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E. H. Roth, C. G. Hoffmann; New Method to Measure Iol- Loops Under Shrinkage of the Capsular Bag. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3794.
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Capsular bag shrinkage after in-the-bag implantation may result in vertical displacement of the IOL due to compression of the IOL-loops that causes a new topography of the whole lens. There have been few approaches to average out the given capsular bag shrinkage by designing the IOL in a way, so that the compression is absorbed in the initial plane of the lens. A measurement device was build to show how the IOL- loops compressed after the shrinking of the capsular bag.
The ISO 11979-3:2006 (ophthalmic implants part 3: mechanical properties and test methods) describes methods of observation of changes of the IOL due to compression of IOL- loops to diameter of 10 mm. These methods are suited for the measurement of forces and movements of the IOL, but they give no information about these conditions, under the 10mm range.Reciprocal effects between IOL- loops and capsular bag can’t be observed with this method. A new vacuum chamber technique was designed to show how the IOL loops act in a simulated capsular bag, while the bag shrinks from 12mm to 8mm.For the simulated capsular bag we use a latex-bag 50mm long and 8mm in diameter closed at one side. This bag is placed in a cylindrical glass vacuum chamber with an inner diameter of 12mm. With pressure applied to the vacuum chamber the diameter of the bag is controlled.The procedure is captured by a video camera and the pictures evaluated by a computer program.
Holes or other defects in the IOL- loops of one-piece-lenses seem to have a bumper- effect at the beginning of the compression, but result mainly in the same structure as those without them do. Old fashioned three-piece-lenses (PMMA or Acrylat) have a very stable behavior compared to one-piece-Silicon-lenses.
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