SURFACE CHARACTERISTICS OF INTRAOCULAR-LENS IMPLANTS - AN EVALUATION USING SCANNING ELECTRON-MICROSCOPY AND QUANTITATIVE 3-DIMENSIONAL NONCONTACTING PROFILOMETRY (TOPO)

The reaction of tissue surrounding an implant, especially the cellular reaction, partially depends on the mechanical surface characteristics (roughness, smoothness) of an implant. Studies on various materials r evealed that roughness in the range of microns could influence cell mi gration and proliferation. Scanning electron microscopy (SEM) is the s tandard, basic tool in ophthalmology for studying the surface characte ristics and surface quality of intraocular lens implants (IOLs). In th is study, we used a noncontacting white-light interferometer (TOPO) (W YKO Corp., Tucson). It is capable of measuring height variations of a surface in nanometers and produces a color-coded three-dimensional gra phical image of the surface topography. We examined five polymethylmed iacrylate (PMMA) intraocular lenses and two polydimediylsiloxane (sili cone) IOLs using SEM and TOPO. All IOLs showed very smooth surfaces on SEM examination and surface irregularities smaller than 15 nm using T OPO analysis. The average roughness of the optic surfaces of PMMA lens es was 6.34 +/- 3.27 nm. Silicone lenses showed even smoother surfaces , with average roughness values of 3.41 +/- 0.38 nm. Surface irregular ities at the micron level are known to influence the cell/implant resp onse. The implants analyzed here showed surface roughness values that are 1000 times smaller, i.e., the nanometer level as opposed to the mi cron level. Therefore, these very fine irregularities should not provo ke specific cell reactions because of their mechanical surface propert ies.