Rigid gas permeable lenses are commonly used to correct vision in keratoconus, though some patients cannot tolerate them. Piggyback or hybrid lens systems can improve comfort by combining a rigid lens with a soft lens. Newer options like mini-scleral lenses and Rose K lenses are designed specifically for keratoconus, vaulting the irregular cornea to improve vision. The Boston PROSE treatment also creates a new smooth optical surface over the cornea using customized prosthetic lenses. While fitting lenses for keratoconus can be challenging, contact lenses are often able to restore vision without surgery.

1. Contact Lens Options
in
KERATOCONUS
Hira Nath Dahal
Institute of Medicine
Maharajgunj, Kathmandu
COE: Advanced Contact lens
Practice

2. Introduction
• Non-inflammatory, progressive thinning
of the cornea that results in apical
protrusion (ectasia) resulting in a high
degree of irregular myopic astigmatism
with observable structural changes appearing
in later stages.

3. • Mild to marked
impairment of vision
occurs, depending on
• extent of induced
irregular astigmatism
• Protrusion of cornea

4. • Bilateral in approximately 96% of the
cases.
• No gender predisposition
Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42(4):297-319
Zadnik K, Barr JT, Edrington TB, et al. Baseline findings in the Collaborative
Longitudinal Evaluation of Keratoconus (CLEK) Study. Invest Ophthalmol Vis Sci
1998;39(13):2537-46.

5. Management
Varies depending on state of
progression of ectasia

6. Does spectacle works in
Keratoconus?
• Yes and No
• Mild keratoconus in early stage can be
corrected with spectacles.
• As the cornea steepens and becomes more
irregular, glasses not capable of providing
adequate visual improvement.

7. Then, does soft contact lens
work?
• It is not better than spectacle lens but it works in
piggy back system
• At very early stage, this way work as equal to spectacle
does.
• But patient may not be satisfied with the level of vision
he has even though it is 6/6
• Shadow effect of texts
• Ghosting of image
• Poor night vision
• Eye fatigue on prolong reading

8. Do they have to suffer from
visual impairment ????
No.... Research in contact lens has brought tremendous
achievements
• Conventional RGP
• Aspheric RGP—latest
Mc Aspheer
• Piggy back system
• Hybrid lens system
Promising options
• Rose K family of lens
• Mini –Scleral lenses
• Rose K XL
• Mc Aspeer
• Boston prose treatment

9. Optics of contact lens!!
Eliminate corneal irregularities with
pre-corneal tear lens formed by these lenses
thus provides better visual correction

10. Rigid gas permeable lenses
• Mostly they are spherical back toric,
• Spherical back curve with peripheral toric for high
corneal astigmatism
• Multicurve or aspheric design also available (Mc
Aspheer)
• Cost effective, easily available, suitable for mild
to moderate keratoconus

11. Divided support or three point
touch
• An apical contact area of two to three millimetres, a
intermediate clearance zone and mid peripheral contact
annulus with conventional edge clearance at the
periphery.
Woodward EG. Contact lenses in abnormal ocular conditions—keratoconus. In: Phillips AJ, Speedwell
L, eds. Contact Lenses.

12. • Fitting: three point conventional fitting philosophy
• Because of three point touch, bearing on irregular
cornea, corneal haze is likely on long standing cases
Latest: superior edge alignment with
modified edge design (S- curve design)

13. On basis of shape and position of
cone
This may be helpful when selecting the design of
contact lens to fit the cornea.
1. Nipple cone:
are round and small.
usually occur near the optical axis or slightly
decentred inferonasally.
2. Sagging (oval) cone:
area of the cone is larger than nipple cones
usually displaced infero-temporally
Larger diameter contact lenses are required.

14. 3. Globus cone:
Globus cones are the largest, involving up to 75
per cent of the cornea
most challenging type to fit.

