance
• self-esteem
• Solve contact lens wear failure

4. Classification:
Refractive surgeries
Cornea based Lenticular based Combined (bioptics)
-RK
-PRK
-LASIK
-LASEK
-SMILE
-Epi-LASIK
-Conductive
Keratoplasty
-Corneal inlays
-Clear lens extraction for
myopia
-Phakic iol
-Prelex clear lens
extraction
With use of multifocal
IOL
Combination of the
two

5. Radial keratotomy(RK):
Radial keratotomy (RK) is a refractive surgical procedure to correct
myopia, developed in 1974. In RK, incisions are made with a diamond
knife. Incisions that penetrate the corneal stroma in a depth of up to
90% of the corneal thickness

6. Photo-Refractive Keratectomy(PRK):
A corneal tissue subtraction/ablation technique in which an excimer
laser is used to remove tissue to alter the shape of the cornea. The high
energy UV light (193 nm) is delivered to the cornea through a pulsating
spot or slit

7. Laser-ASsited in situ Keratomileusis(LASIK):
The most popular laser surgery
technique in which a corneal flap
is created by a mechanical
microkeratome, the flap is folded back
revealing the clear stroma on which
the excimer laser acts and subtracts
corneal tissue.

8. LASEK (LASer Epithelial Keratomileusis):
• It is a similar procedure that combines the benefits of LASIK and PRK.
• The difference between LASIK and LASEK is how deep the cut is — in LASIK, a
laser is used to reshape our cornea by cutting deep into the outer layer of our
eyeball, while LASEK only cuts as deep as the outer layer of the cornea
(epithelium).

9. Small Incision Lenticule Extraction (SMILE):
Small incision lenticule extraction (SMILE) is a relatively new refractive
procedure designed to treat a refractive errors such as myopia,
hyperopia, presbyopia, and astigmatism. The procedure involves using
a femtosecond laser to create a corneal lenticule which is extracted
whole through a small incision without the use of an excimer laser.

10. Epi-LASIK (Epithelial laser in-situ
keratomileusis):
It is an eye surgery that is similar to LASEK. LASEK and epi-LASIK differ
because of the way the epithelial flap is created. The first procedure
uses a 20% alcohol solution, whereas epi-LASIK utilizes a mechanical
device.

11. Conductive Keratoplasty (CK):
• Conductive Keratoplasty (CK) is a
noninvasive procedure which
utilizes radiofrequency energy to
correct presbyopia and low
hyperopia with or without astigmatism.
• It can also be used to correct residual
refractive error after laser in-situ
keratomileusis (LASIK) or cataract surgery.
For more detail : https://eyewiki.aao.org/Conductive_Keratoplasty

12. Corneal inlays:
Corneal inlays, also called keratophakia, are implants placed in the
corneal stroma for correction of presbyopia.
For more detail : https://eyewiki.aao.org/Corneal_Inlays

13. Post refractive surgery contact lens fitting:
• Refractive surgery techniques sometime results in some
unexpected/unpredictable visual outcomes for which contact lenses
may be the only satisfactory form of correction.
• In many cases of high refractive error, modern techniques of
refractive surgery are incapable of correcting the ametropia fully.
However, post-surgical regression of the manifest refractive error can
occur and contact lenses may be required to obtain optimum vision.
• Fitting post-surgical patients with contact lenses can present a unique
challenge because, in many techniques, the corneal integrity is
breached and the cornea’s topography is significantly different from
normal.

