IOLAB Corporation makes two types of intraocular lenses for the replacement of cataracts: one from polymethyl methacrylate (PMMA) and a newer one from silicone. IOLAB ships the lens to the doctor in a two-piece case made from polycarbonate. At a price of $0.53 per case, IOLAB spends about $270,000 per year on lens cases (based on 1994 purchases of 500,000 cases). IOLAB asked us to reduce the cost of the existing lens case and to design a new case to protect and fold the silicone lens. We designed three items

Bak, Michael, \u2795

Davis, Stephen S.

Kalafus, Ken

Remer, Donald S.

Sabar, Ilan

Suntharam, Khannan

Washington, William

Wong, Yu-Tung

English

Keck Graduate Institute

Claremont Colleges
Scholarship @ Claremont
All HMC Faculty Publications and Research HMC Faculty Scholarship
1-1-1996
Intraocular Lens Case Designs
Donald S. Remer
Harvey Mudd College
Stephen S. Davis
Michael Bak '95
Harvey Mudd College
Ken Kalafus
Ilan Sabar
See next page for additional authors
This Article is brought to you for free and open access by the HMC Faculty Scholarship at Scholarship @ Claremont. It has been accepted for inclusion
in All HMC Faculty Publications and Research by an authorized administrator of Scholarship @ Claremont. For more information, please contact
scholarship@cuc.claremont.edu.
Recommended Citation
Remer, D. S., S. S.Davis, M. Bak, K. Kalafus, I. Sabar, S. Khannan, W. Washington, and Y. Wong. "Intraocular Lens Case Designs."
Journal of Industrial Engineering Design (1996). 3-5.
Authors
Donald S. Remer, Stephen S. Davis, Michael Bak '95, Ken Kalafus, Ilan Sabar, Khannan Suntharam, William
Washington, and Yu-Tung Wong
This article is available at Scholarship @ Claremont: http://scholarship.claremont.edu/hmc_fac_pub/338
Student RuthufS
Stephen S. Davis. Michael Oak. Hen Halafus.llan Sahar.
Hhannan Suntharam. Hilliam Hashington. Yu-rung Hong• •
• Client Information
IOlAS makes and sells products for cataract
surgeries, including intraocular lenses, micro-
surgical equipment and instruments, and
AmVisc (a viscoelastic material). IOLAB is the
third largest producer of intraocular lenses in
the U.S. Chiron Vision purchased IOLAB
from Johnson & Johnson in April, 1995.
• Problem Definition
IOLAB asked us to reduce the cost of the
existing intraocular lens case and to design a
new case to fold and protect silicone lenses.
• Proof of Need
a. PMMA lens case
The current lens case, consisting of a base
and a cap, costs $0.53. Other costs
include the costs of ordering, storing, and
documenting the ten different bases and
two different caps.
IOLAS ordered 500,000 lens cases in
1994 at a total cost of $270,000. For the
next five years, IOlAB estimates case
purchases of 600,000 per year.
b. Silicone lens case
IOlAB forecasts that the new silicone
lenses will continue to increase in market
share and will account for 50% of the
total intraocular lens market by 1997. To
encourage doctors to buy IOlAB's lenses,
IOlAB needs to make the lens easier to
fold. IOlAB's competitors already have
lens cases which help the surgeon fold the
lens and IOLAS does not.
tI Analysis of the Problem
a. Cataracts
Cataracts are a common disorder for
people Over 40. A cataract results when
the normally clear lens in the eye
becomes cloudy, usually frotn a natural
deterioration of the lens caused by aging.
This clouding obscures the vision of the
patient and surgery must be performed to
restore the patient's sight. Cataract surgery
involves destruction of the clouded lens
with ultrasound, removal of the lens
debris using a vacuum, and insertion of an
intraocular lens. This surgery is performed
if) about fifteen minutes and the patient
goes home with clear vision and minimal
pain.
b. Intraocular lenses
An intraocular lens (see Figure 1) is a
small diameter optic (5-7 mm) with
haptics. or loops, protruding from the side
