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Fitting Soft Contact Lens Fitting of contact lens

VIEWS: 109 PAGES: 18

									SOFT TORIC CONTACT LENS




                    Fitting Soft Contact Lens

                                      Prof. Dr. Samiha Aboulmagd MD
                                           H d of O hth l l
                                           Head f Ophthalmology
                                                 Department
                                            Al-Azhar University



                                                                      1
               2010




                Fitting of contact lens
                 Power
                 Diameter
                 Base curve




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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                  1
SOFT TORIC CONTACT LENS




                Fitting of soft contact lens
                   Power same as spectacles

                If spherical above 4 D go to table as have to
                   put into consideration the vertex distance
                                 -5….-4.75        +5…..+5.25
                If cylinder is less than 1D get its spherical
                   equivalent and add it to sphere
                If cylindrical more than 1 D use toric contact
                   lens
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                Prof.Dr.S.Aboulmagd 2010




                Fitting of soft contact lens
                Diameter
                Usually as large as or larger than the
                 corneal diameter in order to maintain
                 centration and stability


                      12mm                 13mm   14mm         14.7mm




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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                2
SOFT TORIC CONTACT LENS




                Fitting of soft contact lens
                   Base curve
                    Measured by the keratometer and
                    transformed to base curve table
                   Because of the large diameter, they
                    should be fit Flatter than the flattest
                    K
                   Lens diameter & base curve are
                    inversely related
                                                          5
                Prof.Dr.S.Aboulmagd 2010




                Fitting of soft contact lens
                                                fit,
                  In order to arrive to the same fit
                the base curve of the lens selected
                  should be flattened as the lens
                  diameter is increased
                Example:
                   a pe
                7.7________ 13mm
                8.0 ------------- 14mm
                                                          6
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                      3
SOFT TORIC CONTACT LENS




                Fitting of soft contact lens
                 Small eyes require smaller diameters
                  and steeper base curves
                 Larger eyes require larger diameters
                  and flatter base curves
                  So t e ses a e tted atte than the
                 Soft lenses are fitted flatter t a t e
                  flattest K
                 Movement 0.5mm to 1.0mm

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                Prof.Dr.S.Aboulmagd 2010




                Fitting of soft contact lens
                  Position :
                it should completely cover the cornea
                The uncovered cornea will show
                   irritation and staining.
                                    good clear,
                 Vision must be good, clear constant
                   before during and after blinking.


                                                           8
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                       4
SOFT TORIC CONTACT LENS




                 Soft Lens Evaluation
                 Diameter)
                (Diameter)
                     centering
                Lens centering.
                   – Should cover the complete cornea [ use
                     lens diameter 1.5-2 mm larger than the
                     horizontal visible diameter].
                   – This is observed by using a
                     biomicroscope and shining the beam at
                     the edge of the lens which should be
                     resting on the sclera.


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                Prof.Dr.S.Aboulmagd 2010




                  Soft Lens Evaluation Cont.

                 Movement  while patient is looking up
                     –Mov.will vary between 0.5 and 1.0 mm.
                     –Keratometry =
                        how the lens is fitting on the cornea
                          – mires clear at all times  proper lens fit


                             +      +      +     + +         +

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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                      5
SOFT TORIC CONTACT LENS




                Soft Lens Evaluation
                Cont.(B.C)
                Cont.(B.C)
                    – mires are clear before the blink blurred after
                    and then clear once again
                    .: Too flat  go for steeper                 BC or   diameter


                                 +             + +       +   + +         +
                    – mires are blurry before the blink clear after
                    and then blurry once again
                           .: too steep  go for flatter BC or diameter

                            +        x     +    +    +       +   +   +       +
                                                                                    11
                Prof.Dr.S.Aboulmagd 2010




                Evaluating the Fit for Soft
                CL.(Cont.).
                   – Why:
                        • The blurring mires are caused by the
                          vaulting of the lens over the apex of the
                          cornea.
                        • The mires clear since the pressure of the lid
                          places the lens in the correct area for a
                          moment
                          moment.




