医学课件：硬镜的概述、材料

1、Contact Lensesa bi-lingual course,School of Optometry & Ophthalmology, The Wenzhou Medical College,Evolution and Advances in Contact Lens Materials,Chronology of Contact Lens Development,1887- 88- F.A. Muller (Weisbaden),- Glass (Blown) scleral lenses A. Fick (Zurich), E. Kalt (Paris) 1910s - Zeiss

2、(Switzerland)- Glass (ground) scleral lenses 1930s- W. Feinbloom , T.Obrig,- Glass / plastic scleral contact lenses J. Dallos 1940s- Kevin Touhey- Corneal plastic CLs introduced,Chronology of Contact Lens Development,1960s- Otto Wichterle(Prague)- HEMA material development begins 1970s- Bausch & Lom

3、b (1971)- Introduced soft lenses in U.S. Rynco Scientific (1973)- Introduced CAB material in U.S. Rosenthal, et al (1978)- Introduced Boston material in Canada L. Seidner (1979)- Introduced RGP material in U.S.,Chronology of Contact Lens Development,1980s- Polymer Tech. (1983)- Introduces Boston Len

4、s Solutions Polymer Tech. (1987)- Introduces 1st F-S/A (Equalens) in U.S. 1990s- Polymer Tech. (1990)- Bi-aspheric design (Envision) Polymer Tech. (1994)- Introduces AERCOR low-silicon F-S/A material Polymer Tech. (1995)- Introduced 1st One-bottle RGP system Polymer Tech. (1997) - Introduced BOSTON

5、XO Polymer Tech. (1998)- Introduced MultiVision multifocal presbyopic design,Advantages of PMMA,Excellent optical quality Durable, stable Easy to manufacture and modify “Masks” corneal astigmatism well Neutral ionic charge - lens depositing minimal Wets well, easy to clean with weak surfactants,Disa

6、dvantages of PMMA,Impermeability to gases ( O2 / CO2) causes: Corneal hypoxia Striae Folds in Descemets membrane Central corneal clouding (edema) Microcysts,Methods of Delivering O2 to the Cornea with PMMA,Tear “Pump” / Higher edge lift (clearance) Limited Lens Mass - Thinner lens designs - Smaller

7、lens diameters Fenestrations,Complications of PMMA,Corneal “Warpage”,Central corneal clouding (edema),Folds in Descemets membrane (striae),Endothelial cell changes,Soft Lens Advantages,Good initial comfort Adaptation time shorter Faster / easier to fit Initial cost / per unit cost less Allows for pa

8、rt-time (social) wear Disposable & frequent replacement offers clean lenses,Soft Lens Disadvantages,Quality of vision may be compromised for convenience Impact on eye physiology greater than with RGPs Delicate. easy to damage Expensive over time,Do not “mask” astigmatism well Expensive over time Len

9、s care cumbersome & costly Steady material deterioration requires frequent replacement,What Created the Need for RGP Lenses?,RGP Lens Advantages,Crisp, consistent visual acuity that does not deteriorate Improved corneal physiology/fewer patient problems Ability to “mask” corneal astigmatism better L

10、ast 2-3 times longer than conventional soft lenses Lens care easy and economical Excellent long-term comfort,Tangible Benefits,RGP Lens Advantages,Greater patient loyalty to practice Increased new patient referrals Greater value perception to patient More profitable than disposable soft lenses and s

11、pectacles Greater personal/professional satisfaction Highlights practice as specialty,Intangible Benefits,RGP Lens Disadvantages,Initial comfort better with soft lenses Adaptation time slightly longer than for soft lenses Requires more time / expertise to fit in some cases Initial cost / per unit co

12、st more than for soft lenses,POLYMER TECHNOLOGY History and Product Development,Boston II-1978 Boston IV-1984 Boston Equalens-1986 Boston Lab Cleaner-1988 Boston RXD-1990 Boston Equalens II-1991,Boston Envision-1993 Boston 7-1994 Boston ES-1995 Boston XO-1997 Boston MultiVision-1998 Boston EO-1998 B

13、oston MultiVision Plus-1999,Lens Material Products,Lens Materials,Bulk Properties versus Surface Properties,Silicone Fluorine Methyl Methacrylate Hydrophilic Monomers Cross-Linking Agents,RGP Material Chemical Structure,RGP Lens Materials,Methods of Surface Interaction Ionic Negative surface energy