of the lens. Tile haptics center the lens in
the eve.
Figure 7: Three 70LAB lenses
IOlAB makes lenses from two types of
materials: silicone and polymethyl
methacrylate (PMMA). Silicone lenses have
two advantages over PMMA lenses:
1. silicone lenses do not break as easily as
PMMA lenses, and
2. a flexible silicone lens of the same optic
diameter as a PMMA lens can be folded in
half like a taco. The folded lens can be
inserted into the eye where the lens
unfolds and regains its original shape. A
folded silicone lens requires an incision of
only 3~4 mm, instead of the 5-7 mm
needed to insert an unfolded PMMA lens:
Small incisions « 4 mm) do not require
stitches and lead to fewer post-surgical
complications and faster patient
recoveries.
! Spring 1996 Journal of Industrial Engineering Design
Figure 6: Folding assistant with lens
., Silicone Case Designs
Folding the silicone lens-for'insertion into the
eye requires two pairs of forceps and manual
dexterity. [OlAS asked us for cases which
1. fold the lens,
2. protect the lens from damage,
3. secure the lens in place,
4. allow inspection of the optic,
5. work with IOlAS's injector system, and
6. do not infringe on any patents.
The folding assistant has a ridge in the
middle (see Figure 4:A), two grooves on
either side of the ridge (see Figure 4:8),
and two ledges that support the edges of
the lens (see Figure 4:C). After removing
the lens from the base, the surgeon places
the lens on the folding assistant. The lens
is placed on the ridge along the 6 and 12
We designed seven lens cases. The two best
are the folding assistant (see Figure 4) and the
dual-flex injector (see Figure 7). The folding
assistant snaps into the well of the existing
case and allows the surgeon to fold the lens
with one pair of forceps. The dual-flex
injector folds the lens and pushes the lens out
of the case where the folded lens can be
grabbed with one pair offorceps or the lens
can be placed directly into an injector system
(mechanical device for easier insertion of the
lens into the eye).
1. Folding assistant
The folding assistant is an injection
molded part (see Figure 4) which snaps
into the irrigation well of the current lens
case (see Figure 5). The folding assistant
allows the surgeon to fold the lens with
only one pair of forceps.
Figure 4: Folding assistant
We designed a lens case which holds the
lens in place with pressure on the top and
bottom surfaces of the lens optic (see Figure
3). A rubber spring in the bottom ofthe case
adjusts to the center thickness of the lens.
The exterior of the case looks like a contact
lens case and is about the same size as
IOlAS's current lens case. The base and cap
are connected by a flexible strap: the cap
folds over to cover the base. The
manufacturing, material, and assembly costs
will total about $0.30, twenty cents less than
the price of the current lens case.
Figure 3: Lens case assembly
Figure 5: Folding assistant in well
4. remain intact during shipping,
5. protect the lens, and
6. fit in the existing secondary packaging.
B
I
&&
d. Ideas for cost reduction
After looking at a breakdown of the
molding costs of the case, we saw three
area for cost reduction:
1. change the manufacturing process,
2. change the case material, and
3. reduce the number of different bases
and caps.
Figure 2: JOLAB lens case
A
c. Current lens case
Both the PMMA and the silicone lenses
are packaged in the same case. The
current case is made from polycarbonate
and consists of a base and cap (see:Figure
2:A and Figure 2:B). Plastic pins inside the
base keep the lens from sliding in the case
thus preventing scratches on the optics
and brokenhaptics.
IOlAS uses ten different bases and two
different caps. Nine bases are for PMMA
lenses and the tenth base is for silicone
lenses. The bases are designed around the
diameter of the lens optic and the caps are