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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                                 6
SOFT TORIC CONTACT LENS




                TORIC CONTACT LENS
                   Toric contact lens can be either
                    – Soft
                    – RGP
                   WHICH?? One??
                    meticulous patients prefer RGP as it
                      i      h      i
                    gives a sharper image, normall
                    individuals don’t notice the
                    difference
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                Prof.Dr.S.Aboulmagd 2010




                How Does an Astigmatic See ?




                 Most people would         However, people with
                 see a stopwatch           astigmatism see a
                 this way                  distorted image.


                                                                  14
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                               7
SOFT TORIC CONTACT LENS




                Astigmatic patient:

                    If you have an astigmatic patient and you
                   told him that contact lenses are n`t for you,
                   it may be worth taking another look.

                   Many people with astigmatism
                   can achieve good vision with today`s
                   specially designed
                   Toric contact lens.
                                                             15
                Prof.Dr.S.Aboulmagd 2010




                Available Brands Of Toric CL




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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                           8
SOFT TORIC CONTACT LENS




                Specially Designed Toric Soft
                CL.
                  They correct astigmatism by
                  having more than one power shaped into them,
                  and by having a stabilizing mechanism
                  to keep the contact lens relatively stable on the eye
                  when you blink, look up, down or from side to side.




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                Prof.Dr.S.Aboulmagd 2010




                Specially Designed Toric Soft
                CL.
                      stabilizing mechanism




                                                Le-Torque design

               Double slab- off design

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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                  9
SOFT TORIC CONTACT LENS




                As a Contact Lens Practitioner
                It is your responsibility to decide which
                   type of contact lens the patient should
                   be wearing:               Daily – extended
                   – Regarding the duration: Fr.replacement - disposable
                   – Spherical or Toric, according to the amount
                     of astigmatism present and how much the
                     lens would correct.
                The patient can decide if he needs his
                 lens coloured or not.
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                Prof.Dr.S.Aboulmagd 2010




                When to Use Toric?
                                    CL
                  If spherical soft CL. Do not provide
                     good VA.

                  If cylinder power is over 1.0 D.

                  If cylinder power is greater than
                     spherical power.
                                                                    20
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                   10
SOFT TORIC CONTACT LENS




                Procedure: -6.0 X -2.0 X 180
                                                     -8
                 Transport to minus cylinder
                                                               -6
                 Place Rx on the optical cross
                 Compensate for vertex distance          - 7.37
                in each meridian if +/- 4 and over             - 5.62
                 Take power off the optical cross

                               ORDER
                - 5.62 x –1.75 x 180……………..
                - 5.5 x –1.75 x 180                       21
                Prof.Dr.S.Aboulmagd 2010




                Check the Axis Marking on the Lens
                Depending on the Lens Type


                    Some will have one marking that
                     should position at 6 o`clock.
                    Others will have 3 marking at 6 o`clock
                     area separated by 20 or 30 degrees.
                    Some at the 3 + 9 o`clock observe and
                     use the LARS.
                    Or CAAS
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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                11
SOFT TORIC CONTACT LENS




                  Toric Soft Lens Evaluation
                  Cont.
                  Axis
                     – Check the axis marking on the lens
                       depending on the lens type




               CA
                                             CAAS                             AS

                  Left add                   LARS               Right subtract
                                                                                   23
                  Prof.Dr.S.Aboulmagd 2010




                  Important Tip
                                                    One hour = 30 degree



              L                                                                  R


                  ADD                                                      SUBTRACT


                            10                  180                 170

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                  Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                                12
SOFT TORIC CONTACT LENS




                 Toric Soft Lens Evaluation
                 Cont.                      LARS

                 Axis                                                  CAAS
                           Left eye
                    Sp RX: - 2.0 x - 1.5 x 170
                                                      -15