14. Indications:
• Residual refractive error
• Irregular astigmatism
• Anisometropia
• Night vision problems
• Therapeutic needs
• bandage

15. POST-REFRACTIVE SURGERY
CONTACT LENS FITTING
considerations
• Corneal wound healing
• Reduced corneal
sensitivity
• Maintaining corneal
health
• Oxygen supply to the
cornea
• Need to satisfy basic
fitting principles
POST-REFRACTIVE
SURGERY
CONTACT LENS FITTING
SCL consideration
• Oxygen supply to the
cornea
• Astigmatic correction
POST-REFRACTIVE
SURGERY
CONTACT LENS FITTING
RGP consideration
• Central corneal shape
• Lens centration
problems
• Lens back surface shape
- spherical
- aspheric
- reverse geometry

16. SUGGESTED CONTACT LENS TYPES
• RGPs (high Dk/t) when:
- patient wore RGPs previously
- postsurgical scarring present
- corneal irregularities present
- post-LASIK corneal ectasia
• SCLs in cases of:
- postoperative myopia
- postoperative regular astigmatism
• Scleral lenses (gas permeable) in cases of:
- irregular corneas
-sensitive corneas

17. Contact Lens Fitting Following Radial
Keratotomy (RK)
The post RK patient is often a challenging case for a contact lens fitting.
Post RK CL fitting challenges:
• Central Vs. mid peripheral corneal topography.
• Anisometropia and aniseikonia
• Irregular astigmatism
• Elevation of incisional scars
• Corneal neovascularization
• Fluctuating refractive error
• Postoperative glare and photophobia

18. When to fit lens?
• Following RK, contact lens fitting should be delayed until the incision
have completely and regularly epithelialized and once corneal
topography and refraction have stabilization.
Different lens types and their fitting assessment:
1. RGP lens
2. Mini scleral lens
3. Reverse geometry lens
4. Hybrid lens

19. 1. RGP lens
General Principles:
The ultimate success of any rigid contact lens, regardless of its design,
is predicted on the establishment of three fitting criteria
Criteria 1
• The BOZR much be just steep enough to clear the apex of the cornea.
• Apical clearance is a necessary feature to prevent contact lens from
rocking on the corneal apex.
• Any amount of apical touch can result in lens decentration.

20. Criteria 2
An area of lens bearing (contact point) should be present in the mid
periphery along the horizontal meridian, approx. 3-4mm from the centre
of the cornea.
Criteria 3
The lens should maintain unobstructed movement along the vertical
meridian.

21. BOZR selection:
• Following RK, the cornea will exhibit significant corneal flattening with
only minimal topographical changes in the mid peripheral.
• Therefore, it is important to select a BOZR steep enough to land or
touch the mid peripheral of the cornea approximately 4mm from the
centre.
Techniques to determine radius of curvature:
• Computerized corneal mapping
• Peripheral keratometry
• Preoperative keratometry technique

22. Total diameter:
• Large total diameter (10-11 mm with BOZD 9mm)
If the walls of the incision do not heal in apposition, geographical surface
elevations occurs.
These elevations acts as a shaft on which RGP lens turns resulting the lens to
decenter.
So, large diameter lens will be required

23. Lens Fitting:
• Following RK, the center of the cornea is relatively flat and the mid-
periphery can be irregular and relatively steep.
• Rarely an ideal fitting is achieved with post-RK patient. The
practitioner’s aim should be to achieve a stable lens fit that doesnot
compromise ocular physiology.
• In general, a good fitting lens will exhibit mild central pooling with a
zone of mid-peripheral bearing. A lens that is too steep centrally can
result in bubbles trapped behind the lens because of excessive central
pooling

24. • Desirable features:
• Adequate peripheral clearance
• No inferior bubbles
• Good tear exchange
• Undesirable features:
• Excessive central fluorescein pooling
• Lens decentration
• Bubbles beneath lens
• The objective when fitting the post-RK eye is to achieve a satisfactory fit that
the patient can tolerate and that provides acceptable vision.

25. 2. Mini scleral lens:
• Diameter: 15-18 mm
• High DK material
• Benifical in highly irregular
and/or asymmetric cornea

26. 3. Reverse geometry lenses:

27. • Due to oblate shape of the post RK cornea, once mid-peripheral
alignment has been established with a diagnostic lens, excessive apical
clearance and fixed bubbles mat be present beneath the centre of the
lens.
• Reverse geometry lens design can be used in this case.