designed for different lens diopters.
The following complaints about the case
have been voiced by IOlAB employees and
a doctor:
1. the case is difficult to open,
2. the lenses stick to the cap when the case
is opened,
3. the lenses are difficult to remove from the
case, and
4. the lenses arrive with damaged optics and
broken haptics.
The best option is to build auniversal case -
a case which can hold any of IOlAS's
PMMA lenses (seeTable 1).
• Universal Case Design
Any lens case must
1. be sterilizable by Ethylene Oxide (Eta),
2. be translucent, .
3. be easy to use;
journal of Industrial.Engineering
Table1..Comparison of cost reduction ideas
Journal of Industrial Engineering Design
• Recommendations
We recommend IOLAB:
1. build the PMMAlens case,
2. develop the dual-flex injector case, and
3. build and sell the folding assistant as an
addition to the existing case or as a
separate: piece which can be reused by
the doctor.
4. IOLAB is now evaluating these
recommendations.
• Economic Evaluation
IOLAB requires a payback period less than
three years and a discounted cash flow rate
of return greater than 15%.
Table 1 summarizes the savings for each of
our cost reduction ideas. A universal case is
the best option.
• Acknowledgments
We would like to thank Professors-Joe King
and Phil Cha at Harvey Mudd College for
their assistance with the case designs and
David S. Howard and Dr. Charles S.
Sherwood at IOlAB for their guidance.
• Tools and Methods
We used I-DEAS Master Series by SDRC on
Hewlett Packard computers to make
drawings and to do finite element analyses of
the existing case.
Advantages:
1. Onemotion to fold and eject lens,
2. injector compatible,
3. no forceps required, and
4. in-case inspection of lens optic.
enough to push the lens out of the case.
To prevent the lens from folding the wrong
way, the soft, curved plastic piece is
positioned a short distance below the
lens. If the lens folds down, the plastic
piece forces the lens to bend correctly.
To design the rubber spring inside the new
case, we considered two situations:
1. the pressure on the lens when the lens
and case are in static equilibrium (to
prevent excessive deformation of the lens
from creep, the pressure cannot exceed
203 psig), and the maximum pressure on
the lens and the maximum displacement
of the lens caused by an impact (the
pressure cannot exceed 10,500 psig, the
compressive yield strength of PMMA).
Idea Payback Period Discounted Cash Flow Annual Savings
Rate of Return
retool molds 3 years, 8 months 26% $140,000
universal case < 1 year 230% $140,000
Advantages:
a. attachment for current case,
b. one piece - no moving parts,
c. one pair of forceps folds lens,
d. successful tests, and
e. low cost (about _$0.11 per case).
2. Dual-flex injector
This case has two -sliders (see Flgure z.A)
and a flexible, curved plastic piece (see
Figure 7:8). Grooves cut in the tips of the
two sliders hold the lens (see Figure 7:C).
The flexible piece is folded and sits
between the two sliders. Pushing the
sliders along tracks in the outer shell
squeezes the edges of the lens together
and folds the lens. The sliders also
compress the flexible plastic piece
causing the piece to extend vertically.
When the lens is almost completely
folded, the flexible piece is extended far
We made two folding assistants: one from
aluminum and the other from
polypropylene.
Figure 7: Dual-flex injector
(outer shell not shown)
o'clock axis of the optic (see Figure 6).
The side edges of the optic lie on the
ledges. The surgeon places the forceps on
the edges of the optic and pushes the
edges down into the grooves of the
folding assistant. The grooves allow the
lens to be folded over the ridge. The
surgeon then lifts the folded lens out from
the groove with the pair of forceps.
/' -/? '7 ~
"1\\ .1
~-uI~"- /B
~
-A-
Spring 1996


