98th Annual Meeting DOG 2000

R 251

Changing evolution of biomaterials and their impact on cataract surgery

R. J. Olson

Posterior capsular opacification (PCO) is a significant problem. A sharp posterior edge that is pushed into the posterior capsule will result in decreased PCO1. This biomechanical effect is now evident with several different materials. We must produce a 360o discontinuous bend or the blockage will not work. Some lens designs may lose their PCO advantage by not following these simple rules.

Of interest are the differing rates of PCO between some second-generation and first-generation silicone IOLs. Three studies2-4 have shown with the Allergan PhacoFlex II material statistically significant improvement in PCO with one randomized study showing equivalence in PCO prevention to the squared off edge of Alcon AcrySof. We must be careful about not lumping materials in the same class together if they, indeed, behave differently clinically.

Biocompatibility clinically is most evident in regard to giant cell deposits. Alcon AcrySof5, the hydrophilic acrylic class of lenses6, and some second-generation silicone IOLs6,7 have all evidenced a superior biocompatibility profile over PMMA. First generation silicone has not shown this advantage5. How these superior materials compare with each other from a biocompatibility standpoint is still poorly understood.

Unwanted images are a minor factor as a percent of problems but can be significant for specific patients. Unfortunately, the flattened edge does produce more unwanted images8 and has been a cause for patient demand for explantation.

Inclusions inside of IOLs have been reported with all hydrophobic materials. These inclusions are water9 that makes its way into the lattice structure and are only clinically apparent when their size is roughly 5 microns or larger. AcrySof as a material has, in particular, been prone to this problem with evidence of some mild statistically significant contrast and visual acuity loss6,9.

Foldable lenses 1 mm in actual measured final incision size presently. In review of consecutive patients we found a statistically significant decrease in wound stability in association with the Alcon MA-60 with an average incision size of approximately 4 mm and the SI-40 with an average incision size of 3 mm.

In summary, foldable IOLs have shown real advantages in regard to PCO and biocompatibility.

References:

  1. Nishi O, Nishi K: Preventing posterior capsule opacification by creating a discontinuous sharp bend in the capsule. J Cataract Refract Surg 25(4):521-526,1999.
  2. Hayashi H, Hayashi K, Nakao F: Quantitative comparison of posterior capsule opacification after polymethylmethacrylate, silicone and soft acrylic intraocular lens implantation. Arch Ophthalmol 116:1579-1582,1998.
  3. Olson RJ, Crandall AS: Silicone versus polymethacrylate intraocular lenses with regard to capsular opacification. Ophthalmol Surg Lasers 29(1):55-58,1998.
  4. Wang M, Woung L. Digital retroilluminated photography to analyze posterior capsule opacification in eyes with intraocular lenses. J Cataract Refract Surg 26:56-61,2000.
  5. Hollick EF, Spalton DJ, Ursell PG, Pane MV: Biocompatibility of poly (methyl methacrylate), silicone, and AcrySof intraocular lenses: randomized comparison of the cellular reaction on the anterior lens surface. J Cataract Refract Surg 24:352-360,1998.
  6. Dahliwal DK, Olson RJO, Mamalis N, et al: Visual significance of "glistenings" seen in the AcrySof lens. J Cataract Refract Surg 22:452-457,1996.
  7. Ravalico G, Baccara F, Lovisato A, Tognetto D: Postoperative cellular reaction on various intraocular lens materials. Ophthalmology 104:1084-1091, 1997.
  8. Holladay JT, Lang A, Portney V: Analysis of edge glare phenomena in intraocular lens edge designs. J Cataract and Refract Surg 25 (6):748-752,1999.
  9. Christiansen G, Durcan FJ, Olson, RJO, Chirstiansen K: Prevalence, severity, and visual significance of glistenings seen in AcrySof intraocular lens one to four years from implantation. Submitted to JCRS.

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