                Trial CL lens: - 2.0 x – 1.5 x 180
                                                            Lens marking is 15 to right


                    Lens RX to order: – 2.0 x – 1.5 x 155

                     NOTE LARS SYSTEM APPLIED TO SPECTACLE AXIS
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                  Prof.Dr.S.Aboulmagd 2010




                                                                                   LT
                 Trial lens selection                             RT

                                                                   s               A

             1. Trial lens should be as close as possible to the spectacle lens
                allowing for vertex correction for powers more than -4D.
             2. Cylinder power similar and if not available the lower power.
             3. Axis should be the same, but if not available and falls between two
                available axes, the lens selected will depend on
                which eye is being fitted, as nasal rotation is more likely.
                         y        g       ,                               y
                   Rx: -2.5/-1.5x 15            Right eye: -2.5/-1.5 x 10 …. subtract
                                                Left eye: -2.5/-1.5 x 20……..add

                        Rx: -3.25/-1.25 x 5          Right eye: -3.25/-1.25 x180
                                                     Left eye : -3.25/-1.25 x 10
                                                                               26
                  Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                                  13
SOFT TORIC CONTACT LENS




               Evaluating the Fit for Toric
               Soft CL.(Cont.).
                       acuity
                Visual acuity.
                   Each eye checked then both together.
                   Observe if blurring occurs with blink as
                    keratometer.
                        If occurs lens fit is flat.
                When performing an over refraction if
                 a spherical is found a sphere is
                 added to the lens power
                                                              27
                Prof.Dr.S.Aboulmagd 2010




                Evaluating the Fit for Toric
                Soft CL.(Cont.).
                Allow the lens to settle on the eye for
                 10-20 minutes before you judge the
                 lens fit.




                                                              28
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                           14
SOFT TORIC CONTACT LENS




                Toric Soft Lens Evaluation
                (Summary).
                    Visual acuity       Power
                    Lens centering (over sclera)
                    Movement :
                       – No rotation or less than 15 after blinking in 1ry
                         2ry & 3ry eye movement
                       – 0.5 - 1.0 mm
                    Keratometry:
                       – If blurred after movement  flat
                       – If clears after movement  steep
                    Axis LARS              CAAS

                                                                       29
                Prof.Dr.S.Aboulmagd 2010




                Problems associated with fitting
                soft lenses
                 Hazy or variable vision
                  – Check power, lens not inverted,
                    deposits, re-evaluate the fit.
                  – Longer wearing time
                 Burning & irritation
                  – Re-evaluate the fit, solutions, pollution.
                  – If dry eye ,lens should be of low water
                 Staining of cornea
                  – Decentred lens, protein built up, FB.      30
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                                     15
SOFT TORIC CONTACT LENS




                Problems associated with fitting
                soft lenses
                              oedema,
                    Epithelial oedema vertical striae in
                    cornea, fixed folds in Descemet`s
                    membrane, compression,
                    vascularization at limbus
                    – Due to steep lens that leads to hypoxia,
                      anoxia to cornea
                   Photophobia, excessive tearing
                    – Poorly fitting lens irritating the cornea
                      by friction
                                                                  31
                Prof.Dr.S.Aboulmagd 2010




                A Final Word

                 Astigmatic patients should be given the
                toric contact lens don’t keep them on
                  spherical lenses.
                 If you follow the proper fitting guides
                               e a ded
                  you will be rewarded
                 Toric contact lens calculators are
                  available on the net

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                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                               16
SOFT TORIC CONTACT LENS




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                Prof.Dr.S.Aboulmagd 2010




                                           THANK YOU
                                                 34
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                               17
SOFT TORIC CONTACT LENS




                                           THANK YOU




                                                       35
                Prof.Dr.S.Aboulmagd 2010




PROF.DR.SAMIHA ABOULMAGD                                    18

								
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