Intraocular Lens Case Designs

Scholarship@Claremont

Claremont CollegesScholarship @ ClaremontAll HMC Faculty Publications and Research HMC Faculty Scholarship1-1-1996Intraocular Lens Case DesignsDonald S. RemerHarvey Mudd CollegeStephen S. DavisMichael Bak '95Harvey Mudd CollegeKen KalafusIlan SabarSee next page for additional authorsThis Article is brought to you for free and open access by the HMC Faculty Scholarship at Scholarship @ Claremont. It has been accepted for inclusionin All HMC Faculty Publications and Research by an authorized administrator of Scholarship @ Claremont. For more information, please contactscholarship@cuc.claremont.edu.Recommended CitationRemer, D. S., S. S.Davis, M. Bak, K. Kalafus, I. Sabar, S. Khannan, W. Washington, and Y. Wong. "Intraocular Lens Case Designs."Journal of Industrial Engineering Design (1996). 3-5.AuthorsDonald S. Remer, Stephen S. Davis, Michael Bak '95, Ken Kalafus, Ilan Sabar, Khannan Suntharam, WilliamWashington, and Yu-Tung WongThis article is available at Scholarship @ Claremont: http://scholarship.claremont.edu/hmc_fac_pub/338Student RuthufSStephen S. Davis. Michael Oak. Hen Halafus.llan Sahar.Hhannan Suntharam. Hilliam Hashington. Yu-rung Hong• •• Client InformationIOlAS makes and sells products for cataractsurgeries, including intraocular lenses, micro-surgical equipment and instruments, andAmVisc (a viscoelastic material). IOLAB is thethird largest producer of intraocular lenses inthe U.S. Chiron Vision purchased IOLABfrom Johnson & Johnson in April, 1995.• Problem DefinitionIOLAB asked us to reduce the cost of theexisting intraocular lens case and to design anew case to fold and protect silicone lenses.• Proof of Needa. PMMA lens caseThe current lens case, consisting of a baseand a cap, costs $0.53. Other costsinclude the costs of ordering, storing, anddocumenting the ten different bases andtwo different caps.IOLAS ordered 500,000 lens cases in1994 at a total cost of $270,000. For thenext five years, IOlAB estimates casepurchases of 600,000 per year.b. Silicone lens caseIOlAB forecasts that the new siliconelenses will continue to increase in marketshare and will account for 50% of thetotal intraocular lens market by 1997. Toencourage doctors to buy IOlAB's lenses,IOlAB needs to make the lens easier tofold. IOlAB's competitors already havelens cases which help the surgeon fold thelens and IOLAS does not.tI Analysis of the Problema. CataractsCataracts are a common disorder forpeople Over 40. A cataract results whenthe normally clear lens in the eyebecomes cloudy, usually frotn a naturaldeterioration of the lens caused by aging.This clouding obscures the vision of thepatient and surgery must be performed torestore the patient's sight. Cataract surgeryinvolves destruction of the clouded lenswith ultrasound, removal of the lensdebris using a vacuum, and insertion of anintraocular lens. This surgery is performedif) about fifteen minutes and the patientgoes home with clear vision and minimalpain.b. Intraocular lensesAn intraocular lens (see Figure 1) is asmall diameter optic (5-7 mm) withhaptics. or loops, protruding from the sideof the lens. Tile haptics center the lens inthe eve.Figure 7: Three 70LAB lensesIOlAB makes lenses from two types ofmaterials: silicone and polymethylmethacrylate (PMMA). Silicone lenses havetwo advantages over PMMA lenses:1. silicone lenses do not break as easily asPMMA lenses, and2. a flexible silicone lens of the same opticdiameter as a PMMA lens can be folded inhalf like a taco. The folded lens can beinserted into the eye where the lensunfolds and regains its original shape. Afolded silicone lens requires an incision ofonly 3~4 mm, instead of the 5-7 mmneeded to insert an unfolded PMMA lens:Small incisions « 4 mm) do not requirestitches and lead to fewer post-surgicalcomplications and faster patientrecoveries.! Spring 1996 Journal of Industrial Engineering DesignFigure 6: Folding assistant with lens., Silicone Case DesignsFolding the silicone lens-for'insertion into theeye requires two pairs of forceps and manualdexterity. [OlAS asked us for cases which1. fold the lens,2. protect the lens from damage,3. secure the lens in place,4. allow inspection of the optic,5. work with IOlAS's injector system, and6. do not infringe on any patents.The folding assistant has a ridge in themiddle (see Figure 4:A), two grooves oneither side of the ridge (see Figure 4:8),and two ledges that support the edges ofthe lens (see Figure 4:C). After removingthe lens from the base, the surgeon placesthe lens on the folding assistant. The lensis placed on the ridge along the 6 and 12We designed seven lens cases. The two bestare the folding assistant (see Figure 4) and thedual-flex injector (see Figure 7). The foldingassistant snaps into the well of the existingcase and allows the surgeon to fold the lenswith one pair of forceps. The dual-flexinjector folds the lens and pushes the lens outof the case where the folded lens can begrabbed with one pair offorceps or the lenscan be placed directly into an injector system(mechanical device for easier insertion of thelens into the eye).1. Folding assistantThe folding assistant is an injectionmolded part (see Figure 4) which snapsinto the irrigation well of the current lenscase (see Figure 5). The folding assistantallows the surgeon to fold the lens withonly one pair of