29. 4. Hybrid lens:
• SynergEyes is a high DK hybrid lens that has been used successfully.
• The lens is available in three designs for the post refractive surgery
cornea, particularly for the patients with irregular astigmatism and/or
comfort and centration issues with traditional RGP lens designs.
Fitting procedure:
• Select a diagnostic lens with a BOZR equal to the radius of the mid
peripheral cornea approx. 4mm from the centre.
• Insert lens into the eye with molecular weight fluorescein in the bowl
of the lens

30. • The soft lens skirt should move 0.25mm on blinking

31. POST-FITTING COMPLICATIONS POST-FITTING COMPLICATIONS:
• Significant corneal staining
• Recurrent corneal erosions (RCE)
• Infection
• Vascularization

32. Contact Lens Fitting Following laser refractive
surgery:
Conditions after laser refractive surgery that require contact lens
correction:
• Undercorrection of refractive error
• Overcorrection of refractive error
• Irregular astigmatism
• Decentred ablation zone

33. Contact Lens Fitting Considerations:
• level of patient motivation
• Healed cornea
• Stable topography
LENS FITTING:
• RGPs are the lenses of choice
- better vision
- good physiology
• Need to bridge the central ablated zone
• Hydrogel lens for intolerant cases

34. RGP CONSIDERATIONS:
• Larger total diameter (TD) required
• Keep BOZD small to prevent:
- adherence
- excessive tear pooling
- bubble formation
• Bearing on transition zone
• Edge clearance

35. Trial Lens Design and Fitting Following Laser Refractive Surgery :
• Due to the irregular corneal shape that exists in some post-refractive
surgery cases, keratometry may be difficult and the results unreliable.
When fitting the PRK/LASIK patient, the pre-operative K readings can be
used as a starting point for post-operative RGP lens fitting.
• There are no hard and fast rules when fitting RGP lenses after refractive
surgery. In general, similar fitting philosophies for an RGP lens on a
normal cornea are used.
• The desirable features include:
• Acceptable centration of the optic zone over the pupil.
• Adequate movement with each blink.
• Adequate tear exchange with each blink.
• Adequate edge lift providing 360° clearance.
• Absence of lens-induced corneal staining.

36. • Generally, lenses with large back optic zones (BOZDs) and TDs provide a
more satisfactory fitting as they are able to bridge or vault the ablation
zone.
Post-LASIK Contact Lens Fitting Difficulties:
• Patient disappointment
• Intolerance
• Topographical changes with time

37. Introduction to PK(Penetrating Keratoplasty)
• PK is the surgical removal of the full thickness central cornea and its
replacement with a human donor corneal graft.
• It is the most common and the most successful organ transplant
technique worldwide.

38. Contact Lens Fitting Following Penetrating
Keratoplasty:
Indications for contact lens fitting after PK:
• Anisometropia: Anisometropia is more likely to be induced when
only one eye has been operated on and a similar refractive error or
ocular condition remains in the unoperated eye.
• Regular and irregular astigmatism: Both types of astigmatism can
result from pre-existing astigmatism of either type, or simply as a result
of non-uniform or randomly uneven suture tensions around the full
circle of the PK.

39. Contact Lens Selection for Penetrating Keratoplasty:
• Soft: spherical or toric
-hydrogel
-siloxane hydrogel
• RGP: spherical, aspherical, toric
• RGP: reverse geometry
• Hybrid lens
• Piggy-back
• Scleral

40. RGP Lens:
• Rigid gas permeable lenses are the modality of choice following
penetrating keratoplasty.
• Advantages of RGP:
• Correction of irregular astigmatism
• Provide high oxygen transmissibility
• Custom designs available

41. Contact lens selection for different graft
topography:
Normal topography:
• A relatively normal corneal topography following PK is rare.
• Traditional RGP lens designs.
• Adequate static and dynamic fitting characteristics.

