VIEWS: 109 PAGES: 18 POSTED ON: 4/9/2011
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 2 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 3 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 4 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 7 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. 9 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 + + + + + + 10 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. 12 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 13 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 16 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. 17 Prof.Dr.S.Aboulmagd 2010 Specially Designed Toric Soft CL. stabilizing mechanism Le-Torque design Double slab- off design 18 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. 19 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 22 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 24 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 25 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 32 Prof.Dr.S.Aboulmagd 2010 PROF.DR.SAMIHA ABOULMAGD 16 SOFT TORIC CONTACT LENS 33 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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