14、charge Hydrophobic Poor wettability of silicon,LIPID,PROTEIN,SILICONE ACRYLATE LENS,Silicone Acrylate Materials,Mid-range surface energy Ionic/hydrophobic protein attraction High adhesion tendency Deposits related to silicone content Basis for enzyme cleaners,Clinical Implications of Lens Deposits,D

15、ryness Redness / injection Decreased wearing time Giant papillary conjunctivitis (G.P.C.),Effects of Too Much Silicone,Poor lens wetting Increased deposits Poor machining characteristics Material instability,The “Silicone-Acrylate Barrier”,Fluorosilicone Acrylate Surface,Low surface energy Low adhes

16、ion tendency Attract lipids Deposits related to fluorine content Enzymatic cleaning less helpful,Progression of Rigid Lens Materials,Fluoro-silicone acrylates Harder, better optics, more stable Higher oxygen permeability Improved wettability, deposit resistance. Easier to clean, but can attract lipi

17、ds and lipid-like substances,S/A - F S/A Surface Characteristic Comparison,S/A - F S/A Surface Characteristic Comparison,Minimum Dk/L requirement for CL wear,Ideal DW wear: 24x 10-9(cm x mlO2)/(sec x ml x mmHg) Ideal EW wear:87x 10-9(cm x mlO2)/(sec x ml x mmHg) Acceptable EW:34x 10-9(cm x mlO2)/(se

18、c x ml x mmHg),Equivalent Oxygen Percentage,Oxygen Transmissibility Based on Lens Thickness,RGP Lens material: Dk 50 Lens center thickness: 0.11 mm / Edge thickness 0.12 mm,Oxygen Transmissibility Based on Lens Thickness,RGP Lens material: Dk 50 Lens center thickness: 0.15 mm / Edge thickness: 18 mm

19、,New Oxygen Permeability Methods of Measure,Current PTC gas-to-gas method x 10-11(cm2/sec)(mlO2xmmHg) 35 C ISO / Fatt (ISO 9913-1.2) x 10-11cm3O2 (cm) /(sec)(cm2)(mm Hg) 35 C,Evaluating RGP Lenses Containing UV Blockers,BLOCKED FLUORESCENCE = PSEUDOSTEEP PATTERN,Key Requirements for RGP Materials,Co

20、mfort Oxygen permeability Predictable fitting Wettability Deposit resistance Visual acuity Stability durability,THE CHALLENGE.,THE CHALLENGE.,THE CHALLENGE.,THE CHALLENGE.,Permeability Modulus Toughness Form stability Optics Manufacturing,Protein uptake Protein denaturization Lubricity Tear film int

21、egrity Lipophilicity,Effect of Silicone Content on Permeability,Surface compatibility,% Silicone,Effect of Silicone Content on Surface Properties,Permeability,% Silicone,Traditional Backbone,PMMA based - Dk = 0 Chains pack together tightly,AERCOR Polymer Backbone,Chains are spaced,Oxygen permeabilit

22、y without silicon provides Dk = 15 from the backbone alone,Effect of Cross-Linking on Oxygen Permeability,Undesirable Effects Brittleness Crazing Reduced permeability,POLYMER TECHNOLOGY History and Product Development,Boston ES,FDA approved 1995 Improved flexural resistance/durability Based on Aerco

23、r technology (ISO/Fatt Dk 18 ) Enhanced wetting/deposit resistance Excellent for specialty/thin lens designs Available in 5 handling tints UV blocker,Boston EO,PTC newest RGP material innovation Based on the AERCOR architecture Formulated for increased oxygen transmission, Dk 82 (gas to gas), Dk 58

24、(Iso/Fatt) Maintaining characteristics of wettability, flexural resistance, stability, and durability Stability that allows for standard and thin lens designs,Why BOSTON EO?,Ideal complement to BOSTON ES To provide sufficient oxygen passage for almost all patients needs Good durability in a high Dk/L RGP material Enhanced form stability that allows for standard and thin lens designs,BOSTON XO,“X-tra Oxygen X-ceptional Stability: Thats the XO Story”,Boston XO,Introduced in 1997 F-S/A RGP with superior permeability