Basic GP Multifocal Contact Lens Fitting
and Problem Solving
Stephen P. Byrnes, OD, FAAO
Private Practice – Londonderry, NH
Academic Consultant – Bausch & Lomb
Boston Products Division
byrnes579@aol.com
Choices for the correction of Presbyopia
• Spectacles
– Bifocal or progressives
– Multiple pairs
• Readers
(over contacts)
• Drug store magnifiers
• Contact lenses
– Soft or GP
• Monovision
• Simultaneous vision
– Concentric bifocal
– Aspheric /Muti-aspheric (progressive)
• Translating Vision
– Segment
– Multi-aspheric
– Sphere / asphere
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Demographics
A boomer turns 50 every 7.5 seconds
People live ½ their lives as presbyopes
94% > age 50 need correction
Financially able
Desire to look
Youthful
Baseline Exam Requirements
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Vision requirements
Current / previous contact lens problems
Current manifest refraction
Current K readings
External Examination
– Eyelid position
• Upper eyelid’s relationship to the superior cornea / limbus
• Lower eyelid’s relationship to the lower cornea / limbus
• Vertical aperture
Eyelid muscle tone / elasticity
– Horizontal visible iris diameter
– Pupil size (bright and dim) and location
• Slit Lamp examination
– Eye Lids
– Conjunctiva
– Cornea
– Anterior chamber
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Evaluate these four patients.
What are the obstacles to fitting these patients with Multifocal GP Contact
Lenses?
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Keratometry OU
44.00 sph
44.00 / 45.75@90
44.00 / 45.75@180
47.00 / 47.75@100
RX OU
Add OU
- 1.75 Sph
+1.50
-1.75 -1.75 x 180
+2.00
-1.75 – 2.50 x 90
+1.25
-9.50 -0.50 x 010
+1.50
Patient Selection Criteria
Early and mature presbyopes
Good motivation
Realistic expectations
– Visual performance
– Lifestyle impact
Good hygiene
Defining the patient’s visual needs
• What does the patient do?
– Job
– Hobbies
• How demanding is the patient?
– Perfectionist 20/10
– Lives in a 20/40 world
• What is the patient’s best visual acuity with spectacles?
– Distance – Intermediate – Near
– Required range of vision
The patient’s real vision problem relates to distance intermediate and near vision
tasks encountered every day.
What the patient wants is….
Setting Expectations:
What the patient may have to accept is….
Simultaneous Vision
Explained
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Design Features of Soft Lenses:
Aspheric Anterior Surface
You have fit the patient with soft multifocal contact lenses and tweaked the
prescription. But the patient says “ I want…”
Trial Fitting
Choose a Multi-focal GP CL Trial Set
Use Nomogram to select initial lens
– BC & LD
Over-refract if fit is acceptable
– Determine best distance vision
– Determine best near vision
Compare actual O/R to calculated O/R
Determine the GP Lens
Trial Lens 7.50 / -3.00 / 9.2
Ks 44.25 / 45.75 @90
Spec Rx -4.00 – 1.50 x 180
Distance Power
Tear lens power = BC (diopters) – Flat K (diopters)
X = 45.00 D – 44.25 D
X = +0.75 D
Rx (corneal plane) = tear lens power + trial lens power + x
-3.75 = +0.75 +(-3.00) + x
X = -1.50
Order 7.50 / -4.50 / 9.2
Bifocal / Multifocal
GP Designs
Design # 1
Simultaneous Vision GP Multifocal
• Aspheric Base curve aligns to the cornea
– Provides the progressive add power
• Ability to obtain +2.00 Add
– Hyperbolic Curve is fit 4 D steeper than flat K
• High Dk material is recommended
Design #1
Simultaneous Vision GP Multifocals
VFL® 3
• Simultaneous Vision GP Multifocal contact lenses should not translate during
primary or secondary gaze.
• Regardless of eye position, the lens should remain centered on the cornea
with the optical center directly in front of the pupil.
• The patients will be able to focus on near reading tasks, or their computer
screen, or an object across the street.
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Refining the fit with VFL 3 lenses.
Steepen the Base Curve to make the contact lens center better.
The steep base curve relative to the flatter cornea causes the cornea to
steepen temporarily – spectacle blur.
Translating GP Multifocal Lens Designs
Simultaneous vision enhanced by Translation
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GP multifocal contact lenses are center distance lens designs.
The lenses must center on the cornea for distance and translate upward
during down gaze for enhanced near vision
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A 9.5 mm lens centered on an 11.25 mm cornea is 0.875 mm from the limbus.
How far can the contact lens translate on this cornea during down gaze?
Where does the near power zone reposition in relation to the visual axis?
If the contact lens is de-centered nasally or temporally during primary gaze, the
intermediate and near power zones are closer to the visual axis.
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A smaller lens on the same cornea can translate further.
In this case the centered contact lens is 1.025 mm from the limbus.
More room to translate means greater potential for higher add effect.
Design # 2 Boston® MultiVision
Back Surface: Multi-aspheric with reverse
periphery
Front Surface: Sphere
(optional front aspherics for more add)
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The Boston MultiVison multifocal has the near zone 3.5 mm from the
geometric center of the contact lens.
This lens needs to translate how far to position the near zone in front of the
visual axis?
The Boston MultiVision multifocal contact lens needs to be centered on the
eye to maximize distance vision.
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In this example note how steepening the base curve helps the lens to center.
Also note as the base curve steepens the peripheral reverse geometry curve
also steepens.
Boston MultiVision® High Add
This example demonstrates how a flat peripheral cornea can impede the lens
translation during downgaze.
Design # 3
S-Form Technology
ESSential™ Multifocal Family
Back surface has spherical distance zone and s-curve multi-aspheric
intermediate / near zones
Two basic back surface s-form designs
– Essential
– Essential Extra
3 series - S-form lathing generates Add
– Series 1 largest distance Zone
– Series 2 smaller distance Zone
– Series 3 smallest distance Zone
CSA front surface Enhancement option
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The ESSential Multifocal contact lens has a nearly spherical central distance
zone.
The s-form technology generates the intermediate and near power zones
closer to the geometric center of the lens compared to the Boston MultiVision.
This slide demonstrates the change in lens position and movement as the
base curve is changed.
Note also the change in distance vision, near vision and comfort associated
with the base curve change.
Changing the Lens Diameter changes the Edge Lift of the contact lens.
This changes lens position and movement.
The effect of lid interaction alters the lens performance
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Changing the Series changes the size of the distance zone and the sag of the
lens.
This changes lens centration and movement, impacts vision and comfort.
ESSential Xtra™
Advantages
Extra oxygen – Boston XO
Increases wearing time
Less corneal distortion
Lower edge lift
Improves lens comfort
Larger distance optic zone
Improves lens centering
Less corneal distortion –less spectacle blur
Disadvantages
Lower edge lift design limits Translation
Limits ADD – can’t always get there
ESSential 9.5 / 7.50 ESSential Xtra 9.5 / 7.50
Series 3
Series 3
The ESSential Xtra has a larger distance zone than the original ESSential.
The larger zone decrease glare when the pupil dilates at night
Review
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Patient selection
– Needs and Expectation
– Ks and Spectacle Rx
– Patient’s physical features
Lens selection
– Lens design
– Fitting characteristics
Problem Solving
Thank You