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Editorial | Previous Editorials
September 2003


Protein and Lipid Deposition of Silicone-Hydrogel Contact Lens Materials

Lyndon Jones, PhD FCOptom DipCLP DipOrth FAAO (Dip CL) FIACLE

Associate Professor
School of Optometry
Associate Professor
Departments of Physics, Chemistry & Chemical Engineering (cross-appointed)
Associate Director
Centre for Contact Lens Research

School of Optometry, University of Waterloo, Waterloo OntarioCanada N2L 3G1

Michelle Senchyna, BSc, PhD

Assistant Professor
School Of Optometry and Faculty of Biology
University of Waterloo


Silicone-hydrogel contact lens materials represent a new family of biomaterials, whose properties are unlike any other previously developed for contact lens use. The incorporation of siloxane groups into the base hydrogel material has produced materials that have substantially improved oxygen transmission characteristics compared with conventional soft contact lens materials 1-3 and the results from clinical studies conducted to-date indicate that the number of physiological complications induced by the overnight use of such materials is significantly less than that seen with conventional materials. 4-11

Detailed explanations of the development of silicone hydrogel materials for contact lenses and their polymer chemistry have been described in detail elsewhere. 2, 12-16 The use of silicon-containing flexible contact lenses is not new, as silicone-elastomeric lenses have been used for therapeutic and paediatric applications for many years. 17 These lenses offer exceptional oxygen transmission, but the migration of siloxane moieties to the material surface results in the production of extremely hydrophobic surfaces, resulting in marked lipid deposition. 18 To overcome this, the surfaces of the two commercially available silicone-hydrogel lenses are surface treated, 2, 13, 19, 20 in an attempt to improve the wettability of the materials and to reduce the degree of deposition that would occur on non-treated materials. The surfaces of Focus Night & Day (lotrafilcon) lenses are permanently modified in a gas plasma reactive chamber to create a permanent, ultrathin (25nm), high refractive index, continuous hydrophilic surface. 13, 21 PureVision (balafilcon) lenses are surface treated in a gas plasma reactive chamber which transforms the silicone components on the surface of the lenses into hydrophilic silicate compounds. 2, 19, 20 Glassy, discontinuous silicate “islands” result, 19, 20 and the hydrophilicity of these areas "bridges" over the underlying hydrophobic balafilcon A material.

The deposition of contact lenses with substances derived from the tear fluid is a well-known clinical complication, resulting in reductions in comfort, 22 vision 23 and increased inflammatory responses. 24 Hydrogel materials rapidly spoil with constituents from the tear film, particularly proteins, 25, 26 lipids 27 and mucins. 28 The adsorption of proteins and lipids at the contact lens interface is dependent upon a number of factors. Notable amongst these are material water content, 29, 30 surface charge, 29, 31, 32 wearing period 33 and age of the lens material. 34 Increasing water content and/or ionicity of the lens material greatly enhances protein deposition, 25, 29-32, 35-37 with lysozyme being detectable on FDA group IV lenses after wearing times for as little as one minute. 38 Whilst group IV lenses tend to predominantly deposit lysozyme, neutral group II lens materials (particularly those containing vinyl pyrrolidone) have a tendency to deposit lipid. 33, 39, 40

Information concerning the degree of protein and lipid deposition that occurs on silicone-hydrogel lens materials is of significant clinical importance, as these lenses are intended for in-eye use for up to 30 days without removal. It is imperative that materials worn in this way deposit as little material from the tear film as possible, in order to minimise the potential visual and inflammatory complications detailed above.

Results from our group 41, 42 and others 43-45 indicate that the amount of lysozymedeposited on silicone-hydrogel lens materials is significantly less than that seen on group IV traditional contact lens materials. Figure 1 indicates that silicone-hydrogels typically deposit less than 10 µg of lysozyme after being worn in-eye for 30 days, as compared with an etafilcon-lens (Acuvue), which deposits in the region of 1000 µg of lysozyme after one week of extended-wear.

Figure 1 Degree of lysozyme deposition measured on Focus Night & Day (lotrafilcon), PureVision (balafilcon) and Acuvue (etafilcon). The lotrafilcon and balafilcon lenses were worn for 30 nights continuously and the etafilcon lens was worn for 6 nights without removal. The degree of lysozyme deposition was significantly different between all three lens types (p<0.001).

