2. CONTACT LENS
FITTING OBJECTIVES
• provide best possible vision
• Minimize interference with corneal physiology
• Optomize lens comfort
• Relocate lens bearing area to the mid peripheral area.
3. CONTACT
LENS
OPTION
• SOFT
• Spherical thick positive lens
• Trapezoid lens
• Toric lens
• COMBINATION LENSES SYSTEM
• Piggy back lens
• Hybrid lens
• SCLERAL LENSES
• CORNEAL LENSES
• OTHER SPECIAL DESIGN
3
4. SOFT CONTACT LENS PLAY A VERY LIMITED ROLE IN
CORRECTION OF KERATOCONUS IN THE EARLY STAGES OF
PROGRESSION SOFT LENSES MAY PROVIDE ACCEPTABLE VISUAL
CORRECTION ESPECIALLY IF USED IN COMBINATION WIT
ASTIGMATIC OVER CORRECTION
TWO NEW SOFT LENSES HAVE BEEN INTRODUCED: NOVAKONE (ALDEN
OPTICAL) AND KERASOFT IC (BAUSCH & LOMB)
SOFT
LENSES
ADVANTAGE DISADVANTAGE
Higher level of comfort and
longer wearing times
Visual acuity may be variable in
cases of very high minus lenses.
They are useful where the cone
apex may be displaced
There may be reduced oxygen
transmissibility and te risk of
neovascularization
They are relatively simple to fit Low power diagnostic lenses may
may not provide accurate guide
They are useful for certain group
of patients .eg airline pilot
If the condition has progressed it
may be difficult to change to RGP
5. • ASPHERIC OR MULTICURVE LENSES
• KERA 1 AND 2
• ACUITY K
• ROSE K
MODERATE KERATOCONNUS
KERA 2
ROSE K
QUASAR KNO 7
WOODWARD KC3
Early keratoconnus
• KERA 2/3
• ROSE K
• PROFILE K
• ADVANCED
KERATOCONNUS
• LARGE DIAMETER LENSES
• S – LIM
• DYNA INTRA LIMBAL
SCLERAL LENSES
• PMMA
• GAS PERMEABLE
• Used in advanced
keratoconus where
corneal lens do not work
and corneal surgery is
contraindicated
• ASPHERIC LENSES
• Flatten in curvature from
the centre to curvature
RIGID GAS PERMEABLE LENSES
lenses of first choice
A mid to high dk/t
The aim is to provide best possible vision with maximum comfort for a long period of time
MODERATE/ ADVANCED
KERATOCONNUS
6. PIGGY BANK LENSES 6
• Used for difficult cases for instance
in cases of rgp lens intolerance,
proud nebula in keratoconus
• The system consists of a rigid lens
fitted on top of a soft lens
• The aim is to maintain same level of
visual acuity as with a single lens .
• The rgp lens should be fitted first
• Good centrartion is important
• Carring two type of lenses can be
difficult for long term.
• Try to have the patient use the same
care regime .
Hybrid lens system
The soft perm lenses(ciba
vision)
Is a hybrid lens with a rgp
centre with a sourrounded by a
soft hydrophilic skirt
• Used in rgp lens intolerance
• Provide better comfort than
rgp lenses,better
centration,reasonable visual
acuity.
• Only used in exceptional
cases as it may cause
corneal edema and neo
vascularization
• Disadvantage is frequent
breakage of lenses. Giant
papillary conjunctivitis
7. FITTING
METHODOLIES
/PHYLOSIPHIES
Three point touch
design.
• Most popular and most
widely accepted
• The aim is to distribute
contact lens as evenly as
possible between the cone
and the peripheral cornea.
• The ideal fit should show
an apical contact of 2-3
mm with mid peripheral
annulus .
• Cresent shape periphery is
quite acceptable .
• Adequate edge clearance
is required for tear
exchange.
• Works very well for small
central cones.
Apical clearance
• The lens vaults the cone and clears the
central cornea resting the para central
cornea.
• The lenses tend to be small in diameter
and small optic zone.
• The potencial advantage of reducing
central cornea scarring are outlined by
disadvantages of poor tear film, corneal
edema,poor visual acuity as a result of
bubbles trapped under the lens
• FLAT FITTING
• Places almost entire weight on the lens of
the cone.
• Good visual acuity is obtained by apical
touch
• Alignment can be achieved in early
kertatoconnus.
• This type of fitting phylosphy is useful
7
8. FITTING PROTOCOL 8
• After taking full history and information the preliminary examination should include age occupation and
motivation.
• Any history of previous contact lens intolerance or allergies should be noted.
• Full slit lamp biomicroscopy is important.
• Examine the keratometer reading ,the mires may be very distorted
• Choose the correct base curve start with the base curve equivalent to the steeper of the two keratometer
reading
• Allow the lens to settle for about 20 mins before evaluating the fluorescein pattern.
• Examine the central area , mid peripheral area and the periphery.
• Evalute the lens in the central position