42. Flat central topography:
• central vaulting
• large diameter required (TD: 9.5 - 12.0 mm)
• peripheral design must be optimized
• fenestration if needed
• reverse geometry designs

43. Proud Graft Topography:
• A difficult graft to fit with a contact lens
is one that stands slightly proud of the host cornea.
• The raised step at the host-graft interface often
causes an RGP lens of moderate TD to slide off
the graft when displaced by the lid during a blink.
• large lens diameter (TD)
10.0 – 12.0 mm
• large BOZD to clear the junction
typically 8.5 – 9.0mm

44. Oblate/Plateau Graft Topography:
• Standard RGP design would result in significant apical clearance and
excessive edge clearance from the peripheral cornea.
• Consider reverse geometry.
Tilted graft topography:
• difficult to fit with an RGP lens
• lens decentration is likely
• consider custom soft lens
(sphere/toric)

45. Fitting characteristics
Try to achieve
• Stable fit
• Adequate centration
• Distribution of bearing pressures under the lens

46. Soft contact lens:
Used when RGP lenses provide
• unsatisfactory comfort
• Intolerance of other lens types
• Sutures still in place
• Piggyback fitting
Very careful follow-up is mandatory for any patient using soft lenses
following PK because the low oxygen transmissibility of conventional
hydrogel contact lenses can result in corneal oedema and peripheral
corneal vascularization.

47. Scleral lens:
Advantages:
• Secure fitting
• Stable vision
• Easy handling and maintenance
• Good oxygen supply with high Dk lenses

48. Hybrid lenses
• Improved lens centration
• Stable vision
Significant disadvantages
- poor oxygen supply
- limited parameters
- relatively fragile
- expensive

49. CLINICAL PROFICIENCY CHECHLIST:
• Corneal topography is important in the contact lens management of the postsurgical
patient because it often helps in determining the specific type of lens to be fit.
• Increasingly scleral lenses are the lens of choice in all forms of postsurgical cases.
• For full-thickness keratoplasty, irregular astigmatism is approximately twice that of
regular astigmatism; therefore, rigid GP lenses are the best option for correction.
• After a PKP, a GP lens can be fit as soon as the majority of the post-inflammation has
subsided, which can be as soon as 2 to 3 months after surgery.
• Intralimbal designs with OADs larger than 10 mm are most often the lens of choice in
all forms of corneal transplants. If the cornea is prolate, conventional GP designs are
often successful; if the corneas are oblate, a reverse geometry design is indi- cated; if
mixed astigmatism is present, a bitoric design can be successful; if a graft tilt is
present, a quadrant-specific design is recommended.
• High-Dk GP lens materials are recommended in postsurgical cases.
• In some postsurgical cases, custom soft lenses can be successful. These lenses have in-
creased center thickness and/or reverse geometry peripheral curves to provide some
assistance in masking corneal irregularity.

50. • Piggyback designs can be successful in some postsurgical cases in which GP
lenses alone do not center or are not well tolerated. A silicone hydrogel lens
material should be used in combination with a high-DK GP material. The
power should be placed in the GP lens because only approximately 20% of the
soft lens power comes through in a piggyback optical system.
• Contact lens fitting approaches in DALK are similar to PKP. Once again, corneal
to-pography will help dictate lens design selection.
• In postrefractive surgery cases, two potential outcomes necessitating GP use
are present; one is postsurgical ectasia requiring a keratoconic design or-more
likely. an oblate shape necessitating a reverse geometry design. Scleral and
hybrid designs are also options in these cases.
• Fitting post-Intacs patients can occur typically 3 months after the procedure,
and keratoconic GP designs are often successful with soft lenses and
piggyback designs presenting additional options.
• Post-trauma patients often have corneal flattening in the region of trauma.
There- fore, an intralimbal GP design can be used. If improved cosmesis and
decreased glare symptoms are indicated, a prosthetic contact lens is indicated.

51. References:

52. Thank you