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1、RGP lens for Astigmatism.,School of Optometry & Ophthalmology, Wenzhou Medical College,1,RGP lens for Astig.,Spherical RGP First consideration 3.00D Mostly works Toric RGP A few,2,Spherical RGP lens Fitting principle: refer to last “Chapter” Tear Lens,3,4,5,6,7,Toric RGP Lenses,Stabilized fitting Im
2、proved lens to cornea fitting relationship Better corneal physiology than soft toric lens,8,Fit Toric RGP Lenses,RGP Lenses should move up and down during the blink,42.00,46.00,42.00,46.00,46.00,42.00,46.00,RGP Lenses should not move from side to side,9,Spherical RGP Lenses,A spherical RGP lens on a
3、 moderately astigmatic cornea is a perfect fit,10,Toric RGP Lenses,When there are significant areas of bearing and lift, a special RGP lens can be created,11,Fluorescein Patterns,Highly astigmatic cornea too loose vertically-too much lift,12,45.00,42.00,13,Same cornea with a steeper base curve,Bette
4、r alignment in the vertical,But too much touch in the horizontal,14,Fluorescein Patterns,Astigmatic cornea that is too tight horizontally,15,Double the CurvesDouble the Fun,To fit a cornea with moderate to high amounts of corneal astigmatism, a lens can be designed with two separate curves on the ba
5、ck surface.,Inside/back surface,44.00,42.00,16,17,Double the CurvesDouble the Fun,Because a lens should not move from side to side .the horizontal meridian should be fit on horizontal “K” or slightly steeper than horizontal “K”,18,Double the CurvesDouble the Fun,Because a lens should freely move up
6、and down the vertical meridian should be fit slightly flatter than vertical “K”,19,Front Surface Toric Lenses,When the cornea has less than 2.00 D of corneal astigmatism and there is a discrepancy in the amount of refractive astigmatism,“K”42.00 180 / 42.50 90,Rx-2.50 -2.50 x 180,20,Spherical Rigid
7、Contact Lenses Can Only Impact the Astigmatism Found on the Surface of the Cornea,21,22,23,24,25,Front Surface Toric Lenses,26,Front Surface Toric Lenses,Final 42.00 -2.75 -2.00 x 178 9.4,Prism Ballasted,27,28,29,Double the CurvesDouble the Fun,Parameter Choice Exercise Rx: -3.00D/-4.50Dx180 K: 42.0
8、0D/46.50D90,30,42.00 D,Place the horizontal “K” value on the horizontal axis: 42.00 180,31,46.50 D,Place the vertical “K” value on the vertical axis: 46.50 90,32,42.00 D,46.50 D,Place the sphere power only on the flattest meridian,-3.00 D,33,42.00 D -3.00 D,46.50 D,Place the combined power on the st
9、eepest meridian,-7.50 D (vertexed to -6.75 D),34,42.00 D -3.00 D 42.00 D -3.00 D,46.50 D -6.75 D 45.75 D -6.00 D,Place the combined power on the steepest meridian,35,36,37,38,39,40,41,42,“K” 44.50 180 / 45.00 90,Rx -2.00 DS,Sphere,Toric RGP candidates,43,“K” 41.00 180 / 42.50 90,Rx -3.50 -1.50 x 180
10、,Sphere,Toric RGP candidates,44,“K” 42.50 180 / 45.50 90,Rx -2.50 -3.00 x 175,BACK TORIC,Toric RGP candidates,45,“K” 45.50 180 / 46.00 90,Rx -5.00 -2.50 x 180,FRONT TORIC,Toric RGP candidates,46,“K” 42.50 180 / 45.50 90,Rx +3.00 -5.00 x 170,BITORIC,Toric RGP candidates,47,“K” 44.50 180 / 47.50 90,Rx
11、 plano -4.00 x 180,BITORIC,Toric RGP candidates,48,“K” 42.00 180 / 42.25 90,Rx -1.50 -1.75 x 180,Front TORIC,Toric RGP candidates,49,“K” 40.00 180 / 40.50 90,Rx -6.00 -2.00 x 177,Front TORIC,Toric RGP candidates,50,“K” 45.12 180 / 45.62 90,Rx -2.00 +0.75 x 80,Sphere,Toric RGP candidates,51,“K” 42.50
12、 180 / 44.50 90,Rx -2.75,Toric RGP candidates,Shere,52,Troubleshooting,53,Troubleshooting,54,Key points,When fitting spherical RGP and when Toric ones? When Front toric Back toric bitoric,55,Irregular Astig.,56,57,58,Corneal insufficient nutrition Corneal degeneration Inflammation and trauma ptergerm and warpage Secondary to surgery Secondary to refractive surgery Lid problems,59,Correction options for irregular Astig,Spectacles (poor) Soft contact lens (poor) RGP (available ),60,Thanks,61,