Despite surface treatment of the lens materials, in vitro wetting angle assessment of the two silicone-hydrogel materials indicates that they remain relatively hydrophobic compared with conventional hydrogels. 44, 46, 47 Lipids preferentially deposit onto hydrophobic surfaces and data thus far indicates that lipid deposition on silicone-hydrogels can be a problem for certain patients. 41 Figure 2 reveals data from our laboratory, which indicates that certain classes of lipids preferentially deposit onto silicone-hydrogel lens materials and that silicone-hydrogels deposit greater quantities of lipid than conventional ionic lens materials.

Figure 2 Degree of lipid deposition measured on Focus Night & Day (lotrafilcon), PureVision (balafilcon) and Acuvue (etafilcon). The lotrafilcon and balafilcon lenses were worn for 30 nights continuously and the etafilcon lens was worn for 6 nights without removal. The degree of lipid deposition was significantly different between all three lens types (p<0.001).

Lipid deposition onto conventional lens materials is highly patient dependent 33, 34, 48-50 and this fact is similarly observed with silicone-hydrogel lens materials. Figures 3 and 4 reveal various lipid deposition patterns seen in certain subjects using silicone-hydrogel lenses.

Figure 3 Lipid deposition in the form of lens calculi (jelly-bumps) on a silicone-hydrogel lens. Picture courtesy of Brian Tompkins.
Figure 4 Lipid deposition in the form of a heavy film on the lens surface of a silicone-hydrogel lens. Picture courtesy of Brian Tompkins.
Click to enlarge Click to enlarge

If subjects are seen to be depositing their silicone-hydrogel lenses with lipid then moving to non vinyl pyrrolidone-containing materials (such as Proclear or Acuvue) should reduce this phenomenon. Further options include adding surfactant cleaners containing alcohol (such as Miraflow) or moving to more frequent periods of replacement. 33

In summary, currently available, first-generation silicone-hydrogel lens materials have provided clinicians with materials that allow safe, oedema-free overnight wear for up to 30 continuous nights. They deposit only small amounts of protein from the tear film, but certain patients do have problems related to the deposition of lipids on these materials, due to the relatively hydrophobic nature of the lens surfaces. Subsequent iterations of siloxane-hydrogels should be designed with surfaces that are ideally more hydrophilic, in an attempt to optimise their biocompatibility with the tear film.



We would like to acknowledge the work of Ian Forbes, Derek Louie, Chris May and Jillian Schickler for their assistance in producing the results published in this article.


1. Alvord L, Court J, Davis T, Morgan CF, Schindhelm K, Vogt J, Winterton L: Oxygen permeability of a new type of high Dk soft contact lens material. Optom Vis Sci 1998; 75: 30-6.

2. Tighe B: Silicone hydrogel materials - how do they work ? in Silicone Hydrogels: The Rebirth of Continuous Wear Contact Lenses, D. Sweeney, Editor. Oxford, Butterworth-Heinemann,2000, pp 1 - 21.

3. Morgan CF, Brennan NA, Alvord L: Comparison of the coulometric and polarographic measurement of a high-Dk hydrogel. Optom Vis Sci 2001; 78: 19-29.

4. Brennan NA, Coles ML, Comstock TL, Levy B: A 1-year prospective clinical trial of balafilcon a (PureVision) silicone-hydrogel contact lenses used on a 30-day continuous wear schedule. Ophthalmology 2002; 109: 1172-7.

5. Morgan PB, Efron N: Comparative clinical performance of two silicone hydrogel contact lenses for continuous wear. Clin Exp Optom 2002; 85: 183-92.

6. Papas E, Vajdic C, Austen R, Holden B: High oxygen-transmissibility soft contact lenses do not induce limbal hyperaemia. Curr Eye Res 1997; 16: 942-948.

7. Dumbleton KA, Chalmers RL, Richter DB, Fonn D: Changes in myopic refractive error with nine months' extended wear of hydrogel lenses with high and low oxygen permeability. Optom Vis Sci 1999; 76: 845-9.