forceps.Figure 4: Folding assistantWe designed a lens case which holds thelens in place with pressure on the top andbottom surfaces of the lens optic (see Figure3). A rubber spring in the bottom ofthe caseadjusts to the center thickness of the lens.The exterior of the case looks like a contactlens case and is about the same size asIOlAS's current lens case. The base and capare connected by a flexible strap: the capfolds over to cover the base. Themanufacturing, material, and assembly costswill total about $0.30, twenty cents less thanthe price of the current lens case.Figure 3: Lens case assemblyFigure 5: Folding assistant in well4. remain intact during shipping,5. protect the lens, and6. fit in the existing secondary packaging.BI&&d. Ideas for cost reductionAfter looking at a breakdown of themolding costs of the case, we saw threearea for cost reduction:1. change the manufacturing process,2. change the case material, and3. reduce the number of different basesand caps.Figure 2: JOLAB lens caseAc. Current lens caseBoth the PMMA and the silicone lensesare packaged in the same case. Thecurrent case is made from polycarbonateand consists of a base and cap (see:Figure2:A and Figure 2:B). Plastic pins inside thebase keep the lens from sliding in the casethus preventing scratches on the opticsand brokenhaptics.IOlAS uses ten different bases and twodifferent caps. Nine bases are for PMMAlenses and the tenth base is for siliconelenses. The bases are designed around thediameter of the lens optic and the caps aredesigned for different lens diopters.The following complaints about the casehave been voiced by IOlAB employees anda doctor:1. the case is difficult to open,2. the lenses stick to the cap when the caseis opened,3. the lenses are difficult to remove from thecase, and4. the lenses arrive with damaged optics andbroken haptics.The best option is to build auniversal case -a case which can hold any of IOlAS'sPMMA lenses (seeTable 1).• Universal Case DesignAny lens case must1. be sterilizable by Ethylene Oxide (Eta),2. be translucent, .3. be easy to use;journal of Industrial.EngineeringTable1..Comparison of cost reduction ideasJournal of Industrial Engineering Design• RecommendationsWe recommend IOLAB:1. build the PMMAlens case,2. develop the dual-flex injector case, and3. build and sell the folding assistant as anaddition to the existing case or as aseparate: piece which can be reused bythe doctor.4. IOLAB is now evaluating theserecommendations.• Economic EvaluationIOLAB requires a payback period less thanthree years and a discounted cash flow rateof return greater than 15%.Table 1 summarizes the savings for each ofour cost reduction ideas. A universal case isthe best option.• AcknowledgmentsWe would like to thank Professors-Joe Kingand Phil Cha at Harvey Mudd College fortheir assistance with the case designs andDavid S. Howard and Dr. Charles S.Sherwood at IOlAB for their guidance.• Tools and MethodsWe used I-DEAS Master Series by SDRC onHewlett Packard computers to makedrawings and to do finite element analyses ofthe existing case.Advantages:1. Onemotion to fold and eject lens,2. injector compatible,3. no forceps required, and4. in-case inspection of lens optic.enough to push the lens out of the case.To prevent the lens from folding the wrongway, the soft, curved plastic piece ispositioned a short distance below thelens. If the lens folds down, the plasticpiece forces the lens to bend correctly.To design the rubber spring inside the newcase, we considered two situations:1. the pressure on the lens when the lensand case are in static equilibrium (toprevent excessive deformation of the lensfrom creep, the pressure cannot exceed203 psig), and the maximum pressure onthe lens and the maximum displacementof the lens caused by an impact (thepressure cannot exceed 10,500 psig, thecompressive yield strength of PMMA).Idea Payback Period Discounted Cash Flow Annual SavingsRate of Returnretool molds 3 years, 8 months 26% $140,000universal case < 1 year 230% $140,000Advantages:a. attachment for current case,b. one piece - no moving parts,c. one pair of forceps folds lens,d. successful tests, ande. low cost (about _$0.11 per case).2. Dual-flex injectorThis case has two -sliders (see Flgure z.A)and a flexible, curved plastic piece (seeFigure 7:8). Grooves cut in the tips of thetwo sliders hold the lens (see Figure 7:C).The flexible piece is folded and sitsbetween the two sliders. Pushing thesliders along tracks in the outer shellsqueezes the edges of the lens togetherand folds the lens. The sliders alsocompress the flexible plastic piececausing the piece to extend vertically.When the lens is almost completelyfolded, the flexible piece is extended farWe made two folding assistants: one fromaluminum and the other frompolypropylene.Figure 7: Dual-flex injector(outer shell not shown)o'clock axis of the optic (see Figure 6).The side edges of the optic lie on theledges. The surgeon places the forceps onthe edges of the optic and pushes theedges down into the grooves of thefolding assistant. The grooves allow thelens to be folded over the ridge. Thesurgeon then lifts the folded lens out fromthe groove with the pair of forceps./' -/? '7 ~"1\\ .1~-uI~"- /B~-A-Spring 1996

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Intraocular Lens Case Designs

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