Understanding Primary Polypseudophakia
Primary polypseudophakia is a relatively recent concept in ophthalmology. Optically, polypseudophakia would be considered a special intraocular lens consisting of two rotationally symmetric elements. The first report of placing two intraocular lens implants back-to-back (piggyback) in a highly hyperopic eye was by Jim Gills, MD, in 1993.
With dramatic advances in foldable lens technology allowing for small, self-sealing incisions, this procedure initially gained a qualified general acceptance. However, the previous practice of stacking two acrylic lenses in the capsular bag has since been abandoned due to occasional problems with interlenticular opacification and reduced visual acuity.
When the calculated IOL power exceeds the available range, and placement of a single IOL would result in an unacceptable refractive outcome, it is often worthwhile for the surgeon to place two IOLs in the eye during the same operative session. This is typically seen in patients with axial lengths of less than 20.00 mm, often accompanied by a hyperopic spherical equivalent of +8.00 or greater.
With current technology, the preferred approach is to place two IOLs of different materials in different locations (e.g., a lower-power, thin, biconvex silicone lens in the ciliary sulcus and a higher-power, negative shape factor acrylic lens in the capsular bag).
This is commonly referred to as primary polypseudophakia. With the recent introduction of very high-power, foldable, aspheric, hydrophobic acrylic IOLs available in powers up to +40.00 D (SA60AT – Alcon Laboratories, Ft. Worth, Texas), the need for primary polypseudophakia is expected to become less frequent.
Secondary polypseudophakia would be similar to a piggyback IOL, used to correct a refractive surprise that occurs months or years after the original surgery.
Follow this link for an example of how to do IOL Power Calculations for Polypseudophakia.