8. Keay L, Sweeney DF, Jalbert I, Skotnitsky C, Holden BA: Microcyst response to high Dk/t silicone hydrogel contact lenses. Optom Vis Sci 2000; 77: 582-5.

9. Covey M, Sweeney DF, Terry R, Sankaridurg PR, Holden BA: Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible. Optom Vis Sci 2001; 78: 95-9.

10. du Toit R, Simpson TL, Fonn D, Chalmers RL: Recovery from hyperemia after overnight wear of low and high transmissibility hydrogel lenses. Curr Eye Res 2001; 22: 68-73.

11. Sweeney D, Keay L, Jalbert I, Sankaridurg P, Holden B, Skotnitsky C, Stephensen A, Covey M, Rao G: Clinical performance of silicone hydrogel lenses. in Silicone hydrogels. The rebirth of continuous wear contact lenses, D. Sweeney, Editor. Oxford, Butterworth-Heinemann,2000, pp 90 - 149.

12. Kunzler J, Ozark R. Hydrogels based on hydrophilic side chain siloxanes. in The American Chemical Society Division of Polymeric Materials - Science and Engineering Polym Mater Sci Eng Proc Acs Div, Polym Mater Sci Eng, ACS. 1993. Chicago, Il, USA.
13. Nicolson PC, Vogt J: Soft contact lens polymers: an evolution. Biomaterials 2001; 22: 3273-83.

14. Friends G, Kunzler J, Ozark R: Recent advances in the design of polymers for contact lenses. Macromolecular Symposia 1995; 98: 619-631.

15. Kunzler J: Silicone-based hydrogels for contact lens applications. Contact Lens Spectrum 1999; 14: 9 - 11.

16. Dumbleton K: The physical and clinical characteristics of silicone-hydrogel lenses: How they work?" Silicone Hydrogel Website 2001.

17. Gurland JE: Use of silicone lenses in infants and children. Ophthalmology 1979; 86: 1599-1604.

18. Huth S, Wagner H: Identification and removal of deposits on polydimethylsiloxane silicone elastomer lenses. Int Contact Lens Clin 1981: 19-26.

19. Grobe GL, 3rd: Surface engineering aspects of silicone-hydrogel lenses. Contact Lens Spectrum 1999; 14: 14 - 17.

20. Lopez-Alemany A, Compan V, Refojo MF: Porous structure of Purevision versus Focus Night&Day and conventional hydrogel contact lenses. J Biomed Mater Res (Appl Biomat) 2002; 63: 319 - 325.

21. Weikart CM, Matsuzawa Y, Winterton L, Yasuda HK: Evaluation of plasma polymer-coated contact lenses by electrochemical impedance spectroscopy. J Biomed Mater Res 2001; 54: 597-607.

22. Pritchard N, Fonn D, Weed K: Ocular and subjective responses to frequent replacement of daily wear soft contact lenses. CLAO J 1996; 22: 53-59.

23. Gellatly K, Brennan N, Efron N: Visual decrement with deposit accumulation on HEMA contact lenses. Am J Optom Physiol Opt 1988; 65: 937-941.

24. Mondino B, Salamon S, Zaidman G: Allergic and toxic reactions in soft contact lens wearers. Surv Ophthalmol 1982; 26: 337-344.

25. Baines M, Cai F, Backman H: Adsorption and removal of protein bound to hydrogel contact lenses. Optom Vis Sci 1990; 67: 807-810.

26. Bohnert JL, Horbett TA, Ratner BD, Royce FH: Adsorption of proteins from artificial tear solutions to contact lens materials. Invest Ophthalmol Vis Sci 1988; 29: 362-73.

27. Bontempo AR, Rapp J: Protein-lipid interaction on the surface of a hydrophilic contact lens in vitro. Curr Eye Res 1997; 16: 776-81.

28. Castillo EJ, Koenig JL, Anderson JM, Jentoft N: Protein adsorption on soft contact lenses. III. Mucin. Biomaterials 1986; 7: 9-16.

29. Minarik L, Rapp J: Protein deposits on individual hydrophilic contact lenses: Effects of water and ionicity. CLAO J 1989; 15: 185-188.