15. Aspheric RGP
• Gradually flatten from the centre towards the
periphery, approximating the steep cone vs. flat
periphery curvature relationship seen in keratoconus
• indicated for small to moderate nipple cones
• Various parameters of aspheric lenses can be
adjusted to achieve the best fit. The more advanced
and steeper the cone the greater the rate of
peripheral flattening required for the lens to
approximate the corneal shape

16. So, what if patient cannot
tolerate RGP lenses??
Ans: Combined lens system!!!
 Piggy back system
 Hybrid lens system

17. Piggy back system ????
• Rigid lens fitted over a hydrogel lens increases
comfort resulting in adequate wearing time with
good vision

18. • With availability of super-Dk silicone hydrogel and RGP
lens materials, use of piggyback system has become better
in terms of enhanced oxygen availability to cornea and
reduced risk of complication.
Potential problems ????
Handling and care of two different types of
lenses,
Hypoxia and Neovascularisation
difficulty in obtaining centration of the rigid
lens.

19. Better options than Piggy back !
Hybrid Lens system
• One way to overcome the problems with piggy-back lenses,
yet have the optics of a rigid lens with the comfort of a
hydrogel, is to fuse a soft rim onto a hard central portion.

20. • combine the benefits of rigid lens optics,
including better lens centration and decreased
aberrations, along with the comfort of a soft
lens
Potential complications…
• flexure of the GP centre lens (leading to
astigmatism and decreasing visual results),
• difficulties with insertion and removal of the
lenses, and
• tearing at the GP lens and hydrogel skirt junction.

21. Fully keratoconic designed
lenses??
•Rose k family of lens
•Scleral and Mini scleral lens

22. Rose K
• Unique keratoconus lens design with complex
computer-generated peripheral curves based on
data collected by Dr Paul Rose of Hamilton, New
Zealand.
• Standard diameter: 8.7 mm
• BOZD decreases and
axial edge lift increases
as base curve steepens

23. Rose K1 Vs Rose K2
ROSE K1
ROSE K2
Aspheric back surface
Multiple back curves

24. • Every individual Rose K2 lens has its own aspheric
(ecc)
• value on the front and back, computer designed to
minimize spherical aberration

25. Rose K2 Family of lenses
Rose K2 Xl
• Indications: Keratoconus,
Pellucid Marginal
Degeneration, Post Graft,
Corneal Rings, Post-LASIK
ectasia and dry eye
Rose K2
• Indications: Oval
Keratoconus, Nipple
Keratoconus & early Pellucid
Marginal Degeneration

26. Rose K2 NC
Indications: Moderate &
Steep Nipple Cones
Rose K2 IC
• Indications: Pellucid Marginal
Degeneration, Keratoglobus,
Oval Keratoconus, LASIK-
induced Ectasia and Post
Graft

27. Rose K2 PG
• Indications: For patients who have undergone
penetrating keratoplasty, Oval Keratoconus,
Nipple Keratoconus and Lasik

28. Scleral and Mini-Scleral lens

29. Mini scleral lenses
• Lens diameter:15.0mm and 18.0mm
1) bear on the sclera and
2) vault the cornea
Design to fit all irregular corneas which don’t tolerate any
other RGP or hybrid/Soft lens

30. Optics of Mini scleral lens !!
• Cornea is completely vaulted and almost perfect
opposite corneal shape is created by tears
pooling between the cornea and back surface of
the lens creating an equal and opposite
keratoconic surface ultimately restoring
uniform optical lens and elimination of
astigmatism.
• This result in less ghosting and much crisper
vision

31. Advantages
• better comfort,
• Less mechanical trauma to the cornea,
• better vision.

32. Boston (PROSE) scleral lens
• PROSE is an acronym for "prosthetic
replacement of the ocular surface
ecosystem".
• customized prosthetic corneo-scleral devices for each
patient’s condition and unique eye shape

33. • Prosthetic devices used in prose are transparent domes,
about the size of a nickel, made of gas permeable plastic
(Boston XO2 and Menicon Z) that allows oxygen to reach
the ocular surface
PROSE creates:
• A new transparent, smooth optical
surface over the irregular, damaged or
diseased cornea
• An expanded artificial tear reservoir
that provides constant lubrication while
maintaining necessary oxygen supply

34. Finally…
• Contact lens care of keratoconus patients is often
challenging, complex, and involved, requiring
cost and time on the part of both practitioner and
patient.
•But rewarding too
• However, contact lens wear can restore
vision without the need for surgery
throughout the lifetime of most
keratoconus patients (90%).