30. Fowler S, Korb D, Allansmith M: Deposits on soft contact lenses of various water contents. CLAO J 1985; 11: 124-127.

31. Minno G, Eckel L, Groemminger S, Minno B, Wrzosek T: Quantitative analysis of protein deposits on hydrophilic soft contact lenses: I. Comparison to visual methods of analysis. II. Deposit variation among FDA lens material groups. Optom Vis Sci 1991; 68: 865-872.

32. Sack R, Jones B, Antignani A, Libow R, Harvey H: Specificity and biological activity of the protein deposited on the hydrogel surface. Invest Ophthalmol Vis Sci 1987; 28: 842-849.

33. Jones L, Mann A, Evans K, Franklin V, Tighe B: An in vivo comparison of the kinetics of protein and lipid deposition on group II and group IV frequent-replacement contact lenses. Optom Vis Sci 2000; 77: 503-10.

34. Jones L, Franklin V, Evans K, Sariri R, Tighe B: Spoilation and clinical performance of monthly vs three monthly disposable contact lenses. Optom Vis Sci 1996; 73: 16-21.

35. Garrett Q, Chatelier RC, Griesser HJ, Milthorpe BK: Effect of charged groups on the adsorption and penetration of proteins onto and into carboxymethylated poly(HEMA) hydrogels. Biomaterials 1998; 19: 2175-86.

36. Garrett Q, Garrett RW, Milthorpe BK: Lysozyme sorption in hydrogel contact lenses. Invest Ophthalmol Vis Sci 1999; 40: 897-903.

37. Garrett Q, Laycock B, Garrett RW: Hydrogel lens monomer constituents modulate protein sorption. Invest Ophthalmol Vis Sci 2000; 41: 1687-95.

38. Leahy C, Mandell R, Lin S: Initial in vivo tear protein deposition on individual hydrogel contact lenses. Optom Vis Sci 1990; 67: 504-511.

39. Jones L, Evans K, Sariri R, Franklin V, Tighe B: Lipid and protein deposition of N-vinyl pyrrolidone containing group II and group IV frequent replacement contact lenses. CLAO J 1997; 23: 122-126.

40. Maissa C, Franklin V, Guillon M, Tighe B: Influence of contact lens material surface characteristics and replacement frequency on protein and lipid deposition. Optom Vis Sci 1998; 75: 697-705.

41. Jones L, Senchyna M, Louie D, Schickler J: A comparative evaluation of lysozyme and lipid deposition on Etafilcon, Balafilcon and Lotrafilcon contact lens materials. Invest Ophthalmol Vis Sci 2001; 42: s593 #3186.

42. Senchyna M, Jones L, Louie D, Forbes I, May C: Optimization of methodologies to characterize lysozyme deposition found on balafilcon and etafilcon contact lens materials. Invest Ophthalmol Vis Sci 2002; ARVO abstract # 3082.

43. McNally J, McKenney CD: A clinical look at a silicone hydrogel extended wear lens. Contact Lens Spectrum 2002; 17: 38 - 41.

44. Court JL, Redman RP, Wang JH, Leppard SW, Obyrne VJ, Small SA, Lewis AL, Jones SA, Stratford PW: A novel phosphorylcholine-coated contact lens for extended wear use. Biomaterials 2001; 22: 3261-72.

45. McKenney C, Becker N, Thomas S, Castillo-Krevolin C, Grant T: Lens deposits with a high Dk hydrophilic soft lens. Optom Vis Sci 1998; 75: 276.

46. Bruinsma GM, van der Mei HC, Busscher HJ: Bacterial adhesion to surface hydrophilic and hydrophobic contact lenses. Biomaterials 2001; 22: 3217-24.

47. Jones L, Long J, Chen P: The impact of contact lens care regimens on the in vitro wettability of conventional and silicone-hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2002; ARVO abstract # 3097.

48. Hart D, Tidsale R, Sack R: Origin and composition of lipid deposits on soft contact lenses. Ophthalmol 1986; 93: 495-503.

49. Franklin V, Bright A, Tighe B: Hydrogel polymers and ocular spoilation processes. TRIP 1993; 1: 9-16.

50. Tighe BJ, Jones L, Evans K, Franklin V: Patient-dependent and material-dependent factors in contact lens deposition processes. Adv Exp Med Biol 1998; 438: 745-51.


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